The Sustainability of Irrigation Schemes Under Climate Change

Abstract:

Irrigation is considered to be one of the best practices in agriculture to ensure food security. However water resources that are used for Irrigation activities are increasingly coming under stress, either due to extraction or climate variability and change. To adequately plan and manage water resources so as to ensure their sustainability requires a long term investigations of streamflow and climate. Streamflow analysis and forecasting gives signal of the occurrence of floods and drought situations. However the ability to maximise these early warning signal, especially for small watersheds, require the use of rainfall predictions approaches (Yucel et al., 2015). One approach to extend the predictions of these early warning signals is the coupling of mesoscale numerical weather prediction (NWP) model precipitation estimates with a spatial resolution hydrological model into streamflow estimates (Jasper et al. 2002;Wardah et al. 2008; Yucel et al. 2015). The study explored (1) the potential of the NWP model (WRF) in reproducing observed precipitation over the Tono basin in West Africa, and (2) the potential of a coupled version of WRF with a physics-based hydrological model (WRF-Hydro) in estimating river streamflow. In order to cope with the lack of discharge observation in the Tono basin, the WRF-Hydro performances are evaluated with a water balance approach and dam level observation. The WRF-Hydro predicted dam level is relatively close to the observation (dam level) from January to August (R²=0.93). After this period the deviation from observation increases (R²=0.62). This could be attributed to surface runoff due to peak rainfall (in August) resulting in soil saturation (soil reaching infiltration capacity) into the dam which has not been accounted for in the water balance model. WRF-Hydro has shown to give good estimation of streamflow especially for ungauged stations. Further works requires using WRF-Hydro modeling system for climate projection, and assess the sustainability of the Tono irrigation scheme.