Some common questions on California water (Part II)

by Jay Lund and Josué Medellín-Azuara

This is the second installment of answers to some common questions regarding water problems in California.  Part I examined some common questions on water supplies (questions 1-5).  Part II looks more at common questions on water uses and demands.

6. Wouldn’t more agricultural water use efficiency end California’s water problems?

Irrigated crops are about 80% of human water use in California, so it is an obvious target for conservation attention.  This irrigation supports about $50 billion/year in agricultural production, about 4% of the state’s economy, with a much larger share for many poorer counties.

Water applied to crops for irrigation evapotranspires from the crop to the atmosphere, or runs off to nearby streams, or infiltrates to groundwater. (A tiny amount of water is harvested with the crop’s biomass.) The percent of irrigation water evapotranspired by the crop is often called irrigation efficiency.  Irrigation efficiency can increase with more expensive irrigation technology, such as drip irrigation, which require less water application and often improves crop yields and quality.

For most of California, increasing surface water irrigation efficiency mostly comes from reducing infiltration to groundwater needed to support agriculture and rural residents during drought. Much of current recharge in California’s Central Valley comes from irrigation. Increasing irrigation efficiency also often leads farmers to expand irrigated acreage with the “saved” water, leaving to greater losses of water to the atmosphere, and less water for downstream users and aquifer recharge.  Most promising irrigation efficiency improvement is reduces non-beneficial evaporation from soil and non-recoverable return flows.

Because improving irrigation efficiency mostly comes from reducing the amount of water available for recharge or other uses, saving real water in agriculture mostly means reducing agricultural production (crop evapotranspiration), which has real and sometimes inevitable costs to rural areas.

Grafton, R. Q. et al. (2018), “The paradox of irrigation efficiency,” Science, 24 Aug 2018.

Lund, J., E. Hanak, R. Howitt, A. Dinar, B. Gray, J. Mount, P. Moyle, B. Thompson (2011), “Taking agricultural conservation seriously,”, 15 March 2011.

7. Wouldn’t ending water subsidies for farmers save a lot of water?

The short answer is no.  Water subsidies in California are remarkably rare today.  Historically, the biggest water subsidies in California were for construction of federal (USBR and Army Corps of Engineers) reservoirs and canals.  These largely ended decades ago.  Farmers benefited from these projects with cheaper and more reliable water supplies, which increased the economic value of their lands.  Most original farmers have since sold their lands to other farmers, pocketing most of the federal subsidies in the sale price of their farmlands.  Federal expenditures today for agricultural water supplies in California are now much diminished.

State water project deliveries are now, and have almost always been, entirely funded by the project’s water users.  Some local water agencies, urban and agricultural, have benefited from state water bonds funding some of their capital projects.  It is sometimes argued that these projects would often be built anyway by local and regional water agencies.

Perhaps the biggest water subsidies are the mutual subsidies that come from the economies of scale for larger water supplies and coordinated projects.  When people work together in water, costs are lower, even without external subsidies.

A similar question is, “Would ending federal farm subsidies reduce agriculture and save water in California?”  Our suspicion is that California’s agriculture is profitable enough that ending crop subsidies might change the mix of crops, but would not greatly increase agricultural land fallowing that would reduce actual net water use.  (Also, most of the more profitable fruit, vegetable, and tree nut crops in California do not receive federal subsidies.)

Hanak, E., J. Lund, A. Dinar, B. Gray, R. Howitt, J. Mount, P. Moyle, and B. Thompson (2011), Managing California’s Water:  From Conflict to Reconciliation, Public Policy Institute of California, San Francisco, CA.

Hanak, E., B. Gray, J. Lund, D. Mitchell, C. Chappelle, A. Fahlund, K. Jessoe, J. Medellín-Azuara, D.  Misczynski, and J. Nachbaur, Paying for Water in California, Public Policy Institute of California, San Francisco, CA, March 2014

 8. Would we save a lot of water if we stopped allowing water use for exported crops? Cumulative jobs

If crops were not allowed to be exported, farmers, as businesses, would be forced to grow less profitable crops that could be sold in the US or California.  Because most irrigated crops use similar amounts of water per acre, eliminating crop exports would not save much water.

