Intensity of Flash Rains and the Effect on Drenching and Stabilization Frequency of on-Farm Water Harvesting Systems in Matungulu Sub-County, Machakos County, Kenya

Performance of the water harvesting systems depends on the farming systems, soil characteristics and hydrological factors. This study sought to determine the extent increase in frequency and intensity of flash rains affect drenching (silt removal) and stabilization frequency of on-farm water harvesting systems in Matungulu Sub-County, Machakos County in Kenya. A descriptive survey design was adopted in which some 105 randomly selected respondents were drawn from 5 sub- locations of Matungulu Sub-County. The 105 were selected from 2 Sub-County’s based on livelihood of the 2086 target households that is cash crop farms and grain crop farms. 21 households for each livelihood strategy from each of the five sub-locations taking the odd-numbered items were used. A structured questionnaire was administered to obtain data on farmers’ use of water harvesting systems and their performance in light of climate variability. The data was statistically analyzed and results displayed in tables, graphs and charts. The study established that the Fanya-juu system is the most practiced harvesting system in the area at (n=67, 63.81 %,) followed by Negarimsat (n=38, 36.19%).The results also show the effects of the water stress factors on silt removal for fanya-juu (r=0.1939, p=0.0571) is positive though not supported by statistical level of significance, but positive and significant on negarims (r=0.2698, p=0.0078), contour bunds(r=0.5548, p=0.0001) and contour ridges(r=0.4938, p=0.0001).Based on the climate variability effects on the on-farm water harvesting systems selected, the Fanya-Juu system is the most appropriate for use in the area. The study recommends that farmers in the area should be encouraged through awareness creation to harvest water using the fanya-juu system. Farmers also need to be sensitized and trained on monitoring and evaluation of the effects of climatic variability on the harvesting systems.