Combined estimation of specific yield and natural recharge in a semi-arid groundwater basin with irrigated agriculture

Abstract

A water budget approach is developed to jointly estimate specific yield and natural recharge in an unconfined aquifer with significant seasonal water table fluctuations. Water table fluctuations are due to distinct seasonality in groundwater recharge. The separation of the hydrologic year into two (or more) extended seasons of recharge (wet season) and norecharge (dry season) with accompanying changes in water table allows for a split use of the water table fluctuation (WTF) method, first to estimate specific yield from the water table drop during the dry season (no recharge) and, second, to estimate recharge from the water table rise during the wet season, after considering all other water budget components explicitly. The latter includes explicit computation of groundwater storage with the WTF method. The application of the WTF method requires a large number of water level measurements throughout the unconfined aquifer before and after each season. The advantage of the method is that specific yield and recharge are estimated at the scale of interest to basin hydrologic studies and that the method requires no extensive in situ instrumentation network. Here, the method is demonstrated through a case study in a fractured hard-rock aquifer subject to intensive groundwater pumping for irrigation purposes.

Recharge Estimation of Hard Rock Aquifers under Sahelian Climate Conditions Using Water Table Fluctuation: Case Study of Tougou Catchment, Burkina Faso

“…The WTF method is based on the hypothesis that any water table rise in unconfined aquifer is due to recharge [16]. The employed methodology is based on applying the WTF method in conjunction with the groundwater budget method developed by Marechal et al [8]. The WTF method allows estimating change in groundwater storage based on water level fluctuation (Equation (1)).…”

“…The research aims at characterizing water table fluctuations of the Tougou catchment aquifer and estimating recharge by using a combination of the water balance equation and the water table fluctuation method. The combination of the two approaches is an innovative way to estimate specific yield and direct recharge [8] [9].…”

An Integrated Field Assessment of Groundwater Recharge

“…In the water level fluctuation method for recharge estimation [10,13,16,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43], a rise in the water table, in response to a precipitation-induced recharge event, is converted to an amount of recharge by multiplying the magnitude of the rise by the aquifer's specific yield. The method is attractive because water table measurements are often available, and the method is relatively quick, simple, and easily implemented.…”

Contribution d’un modèle hydrogéologique à fractures discrètes à l’étude des aquifères fracturés du socle Archéen de Touba (Nord-Ouest, Côte d’Ivoire)

“…L'étude de ces systèmes aquifères est donc fondamentale, notamment pour le captage des eaux souterraines (BIÉMI, 1992;BOUKARI et GUIRAUD, 1985;JOURDA, 2005;KOUAMÉ, 1999;SAVADOGO, 1984;SAVANÉ, 1997), leur gestion (BASSOLÉ et al, 2001;DEWANDEL et al, 2006;MARÉCHAL et al, 2006) ainsi que leur protection.…”