Characterization and Atlas of the Blue Nile Basin and its Sub basins Aster Denekew Yilma and Seleshi Bekele Awulachew International Water Management Institute January, 2009 i Table of Contents List of Figures .................................................................................................................. viii List of Tables ................................................................................................................... xiv Acronyms.......................................................................................................................... xv Characteristics of the Blue Nile Basin and its Sub basins .................................................. 1 Blue Nile Basin ................................................................................................................... 1 Topography................................................................................................................. 2 Climate........................................................................................................................ 3 Rainfall.................................................................................................................... 3 Temperature ............................................................................................................ 4 Evaporation ............................................................................................................. 5 Station Data................................................................................................................. 6 Rainfall.................................................................................................................... 7 Evaporation ............................................................................................................. 9 Hydrology ................................................................................................................. 10 Land use/cover .......................................................................................................... 16 Soil ............................................................................................................................ 17 Socio Economic aspect of the basin.......................................................................... 18 Administrative structure of the basin.................................................................... 18 Population ............................................................................................................. 19 Abbay Basin (Ethiopia-Blue Nile).................................................................................... 21 Topography............................................................................................................... 22 Climate...................................................................................................................... 24 Rainfall.................................................................................................................. 24 Temperature .......................................................................................................... 24 Evaporation ........................................................................................................... 26 Climate Stations Data ............................................................................................... 26 Rainfall.................................................................................................................. 27 Evaporation ........................................................................................................... 28 Hydrology ................................................................................................................. 29 Agro-Ecological Zones ............................................................................................. 31 Land Use / Land Cover ............................................................................................. 31 Soil ............................................................................................................................ 32 Geology..................................................................................................................... 33 Socio Economic aspect of the basin.......................................................................... 34 Administrative structure of the basin.................................................................... 34 Population ............................................................................................................. 35 Blue Nile in the Sudan ...................................................................................................... 36 Topography............................................................................................................... 36 Climate...................................................................................................................... 37 Rainfall.................................................................................................................. 37 Temperature .......................................................................................................... 38 Evaporation ........................................................................................................... 40 Climate Stations Data ............................................................................................... 41 Rainfall.................................................................................................................. 41 ii Hydrology ................................................................................................................. 42 Land Cover................................................................................................................ 42 Soil ............................................................................................................................ 43 Socio Economic aspect of the basin.......................................................................... 44 Administrative structure of the basin.................................................................... 44 Population ............................................................................................................. 45 Ethiopia Blue Nile (Abbay Basin) Sub basins.................................................................. 46 Tana Sub Basin ............................................................................................................. 46 Topography............................................................................................................... 47 Climate...................................................................................................................... 48 Rainfall.................................................................................................................. 48 Temperature .......................................................................................................... 49 Evapotranspiration ................................................................................................ 51 Station Data............................................................................................................... 51 Rainfall.................................................................................................................. 51 Temperature .......................................................................................................... 53 Evaporation ........................................................................................................... 54 Hydrology ................................................................................................................. 54 AgroEcological Zones .............................................................................................. 56 Land Cover................................................................................................................ 57 Soil ............................................................................................................................ 58 Geology..................................................................................................................... 59 Socio Economic aspect of the basin.......................................................................... 60 Administrative structure of the basin.................................................................... 60 Jemma Sub Basin.......................................................................................................... 62 Topography............................................................................................................... 62 Climate...................................................................................................................... 63 Rainfall.................................................................................................................. 63 Temperature .......................................................................................................... 64 Evaporation ........................................................................................................... 66 Station Data............................................................................................................... 66 Rainfall.................................................................................................................. 67 Temperature .......................................................................................................... 69 Evaporation ........................................................................................................... 70 Hydrology ................................................................................................................. 71 Land Use ................................................................................................................... 72 Agro-Ecological Zones ............................................................................................. 73 Soil ............................................................................................................................ 74 Geology..................................................................................................................... 75 Socio Economic aspect of the sub basin ................................................................... 76 Administrative structure of the sub basin ............................................................. 76 Muger Sub basin ............................................................................................................... 78 Topography............................................................................................................... 78 Climate...................................................................................................................... 79 Rainfall.................................................................................................................. 79 Temperature .......................................................................................................... 80 iii Evaporation ........................................................................................................... 82 Land use .................................................................................................................... 82 Agro-Ecological Zones ............................................................................................. 83 Soil ............................................................................................................................ 84 Geology..................................................................................................................... 85 Socio Economic aspect of the sub basin ................................................................... 86 Administrative structure of the sub basin ............................................................. 