Abstract:
Intensive irrigation in northwest India has led to growing concerns over the sustainability of
current and future groundwater abstraction. Environmental tracers and measurements of groundwater
residence times can help quantify the renewal processes. Results from 16 paired locations show the interquartile
ranges for residence times in shallow alluvial groundwater (8–50m deep) to be 1–50 years and significantly
less than those from deeper groundwater (76–160m deep) at 40–170 years. The widespread occurrence of
modern tracers in deep groundwater (>60% of sites had >10% modern recharge) suggests that there is low
regional aquifer anisotropy and that deep aquifers are recharged by a significant component of recent recharge
via vertical leakage. Stable isotope and noble gas results at all depths conform to modern meteoric sources
and annual average temperatures, with no evidence of significant regional recharge from canal leakage in this
study area close to the Himalayas.
