Modelling Estimation of the Available Rainwater Resource in Gbédji-Kotovi Clay Area for Supplying Dikes and Dams

摘要

Floods and flows data areuseful for dimensioning of dikes and dams which often include evacuationdevices that regulate flows to ensure the volumes of water. The objective ofthis study is to estimate the available water resource in the village ofGbédji-Kotovi, located in the watershed of Couffo river in Benin by usingsequentially, the HBV (Hydrologiska Byrans Vattenbalansavdelning) and GR4J(Rural Engineering model with 4 daily parameters) climate models.Hydrographs of water levels are simulated according to the calibration period(1994-1999) different from the validation one (1982-1988). Considering the Nash-Sutcliffe model Efficiency coefficient (NSE),the performance of GR4J model during calibration is slightly higher than theperformance of the HBV model, while during the validation, the contrary isnoticed. The annual rainfall average simulated is 1117.7 mm/year while the average observed is 1104.6 mm/year over the period 1981-2005. By 2050, onone hand, the annual flow ratevalues will vary from -19.2 to -11.9%, while the actualevapotranspiration willvary between 0.5 and -5.8; on another hand, thepotential evapotranspiration and the annual precipitation remain constant. Anaverage flow of 187 millions m~(3)/year forannual average water depth of 1094 mm is obtained at Lanta rain station, whichcovers an area of 1664.47 km~(2), while this flow enabled an averageflow of 327.5 millons m~(3)/year to be obtained at thevirtual station of our study area of 2908.15 km~(2). The flow rates corresponding tothe return periods of 10, 25 and 50 years vary from 5.51 to 12.67 m~(3)/sat the outlet of the virtual station; while those at the outletof Lanta station vary from 3.6 to 6.6 m~(3)/s. However, the simulatedwater quantiles cannot be fully mobilized; becauseof the uses, they undergo upstream and downstream. Thus, Gbédji-Kotovi localityrequires the implementation of an integrated water resource management strategythat includes the construction of dikes and dams.