Recharge in karst and dune elements of a semi-arid landscape as indicated by natural isotopes and chloride

A transient flux model for convective infiltration: Forward and inverse solutions for chloride mass balance studies

“…However, the evidential insignificance of mixing (dispersive and diffusive) processes in semiarid media where steep gradients in chloride concentration occur over short distances in chloride profiles at depths that correspond to long timescales has been indicated in many field studies. Negligible dispersion has been previously assumed in arid systems explicitly [Allison et al, 1985;Stone, 1984] [Tyler and Walker, 1994]. In arid regions infrequent but intense rainfall events can result in preferential flow in the active root zone, but only under specific conditions will preferential flow occur below this zone (e.g., drainages where large volumes of runoff accumulate and saturate sediments well below the root zone).…”

Application of chloride profile and water balance methods in estimating groundwater recharge in Luanjing Irrigation Area, Inner Mongolia / Application des méthodes du profil de chlorure et du bilan hydrique pour l'estimation de la recharge hydrogéologique dans le Périmètre Irrigué de Luanjing, Mongolie Intérieure

“…Based on the chloride accumulative method advanced by Allison et al (1985), groundwater recharge, R d (mm year -1 ) is given by:…”

“…Previous studies have shown that many arid regions have experienced little or no direct recharge for millennia (Allison et al, 1990;Scanlon et al, 2003). For example, in the Murray Basin, South Australia, Allison et al (1985), Salama et al (1993), and Herczeg et al (2001) found that the groundwater recharge is only <0.1-1 mm year -1 , and the chloride cumulative time in the profiles ranged from 4000 to 40 000 years, according to the chloride mass balance in natural eucalyptus forest. Most recently, Gates et al (2008) reported mean estimated recharge across the Badain Jaran dune field in northern China of 1.4 mm year -1 , suggesting that diffuse recharge presently plays a minor role in the overall water balance of the desert's shallow Quaternary aquifer.…”

Generalized chloride mass balance: Forward and inverse solutions for one-dimensional tracer convection under transient flux

“…The formalism underlying the calculation of recharge by the conventional CMB using the graphical technique suggested in most recent applications (e.g., Allison et al 1985;Scanlon 1991;Phillips 1994) is presented. The graphical procedure is intended to identlfy a representative interval-averaged chloride concentration, where the intervals represent periods of generally constant water and chloride fluxes.…”