86 Guder Sub basin................................................................................................................ 87 Topography............................................................................................................... 87 Climate...................................................................................................................... 89 Rainfall.................................................................................................................. 89 Temperature .......................................................................................................... 89 Evaporation ........................................................................................................... 91 Land use .................................................................................................................... 91 Agro-Ecological Zones ............................................................................................. 92 Soil ............................................................................................................................ 93 Geology..................................................................................................................... 94 Socio Economic aspect of the sub basin ................................................................... 95 Administrative structure of the sub basin ............................................................. 95 Beles Sub basin ................................................................................................................. 96 Topography............................................................................................................... 96 Climate...................................................................................................................... 98 Rainfall.................................................................................................................. 98 Temperature .......................................................................................................... 98 Evaporation ......................................................................................................... 100 Land use .................................................................................................................. 100 Agro-Ecological Zones ........................................................................................... 101 Soil .......................................................................................................................... 102 Geology................................................................................................................... 103 Socio Economic aspect of the sub basin ................................................................. 104 Administrative structure of the sub basin ........................................................... 104 Dabus Sub basin.............................................................................................................. 105 Topography............................................................................................................. 105 Climate.................................................................................................................... 107 Rainfall................................................................................................................ 107 Temperature ........................................................................................................ 107 Evaporation ......................................................................................................... 109 Land use .................................................................................................................. 109 Agro-Ecological Zones ........................................................................................... 110 Soil .......................................................................................................................... 111 Geology................................................................................................................... 112 Socio Economic aspect of the sub basin ................................................................. 113 Administrative structure of the sub basin ........................................................... 113 Didessa Sub basin ........................................................................................................... 114 Topography............................................................................................................. 114 Climate.................................................................................................................... 116 iv Rainfall................................................................................................................ 116 Temperature ........................................................................................................ 116 Evaporation ......................................................................................................... 118 Land use .................................................................................................................. 118 Agro-Ecological Zones ........................................................................................... 119 Soil .......................................................................................................................... 120 Geology................................................................................................................... 121 Socio Economic aspect of the sub basin ................................................................. 122 Administrative structure of the sub basin ........................................................... 122 Fincha Sub basin ............................................................................................................. 123 Topography............................................................................................................. 123 Climate.................................................................................................................... 125 Rainfall................................................................................................................ 125 Temperature ........................................................................................................ 125 Evaporation ......................................................................................................... 127 Land use .................................................................................................................. 127 Agro-Ecological Zones ........................................................................................... 128 Soil .......................................................................................................................... 129 Geology................................................................................................................... 130 Socio Economic aspect of the sub basin ................................................................. 131 Administrative structure of the sub basin ........................................................... 131 Anger Sub basin.............................................................................................................. 132 Topography............................................................................................................. 132 Climate.................................................................................................................... 134 Rainfall................................................................................................................ 134 Temperature ........................................................................................................ 134 Evaporation ......................................................................................................... 136 Land use .................................................................................................................. 136 Agro-Ecological Zones ........................................................................................... 137 Soil .......................................................................................................................... 138 Geology................................................................................................................... 139 Socio Economic aspect of the sub basin ................................................................. 140 Administrative structure of the sub basin ........................................................... 140 Wenbera Sub basin ......................................................................................................... 141 Topography............................................................................................................. 141 Climate.................................................................................................................... 143 Rainfall................................................................................................................ 143 Temperature ........................................................................................................ 143 Evaporation ......................................................................................................... 145 Land use .................................................................................................................. 145 Agro-Ecological Zones ........................................................................................... 146 Soil .......................................................................................................................... 147 Geology................................................................................................................... 148 Socio Economic aspect of the sub basin ................................................................. 149 Administrative structure of the sub basin ........................................................... 149 Beshelo Sub basin ........................................................................................................... 150 v Topography............................................................................................................. 150 Climate.................................................................................................................... 152 Rainfall................................................................................................................ 152 Temperature ........................................................................................................ 152 Evaporation ......................................................................................................... 154 Land use .................................................................................................................. 154 Agro-Ecological Zones ........................................................................................... 155 Soil .......................................................................................................................... 156 Geology................................................................................................................... 157 Socio Economic aspect of the sub basin ................................................................. 158 Administrative structure of the sub basin ........................................................... 158 Welaka Sub basin............................................................................................................ 159 Topography............................................................................................................. 159 Climate.................................................................................................................... 