In a July 6, 2014 op-ed for The Sacramento Bee, three prominent California water experts challenge some claims that they say are hindering the search for solutions to California’s water shortages. We reprint the commentary here with a sidebar on some of the calculations supporting the article.
By Jay Lund, Jeffrey Mount and Ellen Hanak
As the effects of the drought worsen, two persistent water myths are complicating the search for solutions. One is that environmental regulation is causing California’s water scarcity. The other is that conservation alone can bring us into balance. Each myth has different advocates. But both hinder the development of effective policies to manage one of the state’s most important natural resources.
Let’s consider the first myth, that water shortages for farms are the result of too much water being left in streams for fish and wildlife. Claims are circulating that California’s farms have lost 4 million acre-feet annually because of environmental policies, and some have even suggested that the severe, long-term declines in groundwater levels in the San Joaquin Valley are a result of environmental cutbacks.
Since the early 1990s, efforts to improve environmental conditions have indeed reduced water supply reliability, particularly for San Joaquin Valley farmers who rely on exports from the Sacramento-San Joaquin Delta. But blaming these efforts for today’s critical supply issues vastly overstates the role of environmental regulations.
By our calculations, restrictions on Delta exports, coupled with new restrictions on flows on the San Joaquin River, have cost San Joaquin Valley farmers no more than 1.5 million acre-feet per year in reduced water deliveries — a sizable amount, but far less than 4 million acre-feet. During the current drought emergency, environmental restrictions have been significantly relaxed to make more water available for farms and cities, with most of the remaining Delta outflows dedicated to keeping water in the Delta fresh enough for local farmers.
And while reduced surface water has likely accelerated groundwater overdraft in the Valley – especially since new Delta pumping restrictions in the late 2000s – the notion that environmental restrictions are the origin of overdraft is unfounded.
According to the U.S. Geological Survey, farmers in the Valley have been mining groundwater at an average annual rate of 1.5 million acre-feet per year since long before Richard Nixon signed the Endangered Species Act in 1972. Nothing seems to change this overall pattern, including construction of the State Water Project. Water demand in the San Joaquin Valley simply exceeds available supply. What’s more, the Valley’s water demands are likely increasing with the shift to permanent orchards and vineyards – now more than 40 percent of total irrigated farm acreage.
What about the second myth? Can conservation really create abundant “new” water? Of course, new technology and changing water use habits have yielded long-term declines in per capita water consumption in California, and this drought is likely to spur more reductions. New irrigation techniques and better crop varieties, along with rising commodity prices, have helped California’s agricultural industry steadily increase production and profits. Farmers have become more economically efficient in using their water.
Some claim that potential dramatic yields of more than 10 million acre-feet of new water – equivalent to 10 full Folsom Reservoirs — can be had from conservation measures that draw half from agricultural and half from urban users. But this is just not credible.
In fact, conservation does not always yield new water, because the water saved is often not wasted in the first place — it is already reused.
This is especially true in agriculture.Irrigation water that is not consumed by crops flows back into rivers or seeps into groundwater basins. Indeed, the single largest source of groundwater recharge in the Central Valley is irrigation. Studies from around the world consistently show that increased irrigation efficiency often does not decrease net water use. Indeed, these technologies often encourage farmers to plant more crops, worsening long-term declines in groundwater availability. The only way to generate reductions in water use on the scale imagined is to fallow several million acres of farmland.
In the urban environment, steady reductions in per capita water use since the early 1990s have allowed total urban use to remain steady at about 8.5 million acre-feet annually, despite the addition of 7 million new residents. Further savings — especially from more drought-tolerant landscapes — will be needed. But because about a third of urban water already gets reused — it also returns to rivers or groundwater basins — it’s simply not possible to achieve the level of new water that some have imagined.
The reality is that conservation is a valuable and necessary part of a portfolio of approaches to water supply management, but it will not produce vast quantities of new water for California.
