Ann Waithaka^1,, Shadrack Murimi¹, Kennedy Obiero¹

Watersheds and water resources are highly vulnerable to land use/land cover changes (LULCC) as they directly influence hydrological characteristics in terms of water quantity. This study aimed at assessing the effects of land use/land cover changes (LULCC) on Surface runoff contribution to discharge (SURQ), lateral flow contribution to discharge (LATQ) and groundwater contribution to discharge (GWQ) of River Ruiru watershed, Kiambu County. The study integrated the use of remote sensing, GIS and hydrological modeling to collect and analyze data. Results of the study indicated that built-up areas, annual crops (mixed farming) and perennial crops (Tea and coffee farming) increased by 1.83%, 15.05% and 10.90% from 1984 to 2017 while grassland, shrubland and forestland decreased by 6.21%, 11.92% and 10.06%. Consequently, SWAT model results indicated that land use/land cover changes that occurred in River Ruiru watershed between 1984 and 2017 had effects on Surface runoff (SURQ), lateral flow (LATQ) and groundwater contribution to discharge (GWQ) which increased from 30.25 mm/yr, 8.48mm/yr and 9.95mm/yr to 181.25mm/yr, 11.44mm/yr and 10.66mm/yr respectively. The results from this study will help in understanding the effects of LULCC on the quantity of discharge which is one component of the knowledge base required in applying the principles of integrated water resources management (IWRM) thus providing critical input to the decision making on water resources management and planning.

land use change, land cover change, discharge, River Ruiru watershed, SWAT model