Estimation of depression-focussed groundwater recharge using chloride mass balance: problems and solutions across scales

Pavlovskii, Igor; Hayashi, Masaki; Cey, Edwin E.

Estimation of depression-focussed groundwater recharge using chloride mass balance: problems and solutions across scales | Estimation de la recharge des eaux souterraines dans des zones de dépressions à l’aide du bilan massique en chlorures: problèmes et solutions à toutes les échelles Estimación de la recarga del agua subterránea concentrada en depresiones utilizando el balance de masa de cloruro: problemas y soluciones a través de distintas escalas 基于氯质量平衡法的以洼地为目标的地下水补给量估算:跨尺度的问题和解决方案 Estimativa de recarga de águas subterrâneas concentrada em depressões topográficas usando balanço de massa de cloreto: problemas e soluções em escalas

2019

Pavlovskii, Igor | Hayashi, Masaki | Cey, Edwin E.

This study evaluates the applicability of the chloride mass balance (CMB) method for groundwater recharge estimation in a semi-arid region in Canada, where recharge largely occurs under topographic depressions. The CMB applicability was tested at three scales: point-scale recharge rates at different topographical positions; average recharge rates incorporating multiple topographical positions on a local scale; and an identification of spatial trends of recharge on a regional scale. Agricultural chloride inputs were shown to be a major factor affecting chloride concentrations at all three scales, where elevated chloride concentrations in the shallow subsurface affected by agricultural inputs surpassed background concentrations by an order of magnitude. The propagation depth of elevated concentrations varied among study sites from being largely confined to the unsaturated zone to extending well into the saturated zone. Lateral chloride redistribution further affected the CMB applicability for point-scale recharge rates. Specific solutions enabling the CMB application in these conditions are presented, including runoff concentration measurements for point-scale estimates, using groundwater age tracers on a local scale, and using the harmonic mean concentration of a large number of samples on a regional scale.

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