As the late Sen. Daniel Patrick Moynihan said, “Everyone is entitled to his own opinion, but not to his own facts.” Californians need to make continued progress in managing our scarce water resources to get through this drought – and future droughts – while protecting the state’s economy, society and environment. This requires a common understanding of the causes of water scarcity, and practical, reasoned solutions — not blame games and wishful thinking.
Jay Lund is director of the UC Davis Center for Watershed Sciences and a professor of civil and environmental engineering. Jeffrey Mount and Ellen Hanak are senior fellows at PPIC.
On the numbers
By Jay Lund
Here are some of the calculations supporting the “environmental water” and water conservation impacts described in the above commentary.
Effects of environmental flow requirements on agricultural water use
Our standard here was pretty high. We looked for actual reductions in overall agricultural water use resulting from environmental flow requirements.
We have been unable to identify large reductions in urban and agricultural water use in most of California. In most areas, water use has remained about steady or increased slowly. While environmental requirements have often changed or disrupted water operations, raised operating costs or reduced expansions in water use, they usually have not caused major reductions in water delivered to end users of water.
The biggest delivery impact of environmental requirements is to users of water from the Sacramento-San Joaquin Delta. There, the U.S. Endangered Species Act has caused actual long-term reductions in water supply, mostly for agricultural water users.
To keep things simple, we looked at overall water pumping from the state and federal water projects in the Delta. The results were surprising (Table 1). The largest amount ever exported directly from the Delta was almost 6.6 million acre-feet (maf) in 2011.
Table 1: Average Annual State and Federal Exports from Delta, Excluding Major Droughts (in millions of acre-feet). Source: California Department of Water Resources Dayflow data.
|Period||Total Delta exports||Federal||State|
In the era before the last big drought and endangered species listings (1978-1988), annual Delta exports averaged 4.8 maf. After the 1988-1992 drought, when more species became listed, annual average Delta exports increased to 5.3 maf. Following the Wanger decision of 2007 on biological opinions covering listed species, Delta exports decreased to 4.7 maf/yr, on average, not counting this drought water year.
Comparing this to average Delta direct exports from 1978-1988 — after the State Water Project came on line but before most endangered species listings — the longer-term reduction in water supply due to environmental flows is only about 0.1-0.2 maf/yr.
Compared with 2007-2013 export levels, this looks like about a 0.6 maf/yr average annual reduction in Delta water exports. (The baseline for comparison is clearly important.) Agriculture bore the brunt of these reductions, and farmers likely compensated for most of it by increasing groundwater pumping in the southern Central Valley (Chou 2012).
There also appears to have been some shifts in how water has been allocated, particularly with reductions in federal deliveries to agricultural contractors south of the Delta — the result of the Central Valley Project Improvement Act in late 1992. The law dedicated a project yield of 800,000 acre-feet a year (600,000 acre-feet in dry years) for the protection of salmon and other environmental purposes, with some of the environmental flows being reused by projects downstream.
Nevertheless, Westlands Water District and smaller west-side irrigation districts have seen large reductions in their federal water allocations from the Delta. At the same time, some State Water Project contractors including irrigators in southern Central Valley have seen growing water deliveries from the Delta and farmers selling water to cities and for environmental use (Hanak and Stryjewski 2012).
Most recently, the court settlement to restore salmon runs on the San Joaquin River is likely to further reduce water supplies to some agricultural water users. Allocations for instream flows will range from about 115 thousand acre-feet (taf) a year in critically dry years to 670 taf/yr in wet years, with the “normal” year range 360 taf/yr — 470 taf/yr (State Water Resources Control Board 2013). However, much of this water is to be available for recapture by downstream water users, including irrigators south of the Delta. Water allocations for the restoration efforts have been substantially curtailed during this drought year to minimize impacts to growers.
Adding up the numbers — and allowing for some urban impacts of post-Wanger cutbacks to the Delta and some substitutions of federal water project reductions with increased State Water Project exports following the Central Valley Project Improvement Act — we estimate that agricultural water users south of the Delta experienced on average no more than a 1.5 maf/yr reduction in supplies because of environmental regulations.