161 Rainfall................................................................................................................ 161 Temperature ........................................................................................................ 161 Evaporation ......................................................................................................... 163 Land use .................................................................................................................. 163 Agro-Ecological Zones ........................................................................................... 164 Soil .......................................................................................................................... 165 Geology................................................................................................................... 166 Socio Economic aspect of the sub basin ................................................................. 167 Administrative structure of the sub basin ........................................................... 167 North Gojam Sub basin................................................................................................... 168 Topography............................................................................................................. 168 Climate.................................................................................................................... 170 Rainfall................................................................................................................ 170 Temperature ........................................................................................................ 170 Evaporation ......................................................................................................... 172 Land use .................................................................................................................. 172 Agro-Ecological Zones ........................................................................................... 173 Soil .......................................................................................................................... 174 Geology................................................................................................................... 175 Socio Economic aspect of the sub basin ................................................................. 176 Administrative structure of the sub basin ........................................................... 176 South Gojam Sub basin................................................................................................... 177 Topography............................................................................................................. 177 Climate.................................................................................................................... 179 Rainfall................................................................................................................ 179 Temperature ........................................................................................................ 179 Evaporation ......................................................................................................... 181 Agro-Ecological Zones ........................................................................................... 181 Soil .......................................................................................................................... 182 Geology................................................................................................................... 183 Socio Economic aspect of the sub basin ................................................................. 184 Administrative structure of the sub basin ........................................................... 184 vi Dinder Sub basin............................................................................................................. 185 Topography............................................................................................................. 185 Climate.................................................................................................................... 187 Rainfall................................................................................................................ 187 Temperature ........................................................................................................ 187 Evaporation ......................................................................................................... 189 Land use .................................................................................................................. 189 Agro-Ecological Zones ........................................................................................... 190 Soil .......................................................................................................................... 191 Geology................................................................................................................... 192 Socio Economic aspect of the sub basin ................................................................. 193 Administrative structure of the sub basin ........................................................... 193 Rahad Sub basin.............................................................................................................. 194 Topography............................................................................................................. 194 Climate.................................................................................................................... 196 Rainfall................................................................................................................ 196 Temperature ........................................................................................................ 196 Evaporation ......................................................................................................... 198 Land use .................................................................................................................. 198 Agro-Ecological Zones ........................................................................................... 199 Soil .......................................................................................................................... 200 Geology................................................................................................................... 201 Socio Economic aspect of the sub basin ................................................................. 202 Administrative structure of the sub basin ........................................................... 202 Watersheds and Micro Watersheds (Learning sites) ...................................................... 204 Gilgel Abay Watershed............................................................................................... 204 Topography............................................................................................................. 204 Climate.................................................................................................................... 205 Rainfall................................................................................................................ 205 Temperature ........................................................................................................ 205 Evaporation ......................................................................................................... 207 Hydrology ............................................................................................................... 207 Land Use/Cover ...................................................................................................... 208 Soil .......................................................................................................................... 209 Geology................................................................................................................... 209 Socio Economic aspect of the watershed................................................................ 210 Administrative structure of the watershed .......................................................... 210 Gumera Watershed...................................................................................................... 212 Topography............................................................................................................. 213 Climate.................................................................................................................... 215 Rainfall................................................................................................................ 215 Temperature ........................................................................................................ 215 Evaporation ......................................................................................................... 217 Station Data............................................................................................................. 217 Rainfall................................................................................................................ 217 Temperature ........................................................................................................ 218 vii Evaporation ......................................................................................................... 219 Hydrology ............................................................................................................... 220 Land Use/Cover ...................................................................................................... 220 Soil .......................................................................................................................... 221 Geology................................................................................................................... 222 Socioeconomic Aspect of the Watershed ............................................................... 223 Administrative Structure of the Watershed......................................................... 223 Population ........................................................................................................... 224 Koga Sub Watershed................................................................................................... 225 Topography............................................................................................................. 225 Climate.................................................................................................................... 226 Rainfall................................................................................................................ 226 Temperature ........................................................................................................ 227 Hydrology ............................................................................................................... 227 Micro Watersheds ....................................................................................................... 228 Anjeni.......................................................................................................................... 228 Topography............................................................................................................. 228 Climate.................................................................................................................... 229 Rainfall................................................................................................................ 229 Temperature ........................................................................................................ 229 Land Use ................................................................................................................. 