Abstract:
Climate change has a significant impact on water availability and agriculture water demand
due to high evapotranspiration. This study aimed to evaluate the future surface water
availability under the RCP scenario for crop production in the Woybo catchment. Six climate
models were obtained from CORDEX Africa under the RCP4.5 and 8.5 scenarios, and the
projection analysis was done from 2041–2070 and the 2071-2100 period. After evaluating its
performance through statistical indices, the rainfall-runoff HEC-HMS model was used to
simulate future stream flow. The CROPWAT 8.0 model was also used to determine the current
and future crop water demand. The model revealed that it acceptably reproduced the volume
and pattern of the observed hydrograph with a value of NSE = 0.66 & RVE = 1.57 for the
calibration period and NSE = 0.56 & RVE = 9.75 for the validation period. The trend of
selected climate variables was evaluated by Mann-Kendall’s tests and Sen’s slope estimators
at a 5% significance level. Under the RCP4.5 and 8.5 scenarios, projections of both mid- and
long-term annual rainfall showed decreasing and increasing trends, respectively. Under the
RCP4.5 and 8.5 scenarios, the projections of both mid- and long-term annual rainfall showed
decreasing and increasing trends. However, the potential evapotranspiration and maximum
and minimum temperatures predict an increasing trend in all RCM models. The amount of
annual stream flow will decrease by 17.29% to 4.87%, with a likely increase in annual
potential evapotranspiration of 0.21–8.9% over the catchment. According to the result, the
impact is season-dependent, with increased stream flow in the main rainy season but lower
flow in the short rainy season and dry seasons. Future crop water requirements and irrigation
water requirements are expected to increase for the maize crop due to increased rainfall and
higher evapotranspiration in all climate models. This increased crop water demand and
aggravated the soil moisture deficit in the catchment. The mid-growth stage had the highest
incremental CWR and IWR, while the early and late stages had low CWR and IWR. Because
the leaf area index (LAI) and plant height increased regularly from the initial to mid-season
stages, increasing transpiration. As a result, this research contributes to increased crop yield
and the development of adaptive strategies for the proper management of water resources
