Groundwater flow in a relatively old oceanic volcanic island: The Betancuria area, Fuerteventura Island, Canary Islands, Spain

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

“…The existence of a low-permeability clay-rich debrisavalanche deposit at the IGV bottom related to the landslide origin of this valley [24,31,34,35] enhances the relatively fast groundwater flow along this valley from TPVC and LCC to the northern coast ( Figure 2). This conceptual hydrogeological functioning of Las Cañadas aquifer [33] is in accordance with the conceptual hydrogeological functioning proposed by [3,36] for this type of volcanic islands [5,6,37,38]. [33].…”

“…The atmospheric chloride mass balance (CMB) is an appropriate, widely used method for net aquifer recharge in volcanic island environments [5,6,20,47,48]. 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].…”

“…Oceanic volcanic islands are often characterized by a rugged topography that favours conditions for enhancing recharge in summit areas where precipitation and aquifer recharge rates are usually higher than in the lowlands and coastal plains [4][5][6]. However, the evaluation of aquifer recharge is a complex task subjected to different kinds of uncertainty [7][8][9] induced by the high spatial and temporal variability of precipitation [10], heterogeneities in soil and land use [11], few sampling and monitoring points [12], as well as the techniques used and the subsequent hydrological meaning and timing of estimates [13].…”

“…For this objective, atmospheric bulk deposition, groundwater, and recharge water were periodically monitored in selected points in Las Cañadas Caldera (hereafter LCC) summit area in central-northern Tenerife Island (Figure 1) during the wet hydrological year [2005][2006]. Additional research was conducted to identify the potential contribution of chloride to groundwater from endogenous HCl degassing from the volcanic-hydrothermal system because this external source of chloride may invalidate the widespread use of the CMB method for aquifer recharge evaluations in Tenerife Island, as reported in other active volcanic islands [5,6,21]. The chloride-to-bromide molar (hereafter Cl/Br) ratio was an efficient tracer used to select recharge water samples having atmospheric origin of chloride [21][22][23].…”

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

“…Numerical groundwater models have been constructed for the whole island of Gran Canaria (old and rather obsolete) and of Tenerife (updated three times for the Water Plan) and also for some local areas, such as La Aldea Valley on Gran Canaria [9], Los Rodeos aquifer on Tenerife [11] and the Betancuria volcanic Massif on Fuerteventura [32]. However, all of these models give rather uncertain results due to the uncertainty of parameters and the scarce and sometimes low reliability of the data available for calibration.…”