PREDICTING IMPACT OF CLIMATE CHANGE ON WATER REQUIREMENTS FOR DIRECTLY SOWN RAIN-FED SWEET POTATO IN THE SEMI-ARID KATUMANI REGION, KENYA

Abstract

Background: In the wake of the changing climate, the current water crisis has increasing relevance for the human race, hence estimation is an integral part of planning, development and management of water resources of the country based on several meteorological parameters. Hypothesis. No significant changes in water requirements sweet potato crop for the next 20 years in Katumani, Kenya. Methodology: The study predicted the implications of climate change on crop water requirements for the short rain seasons between 1991-2016 (baseline climate) and future from 2020-2039 (climate change) in Katumani with the aid of the CROPWAT 8.0 model. Crop Water Requirements (CWR) were projected in two scenarios: i) Average rainfall and temperature of baseline period (1991-2016), ii) rainfall and temperature predicted in 2039 based on Relative Concentration Pathways (RCP); 8.5 and 2.6 scenarios, adopting the global circulation models (GCM) of IPSL-CM5A-MR and GFDL-CM3 for predicting monthly rainfall and temperature, respectively. To achieve effective water allocation and planning, data on sweet potato water requirements, irrigation withdrawals, soil types and climate conditions were gathered from the study area. Assumptions: The study assumed no change in the conditions relating to irrigation and crop production in the future. Results: Sweet potato water requirement in the baseline period were modelled at 579.9mm whereas predicted under RCP 2.6 and 8.5 to be 634.1 and 639.3mm, respectively. Averagely, a 16.7% decrease in effective rainfall may increase the overall sweet potato WR by 10.2%. This may be due to increased temperature and reduced rainfall. Implication: Short rain season is the most appropriate for production of rain fed crops in Katumani. Conclusion: This study is useful in explaining the adverse impacts of climate change mostly on sweet potato water needs in Katumani and in helping to plan and manage water resources for many other crops in arid regions.