FACTORS INFLUENCING RIVER DISCHARGE IN MOIBEN RIVER CATCHMENT, KENYA

Abstract

This study examines the factors influencing river discharge in the Moiben River catchment, Kenya by looking at the shifts in the trends of river discharge, the changes that are associated with the changes in land uses and the socio-economic influences from the period 1995 to 2024.Some of the environmental and socio-economic changes over the period are farm land expansion, deforestation, and increasing water needs of the people. These shifts have raised concerns about fluctuating river discharge, water scarcity and the sustainability

of available water for both the people and ecological needs. Kenya is among the water- deficient nation with a yearly per capita water supply being less than 1000 m3; therefore,

its water sources needs conservation. Most of the water needs in the Kenyan watersheds are influenced by the human activities around these watersheds. In the case of the Moiben River catchment, discharge fluctuations, declining water levels, and water shortages have been observed but limited research has been conducted to investigate the exact reasons behind the declining and fluctuating river discharge. The primary objective of the study is to assess the key factors influencing river discharge in this area, which is important for local water supply and resource governance. The study utilized GIS-based methods and satellite images to analyze the changing LULC, alongside data from hydrological data such as river discharge and rainfall records. Household surveys and key informant interviews assessed socio-economic factors influencing discharge patterns. Statistical and geospatial techniques were used to establish relationships among these factors, and also hydrological modelling using HEC-HMS was utilized to simulate the peak discharge over the period. The findings revealed fluctuations in river discharge, with a slight but statistically insignificant upward trend at p < 0.05 (Qt = 0.8534t + 112.96, R2=0.0221, p=0.530). Wet season discharge (1.25±0.12 m3/s) was higher than the dry season (1.07±0.41 m3/s). LULC analysis showed cropland expansion (51.48% to 77.67%) and forest cover slightly increased from (30.53% to 31.22%), while rangeland and grassland have declined. Temperature rose significantly (r= 0.926, p= 0.074), while rainfall was moderate (r= 0.751, p= 0.249). Cropland (r= 0.922, p= 0.078) and built area (r= 0.914, p= 0.086) increased with time. River discharge had positive correlations with forest cover (r= 0.964, p= 0.036) and rangeland (r= 0.983, p= 0.017) changes and the peak discharge was 87.9m3/s in a 30-year return period. The results will inform sustainable water resource management and sustainable land use planning measures, providing valuable insights benefiting policymakers, conservation agencies, and local communities to mitigate the implications of the changing climate and land uses on river discharge through practices such as reforestation, adoption of water-efficient irrigation methods, protection of riparian zones, and promotion of sustainable land management techniques. The findings from this research will contribute to improving water conservation and enhancing resilience for this region.