230 Soil .......................................................................................................................... 231 Andit ........................................................................................................................... 232 Topography............................................................................................................. 232 Climate.................................................................................................................... 233 Rainfall................................................................................................................ 233 Temperature ........................................................................................................ 234 Land Use ................................................................................................................. 234 Reference: ....................................................................................................................... 236 viii List of Figures Figure 1: Blue Nile Basin and its sub basins ...................................................................... 2 Figure 2: Topography of the Blue Nile Basin..................................................................... 3 Figure 3: Rainfall distribution in the Blue Nile Basin ........................................................ 4 Figure 4: Mean Monthly Temperature for the Blue Nile Basin.......................................... 5 Figure 5: Potential Evapotranspiration in the Blue Nile Basin........................................... 6 Figure 6: Main Meteorological Stations in the Blue Nile Basin......................................... 7 Figure 7: Chart showing the Mean Annual Rainfall at Stations in Sudan .......................... 8 Figure 8: Map showing the location and Mean Annual Rainfall at Stations in Sudan....... 8 Figure 9: Chart showing the Mean Annual Rainfall at Stations in Ethiopia ...................... 9 Figure 10: Chart showing the Mean Monthly Evaporation at Stations in Sudan ............... 9 Figure 11: Mean Annual Evaporation for the Stations in Sudan ..................................... 10 Figure 12: Chart showing the Mean Annual Evaporation at Stations in Ethiopia............ 10 Figure 13: Hydrological Stations in the Blue Nile............................................................ 11 Figure 14: Chart showing the Monthly Discharge in MCM for the months July - October at El Diem Stations in Sudan ............................................................................................ 11 Figure 15: Chart showing the Annual Discharge at El Diem Stations in Sudan .............. 12 Figure 16: Chart showing Monthly Flow at Sennar Station ............................................. 12 Figure 17: Chart showing Monthly Flow for the months of July - October at Sennar Station ............................................................................................................................... 13 Figure 18: Chart showing Annual Flow at Sennar Station ............................................... 13 Figure 19: Chart showing Monthly Inflow at Dinder Station........................................... 14 Figure 20: Chart showing Mean Monthly InFlow at Dinder Station................................ 14 Figure 21: Chart showing Monthly Flow at Abbay Station near Bahirdar....................... 15 Figure 22: Chart showing Mean Monthly Flow at Abbay Station near Bahirdar............. 15 Figure 23: Chart showing Monthly Flow at Abbay Station near Kessie .......................... 16 Figure 24: Chart showing Mean Monthly Flow at Abbay Station near Kessie ................ 16 Figure 25: Land Cover for the Blue Nile Basin................................................................ 17 Figure 26: Major Soil Classes for the Blue Nile Basin..................................................... 18 Figure 27: Administrative Regions in the Sudan and Ethiopia part of the Blue Nile....... 19 Figure 28: Population in the Blue Nile Basin ................................................................... 20 Figure 29: Abbay Basin (Blue Nile Sub basin) ................................................................ 21 Figure 30: Irrigation Potential Areas and Dam Sites in the Abbay Basin ........................ 22 Figure 31: Topography of the Abbay Basin ..................................................................... 23 Figure 32: Slope of the Abbay Basin................................................................................ 23 Figure 33: Rainfall Distribution in the Abbay Basin ........................................................ 24 Figure 34: Maximum Temperature in the Abbay Basin ................................................... 25 Figure 35: Minimum Temperature in the Abbay Basin.................................................... 25 Figure 36: Potential Evapotranspiration in the Abbay Basin............................................ 26 Figure 37: Meteorological Stations in the Abbay Basin................................................... 27 Figure 38: Annual Rainfall at Bahirdar Station ................................................................ 28 Figure 39: Annual Rainfall at Dedessa Station................................................................. 28 Figure 40: Annual Evaporation at Bahirdar Station ......................................................... 29 Figure 41: Hydrological Stations in Abbay Basin ............................................................ 30 ix Figure 42: RunOff at Abbay near Bahirdar Station .......................................................... 30 Figure 43: Major Agro-Ecological Zones in the Abbay Basin ......................................... 31 Figure 44: Land Cover in the Abbay Basin ...................................................................... 32 Figure 45: Major Soil Types in Abbay Basin ................................................................... 33 Figure 46: Geology of the Abbay Basin ........................................................................... 34 Figure 47: Administrative Regions of Abbay Basin......................................................... 35 Figure 48: Population in the Abbay Basin........................................................................ 35 Figure 49: Topography of the Blue Nile in Sudan............................................................ 36 Figure 50: Slope of the Blue Nile in Sudan ...................................................................... 37 Figure 51: Rainfall Distribution of the Blue Nile in Sudan .............................................. 38 Figure 52: Maximum Temperature of the Blue Nile in the Sudan ................................... 39 Figure 53: Minimum Temperature of the Blue Nile in Sudan.......................................... 39 Figure 54: Potential Evaportranspiration of the Blue Nile in Sudan ................................ 40 Figure 55: Main Meteorological Stations in the Blue Nile in Sudan................................ 41 Figure 56: Hydrological Stations in the Blue Nile in Sudan ............................................ 42 Figure 57: Land Cover in the Blue Nile in Sudan ............................................................ 43 Figure 58: Major Soils in the Blue Nile in Sudan............................................................. 44 Figure 59: Population in the Blue Nile in Sudan .............................................................. 45 Figure 60: Tana Sub basin ................................................................................................ 46 Figure 61: Irrigation Potential in the Tana Sub Basin ...................................................... 47 Figure 62: Topography of the Tana Sub Basin................................................................. 48 Figure 63: Rainfall Distribution in the Tana Sub Basin ................................................... 49 Figure 64: Maximum Temperature in the Tana Sub Basin............................................... 50 Figure 65: Minimum Temperature in Tana Sub Basin ..................................................... 50 Figure 66: Potential Evapotranspiration in the Tana Sub Basin ....................................... 51 Figure 67: Meteorological Stations in the Tana Sub Basin .............................................. 52 Figure 68: Chart showing Annual Rainfall at Bahir Dar Station...................................... 53 Figure 69: Chart showing Annual Rainfall at BahirDar Station....................................... 53 Figure 70: Mean Monthly Maximum and Minimum Temperature at Bahirdar Station ... 54 Figure 71: Annual Evaporation at Bahirdar Station ......................................................... 54 Figure 72: Hydrological Stations in the Tana Sub Basin.................................................. 55 Figure 73: Monthly Flow at Abbay Station near Bahirdar ............................................... 55 Figure 74: Mean Monthly Flow at Abbay Station near Bahirdar ..................................... 56 Figure 75: Agro-Ecological Zones in the Tana Sub Basin ............................................... 57 Figure 76: Land Cover in the Tana Sub Basin.................................................................. 58 Figure 77: Major Soil Types in Tana Sub Basin............................................................... 59 Figure 78: Geology of the Tana Sub Basin....................................................................... 60 Figure 79: Weredas in Tana Sub Basin............................................................................. 61 Figure 80: Population Density of Weredas in Tana Sub basin ......................................... 61 Figure 81: Jemma Sub basin ............................................................................................. 62 Figure 82: Topography of Jemma Sub Basin ................................................................... 63 Figure 83: Rainfall Distribution of the Jemma Sub Basin................................................ 64 Figure 84: Maximum Temperature in Jemma Sub Basin ................................................. 65 Figure 85: Minimum Temperature in Jemma Sub Basin.................................................. 65 Figure 86: Potential Evapotranspiration in Jemma Sub Basin.......................................... 66 Figure 87: Meteorological Stations in Jemma Sub Basin................................................. 67 x Figure 88: Mean Monthly Rainfall at Debre Berihan Station........................................... 68 Figure 89: Mean Annual Rainfall at Debre Berihan Station............................................. 68 Figure 90: Mean Monthly Rainfall at Fiche Station ......................................................... 69 Figure 91: Mean Annual Rainfall at Fiche Station ........................................................... 69 Figure 92: Mean Monthly Maximum and Minimum Temperature at Debre Berihan Station ............................................................................................................................... 70 Figure 93: Mean Monthly Maximum and Minimum Temprature at Fiche Station.......... 70 Figure 94: Annual Evaporation at Debre Berihan Station ................................................ 71 Figure 95: Annual Evaporation at Fiche Station............................................................... 71 Figure 96: Hydrological Stations in Jemma Sub Basin .................................................... 72 Figure 97: Land Use in Jemma Sub Basin........................................................................ 73 Figure 98: Agro-Ecological Zones in Jemma Sub Basin.................................................. 74 Figure 99: Major Soil Types in Jemma Sub Basin ........................................................... 75 Figure 100: Geology of Jemma Sub Basin ....................................................................... 76 Figure 101: Weredas in Jemma Sub Basin ....................................................................... 