Estimating groundwater recharge from water isotope (δ²H, δ¹⁸O) depth profiles in the Densu River basin, Ghana

Figures & data

Fig. 1 Map of the study area showing the geology and the location of the three investigated sites and the two meteorological stations.

Fig. 2 Measured total porosity (Δ), water content (◊), deuterium (

), and modelled water (grey line) and deuterium (black line) contents with depth at: (a) Adwumoku, (b) Teacher Mante and (c) Ayikae Doblo.

Fig. 3 Monthly precipitation and deuterium content of the two meteorological stations at Kibi and Nsawan; the isotope contents were measured in Kibi precipitation.

Fig. 4 The isotope composition of precipitation (•) with the local Meteoric Water Line (LMWL, –––) and the isotopic composition and regression lines of the soil water at the sites: Adwumoku (Δ, –––), Teacher Mante (

, - - -), and Ayikae Doblo (×, - - -).

Table 1  Soil hydraulic parameters of the three study sites

Site	θr (cm^3cm^-3)	θs (cm^3cm^-3)	α (cm^-1)	n	K s(cm d^-1)	αL (cm)	D w (cm^2 d^-1)
Adwumoku	0	0.41	0.001	4.9	274	15	2
Teacher Mante	0	0.41	0.003	3.2	205	5	2
Ayikae Doblo	0	0.39	0.0025	3.5	274	2	2
θr: residual water content; θs: saturated water content; α,n: empirical shape parameters of the retention function; K s: saturated hydraulic conductivity; αL: longitudinal dispersivity; D w: diffusion coefficient.

Table 2  Mean annual groundwater recharge (mm/year) resulting from transient flow and transport modelling, the approximate peak-shift method, and the water balance at the three observation sites in the Densu River basin

	Transient modelling	Peak-shift method	Water balance
Adwumoku	101	250	21
Teacher Mante	94	120	75
Ayikae Doblo	182	110	135