Abstract:
The trends of evapotranspiration and runoff in hydrological basins are heavily dependent on climatic patterns and their
amounts vary as a result of changes in anthropogenic activities. Muringato basin situated in the Upper Tana River Basin, in
Kenya has experienced changes in climatic patterns and increased anthropogenic activities. These changes necessitate the
need to understand the future trends of evapotranspiration and runoff for sustainable water utilisation and conservation.
This research predicted the trends of evapotranspiration and runoff from 2021 to 2030 using the Seasonal Autoregressive
Integrated Moving Average (SARIMA) model S{(1,1,1), (1,1,1)12} for each component. The models used time series
datasets for evapotranspiration and runoff from 1990 to 2020 as the input. The time series datasets were divided into two:
1990–2012 for model calibration and 2013–2020 for model validation. This division was informed by best practices in
SARIMA modelling. The forecasting results showed that the high values of evapotranspiration and runoff observed from
2017 would be sustained. Maximum evapotranspiration values of 140–150 mm would be observed in February 2024, May
2028 and 2029. The highest runoff amounts of 60–70 mm would be observed in May 2028 and 2029. The continuously
changing trends of evapotranspiration and runoff, especially the high runoffs need to inform the environmental conservation
policies and sustainable utilisation of the resources in the basin. This would ensure the existence of the Muringato
basin with a healthy water balance.
