Rainfall-runoff modelling to determine continuous time series of daily streamflow in the Umba River, Kenya

Abstract

Long time series of streamflow data are required to understand the flow characteristics of a
river that could be applied for various watershed and water resource management plans. A
reliable estimate of river flows generated from catchments are commonly obtained by water
level observations from in situ gauging stations. However, sufficient streamflow observations
are not available due to missing flow records and limited observation periods in the Umba
River, a transboundary river basin shared between Kenya and Tanzania. Hence, it was
necessary to undertake a study on hydrological simulation by developing an appropriate model
to the watershed. A rainfall-runoff model was developed using the Hydrologic Engineering
Center - Hydrologic Modelling System (HEC-HMS). The model was simulated to generate a
continuous time series of daily streamflow for the last 30 years (1988 to 2017). The computed
streamflow results were then used to infill the missing records and to extend the flow data of
the river. The study is expected to inform management decisions for efficient water resource
allocation in the basin. Hence, a continuous collection of data on hydrology is recommended
to ensure the provision of sustainable water flows in the river.