Drought & laws spark interest in groundwater recharge

Your best practice | Fall 2020
California groundwater recharge
The field flooding of trees in winter represents the relatively newer (and chancier) practice of groundwater recharge.

There is recent renewed interest in groundwater recharge in California, bringing new science, institutions, markets and investments into practice.

The interest has been driven by a couple of linked factors: drought and a law change. The policy change was the adoption of a new California law requiring groundwater controls to arrest the decline of water levels in many aquifers in California. The new law, called the Sustainable Groundwater Management Act, was instigated by a recent intense drought. That drought drastically reduced the availability of water from California’s vast river water storage and delivery systems. Shallow wells went dry, especially rural community and individual water systems. Deep wells also lost production and had to be drilled deeper causing subsidence, which is the irreversible sinking of the land surface where deep, water-swollen clays get squeezed, lose their water and collapse.

These impacts prompted the California legislature to act and deliver this new law that controls groundwater use. California has had groundwater management plans for some time, but they were not enforceable. The law creates new local agencies chartered to implement controls as necessary. Avoiding the most drastic controls drives the need for more groundwater recharge.

Groundwater recharge occurs on sandy soils with deeper geology that allows for deep percolation. California’s recent renaissance in groundwater recharge is both a redeployment of what has been done in the past with a significant reinvestigation as to “where,” as well as “how.” Natural recharge continues to occur in the main rivers and streams where the coarsest materials reside. Irrigation district canals also recharge water because they often follow older stream beds that are no longer the main channel. 

Significant recent attention has been focused on restoring agricultural land recharge and better connecting the irrigation distribution facilities to the best lands for recharge. By paying for improvements for access to such lands, those who cannot recharge will likely form partnerships with those who can, creating novel markets for water trading as a result. The new information and ongoing investigations are driven to accomplish the work of replenishing our depleted groundwater and improving groundwater regionally. Most previous efforts have been implemented locally. Groundwater users who have no ability to conduct local effective recharge because their conditions are not capable are now more acutely aware of the need to work with others who can recharge in order to make a difference. If they do not participate, it is quite apparent to them that their “fair share” (California law, the “correlative right”) of groundwater under their land could be substantially less than if they work with regional neighbors who do have the right conditions for recharge.

Significant recent attention has been focused on restoring agricultural land recharge and better connecting the irrigation distribution facilities to the best lands for recharge.

Groundwater recharge has a long history in California. An early example is the Consolidated Irrigation District in central Fresno County. They have used basins like Rhodes Pond in older, sandy stream channels since the 1930s. Many agricultural water districts with sandy soils have continuously encouraged over-irrigation in wet years as well. The desire to improve groundwater recharge is also forcing water managers to look at reservoir operations. Previously, water was held as long as possible to maximize the water available for crop irrigation. In wet years that had the potential to keep storage too full resulting in flood releases. Putting it in groundwater intentionally earlier in the winter decreases the potential for loss.

Consolidated Irrigation District “Rhodes pond” — one of the oldest groundwater recharge systems in the San Joaquin Valley

All of the techniques for recharge (use of agricultural lands, basins, water delivery systems and injection wells) are being reinvestigated with new support information.

While recharge is a hot topic and it is clear that implementation will be an important tool for improving groundwater conditions in California, there is ample evidence that it may not be enough to meet the new groundwater law objectives. That means demand management strategies will also play a significant role. Stay tuned.

Sargeant J. Green is a water management specialist with the Center for Irrigation Technology and California Water Institute at California State University, Fresno. He is also associate director of the Water Resources and Policy Initiatives program for the CSU Chancellor’s office. 
Reference: Water for a thirsty land: the Consolidated Irrigation District and its canal development history. J. Randall McFarland. December 1996.

Recent information developed related to techniques for recharge:

  • Mapping of recharge soils with high infiltration rates – California Water Institute, 2009[1], Soil Agricultural Groundwater Banking index – UC Cooperative Extension, 2015[2]
  • Linking water delivery systems to agricultural lands – A “Groundwater Recharge Assessment Tool,” Sustainable Conservation, 2017[3]
  • Electromagnetic surveys to determine subsurface areas conducive to recharge – Stanford University, 2016[4]
  • Flood-MAR, a California Department of Water Resources program to enhance groundwater recharge, 2018[5]
3 http://www.groundwaterrecharge.org/
4 https://mapwater.stanford.edu/



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