77 Figure 102: Population Density of the Weredas in Jemma Sub basin.............................. 77 Figure 103: Topography of Muger Sub basin................................................................... 78 Figure 104: Slope Percentage in Muger Sub basin........................................................... 79 Figure 105: Annual Rainfall distribution in Muger Sub Basin......................................... 80 Figure 106: Maximum Temperature in Muger Sub Basin................................................ 81 Figure 107: Minimum Temperature in Muger Sub Basin ................................................ 81 Figure 108: Potential Evapotranspiration in Muger Sub Basin ........................................ 82 Figure 109: Land Use in Muger Sub Basin ...................................................................... 83 Figure 110: AgroEcological Zones in Muger Sub Basin.................................................. 84 Figure 111: Major Soil Types in Muger Sub Basin.......................................................... 85 Figure 112: Geology of Muger Sub Basin........................................................................ 86 Figure 113: Population Density of Weredas in Muger Sub basin .................................... 87 Figure 114: Topography of Guder Sub Basin................................................................... 88 Figure 115: Slope Percentage in Guder Sub Basin........................................................... 88 Figure 116: Rainfall Distribution in Guder Sub Basin ..................................................... 89 Figure 117: Maximum Temperature in Guder Sub Basin ................................................ 90 Figure 118: Minimum Temperature in Guder Sub Basin ................................................. 90 Figure 119: Potential Evapotranspiration in Guder Sub Basin......................................... 91 Figure 120: Land Use in Guder Sub Basin ....................................................................... 92 Figure 121: AgroEcological Zones in Guder Sub Basin .................................................. 93 Figure 122: Major Soil Types in Guder Sub Basin........................................................... 94 Figure 123: Geology of Guder Sub Basin......................................................................... 95 Figure 124: Population Density of Weredas in Guder Sub Basin .................................... 96 Figure 125: Topography of Beles Sub Basin.................................................................... 97 Figure 126: Slope Percentage of Beles Sub Basin............................................................ 97 Figure 127: Rainfall Distribution in Beles Sub Basin ...................................................... 98 Figure 128: Maximum Temperature in Beles Sub Basin.................................................. 99 Figure 129: Minimum Temperature in Beles Sub Basin .................................................. 99 Figure 130: Potential Evapotranspiration in Beles Sub Basin ........................................ 100 Figure 131: Land cover in Beles Sub Basin ................................................................... 101 Figure 132: AgroEcological Zones in Beles Sub Basin ................................................. 102 xi Figure 133: Major Soil Types in Beles Sub Basin.......................................................... 103 Figure 134: Geology of Beles Sub Basin........................................................................ 104 Figure 135: Population Density of Weredas in Beles Sub Basin.................................... 105 Figure 136: Topography of Dabus Sub Basin ................................................................ 106 Figure 137: Slope Percentage in Dabus Sub Basin......................................................... 106 Figure 138: Rainfall Distribution in Dabus Sub Basin ................................................... 107 Figure 139: Maximum Temperature in Dabus Sub Basin .............................................. 108 Figure 140: Minimum Temperature in Dabus Sub Basin............................................... 108 Figure 141: Potential Evapotranspiration in Dabus Sub Basin....................................... 109 Figure 142: Land Cover in Dabus Sub Basin ................................................................. 110 Figure 143: AgroEcological Zones in Dabus Sub Basin ................................................ 111 Figure 144: Major Soil Types in Dabus Sub Basin ........................................................ 112 Figure 145: Geology of Dabus Sub Basin ...................................................................... 113 Figure 146: Population Density of Weredas in Dabus Sub Basin .................................. 114 Figure 147: Topography of Didessa Sub Basin .............................................................. 115 Figure 148: Slope Percentage of Didessa Sub Basin ...................................................... 115 Figure 149: Rainfall Distribution in Didessa Sub Basin................................................. 116 Figure 150: Maximum Temperature in Didessa Sub Basin............................................ 117 Figure 151: Minimum Temperature in Didessa Sub Basin ............................................ 117 Figure 152: Potential Evapotranspiration in Didessa Sub Basin .................................... 118 Figure 153: Land Cover in Didessa Sub Basin............................................................... 119 Figure 154: AgroEcological Zones in Didessa Sub Basin.............................................. 120 Figure 155: Major Soil Types in Didessa Sub Basin...................................................... 121 Figure 156: Geology of Didessa Sub Basin.................................................................... 122 Figure 157: Population Density of Weredas in Didessa Sub Basin................................ 123 Figure 158: Topography of Fincha Sub Basin................................................................ 124 Figure 159: Slope Percentage in Fincha Sub Basin ........................................................ 124 Figure 160: Rainfall Distribution in Fincha Sub Basin .................................................. 125 Figure 161: Maximum Temperature in Fincha Sub Basin.............................................. 126 Figure 162: Minimum Temperature in Fincha Sub Basin .............................................. 126 Figure 163: Potential Evapotranspiration in Fincha Sub Basin ...................................... 127 Figure 164: Land Cover in Fincha Sub Basin................................................................. 128 Figure 165: AgroEcological Zones in Fincha Sub Basin ............................................... 129 Figure 166: Major Soil Types in Fincha Sub Basin........................................................ 130 Figure 167: Geology of Fincha Sub Basin...................................................................... 131 Figure 168: Population Density of Werdas in Fincha Sub Basin ................................... 132 Figure 169: Topography of Anger Sub Basin................................................................. 133 Figure 170: Slope Percentage of Anger Sub Basin......................................................... 133 Figure 171: Rainfall Distribution of Anger Sub Basin ................................................... 134 Figure 172: Maximum Temperature in Anger Sub Basin .............................................. 135 Figure 173: Minimum Temperature in Anger Sub Basin ............................................... 135 Figure 174: Potential Evapotranspiration of Anger Sub Basin....................................... 136 Figure 175: Land Cover in Anger Sub Basin ................................................................. 137 Figure 176: AgroEcological Zones in Anger Sub Basin ................................................ 138 Figure 177: Major Soil Types in Anger Sub Basin......................................................... 139 Figure 178: Geology of Anger Sub Basin....................................................................... 140 xii Figure 179: Population Density of Weredas in Anger Sub Basin .................................. 141 Figure 180: Topography of Wembera Sub Basin ........................................................... 142 Figure 181: Slope Percentage of Wembera Sub Basin ................................................... 142 Figure 182: Rainfall Distribution in Wembera Sub Basin.............................................. 143 Figure 183: Maximum Temperature in Wembera Sub Basin]........................................ 144 Figure 184: Minimum Temperature in Wembera Sub Basin.......................................... 144 Figure 185: Potential Evapotranspiration in Wembera Sub Basin ................................. 145 Figure 186: Land Cover in Wembera Sub Basin ............................................................ 146 Figure 187: AgroEcological Zones in Wembera Sub Basin........................................... 147 Figure 188: Major Soil Types in Wembera Sub Basin ................................................... 148 Figure 189: Geology of Wembera Sub Basin ................................................................. 149 Figure 190: Population Density of Weredas in Wembera Sub Basin............................. 150 Figure 191: Topography of Beshelo Sub Basin.............................................................. 151 Figure 192: Slope Percentage in Beshelo Sub Basin ...................................................... 151 Figure 193: Rainfall Distribution in Beshelo Sub Basin ................................................ 152 Figure 194: Maximum Temperature in Beshelo Sub Basin............................................ 153 Figure 195: Minimum Temperature in Beshelo Sub Basin ............................................ 153 Figure 196: Potential Evapotranspiration in Beshelo Sub Basin .................................... 154 Figure 197: Land Cover in Beshelo Sub Basin............................................................... 155 Figure 198: AgroEcological Zones in Beshelo Sub Basin ............................................. 156 Figure 199: Major Soil Types of Beshelo Sub Basin ..................................................... 157 Figure 200: Geology of Beshelo Sub Basin.................................................................... 158 Figure 201: Population Density of Weredas in Beshelo Sub Basin ............................... 159 Figure 202: Topography of Welaka Sub Basin............................................................... 160 Figure 203: Slope Percentage in Welaka Sub Basin....................................................... 160 Figure 204: Rainfall Distribution in Welaka Sub Basin ................................................. 161 Figure 205: Maximum Temperature in Welaka Sub Basin ............................................ 162 Figure 206: Minimum Temperature in Welaka Sub Basin............................................. 162 Figure 207: Potential Evapotranspiration in Welaka Sub Basin..................................... 163 Figure 208: Land Cover in Welaka Sub Basin ............................................................... 164 Figure 209: AgroEcological Zones in Welaka Sub Basin .............................................. 165 Figure 210: Major Soil Types in Welaka Sub Basin ...................................................... 166 Figure 211: Geology of Welaka Sub Basin .................................................................... 167 Figure 212: Population Density of Weredas in Welaka Sub Basin ................................ 168 Figure 213: Topography of North Gojam Sub Basin...................................................... 169 Figure 214: Slope Percentage in North Gojam Sub Basin.............................................. 169 Figure 215: Rainfall Distribution in North Gojam Sub Basin ........................................ 170 Figure 216: Maximum Temperature in North Gojam Sub Basin ................................... 