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Case Studies | Hydrology Science | Kenya | Volume 13 Issue 7, July 2024 | Popularity: 5.1 / 10

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Understanding the Hydrology of the Nyando River Basin using Hydrological Modelling

Nancy C. Koech

Abstract: The Nyando River is the main water source to all water users in the Nyando River Basin. Low river flows during dry periods affect socio-economic development in the upstream and downstream part of the river basin. Hence in this study input and output water balance components were assessed using the SWAT model and existing hydrogeological surveys investigated in the river basin. Scarce input climatic data in the catchment areas of the river basin were improved using inverse distance weighting and temperature lapse rate techniques. In addition, the SWAT model was parameterized using water withdrawals and existing hydrogeological information. During calibration of the model simulated and observed river flows corresponded well with achieved values of R2 and NSE ranging from 0.51 to 0.90. The output water balance components are actual evaporation and transpiration, deep aquifer recharge and river runoff at the outlet of the study area with mean annual values of 1279 mm/a, 62 mm/a and 228 mm/a respectively. Rainfall is the main input water balance component with mean annual value of 1572 mm/a and annual change in water storage range between ?160 mm/a. Results showed that about 80% of the surface water in the catchment is lost through evaporation and transpiration while about 3% recharges groundwater. In addition, approximately 17% is available annually in the catchment for use. Therefore, proper planning and management of water resources in the river basin is required to reduce water shortage during prolonged droughts and also to meet increasing water demands.

Keywords: Nyando, Kipchorian, Ainapng'etuny, water balance, SWAT model and hydrogeological survey

Edition: Volume 13 Issue 7, July 2024

Pages: 184 - 195

DOI: https://www.doi.org/10.21275/SR24629001557

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