Groundwater recharge in natural dune systems and agricultural ecosystems in the Thar Desert region, Rajasthan, IndiaRecharge d’un aquifère dans des systèmes naturels dunaires et des ecosystems agricoles dans la region désertique du Thar, au Rajasthan en IndeRecarga de aguas subterráneas en sistemas de dunas naturales y ecosistemas agrícolas en la región del desierto de Thar, Rajasthan, India印度拉贾斯坦邦塔尔沙漠地区天然沙丘系统和农业生态系统的地下水补给Recarga de água subterrânea em sistemas de dunas naturais e em ecossistemas agrícolas da região do Deserto de Thar, Rajastão, Índia

Water and nutrient availability for crop production are critical issues in (semi)arid regions. Unsaturated-zone Cl tracer data and nutrient (NO3 and PO4) concentrations were used to quantify recharge rates using the Cl mass balance approach and nutrient availability in the Thar Desert, Rajasthan, India. Soil cores were collected in dune/interdune settings in the arid Thar Desert (near Jaisalmer) and in rain-fed (nonirrigated) and irrigated cropland in the semiarid desert margin (near Jaipur). Recharge rates were also simulated using unsaturated zone modeling. Recharge rates in sparsely vegetated dune/interdune settings in the Jaisalmer study area are 2.7–5.6 mm/year (2–3% of precipitation, 165 mm/year). In contrast, recharge rates in rain-fed agriculture in the Jaipur study area are 61–94 mm/year (10–16% of precipitation, 600 mm/year). Minimum recharge rates under current freshwater irrigated sites are 50–120 mm/year (8–20% of precipitation). Nitrate concentrations are low at most sites. Similarity in recharge rates based on SO4 with those based on Cl is attributed to a meteoric origin of SO4 and generally conservative chemical behavior in these sandy soils. Modeling results increased confidence in tracer-based recharge estimates. Recharge rates under rain-fed agriculture indicate that irrigation of 20–40% of cultivated land with 300 mm/year should be sustainable.