Simulating Streamflow in Response to Climate Change in The Upper Ewaso Ngiro Catchment, Kenya

Omwoyo AM, Muthama NJ, Opere A, Onwonga R. "Simulating Streamflow in Response to Climate Change in The Upper Ewaso Ngiro Catchment, Kenya." Journal of Climate Change and Sustainability. 2017;1(2):12-29.


The study simulated streamflow response under changing climate for Ewaso Ngiro river in Upper Ewaso
Ngiro Catchment (UENC), using Soil and Water Assessment Tool (SWAT). Data from National Centre
for Meteorological research (CNRM) model of Co-Ordinated Regional Downscaling Experiment
(CORDEX) was used to generate climate change scenarios (temperature and rainfall) for representative
concentration pathway (RCP) 4.5 and 8.5 from 2021-2080 relative to the baseline 1976-2005. SWAT
model was set up using historical daily rainfall and temperature data, soils, Digital Elevation Model and
land cover map, and calibrated against observed streamflow. Decreasing trend in historical rainfall and
streamflow was observed while increasing trend was observed for temperature. Projections indicated
increasing trend in temperature in both RCPs, with RCP 8.5 having higher increase (1.1-2.60 C) than
RCP 4.5 (1.0-1.70 C). Rainfall was found to increase from March-November, and decreased in
December-February in all scenarios. Change in total annual rainfall ranged from 0.1-18.5% in 20212050
and 1.2-18.7% in 2051-2080, which corresponded to increase in streamflow of 20.9-23.6% and
21.2-28.2% respectively. Streamflow in March-May decreased (-26 to -10%) in all scenarios and
increased in June-February (9-114%). This was found contrary to streamflow patterns simulated in
neighboring catchments where studies indicate increasing streamflow trend in March-May. Streamflow
response was found to be sensitive to changes in rainfall, thus emphasis should be put on water
conservation and catchment management including protection of headwater forests through agroforestry,
afforestation and reforestation.
Key words: Climate change, Streamflow, Simulation, Upper Ewaso Ngiro Catchment

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