Economically, a disproportionate amount of revenue and jobs in California’s agriculture comes from exported crops (almonds) and crop-derived products (wine).  Banning crop exports would reduce the price of almonds for Californians, while greatly reducing rural employment and revenues and increasing rural poverty.

Medellin-Azuara J., J. Lund, R. Howitt. 2015. Jobs per drop irrigating California crops, CaliforniaWaterBlog, April 28, 2015.

9. If everyone dried their lawns, wouldn’t that end our water problems?

Roughly, urban water use is about 20% of human water use in California and 10% of total water supplies in California.  Landscape irrigation is about 50% of urban water use, statewide.  So, drying up all urban landscaping in California (reducing urban water use by 50%), would only make 5% more water available in California.  This would easily be enough water to support expansion of many wetlands in California, supporting waterfowl and some fishes.  Or, if reallocated to farms, drying all urban landscaping might allow expansion of agriculture by about 12% or about enough to end groundwater overdraft in the Central Valley.  It would help, but is no panacea.

Drying all urban lawns and landscaping would not nearly be enough to end all water shortages among environmental, agricultural, and other urban water users.

Drying lawns every year would also eliminate the easiest drought response available to cities.

California Department of Water Resources (2014). California Water Plan Update 2013. Volume 3: Resource Management Strategies. Department of Water Resources, Sacramento, California.

10. Wouldn’t giving up on Delta smelt free enough water for agriculture and ending groundwater overdraft?

The restrictions on Delta water exports and operations that solely support Delta smelt have only a small effect on Delta exports, even during drought years.  (The restrictions reduce water exports more in wetter years.)  Uncaptured water, and Delta outflows needed to maintain in-Delta and water export water quality is generally much higher.  Two studies came this conclusion, independently.  Most water flowing into the Delta in wetter periods flows out because it is not captured from lack of infrastructure (which is costly to expand), rather than environmental regulations.

Lost water deliveries

Gartrell G, Mount J, Hanak E, Gray B. 2017. A new approach to accounting for environmental water: insights from the Sacramento–San Joaquin Delta. Public Policy Institute of California. San Francisco, CA

Reis, G. J, Howard, J. K, & Rosenfield, J. A. (2019). “Clarifying Effects of Environmental Protections on Freshwater Flows to—and Water Exports from—the San Francisco Bay Estuary”. San Francisco Estuary and Watershed Science, 17(1)

Some larger lessons

California is often a dry place with many water users and uses, and there will be disputes over who should get how much water when.  In such an environment it is easy and popular to call for others to conserve water.  Sometimes water conservation does not make more water available, but only shifts water from one user to another or away from groundwater recharge.  Still, careful and thoughtful water conservation in all water use categories is important and will likely be increasingly useful in the future, despite its costs.

Part I link, for questions 1-5:

Jay Lund is a Professor of Civil and Environmental Engineering at the University of California, Davis.  Josué Medellín-Azuara is an Acting Associate Professor of Civil and Environmental Engineering at the University of California, Merced.

About jaylund

Professor of Civil and Environmental Engineering Director, Center for Watershed Sciences University of California - Davis
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4 Responses to Some common questions on California water (Part II)

  1. Kory says:

    “Drying lawns every year would also eliminate the easiest drought response available to cities.” Such cynicism – what about storing the water we save on irrigation (for a rainy day, so to speak)? I agree that converting lawns to whatever is regionally appropriate isn’t going to “save us,” but, agricultural transfers aside, reducing urban water use on irrigation does have benefits (reduced energy for transportation and treatment, for one example). Put it this way, if 50% of urban use is for irrigation, what does it say that the Carbad desal plant provides 9% of SDCWA’s water supply?

    “Because most irrigated crops use similar amounts of water per acre, eliminating crop exports would not save much water.” I don’t think that’s true; see, for example:

    • jaylund says:

      A bit so, but not such a bad assumption, especially because the export crops often use less water and bring higher prices.

  2. Douglas Deitch says:

    .. and regarding the SLR caused inevitable Golden Gate dams (plural for redundancy, commerce/locks, hydroelectric, gates, etc…?) as run down @
    your response, reaction, and argument pro or con is/would be what, my good engineer Professor/Dr. Lund?

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