Estimating groundwater recharge following land-use change using chloride mass balance of soil profiles: a case study at Guyuan and Xifeng in the Loess Plateau of ChinaEstimation de la recharge des eaux souterraines après changement d’occupation du sol au moyen du bilan chlorures sur profils pédologiques : étude de cas à Guyuan et Xifeng sur le Plateau lœssique de ChineEstimación de la recarga de agua subterránea siguiendo los cambios de usos de la tierra utilizando el balance de masa de cloruro de los perfiles de suelos: un caso de estudio en Guyuan y Xifeng en el loess del Plateau de China利用土壤剖面氯质量平衡评估土地利用变化条件下地下水补给:以中国黄土高原固原和西峰为例Estimativa de recarga das águas subterrâneas na sequência de alterações do uso do solo usando o balanço de massa do cloreto em perfis de solo: um caso de estudo em Guyuan e Xifeng no Planalto de Loess, na China

Groundwater recharge is affected by land use in (semi)arid areas. A new application of the chloride-mass-balance approach has been developed to estimate the reduction in groundwater recharge following land-use change by comparing chloride concentrations below the root zone and above the base of the chloride accumulation zone, before and after the land-use conversion. Two sites in the Loess Plateau of central China have been selected for study. Results from the Guyuan terrace region show that groundwater recharge beneath natural sparse small-grass was 100 mm/year, but the conversion to winter wheat about 100 years ago has reduced groundwater recharge to 55 mm/year. At the Xifeng Loess Plain the conversion from winter wheat, with groundwater recharge at 33 mm/year, to apple orchard 7 years ago has led to chloride accumulation to 5 m below land surface, suggesting the recharge rate has been reduced. This is in agreement with previous studies in these areas which have shown that the regional afforestation and other land-use conversions have resulted in deep soil desiccation and have caused an upper boundary to form with low matrix potential, thus preventing the soil moisture from actually recharging the aquifer.