Estimating annual groundwater recharge coefficient for karst aquifers of the southern Apennines (Italy)

Abstract

Abstract.To assess the mean annual groundwater recharge of the karst aquifers in the southern Apennines (Italy), the estimation of the mean annual groundwater recharge coefficient (AGRC) was conducted by means of an integrated approach based on hydrogeological, hydrological, geomorphological, land use and soil cover analyses. Starting from the hydrological budget equation, the coefficient was conceived as the ratio between the net groundwater outflow and the precipitation minus actual evapotranspiration (P − ETR) for a karst aquifer. A large part of the southern Apennines, which is covered by a meteorological network containing 40 principal karst aquifers, was studied. Using precipitation and air temperature time series gathered through monitoring stations operating in the period 1926-2012, the mean annual P − ETR was estimated, and its distribution was modelled at a regional scale by considering the orographic barrier and rain shadow effects of the Apennine chain, as well as the altitudinal control. Four sample karst aquifers with available long spring discharge time series were identified for estimating the AGRC. The resulting values were correlated with other parameters that control groundwater recharge, such as the extension of outcropping karst rocks, morphological settings, land use and covering soil type. A multiple linear regression between the AGRC, lithology and the summit plateau and endorheic areas was found. This empirical model was used to assess the AGRC and mean annual groundwater recharge in other regional karst aquifers. The coefficient was calculated as ranging between 50 and 79 %, thus being comparable with other similar estimations carried out for karst aquifers of European and Mediterranean countries. The mean annual groundwater recharge for karst aquifers of the southern Apennines was assessed by these characterizations and validated by a comparison with available groundwater outflow measurements.These results represent a deeper understanding of an aspect of groundwater hydrology in karst aquifers which is fundamental for the formulation of appropriate management models of groundwater resources at a regional scale, also taking into account mitigation strategies for climate change impacts. Finally, the proposed hydrological characterizations are also supposed to be useful for the assessment of mean annual runoff over carbonate mountains, which is another important topic concerning water management in the southern Apennines.

Enhanced groundwater recharge rates and altered recharge sensitivity to climate variability through subsurface heterogeneity

“…Focused recharge is known to be an important process of recharge generation in regions with heterogeneous subsurface characteristics (4, 28) and its strong impact on overall groundwater recharge amounts has been shown in several studies at the catchment scale (29)(30)(31). Our recharge sensitivity analysis reveals that accounting for this process and the variability of soil storages at a much larger spatial scale results in different recharge sensitivities compared with a homogeneous subsurface representation that does not consider focused recharge.…”

Hydrogeology of continental southern Italy

“…The latter was attributed by relying on results of hydrological budgets carried out on homogeneous hydrogeological units (Allocca, Manna, & De Vita, 2014;Boni, Bono, & Capelli, 1982;Celico, 1986). Geometries of outcropping areas were digitalized in a vector format and implemented in a Geographical Information System (GIS), georeferenced in the UTM projection and European Datum 1950.…”

“…Therefore, the latter have a general high permeability grade especially in the surficial epikarst zone (Petrella, Capuano, & Celico, 2007. These characteristics coupled with extended endorheic morphologies lead to a high groundwater recharge rate, varying between 48% and 78% of the mean annual effective precipitation (Allocca et al, 2014(Allocca et al, , 2015 in dependence of the relative abundance of limestone and dolomite lithologies, as well as ash-fall pyroclastic covers (Celico et al, 2010;De Vita & Nappi, 2013;Fusco, Allocca, & De Vita, 2017;Fusco, De Vita, Napolitano, Allocca, & Manna, 2013). Groundwater flow directions are controlled by geometric relationships of the permeability boundaries with the adjoining low-permeability Meso-Cenozoic terrigenous complexes.…”

“…Instead, at a large denominator scale, the behaviour of these composite groundwater bodies can be considered as unitary with a common circulation pattern (Celico, 1983). Besides the recharge from the effective rainfall, alluvial aquifers are fed directly by (Allocca et al, 2014;Bureau of Reclamation, 1985;Celico, 1986;Civita, 1975) based on relationships among permeability grade, hydraulic conductivity and groundwater recharge coefficient, determined as the ratio between groundwater recharge and effective precipitation. On the right side, conceptual relationships between depth of groundwater circulation and its dependence from surface topography are also shown.…”

Groundwater Recharge Assessment in the Karstic Aquifers of North Khorasan, Iran in APLIS Method

“…Methods based on GIS, which utilize geographic attributes of parameters such as geology, altitude, slope, soil type, vegetation and mean annual precipitation, are often applied in order to determine the spatio-temporal distribution of recharge of karst formation (Andreo et al 2008;Allocca et al 2014). In this regard, calculation of recharge through conventional methods (evapotranspiration, natural, chemical or synthetic isotopic tracing, and calculation of precipitation against time) or through numerical models has limitations such as lack of access to accurate and periodic data (Radulovic et al 2012).…”