171 Figure 217: Minimum Temperature in North Gojam Sub Basin.................................... 171 Figure 218: Potential Evapotranspiration in North Gojam Sub Basin............................ 172 Figure 219: Land Use in North Gojam Sub Basin.......................................................... 173 Figure 220: AgroEcological Zones in North Gojam Sub Basin ..................................... 174 Figure 221: Major Soil Types in North Gojam Sub Basin ............................................. 175 Figure 222: Geology of North Gojam Sub Basin ........................................................... 176 Figure 223: Population Density of Weredas in North Gojam Sub Basin ....................... 177 Figure 224: Topography of South Gojam Sub Basin...................................................... 178 xiii Figure 225: Slope Percentage in South Gojam Sub Basin.............................................. 178 Figure 226: Rainfall Distribution of South Gojam Sub Basin........................................ 179 Figure 227: Maximum Temperature in South Gojam Sub Basin ................................... 180 Figure 228: Minimum Temperature in South Gojam Sub Basin.................................... 180 Figure 229: Potential Evapotranspiration in South Gojam Sub Basin............................ 181 Figure 230: AgroEcological Zones in South Gojam Sub Basin ..................................... 182 Figure 231: Major Soil Types in South Gojam Sub Basin ............................................. 183 Figure 232: Geology of South Gojam Sub Basin ........................................................... 184 Figure 233: Population Density of Weredas in South Gojam Sub Basin ....................... 185 Figure 234: Topography of Dinder Sub Basin, part of Ethiopia..................................... 186 Figure 235: Slope Percentage in Dinder Sub Basin, part of Ethiopia............................. 186 Figure 236: Rainfall Distribution in Dinder Sub Basin, part of Ethiopia ....................... 187 Figure 237: Maximum Temperature in Dinder Sub Basin, part of Ethiopia .................. 188 Figure 238: Minimum Temperature in Dinder Sub Basin, part of Ethiopia................... 188 Figure 239: Potential Evapotranspiration in Dinder Sub Basin, part of Ethiopia........... 189 Figure 240: Land Use in Dinder Sub Basin, part of Ethiopia......................................... 190 Figure 241: AgroEcological Zone in Dinder Sub Basin, part of Ethiopia...................... 191 Figure 242: Major Soil Types in Dinder Sub Basin, part of Ethiopia ............................ 192 Figure 243: Geology of Dinder Sub Basin, part of Ethiopia .......................................... 193 Figure 244: Population Density of Weredas in Dinder Sub Basin, part of Ethiopia ...... 194 Figure 245: Topography of Rahad Sub Basin, part of Ethiopia ..................................... 195 Figure 246: Slope Percentage in Rahad Sub Basin, part of Ethiopia.............................. 195 Figure 247: Rainfall Distribution in Rahad Sub Basin, part of Ethiopia ........................ 196 Figure 248: Maximum Temperature in Rahad Sub Basin, part of Ethiopia ................... 197 Figure 249: Minimum Temperature in Rahad Sub Basin, part of Ethiopia.................... 197 Figure 250: Potential Evapotranspiration in Rahad Sub Basin, part of Ethiopia............ 198 Figure 251: Land Use in Rahad Sub Basin, part of Ethiopia.......................................... 199 Figure 252: AgroEcological Zones in Rahad Sub Basin, part of Ethiopia ..................... 200 Figure 253: Major Soil Types in Rahad Sub Basin, part of Ethiopia ............................. 201 Figure 254: Geology of Rahad Sub Basin, part of Ethiopia ........................................... 202 Figure 255: Population Density of Weredas in Rahad Sub Basin, part of Ethiopia ....... 203 Figure 256: Topography of Gilgel Abbay Watershed .................................................... 204 Figure 257: Rainfall Distribution in Gilgel Abbay Watershed....................................... 205 Figure 258: Maximum Temperature in Gilgel Abbay Watershed .................................. 206 Figure 259: Minimum Temperature in Gilgel Abbay Watershed................................... 206 Figure 260: Potential Evapotranspiration in Gilgel Abbay Watershed .......................... 207 Figure 261: Annual RunOff at Gilgel Abbay Station ..................................................... 208 Figure 262: Land Cover in Gilgel Abbay Watershed ..................................................... 208 Figure 263: Major Soil Types in Gilgel Abbay Watershed ............................................ 209 Figure 264: Geology of Gilgel Abbay Watershed .......................................................... 210 Figure 265: Weredas in Gilgel Abbay Watershed .......................................................... 211 Figure 266: Population Density for Weredas in Gilgel Abbay Watershed..................... 212 Figure 267: Gumera Watershed...................................................................................... 213 Figure 268: Topography of Gumera Watershed ............................................................. 214 Figure 269: Slope of Gumera Watershed........................................................................ 214 Figure 270: Rainfall Distribution in Gumera Watershed................................................ 215 xiv Figure 271: Maximum Temperature in Gumera Watershed........................................... 216 Figure 272: Minimum Temperature in Gumera Watershed ........................................... 216 Figure 273: Potential Evapotranspiration in Gumera Watershed ................................... 217 Figure 274: Annual Rainfall at Debre Tabor Station...................................................... 218 Figure 275: Maximum Temperature at Debre Tabor Station ......................................... 218 Figure 276: Minimum Temperature at Debre Tabor Station .......................................... 219 Figure 277: Mean Monthly Evaporation at Debre Tabor Station ................................... 219 Figure 278: Annual Evaporation at Debre Tabor Station ............................................... 220 Figure 279: Annual RunOff at Gumera Station near Bahirdar ....................................... 220 Figure 280: Land Use in Gumera Watershed ................................................................. 221 Figure 281: Major Soil Types in Gumera Watershed..................................................... 222 Figure 282: Geology of Gumera Watershed................................................................... 223 Figure 283: Weredas in Gumera Watershed................................................................... 224 Figure 284: Population of Weredas in Gumera Watershed ............................................ 225 Figure 285: Topography of Koga Watershed ................................................................. 226 Figure 286: Annual Rainfall at Merawi Station.............................................................. 227 Figure 287: Topography of Anjeni Micro Watershed .................................................... 228 Figure 288: Monthly Rainfall of Anjeni Watershed ....................................................... 229 Figure 289: Maximum and Minimum Temperature in Anjeni Watershed ..................... 230 Figure 290: Land Use of Anjeni Waterhsed ................................................................... 231 Figure 291: Soil Types in Anjeni Watershed.................................................................. 232 Figure 292: Topography of Andit Watershed................................................................. 233 Figure 293: Rainfall in Andit Watershed........................................................................ 234 Figure 294: Land Use of Andit Watershed ..................................................................... 235 List of Tables Table 1: RunOff for the 16 Sub Basins of Abbay Basin................................................... 29 Table 2: Population of Weredas in Gilgel Abbay Watershed......................................... 211 Table 3: Population of Weredas in Gumera Watershed.................................................. 224 xv Acronyms CSA Central Statistical Agency ENTRO Eastern Nile Technical Regional Office FAO Food and Agriculture Organization of the United Nations GHCN The Global Historical Climatology Network GLC Global Land Cover IDIS Integrated Database Information System MoA Ministry of Agriculture MoWR Ministry of Water Resources SCRP Soil Conservation Research Program SRTM Shuttle Radar Topography Mission 1 Characteristics of the Blue Nile Basin and its Sub basins Under the challenge Program for Water and Food, the Improved Water and Land Management in the Ethiopian Highlands and its Impact on Downstream Stakeholders Dependent on the Blue Nile (Up Stream-Down Stream) project focuses on the Blue Nile basin. This document deals with the characterization of the Blue Nile Basin and its sub basins. The characterization generally looks into the topography, climatic conditions, hydrology and land use/ land cover, soil and other related properties of the basin and its sub basins. The basin, as well as selected sub basins, watersheds, and micro watersheds are considered and presented separately to help provide basic information at watershed to basin level and lay basis for other research components. Blue Nile Basin The Blue Nile is located between 160 2’ N and 70 40’ N latitude, and 320 30’ E and 390 49’ E longitude. It has an estimated area of 311,437 sq. km. From its source Gish Abbay in West Gojam, Abbay flows northward as the Gilgel Abbay into Lake Tana. The Blue Nile River (also called Abbay River in Ethiopia) exits from the south east of Lake Tana and flows south and then westwards cutting a deep gorge towards the western part of Ethiopia. A number of tributaries joined Abbay river in Ethiopia: Beshilo, Derame, Jema, Muger, Finchaa, Didessa and Dabus from the east and south; and the Suha, Chemoga, Keshem, Dera and Beles from the north. The Dinder and Rahad rise to the west of Lake Tana and flow westwards across the border joining the Blue Nile below Sennar. In the Sudan, the Blue Nile flows on the plain desert until it reaches the confluence, where it meets with White Nile in Khartoum. The basin is sub divided into 18 major sub basins namely, Lower Blue Nile, Upper Blue Nile, Dinder, Rahad, Tana, Beshelo, Beles, Dabus, Diddessa, Jemma, Muger, Guder, Fincha, Anger, Wenbera, South Gojam, North Gojam and Welaka. Figure 1 shows these 18 sub-basins 2 Figure 1: Blue Nile Basin and its sub basins Topography The topography of the Blue Nile divides the basin in to two main features, the ragged topography, mountainous areas in the Ethiopian highlands and the flat topography in the lowlands in the Sudan. Based on the SRTM DEM with 90 meters resolution and GIS modeling, the altitude in the Blue Nile ranges from 344 meter above sea level (masl) downstream in Sudan at Khartoum to 4261 masl in the Upper Blue Nile in the Ethiopian highlands. The lowlands in Sudan flatten below 700 masl. The Ethiopian highlands extend from 1500 masl up to 4260 masl. Where as the Ethiopian lowlands flatten from 1000 masl up to 500 masl. See Figure 2. 