Assessment the climate change impact on the future evapotranspiration and flows from a semi-arid environment

The present paper aims to evaluate future changes in evapotranspiration and flows from semi-arid environments, using Essaouira basin (Morocco) as an example. In order to achieve this objective, the Rural Genius model (GR2M) has been used under representative concentration pathway (RCPs) 2.6, 4.5 and 8.5 of Coupled Model Intercomparison Project (CIMP5) model. The statistical tests of Pettitt and Mann-Kendall were used to determine trend sense of evapotranspiration and flow series. For the historical evapotranspiration, the statistical tests show an upward of 4.2% from 1978 to 2005. Concerning the historical flows, they show an upward for Igrounzar and Zelten stations and downward for Adamna station. Using the same statistical tests and under the three RCP scenarios, the future evapotranspiration series shows an upward trend. The combined application of GR2M model results and statistical tests for the 2020–2050 period shows an upward trend in future flows of the Igrounzar station, Zelten and Adamna under RCPs 2.6 and 8.5 scenarios, with an excess of 20, 28.8 and 19.70%, respectively, for RCP 2.6 scenario and 44.4, 53.8 and 43.7%, respectively, for the RCP 8.5 scenario. For the same period and under the RCP 4.5 scenario, the future flows show a downward trend of 42.5%, 42.1% and 40.6% by the Igrounzar, Zelten and Adamna stations, respectively. However, the results of this paper can be a basis for decision-makers for better management and protection of water resources in the Essaouira watershed by building hillside reservoirs along the Igrounzar, Zelten and Ksob wadis.