Aholi, Joel2026-02-242026-02-242025-08https://ir-library.ku.ac.ke/handle/123456789/32558A Thesis Submitted in Partial Fulfilment of the Requirements for the Award of Degree of Master of Science in Hydrology and Water Resources in the School of Pure and Applied Sciences, Kenyatta University, August 2025. Supervisors 1. Dr. Mary Makokha-Department of Geography 2. Dr. Kennedy Obiero- Department of GeographyVariation in rainfall on monthly, seasonal and annual time scales, land cover changes and anthropogenic activities determine streamflow response, which is of great concern for water resource management and conservation at a watershed. In Zaaba sub catchment, the main problem is anthropogenic activities like encroachment on riparian areas and forested areas. The main study objective was to determine streamflow response to rainfall variability in Zaaba sub catchment. Specific objectives of the study were: (i) To determine rainfall trends for Zaaba River sub catchment from 1991 to 2020, (ii) To determine discharge trends for Zaaba River from 1991 to 2020, (iii) To determine current discharge of Zaaba River, and (iv) To establish factors that influence hydrological response of Zaaba River. Historical rainfall data from Kenya Meteorological Department and historical discharge data from Water Resources Authority were used to determine rainfall and discharge trends. Land cover data for 2001, 2011 and 2020 was downloaded from USGS website https://www.earthexplorer.usgs.gov/. Field experiments determined current discharge for Zaaba River. Focus Group Discussions, interviews and questionnaires were used to determine factors influencing hydrological response of the river. Regression analysis determined the correlation between rainfall and discharge. Mann Kendall test was used for trend detection. A slightly increasing monthly rainfall trend was observed at α = 0.05 with P-value = 0.037 and Qr = 0.125. There was slightly increasing trend in MAM rainfall with Qr = 0.030 and P-value = 0.043 while OND had a slightly increasing trend with Qr = 0.136 and P-value = 0.046. Trend analysis of annual rainfall revealed the existence of slightly increasing trend in annual rainfall with Qr = 1.081 and P-value = 0.010. Discharge trend analysis at α = 0.05 revealed monthly discharge for the study period had slight increasing trend with Qd = 1.070 and P-value = 0.010.A slightly increasing trend in discharge for MAM with Qd = 0.75 and P-value = 0.009 while OND discharge had an increasing trend with Qd = 2.018 and P-value = 0.008. Annual discharge trend analysis indicated an increasing trend with Qd = 0.085 and P value =0.009. The trend analysis of rainfall and discharge revealed the existence of trend on monthly, seasonal and annual time scales. Regression analysis between rainfall and discharge data monthly timestep revealed a moderately positive relationship with r = 43.1%. At seasonal time step, the relationship was positive, although very weak with r = 12.4% for MAM and 6.7% for OND. At annual time step, r = 5.1%, indicated a weak positive relationship. The field experiments resulted in current discharge of May 2024 for Zaaba River as 42.36 m3 /s. Statistical analysis revealed that major land cover changes occurred between 2001 and 2020 where agricultural area that decreased from 50.05% (2001) to 32.8% (2020) as buildup areas increased from 5.06% in 2001 to 17.68% in 2020 as attributed to increased population, expansion of urban areas and encroachment into river riparian that decreased from 5.18% (2001) to 0.87% (2020). 83% of the respondents revealed that agriculture is the main activity leading to intense run off generation. However, other activities that increase run off and lower ground water recharge are brick making, pottery, quarrying and small-scale gold mining. This study’s findings would encourage capacity building on increasing rainfall trends in order to take measures to control floods and enact policies that would encourage community participation in reafforestation programs in Maragoli Hill Forest and policy on restoration and protection of wetlands and riparian areas.enThesis