Assessment of Rainfall Impact on Groundwater Vulnerability for Agricultural Production

Abstract

The research study was conducted in Northern Lake Victoria basin to assess rainfall impact on groundwater as a fresh water source on 30 farms for agricultural production. Depth Aquifer Recharge and Transmissivity (DART) index quantitative method was applied that revealed that rainfall was directly related to groundwater vulnerability index. Positive DART index was realized during long rainfall season between April and June, and during short rainfall season in September and October. The other months had negative values during dry season. DART indices ranged between -8.40 and 2.50 with positive values representing more resilience to negative impact of erratic rainfall. There were two groundwater vulnerability Index Thresholds of -8.40 and -4.80 that marked onset of long and short rainfall seasons respectively. Mann-Kendall trend analysis and t-test performed indicated a downward trend and a significant difference of groundwater vulnerability index values because of seasonal rainfall changes that caused wells to dry up thus increasing water insecurity. The research study results confirmed the severity of rainfall patterns on groundwater recharge that can affect agricultural production and food security to households.