Spatial average aquifer recharge through atmospheric chloride mass balance and its uncertainty in continental Spain

Abstract

The atmospheric chloride mass balance (CMB) method allows spatial evaluations of the average diffuse aquifer recharge by rainfall (trueR¯) in large and varied territories when long‐term steady conditions can be assumed. Often, the distributed average CMB variables necessary to calculate trueR¯ have to be estimated from the available variable‐length data series, which may be of suboptimal quality and spatial coverage. This paper explains the use of these data and the reliability of the results in continental Spain, chosen as a large and varied territory. The CMB variables have been regionalized by ordinary kriging at the same 4976 nodes of a 10 km × 10 km grid. Nodal trueR¯ values vary from 14 to 810 mm year–1, 90% ranging from 30 to 300 mm year–1. The recharge‐to‐precipitation ratios vary from 0.03 in low‐permeability formations and semiarid areas to 0.65 in some carbonate massifs. Integrated average results for the whole of continental Spain yield a potential aquifer recharge of 64 km3 year−1, the net recharge over permeable formations (40% of the territory) being 32 km3 year−1. Two main sources of uncertainty affecting trueR¯ (given by the coefficient of variation, CV), induced by the inherent natural variability of the variables (CVR) and from mapping (CVRK), have been segregated. The average CVR is 0.13 and could be improved with longer data series. The average CVRK is 0.07 and may be decreased with better data coverage. The trueR¯ estimates were compared with other regional and local recharge estimates, trueR¯ being 4% and 1% higher, respectively. Copyright © 2012 John Wiley & Sons, Ltd.

Integrated assessment of future potential global change scenarios and their hydrological impacts in coastal aquifers. A new tool to analyse management alternatives under uncertainty in the Plana Oropesa-Torreblanca aquifer

“…The mean historical recharge (85 mm/year) obtained from this infiltration rate coefficient is quite similar to the mean (89 mm/year) estimated by other authors who applied 25 an atmospheric chloride mass balance (Alcalá and Custodio, 2014).…”

Comments on Uncertainty in Groundwater Governance in the Volcanic Canary Islands, Spain

“…There is also an application to the Las Cañadas aquifer on central Tenerife Island [25]. Results compare reasonably with what is obtained for the Iberian Peninsula as a whole [26] and at local level [27]. They have been partly developed inside the wider scope research Project REDESAC (www.redesac.upc.es).…”

Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

“…Net aquifer recharge means the groundwater fraction that remains in the aquifer after discounting groundwater up-take by direct evaporation and deep-rooted vegetation from direct rainfall and runoff infiltration through the vadose zone after some delay, smoothing out the variability inherent to rainfall events [17,49,50]. In what follows, net aquifer recharge is expressed simply as recharge.…”

“…This correction is easy but if gaps tend to correspond to a given period of the year or omit exceptional events, yearly results may be biased [9,50]. The CR data from successive monthly and bimonthly i samples in galleries were averaged by the corresponding discharge flow to deduce average-weighted yearly values [14].…”

“…Note that no-forced trends in CR and flow dynamics were observed in galleries ESU and FFA ( Figure 5). This is a prerequisite of steady conditions for recharge evaluations [9,50]. ) in galleries and boreholes S-1 and S-2.…”