Standard Article

146 Aquifer Recharge

Part 13. Groundwater

  1. John R Nimmo1,
  2. Richard W Healy2,
  3. David A Stonestrom1

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa161a

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Nimmo, J. R., Healy, R. W. and Stonestrom, D. A. 2006. Aquifer Recharge. Encyclopedia of Hydrological Sciences. 13:146.

Author Information

  1. 1

    United States Geological Survey, Menlo Park, CA, US

  2. 2

    United States Geological Survey, Denver, CO, US

Publication History

  1. Published Online: 15 APR 2006


Aquifer recharge is important both for hydrologic understanding and for effective water resource management. Temporal and spatial patterns of unsaturated-zone processes such as infiltration largely determine its magnitude. Many techniques of recharge estimation exist. Water budget methods estimate all terms in the continuity equation except recharge, which is calculated as the residual. Detailed hydrologic models based on water-budget principles can produce recharge estimates at various scales. Empirical methods relate recharge to meteorologic and geographic parameters for a specific location. Surface-water methods include stream-hydrograph analyses to estimate baseflow (groundwater discharge) at lower elevations in a watershed, which is taken to equal the recharge that has occurred at higher elevations. Subsurface methods include analysis of water-table fluctuations following transient recharge events, as well as diverse unsaturated-zone methods. The zero-flux plane method determines the recharge rate from the change in water storage beneath the zero-flux depth, a boundary between water moving upwards due to evapotranspiration and water moving downward due to gravity. Lysimeter methods use buried containers filled with vegetated soil to mimic natural conditions. Water exiting the bottom is considered to be recharge. Darcian methods for estimating flux densities use unsaturated hydraulic conductivities and potential gradients, indicating recharge rates under appropriate conditions. Chemical mass-balance methods use conservative tracers that move with recharging water. Tracer concentrations in deep unsaturated-zone water, together with tracer input rates, indicate recharge rates. Distinct chemical “markers” can indicate travel times, hence, recharge rates. Thermal methods use heat as a tracer. Moving water perturbs temperature profiles, allowing recharge estimation. Geophysical methods estimate recharge based on water-content dependence of gravitational, seismic, and electromagnetic properties of earth materials.


  • aquifer;
  • baseflow;
  • Darcy's law;
  • geophysical methods;
  • ground water;
  • hydraulic conductivity;
  • hydrograph analysis;
  • heat;
  • lysimeter;
  • models;
  • recharge;
  • remote sensing;
  • water balance;
  • saturated zone;
  • solute;
  • tracer;
  • unsaturated zone;
  • vadose zone