3 Figure 2: Topography of the Blue Nile Basin Source: The data source is IWMI IDIS. This dataset represents the Shuttle Radar Topography Mission (SRTM) subset at 90m resolution. The original data was downloaded from USGS EROS data centre. Climate Rainfall Rainfall ranges between 126 mm and 2200 mm per year in the basin. The lowest rainfall recorded from 126 up to 500 in Blue Nile in the Sudan, and extending from 500 to 1100 mm upstream of Rosaries. The Ethiopian highlands having highest rainfall ranging from 1500 to 2200 mm, whereas, the Ethiopian lowlands having 1000 mm up to 1500 mm, with the lowest rainfall recorded in the Beshelo, Jemma and Guder and parts of Dinder and Rahad. Figure 3 provides the rainfall distribution map of the Blue Nile. 4 Figure 3: Rainfall distribution in the Blue Nile Basin Source: The data source is IWMI IDIS. The original data set is from the World Climate Atlas, average monthly precipitation data was derived from GHCN (The Global Historical Climatology Network) Temperature There is high correlation between the temperature and the altitude as it can be observed from the spatial distribution of the temperature. As shown on Figure 4, the highest temperature observed is in the north western part of the Blue Nile in Sudan, the highest temperature being 28oC - 30oC. Lower temperature observed in the highlands of Ethiopia in the central and eastern part of the basin. The lowest mean annual temperature ranges from 5oC to 9oC. 5 Figure 4: Mean Monthly Temperature for the Blue Nile Basin Source: The data source is IWMI IDIS. The original data set is from the World Climate Atlas, average monthly Temperature data was derived from GHCN (The Global Historical Climatology Network) Evaporation Potential Evapotranspiration (PET) in the basin ranges between 1056 mm and 2292 mm per year. High PET is observed between 2200 mm and 2292 mm per year in most parts of Sudan; Al Jasira, Qadarif, and Sennar regions. A relatively lower PET is observed in the other parts of Sudan ranging from 1800 to 2200 mm per year. This is highly correlated with the temperature and rainfall distribution. Higher PET is also observed in the North western parts of Ethiopia, in Dinder and Rihad, ranging from 1800 to 2200 mm per year. The Eastern and southern parts having lower PET ranging between 1200 and 1800 mm per year and the lowest PET below 1200 mm per year observed in the parts of the highlands, see Figure 5. 6 Figure 5: Potential Evapotranspiration in the Blue Nile Basin Source: The data source is IWMI IDIS. The original data is from the World Climate Atlas monthly reference evapotranspiration 10 arc data, derived from GHCN Station Data There are 94 meteorological stations in Ethiopia, which are georeferenced, and for some of which there are records. There are also six key stations in Sudan. The meteorological stations are located through out the basin are shown in Figure 6. 7 Figure 6: Main Meteorological Stations in the Blue Nile Basin Rainfall Rainfall stations data are obtained for 27 stations in Ethiopia and 3 stations in Sudan. The three stations in Sudan, El-Damazin, Sennar, and Khartoum have data for 20 years (1980- 2000). Mean annual rainfall for these stations show 700 mm, 415 mm, and 119 mm respectively, see Figure 7. 8 M e an Annual R ainfall for S tations in Sudan 701 415 119 0 100 200 300 400 500 600 700 800 E L-Dam az in S ennar K hartum S ta tions M ea n A nn ua l R ai nf al l (m m ) M A RF (m m ) Figure 7: Chart showing the Mean Annual Rainfall at Stations in Sudan Figure 8: Map showing the location and Mean Annual Rainfall at Stations in Sudan 9 The stations in Ethiopia have data for 20 years (1980-2000) though some of them are incomplete. Mean annual rainfall for the stations vary between a minimum of 613 mm (at Humera) and a maximum of 1820 mm (at Chagni). M ean Ann u a l Ra in fa ll fo r S ta tio ns in E th io p ia 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Add is Zem en Agaro Alem Ketema Ambo Bah ir D ar S ynop tic Chagni Debark Debre Berhan Debre M arkos Debre T abor De jen Eb ina t F iche F inote Se lam Gedo Gonder Hum era Kunze la M eha l M eda M eha l S e lam Meraw i M etem a M otta Nefas M ewcha Pawe Wege l T ena M ean A nnual Ra infa ll Figure 9: Chart showing the Mean Annual Rainfall at Stations in Ethiopia Evaporation Evaporation stations data are obtained for 12 stations in Ethiopia and for 3 stations in Sudan. The mean monthly evaporation for the stations in Sudan, El-Damazin, Sennar, and Khartoum are 340 mm, 390 mm, and 568 mm respectively, shown in Figure 10. Mean Month ly E vaporations for S tations in S udan 340 390 568 0 100 200 300 400 500 600 EL-Damazin Sennar Khartum Statio n s M ea n M on th ly Ev ap or at io n (m m ) M ean M onthly E vap(m m ) Figure 10: Chart showing the Mean Monthly Evaporation at Stations in Sudan 10 M ean A nnual E vaporation for S tat ions in S udan 0 2000 4000 6000 8000 E L-Dam az in S ennar K hartum S ta tions M ea n An nu al Ev ap or at io n (m m ) M ean A nnual E vap(m m ) Figure 11: Mean Annual Evaporation for the Stations in Sudan The mean monthly evaporation for the stations in Ethiopia ranges between a minimum of 101 mm (at Ambo station) and a maximum of 228 mm (at Gonder station). Mean An nu al E vapo ration fo r S tation s in E th iop ia 0 500 1000 1500 2000 2500 3000 A lem Ketema Ambo BahirD ar Agaro Ch agni De breBerhan De breMa rko s Fich e F inote S elam Gonder Meha l M eda Motta M ean A nnual E vaporat ion Figure 12: Chart showing the Mean Annual Evaporation at Stations in Ethiopia Hydrology In the Ethiopian part of the basin, there are some 138 hydrological gauging stations with which 45 stations have some sporadic sediment data. However, there are a number of gauging station records for flow data with a limited number of years. There are five main gauging stations in the Sudan part. These are at Khartoum, Sennar, Dinder, Rahad and El Diem. The main hydrological gauging stations are shown in Figure 13. 11 Figure 13: Hydrological Stations in the Blue Nile A long time series data from 1920-1992, is used to see the flow pattern in the El Diem station, the station at the border of Sudan and Ethiopia. At El Diem, an average outflow of 43,022 Mm3 per year is observed. Flow at this station for the last 70 years shows high discharge during the high rainy season July – October, with its pick in August (with a mean of 15,034 Mm3). M onthly Discharge at El Diem Station 0 5000 10000 15000 20000 25000 30000 1920 1924 1928 1932 1936 1940 1944 1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 Year M on th ly D is hc ar ge July A ug us t S ep tem be r O c tober Figure 14: Chart showing the Monthly Discharge in MCM for the months July - October at El Diem Stations in Sudan 12 Annual D ischarge at E lD iem S tation 0 10000 20000 30000 40000 50000 60000 70000 80000 19 20 19 25 19 30 19 35 19 40 19 45 19 50 19 55 19 60 19 65 19 70 19 75 19 80 19 85 19 90 A nn ua l D is ch ar ge (M m 3) A nnual Dis c harge Figure 15: Chart showing the Annual Discharge at El Diem Stations in Sudan 10 years data was obtained for SENNAR station (1992-2001) at decadal interval. An average flow of 3834 mm per year is observed at the station for 1992-2001. Flow at SENNAR station for the 10 years shows high discharge during the high rainy season July, August, September and October with an average of 6,608 mm, 15,893 mm, 10,225 mm, and 5,474 mm respectively; with the highest peak in August. Month ly F lo w at S en nar S tation 0 5000 10000 15000 20000 25000 Jan-92 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 M onths M on th ly F lo w (m m ) Figure 16: Chart showing Monthly Flow at Sennar Station 13 Month ly F low Ju ly-October at S E N N AR S tation 0 5000 10000 15000 20000 25000 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Ye a rs M on th ly F lo w in m m Jul A ug S ep Oct Figure 17: Chart showing Monthly Flow for the months of July - October at Sennar Station Annual F low at S ennar S tation 0 10000 20000 30000 40000 50000 60000 70000 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 A nnual F low Figure 18: Chart showing Annual Flow at Sennar Station Mean monthly inflow at DINDER station is high in the months of July – October; a maximum of 956 MCM in August is observed. Inflow at DINDER station is shown in Figure 19. 14 M ean Mon th ly In flow at D IN D E R S tation 0 200 400 600 800 1000 1200 July Aug Sep Oc t No v De c Jan Feb Mar Apr May June Months M ea n M on th ly In flo w (M CM ) M ean M onthly Inflow Figure 19: Chart showing Monthly Inflow at Dinder Station RAHAD station has inflow data for 50 years for the years 1950-2000. As the other stations, high flow is observed in the months July-October. The highest mean inflow is in September with 360 MCM, see Figure 20. Mean M onth ly In flow at R AH AD S tation 0 50 100 150 200 250 300 350 400 July Aug Sep Oct N ov Dec Jan Feb Mar Apr May June M onths M ea n M on th ly In flo w (M CM ) M ean M onthly Inflow Figure 20: Chart showing Mean Monthly InFlow at Dinder Station The mean Monthly flow at Abbay Station near Bahir Dar shows high flows in the months of August - November. The Mean monthly flow at this station also shows the peak in September, see Figure 21 and Figure 22. 15 Month ly F low at Abbay S tation near B ah irdar 0 500 1000 1500 2000 2500 19 80 19 82 19 84 19 86 19 88 19 90 19 92 19 94 19 96 19 98 20 00 Years M on th ly F lo w in M C M A UG S E P O CT NO V Figure 21: Chart showing Monthly Flow at Abbay Station near Bahirdar M ean Month ly F low at Abbay S tation near B ah irdar 0.000 200.000 400.000 600.000 800.000 1000.000 JAN FEB MAR APR MAY JUN JUL AUG SEP OC T NO V DEC M onths M ea n M on th ly F lo w in M C M M ean M onthly F low Figure 22: Chart showing Mean Monthly Flow at Abbay Station near Bahirdar Time series of flow data at Abbay Station near Kessie was obtained for the years 1980- 2000 at monthly interval. A mean flow of 17384.88 MCM per year is observed at the station. Flow at this station through the 20 years shows high discharge during the months of July, August, September, and October with mean monthly flow of 2978 MCM, 6687 MCM, 3252 MCM, and 1549 MCM respectively; with the highest peak in September. 16 Month ly F low at Abbay S tation N ear K essie 0.00 2000.00 4000.00 6000.00 8000.00 10000.00 12000.00 14000.00 16000.00 19 80 19 82 19 84 19 86 19 88 19 90 19 92 19 94 19 96 19 98 20 00 Ye a rs M on th ly F lo w in M CM JULY A UG S E P T O CT Figure 23: Chart showing Monthly Flow at Abbay Station near Kessie The Mean Monthly Flow at the Abbay Station near Kassie is also shown in Figure 24. Mean Month ly F low at Abbay S tation N ear K essie 0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00 7000.00 8000.00 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NO V DEC M onths M ea n M on th ly F lo w in M CM M ean M onthly F low Figure 24: Chart showing Mean Monthly Flow at Abbay Station near Kessie Land use/cover Global Land Cover 2000 by (GLC, 2000) at a resolution of 1 km is used to show the different land cover of the basin. Based on the GLC land cover classification, the basin is dominated by cultivated areas and croplands particularly upstream in the eastern parts of the basin and in the irrigated areas of the Sudan downstream of Rosaries. Upstream of the Sennar dam, mainly covered by cultivated areas, shrub land, grass land and herbaceous cover. The lower plain up to Khartoum is sparsely covered with herbaceous and shrubs, 17 with parts of bare areas. Most of the western parts of Ethiopia are sparse herbaceous and shrubs and the eastern part are dominated by crop land and cultivated areas. Figure 25: Land Cover for the Blue Nile Basin Source: The data source is IWMI IDIS, The dataset represents the subset of Global Land Cover 2000 (GLC 2000), land-cover at 1 Km resolution. Originator of the data is Global Vegetation Monitoring Unit (http://ies.jrc.cec.eu.int/263.htm1). Soil FAO SOTER (Food and Agriculture Organization’s Soil and Terrain Database) is used for the classification of major soil types of the whole basin. Based on the FAO soil classification, most of the Sudan parts is dominated by the Eutric Vertisols. The Ethiopian part is mainly dominated by Umbric Nitisols in the south eastern part and Lithic Leptosols, in the north eastern part, see Figure 26. 18 Figure 26: Major Soil Classes for the Blue Nile Basin Source: FAO SOTER (The Soil and Terrain Database for Northeaster Africa) Socio Economic aspect of the basin Administrative structure of the basin The administrative regions in Ethiopia consist of three regional states namely, Amhara Regional State, Oromia Regional State and Benishangul-Gumuz Regional State. The administrative structure in Sudan also consists of five states called, Khartoum State, Al Jazira State, Qadarif State, Sennar State, and Blue Nile State. 