TITLE:
Modelling Estimation of the Available Rainwater Resource in Gbédji-Kotovi Clay Area for Supplying Dikes and Dams
AUTHORS:
Kassa Issifou Mounou Sambieni, François de Paule Codo
KEYWORDS:
Rainwater, Modelling, Couffo Watershed, Gbédji-Kotovi, Dikes and Dams
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.10 No.2,
April
29,
2020
ABSTRACT: Floods and flows data are
useful for dimensioning of dikes and dams which often include evacuation
devices that regulate flows to ensure the volumes of water. The objective of
this study is to estimate the available water resource in the village of
Gbédji-Kotovi, located in the watershed of Couffo river in Benin by using
sequentially, 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 the
performance of the HBV model, while during the validation, the contrary is
noticed. 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, on
one hand, the annual flow rate
values will vary from -19.2 to -11.9%, while the actual
evapotranspiration will
vary between 0.5 and -5.8; on another hand, the
potential evapotranspiration and the annual precipitation remain constant. An
average flow of 187 millions m3/year for
annual average water depth of 1094 mm is obtained at Lanta rain station, which
covers an area of 1664.47 km2, while this flow enabled an average
flow of 327.5 millons m3/year to be obtained at the
virtual station of our study area of 2908.15 km2. The flow rates corresponding to
the return periods of 10, 25 and 50 years vary from 5.51 to 12.67 m3/s
at the outlet of the virtual station; while those at the outlet
of Lanta station vary from 3.6 to 6.6 m3/s. However, the simulated
water quantiles cannot be fully mobilized; because
of the uses, they undergo upstream and downstream. Thus, Gbédji-Kotovi locality
requires the implementation of an integrated water resource management strategy
that includes the construction of dikes and dams.