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Title: Importance of river water recharge to the San Joaquin Valley groundwater system

Groundwater is not a sustainable resource, unless abstraction is balanced by recharge. Identifying the sources of recharge in a groundwater basin is critical for sustainable groundwater management. In this paper, we studied the importance of river water recharge to groundwater in the south-eastern San Joaquin Valley (24,000 km 2, population 4 million). We combined dissolved noble gas concentrations, stable isotopes, tritium, and carbon-14 analyses to analyse the sources, mechanisms, and timescales of groundwater recharge. Area-representative groundwater sampling and numerical model input data enabled a stable isotope mass balance and quantitative estimates of river and local recharge. River recharge, identified by a lighter stable isotope signature, represents 47 ± 4% of modern groundwater in the San Joaquin Valley (recharged after 1950) but only 26 ± 4% of premodern groundwater (recharged before 1950). This implies that the importance of river water recharge in the San Joaquin valley has nearly doubled and is likely the result of a 40% increase in total recharge, caused by river water irrigation return flows and increased stream depletion and river recharge due to groundwater pumping. Compared with the large and long-duration capacity for water storage in the subsurface, storage of water in rivers is limited in timemore » and volume, as evidenced by cold river recharge temperatures resulting from fast infiltration and recharge. Finally, groundwater banking of seasonal surface water flows and expansion of managed aquifer recharge practices therefore appear to be a natural and promising method for increasing the resilience of the San Joaquin Valley water supply system.« less
ORCiD logo [1] ;  [2] ;  [1] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division
  2. California State Univ. (CalState), Hayward, CA (United States). Dept. of Earth & Environmental Sciences
Publication Date:
Report Number(s):
Journal ID: ISSN 0885-6087; 888241
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Hydrological Processes
Additional Journal Information:
Journal Volume: 32; Journal Issue: 9; Journal ID: ISSN 0885-6087
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE; LLNL Laboratory Directed Research and Development (LDRD) Program; California State Water Boards (United States)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1432559