19 Figure 27: Administrative Regions in the Sudan and Ethiopia part of the Blue Nile Population Total Population of Ethiopia is around 73 million in 2006 (WDI, 2006) currently estimated to surpass 80 million, with a total area of about 1.13 million km2. Total Population of Sudan is around 37 million with a total area of about 2.51 km2 (WDI, 2006). The population density for the Blue Nile, derived from the Land Scan population 2002 is shown in Error! Reference source not found.. 20 Figure 28: Population in the Blue Nile Basin Source: The data source is IWMI IDIS, the original dataset is from 2002 Global Population Database 21 Abbay Basin (Ethiopia-Blue Nile) The Ethiopia part of Blue Nile also called Abay Basin in Ethiopia is located in the northwestern region of Ethiopia between 70 40’ N and 120 51’ N latitude, and 340 25’ E and 390 49’ E longitude. It covers an area of approximately 199,812 sq km. It shares a boundary with the Tekeze basin to the north, the Awash basin to the east and south east, the Omo-Gibe basin to the south, and the Baro-Akobo basin to the south west. The country’s largest freshwater lake, Lake Tana, the source of the Blue Nile (Abbay) river is located to the north of the basin. The Abbay basin accounts for a major share of the country’s irrigation and hydropower potential. It has an irrigation potential of 815,581 ha and a hydro potential of 78,820 GWH/yr. The basin has an average annual run-off estimated to 54.8 BCM (Awlachew et.al., 2007). The basin is subdivided into 16 sub basins based on the major rivers in the basin, the Abbay River and its tributaries. Figure 29: Abbay Basin (Blue Nile Sub basin) The irrigation potential sites identified by the Master Plan study conducted by the ministry of Water Resources are shown in Figure 30 below. 22 Figure 30: Irrigation Potential Areas and Dam Sites in the Abbay Basin Topography The topography of the Abbay basin signifies two distinct features; the highlands, ragged mountainous areas in the center and eastern part of the basin and the lowlands in the western part of the basin. The altitude in the basin ranges from 498 masl in the lowlands up to 4261 masl in the highlands. The Ethiopian highlands extend from 1500 masl up to as high as 4260 masl, with a slope of greater than 25 percent in the eastern part. Where as the Ethiopian lowlands flatten 1000 masl to 500 masl with a slope of less than 7 percent, in Dinder and Rahad sub basins. The maps below in Figure 31 and Figure 32 show the elevation and the slope of the basin. 23 Figure 31: Topography of the Abbay Basin Figure 32: Slope of the Abbay Basin 24 Climate Rainfall Rainfall ranges between 787 mm and 2200 mm per year; The Ethiopian highlands having highest rainfall ranging from 1500 to 2200 mm, whereas lowlands having rainfall less than 1500 mm. The lowest rainfall recorded less than 1000 mm per annum in the Beshelo, Welaka, Jemma, Muger, Guder, and parts of Dinder and Rahad. Figure 33: Rainfall Distribution in the Abbay Basin Temperature The highest temperature observed in the north western part of the basin, in parts of Rihad, Dinder, Beles and Dabus, the maximum temperature being 28oC - 38oC and minimum temperature 15 oC – 20 oC. Lower temperature observed in the highlands of Ethiopia in the central and eastern part of the basin. The maximum and minimum temperature ranges from 12 oC – 20 oC and -1oC to 8oC respectively. 25 Figure 34: Maximum Temperature in the Abbay Basin Figure 35: Minimum Temperature in the Abbay Basin 26 Evaporation Potential Evatpotranspiration (PET) in the basin ranges between 1056 mm and 2232 mm per year. High PET is observed between 1800 mm and 2232 mm per year in North Western parts of the basin, in Dinder, Rahad, and parts of Beles and Didessa sub basins. The Eastern and southern parts having lower PET ranging between 1200 and 1800 mm per year and the lowest PET below 1200 mm per year observed in the parts of the highlands. This is highly correlated with the temperature. Figure 36: Potential Evapotranspiration in the Abbay Basin Climate Stations Data There are 94 meteorological stations georeferenced in the basin. However data availability is limited for the stations. 27 Figure 37: Meteorological Stations in the Abbay Basin Rainfall BahirDar station is located near to Lake Tana (11.6 degree Latitude, and 37.4 degree Longitude). An average annual rainfall of 1292.5 mm is recorded for 20 years (1980- 2000) at the station. 28 Annual R ainfall at B ahir D ar S taion 0 .0 200 .0 400 .0 600 .0 800 .0 1000 .0 1200 .0 1400 .0 1600 .0 1800 .0 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 Ye a rs Ra in fa ll in m m A nnual Rainfall Figure 38: Annual Rainfall at Bahirdar Station The Dedessa station has a record for the years 1983-2006, though data is also incomplete. The station records an average annual rainfall amount of about 1421 mm. Annual R ain fa ll at D edessa S tation 0 500 1000 1500 2000 1994 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 A nnual Rainfall Figure 39: Annual Rainfall at Dedessa Station Evaporation Evaporation at BahirDar station for four years shows an annual average of 1634 mm/yr. 29 M e an Annual Ev aporation at B ahir D ar S tation 0.0 500.0 1000.0 1500.0 2000.0 2500.0 1997 1998 1999 2000 Mean Annua l Evapora tion Figure 40: Annual Evaporation at Bahirdar Station Hydrology Abbay sub basin has 16 sub basins, which covers a total surface area of about 199,812 sq km. The area and gross runoff depth of each sub basin of the Abbay basin is shown in Table 1 below. The runoff for each drainage unit is gross runoff, which does not take evaporation and other channel losses into account. Table 1: RunOff for the 16 Sub Basins of Abbay Basin Unit Name Area (Km2) Gross runoff depth (mm) Didessa 19,943 651 South Gojam 17,029 543 Guder 7,123 537 Anger 8,027 527 Lake Tana 15,294 514 North Gojam 14,618 486 Dabus 21,367 466 Beshilo 13,453 455 Fincha 4,154 450 Muger 8,318 423 Jemma 16,033 422 Welaka 6,517 410 Wombera 13,163 410 Beles 14,426 378 Rahad 8,401 339 Dinder 15,128 276 7287 Source: (MoWR, 1999) 30 Figure 41: Hydrological Stations in Abbay Basin The hydrological station, Abbay near Bahir Dar Station, has a record for the years 1980- 2000, though data for some years are missing. The station records an average annual runoff amount of 3576 Mm3. R unoff at Abbay ne ar B ahir D ar S tation 0.000 1000.000 2000.000 3000.000 4000.000 5000.000 6000.000 7000.000 19 80 19 82 19 84 19 86 19 88 19 90 19 92 19 94 19 96 19 98 20 00 Runoff Figure 42: RunOff at Abbay near Bahirdar Station 31 Agro-Ecological Zones The agro-ecology of the basin is divided into three major climatic zones, cold to very cold, tepid to cold, and hot to warm, and further divided into moist, sub moist, humid and sub humid, see Figure 43: Major Agro-Ecological Zones in the Abbay Basin. Figure 43: Major Agro-Ecological Zones in the Abbay Basin Land Use / Land Cover The land cover for the basin is mainly characterized by dominantly cultivated, in the eastern part, and grass land, wood lands, and forest to the western part according to the Ministry of Water Resources (Ethiopia) land cover classification. 32 Figure 44: Land Cover in the Abbay Basin Source: The data source is ENTRO. The original dataset is from Ministry of Water Resources, Ethiopia. Soil The major dominant soil types in the basin are Alisols and Leptisols, followed by Nitosols, Vertisols, Cambrisols, Fluvisols and Luvisols. 33 Figure 45: Major Soil Types in Abbay Basin Source: The data source is ENTRO. The original dataset is from Ministry of Water Resources, Ethiopia. Geology The geology of the basin signifies different formations such as Basalt, Alluvium, Lacustrine deposit, sand stone, granite and marbles. The dominant rock is Basalt (Tarmaber basalt, followed by Ashange basalt, and Amba Aiba basalt). 34 Figure 46: Geology of the Abbay Basin Source: The data source is Ministry of Water Resources of Ethiopia. Socio Economic aspect of the basin Administrative structure of the basin The administrative structure of the country is hierarchical, from regional states, to zones, Weredas and Peasant Associations (PA) or Kebeles. According to the current regional structure, the basin covers three regional states namely Amhara regional state, Oromia regional state, and Benishangul-Gumus regional state. 35 Figure 47: Administrative Regions of Abbay Basin Population From the total population projected close to 79 million the population for the Ethiopian part of Blue Nile region by July 2008 is about 27 million (CSA, 2007). Figure 48: Population in the Abbay Basin Source: The map is created based on the Central Statistics Agency data on population (CSA, 2007) 36 Blue Nile in the Sudan The Blue Nile enters the Sudan from Ethiopia flowing downstream until it reaches the Roseries Dam. In addition the Dinder and Rahad rivers rise to the west of Lake Tana and flow westwards across the border joining the Blue Nile below Sennar. In the Sudan, the Blue Nile flows on the plain desert until it reaches the confluence, where it meets with White Nile in Khartoum. Topography The altitude in the basin ranges from 370 masl in the lowlands up to 1480 masl in the eastern and southern parts of the basin. Western part of the basin, from upstream of Sennar up to Khartoum flattens below 450 masl. A slope of less than 3 percent characterizes the basin, while a slope of greater than 15 percent is observed in the south and in the eastern parts of the basin which have an altitude of greater than 500 masl. Figure 49: Topography of the Blue Nile in Sudan 37 Figure 50: Slope of the Blue Nile in Sudan Climate Rainfall Rainfall in the Blue Nile of the Sudan part, ranges from 126 mm up to 1288 mm. In the northern part lower rainfall is observed from 126 – 300 mm where as higher rainfall greater than 750 mm is observed upstream of Rosaries. 38 Figure 51: Rainfall Distribution of the Blue Nile in Sudan Temperature The maximum and minimum temperature in the basin ranges from 30 oC - 38 oC and 16oC - 23oC respectively. The highest temperature observed in the northern part of the sub- basin, the maximum temperature being 36oC - 38oC. Lower temperature observed in the borders of Ethiopia in the southern part of the basin. 39 Figure 52: Maximum Temperature of the Blue Nile in the Sudan Figure 53: Minimum Temperature of the Blue Nile in Sudan 40 Evaporation Potential evapotranspiration is high in Al Jazira and parts of Qadarif ranging between 2250-3000 mm/yr. The southern part of the basin, the Blue Nile state has lower PET below 2150 mm/yr. Figure 54: Potential Evaportranspiration of the Blue Nile in Sudan 41 Climate Stations Data Rainfall Metreological Stations data are obtained for five stations in Sudan; Khartoum, Wad Medani, Sennar, Hawata, and Roseries. The meteorological stations are shown in Figure 55. Figure 55: Main Meteorological Stations in the Blue Nile in Sudan 42 Hydrology Five hydrological stations are available in the Sudan part. Long term time series data is available for these stations. The hydrological stations are shown in Figure 56. Figure 56: Hydrological Stations in the Blue Nile in Sudan Land Cover The land cover of the basin is shown in the map below according to the GLC land cover classification. Upstream of Roseries is covered with shrub and deciduous. The central part of the basin, upstream of the Sennar dam, mainly covered by cultivated areas, Shrub land, grass land and herbaceous cover. The lower plain down stream of Sennar up to Khartoum is sparsely covered with herbaceous and shrubs, with most parts of bare areas. 43 Figure 57: Land Cover in the Blue Nile in Sudan Soil The major dominant soil types in the basin are Vertisols, followed by Cambisols, and Luvisols, with occurrences of Alisols, Leptosols, Nitisols, Fluvisols and Arinosols in smaller units. 44 Figure 58: Major Soils in the Blue Nile in Sudan Socio Economic aspect of the basin Administrative structure of the basin The administrative structure of the country is divided into independent states, According to the current state structure, the basin covers five states namely Khartoum state, Al- Jazira state, Qadarif