The Real Water Crisis

Soil and groundwater salinization

in Western San Joaquin Valley

Drainage-impaired land in San Joaquin Valley, Victor Miguel Ponce

Fresno -- The small towns of Mendota and Firebaugh lie along the San Joaquin River.    Dependent on construction and agricultural jobs, the towns have been suffering greatly from the recession and drought.  

The towns are surrounded by once-fertile farmland, that was reclaimed for agriculture in the 1950's and 1960's.    Much of the farmland is now fallowed, and landowners are clamoring for irrigation water to be restored.     But the land has much more serious issues than the drought    The towns lie on the edge of 400,000 acres of increasingly salt-impaired soils in Western Fresno County, that are also experiencing increasingly severe groundwater contamination.

The arid soils in the Western Fresno are derived from marine sediments and have high salt and sodium content, as well as heavy metals such as selenium and chromium.  

Irrigation water from the Delta naturally contains salts. The crops take up the water and leave salts in the soil. Additional water is added to flush out the salts in order to maintain crop productivity, but it also leaches selenium, boron, arsenic, molybdenum and other harmful minerals and salts from an ancient ocean bed in the Western San Joaquin Valley. The contaminated drainage water collects on top of the Corcoran Clay Barrier and eventually reaches the root zone of plants.

As the area has continued to be flooded with irrigation water, the water table has risen, and is now within six feet of the surface in most of the low-lying areas in the valley.    The salty groundwater is wicking up into the root zone of crops, sometimes creating a layer of salt on the soil surface. 

These lands are becoming increasingly limited in the crops they can grow, and will have to be completely retired unless some solution can be found to drain them.    A recent US Geological survey found that 48% of the irrigated cropland in Western Fresno is saline-sodic, up from 33% in 1985.

The Federal Bureau of Reclamation has looked into solving the drainage problems by creating gravel evaporation ponds, but the cost is enormous, since one acre of evaporation pond is needed for every nine acres of land.   In 2007, a proposed combination of retirement of 200,000 acres of land and construction of 2000 acres of evaporation ponds was estimated to cost 2.7 billion dollars.

Westlands has instead proposed to take responsibility for the drainage issues, in exchange for a permanent contract for approximately 1 million acre-feet of water. The water district is looking at using gravel evaporation beds instead of evaporation ponds, but the technology has never been proven to work and disposal of the salts is still problematic.  

These options do not solve the regional issues.   Meanwhile, the specter has been raised of water rights being resold for development.  In a recent deal, a Westside farmer in Kings County sold the rights to 14,000 acre feet to the Mojave Water Agency in San Bernardino county for $77 million, or $5,500 an acre foot.   

The out of district water sale could be the first of many.   A water transfer bill is currently pending in Congress that could remove many restrictions on in-district or agricultural use of CVP water.     If the hundreds of thousands of acres of low-lying land are abandoned due to salinity, and the water rights are resold to out of area development, the economic consequences for rural towns in the Valley will be severe.   There is currently no proposal to provide compensation for the economic impacts of allowing the soils to continue to deteriorate.

An even more serious consequence to these communities is the salinization of the deep groundwater in the area.   Some computer models show that salts could be percolating not just into the shallow groundwater, but into the deep aquifers.   In several decades, this could slowly make all of the groundwater in the area unsuitable for drinking or agricultural use.   It would severely impact rural towns that rely on well water not only for irrigation, but for drinking and residential use.

It is well to consider the example of Babylon, an ancient civilization which struggled with the same salinity issues millennia ago   Tablets tell of fields turning white, and crop records show increasing shifts to barley because less salt-tolerant wheat could not be grown.   Thousands of years later, 20% of the land in Iraq still cannot be farmed.

References: 

Groundwater Availability of the Central Valley Aquifer, California

See http://pubs.usgs.gov/pp/1766/

2009 California Climate Adaptation Strategy Discussion Drafthttp://www.energy.ca.gov/2009publications/CNRA-1000-2009-027/CNRA-1000-2009-027-D.PDF

Central Valley Water Resource Control Board, Salinity in the Central Valley, May 2006http://www.swrcb.ca.gov/rwqcb5/water_issues/salinity/initial_development/swrcb-02may06-ovrvw-rpt.pdf

US Department of Agriculture, Soil Survey of Fresno County,  Western Parthttp://soildatamart.nrcs.usda.gov/Manuscripts/CA653/0/fresno.pdf

Sustainability of irrigated agriculture in the San Joaquin Valley, California.   Proceedings of the National Academy of Sciences, September 5, 2005.    Gerrit Schoups,  Jan W. Hopmans et. al. http://www.pnas.org/content/102/43/15352.full

US Department of Agriculture, Soil Survey of Western Fresno County

Source: Rainbow Report

Source: Rainbow Report