Hydraulic performance of small basin irrigation

Abstract

Small basin irrigation as a method of applying water is widely used in many parts of Kenya and will likely remain important as energy shortage discourages the use of alternative energy-intensive methods. Demand f or- both energy and water are already encouraging efforts to improve the watering efficiency using small basin irrigation. The analytical solutions for determining water distribution from a peripheral point of a small basin have not been studied previously in Kenya. Hydraulics of water flow in a small basin are of vital importance for designing efficient small basin irragation systems. The ability to analyse and to synthesize the hydraulics of small basin cheaply and efficiently require in-field trials. This should provide an important new tool for use in an attempt to improve the performance of small basin irrigation systems. The results of hydraulics of water flow and hydraulic performance distribution of small basin irrigation with water from one corner of the basin, based on an experimental study conducted at Eldume Irrigation· Scheme, in Baringo, Kenya, are presented. The study of small basin hydraulics was undertaken to determine its performance and to identify and develop appropriate design procedures for small basin irrigation. The observed small basin irrigation process occured in three distinct phases namely, advance, ponding and depletion. The relation between advance distance and time is curvilinear, while depletion occurs nearly linearly at a constant time. The results obtained by least-squares regression technique used to find advance power equations suggest that the change in basin size has no significant effect on the water advance equation. Further there is little effect of irrigation event on advance equations but the water advance rate increases with applied water flow rate to the basin. A generalised advance function applicable to Eldume soil -conditions characterised mainly by the infiltration curves can be written as: z b X = uQ t . This generalised advanced function can be used to carefully extrapolate to other flow rates (Q) and basin sizes (X) other than the studied values. The results of volume balance approach were comparable with the independently derived advanced equation based on measured advance data and it seems that starting from a well determined infiltration equation., advance equations can be derived for different infiltration equations. Further, the dimensional analysis has been identified and found to have useful potential in the design of efficient small basin irrigation. Suggestions are made for future research possibilities in small basin irrigation.