This is not a trivial amount, but it is less than a 6 percent reduction for statewide agricultural water use. Many of the environmental requirements have shifted water allocations and increased costs rather than reduced net use of water.
Taking more water from the Delta would be less expensive than many alternative water supply and conservation actions. Increasing fluctuations in the amount of water available from the Delta are also a major reliability and cost concern. But did the environment ”take” this water, thereby reducing urban and agricultural water use, or just shift existing supplies from among water users? The answer seems to be all of the above.
How much “new water” does water conservation provide?
Water conservation does not always make more water available for use. Consider this example of washing a boat:
Last week I sailed from Vallejo to the Delta. While docked in Vallejo, I resisted the temptation to hose off the boat with fresh municipal water because the city is encouraging water conservation during the drought. By not washing the boat in Vallejo, about 20 gallons of fresh water became available for other urban uses rather than ending up in San Francisco Bay.
But then, while anchored off Mildred atoll, I washed the boat by heaving buckets of fresh water onto the deck. Almost all the water returned to the Delta for eventual use by farms or cities, or flowed out to San Francisco Bay. (I’m debating how much less evaporation occurred from the Delta because the surface area of my boat evaporates less than water surface area.)
Likewise, because water has further use downstream, water conservation in inland cities is less effective than water conserved in coastal cities. Switching from thirsty lawns to drought-tolerant plants frees up water for other uses.
To estimate the likely benefit of urban water conservation in California, former UC Davis graduate student Ryan Cahill and I recently examined the effect of reducing California’s per capita urban water use to levels common in Australia — some of the lowest in the world for prosperous economies with dry climates. We found it would reduce gross water use in California by about 2.1 maf/year and reduce net water use (making new water available for others) by about 1.5 maf/yr. This, again, is not a trivial amount. But it is less than 6 percent of the state’s agricultural water use.
In agriculture, most net water losses are to “evapotranspiration” – the amount of water consumed to grow crops. Almost all the excess water applied to fields already returns to recharge aquifers or supply rivers downstream where, in most cases, it is used again to grow crops or supply cities.
Improved plant breeding and farming has increased crop yields for decades, but has not greatly changed net water use per acre of agriculture. The large increases in agricultural “efficiency” often called for would mostly reduce aquifer recharge in wet years, jeopardizing water storage for dry years and not make much water available for other uses (Lund et al. 2011; Lin 2013). It is possible to reduce unproductive water losses from evaporation in fields, but only by a small amount and at a substantial management expense. Without reducing crop production — meaning fallowing land — surprisingly little net water can be saved from agriculture.
Cahill, R. and J.R. Lund, “Residential Water Conservation in Australia,” Journal of Water Resources Planning and Management, ASCE, Vol. 139, No. 1, Jan./Feb. 2013, pp. 117-121.
Chou, H., “Groundwater Overdraft in California’s Central Valley: Updated CALVIN Modeling Using Recent CVHM and C2VSIM Representations,” MS Thesis, UC Davis, 2012.
Hanak, E. and E. Stryjewski (2012) California’s Water Market, By the Numbers: Update 2012. Public Policy Institute of California, November 2012
Lin, C. (2013). “Paradox on the Plains: As water efficiency increases, so can water use. California WaterBlog, Aug. 13, 2013
Lund, J. and E. Hanak (2014) “Resistance is futile: Inevitable changes to water management in California.” California WaterBlog, Jan. 7, 2014
Lund, J., Hanak, E., Howitt, R., Dinar, A., Gray, B., Mount, J., Moyle, P., Thompson, B. (2011). “Taking agricultural conservation seriously.” California WaterBlog, March 15, 2011. (Lists references from the research literature on agricultural water use and conservation.)
State Water Resources Control Board (2013). Order Approving Change and Instream Flow Dedication (San Joaquin River), Sept. 28, 2012