International Rainwater Catchment Systems Conference
Catchment: An Answer to the Water Scarcity of the Next Millennium."
Petrolina, Brazil - July 1999
Section 3: Rainwater Catchment and Droughts
Modelling of Rainwater Catchment and Utilization on
Farmsteads in Sipili, Kenya
Nicholas Kiggundu & R. K. Muni
Department of Agricultural Engineering
Undependable and erratic rainfall patterns, with frequent
rainless periods within the rainy season in Sipili location, a semiarid area in
Kenya, is the primary natural limiting factor to the rain-fed agricultural
production potential of the area. Although the average annual rainfall of 600 -
800 mm would appear sufficient for one or two good crops per year, at times,
the harvest is poor or there would be a total crop failure due to poor rainfall
distribution. The level of supplemental irrigation mainly for horticultural
crops is inadequate since farmers lack guidance on how efficiently harvested
rainwater could be utilized for maximum returns.
A computer model was developed based on the mass balance
equation to facilitate simulation of water utilization from different tank
capacities meant to provide water for domestic use, watering two grade dairy
cows and supplemental irrigation of a cabbage crop. The maximum cropped areas
for different planting decades (10-day period) of the year up to crop maturity
were determined for tank capacities of 50, 100, 150, 200, and 250 m3.
The optimum cropped area for each tank capacity could be obtained when planting
was done on the 14th decade. The maximum cropped area could be
achieved when planting was done on the 2nd, 14th and 26th
decades for 50, 100, and 150 m3 tanks and on the 1st, 13th
and 25th decades for 200 and 250 m3 tanks. Such results
would give farmers in Sipili and its environs an opportunity to strategize for
the highest market prices of the cabbage crop or the highest crop yield.
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