Storm drains and level ditches
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CTA. 2007. Storm drains and level ditches. Rural Radio Resource Pack 07/1. Wageningen, The Netherlands: CTA.
Permanent link to this item: http://hdl.handle.net/10568/57343
On sloping land, storm ditches can protect land from erosion, while level ditches increase infiltration of rainwater runoff.
Cue: One of the most popular methods of trapping rainwater in fields, particularly on sloping land, is through the use of contour ridges or bunds. These are raised ridges of soil or rock constructed across the slope, which stop the flow of run off, thereby encouraging water to infiltrate into the soil and preventing soil erosion. Another method is to dig a ditch across the slope. As with the contour ridge, the ditch must not go up or down, but must be perfectly level, to prevent the rain water accumulating in one place; for this reason they are called ?level ditches?. Water collects in the ditch and slowly seeps into the ground: this water then moves down the slope through the soil and is available for plants. Many farmers use level ditches to irrigate either fruit trees or fodder shrubs for livestock, which they plant in a line just below the ditch. Martin Sishekanu is the chief agricultural specialist responsible for land husbandry in the Zambian agriculture ministry. He spoke recently to Chris Kakunta about steps to encourage rainwater harvesting in hilly areas in the eastern part of the country. Chris began by asking him what technologies the Ministry was promoting, particularly to those cultivating fruit trees and fodder shrubs. IN: ?One, if it is a sloping ground?? OUT: ??consider the area of water harvesting.? DUR?N: 5?54? BACK ANNOUNCEMENT: Martin Sishekanu, a land husbandry specialist with the Zambian Ministry of Agriculture. The interview comes from a radio resource pack produced by CTA. Transcript Sishekanu One, if it is a sloping ground, we would like to break the slope by having a storm drain constructed by the foot of the hill. This storm drain, once it is constructed it will stop the water which comes and runs which adds also to the erosion of the ground, it stops it, it breaks the energy that erodes the soil and it gently and safely takes this water. Now where we take the water is important. In most cases we use natural depressions, and in some cases we can even divert this water into a water reservoir where we can store the water, which we can use eventually, even during the dry season, for irrigating our fruit trees. And in some cases we use level ditches. Now when the slope is not that great, when we use a level ditch, what we are doing is we would like to intercept the water that would have gotten lost and temporarily store this water, to allow it to filter into the ground. And as the water filters into the ground, it moves slowly down the slope and when we have our tree crops planted below this ditch, the tree crops will be continuously receiving the water that has been allowed to be stored in the ground. Kakunta That is very interesting Mr Sishekanu. Is it a system that you have been advising small-scale farmers to do here in Eastern Province? Sishekanu Yes in Eastern Province we have advised some farmers, particularly in the area of the utilisation of level ditches, which you can put and dig along the contour to store some water which eventually will be able to recharge the underground water system and make available some water during the dry season below where the ditch is. And then in some cases, like in the area of Chipangali, actually there is a rock that we have harvested water from. Using that rock catchment, we have put a rim, a small block where we have captured this water. Instead of the water coming from the rock to run and erode fields, we have diverted it into a water tank and from this water tank farmers are tapping the water to be able to apply in their fields. Kakunta Is this a new technology we are talking about? Because most often, like you indicated, rainwater is actually let go without being tapped the way you have explained? Sishekanu Well to some extent we may call it new but it is an old system. If you remember, even in the villages when the rain is falling you will find that we put either dishes or buckets by the corners of our houses and we capture water. That is already water harvesting. So the technology is old, but it is the mechanism in which to use and tap this water and utilise it for our own betterment that might be termed as new. Kakunta Now what are some of the benefits for a small-scale farmer to use this system that you have recommended in terms of raising fruit trees as well as fodder crops for livestock? Sishekanu The benefit is basically that without water our tree crops will not perform very well and therefore when we tap this water it will enhance the productivity of our trees and shrubs such that at the time when the browsing material in the natural environment is completely dry, there will still be some moisture that will be still available to support the growth of the shrubs from which we can be able to support our livestock. Kakunta Wonderful. Now what type of physical factors do you need to establish the system for it to actually work out well for the small-scale farmer? Sishekanu Well basically the level ditches would require that the area has some sandy-related soils where it is not going to over flood; it will be able to absorb the water and allow it to infiltrate. Now in the case of where run off might be higher because of clay soils, particularly when there is also a hill, we will need to capture that water and divert it safely. At the same time, there is also the system where you dig ditches. These ditches will also be capturing water and you plant your fruit trees just by the side of the ditch and in some clay soils that will be quite handy and helpful. Kakunta So from your own experiences here in Eastern Province, what lessons have you learnt in terms of rainwater harvesting which are practically useful for the small-scale farmers? Sishekanu The level ditch system has been practically useful for the small-scale farmers because it helps to recharge the underground water reservoir and therefore, even where they have shallow wells, the shallow wells will be facilitated to receive water for a longer period of time than when they are absent. Kakunta Is there anything that I have left out that you would like to put across in as far as the subject rainwater harvesting is concerned? Sishekanu Basically I would say that if we harvest the water we will reduce the destruction of our soils and meanwhile we will enhance the productivity of our crops and therefore it will be important that we consider the area of water harvesting. End of track.