The Collapse of Water Exports – Los Angeles, 1914

by Jay Lund


Collapse of Los Angeles aqueduct pipeline through Antelope Valley from a major flood in February, 1914 (3-months after the aqueduct’s official opening). LADWP historic photo archives.

“In February, 1914, the rainfall in the Mojave Desert region exceeded by nearly fifty per cent in three days the average annual precipitation.

Where the steel siphon crosses Antelope valley at the point of greatest depression, an arroyo or run-off wash indicated that fifteen feet was the extreme width of the flood stream, and the pipe was carried over the wash on concrete piers set just outside the high water lines. The February rain, however, was of the sort known as a cloud-burst, and the flood widened the wash to fifty feet, carried away the concrete piers, and the pipe sagged and broke at a circular seam. The water in the pipe escaped rapidly through the break under a head of 200 feet, and the steel pipe collapsed like an emptied fire hose for nearly two miles of its length. In some places the top of the pipe was forced in by atmospheric pressure to within a few inches of the bottom. The pipe is ten feet in diameter, and the plates are 1/4 and 5/16 of an inch thick. Many engineers pronounced the collapsed pipe a total loss, and advised that it be taken apart, the plates re-rolled and the siphon rebuilt.

The damage was repaired, however, by the simple expedient of turning the water on after the break was mended, relying on the pressure to restore the pipe to circular form. The hydraulic pressure, under gradually increasing head, restored the pipe to its original shape without breaking any of the joints or shearing the rivets, and a month after the collapse the siphon was as good as new. The total cost of repairing the siphon was only $3,000. It would have cost about $250,000 to take it apart and rebuild it” (LABPSC 1916).


LADWP historic photo archives.

Water management and policy has always faced challenges, even unexpected ones following great technical triumphs. California’s water problems have never been easy.

But sometimes challenges require only creative solutions based on fundamental insights and a willingness, occasionally driven by desperation, to venture forth and adapt.


Jay Lund is the Director of the Center for Watershed Sciences and Professor of Civil and Environmental Engineering at the University of California – Davis.

Further reading

Complete report on construction of the Los Angeles aqueduct, Los Angeles Board of Public Service Commissioners, Los Angeles, CA 1916. (pp. 20-21)

Water and Power Associates. Construction of the Los Angeles Aqueduct

LADWP historic photo archives

YouTube – Construction of the Owens Valley Project

Posted in California Water | Tagged | 1 Comment

Conservation of inland trout populations in California

by Robert Lusardi

This article originally appeared in California Trout’s The Current. For the full issue, click here.

Photo by Mike Wier.

Native fish conservation and recovery is an onerous task.  While there are many threats, hybridization has played an integral role in the demise of numerous inland trout species throughout the western United States.  Nowhere is this more evident than California where introduced rainbow trout have threatened the genetic integrity of California golden trout, Little Kern golden trout, Kern River rainbow trout, Paiute cutthroat trout, and Lahontan cutthroat trout.  Species recovery, however, is challenging.  Managers must often balance short-term goals of reversing a trend towards extinction with long-term species persistence.  These objectives rarely align, in part because they operate at different time scales, but also because threats can shift through time as a result of management intervention.  Lusardi et al. (2015) recently examined this phenomenon in the Little Kern golden trout (Oncorhynchus mykiss whitei), an endemic species to the Little Kern River watershed in the southern Sierra Nevada.  Similar to many western inland trout populations, introductions of coastal rainbow trout greatly reduced the range of Little Kern golden trout by approximately 90% with fewer than 5,000 individuals isolated in five small headwater streams by 1975 (Moyle 2002).  The primary cause of decline was hybridization with introduced rainbow trout.

In order to improve Little Kern golden trout genetics and reduce the threat of hybridization, recovery actions focused on isolating populations with instream barriers (many of which were natural), eradicating hybrid populations using piscicides such as rotenone, and re-establishing unhybridized populations using hatchery fish.  Similar strategies have been used on other California endemic inland trout such as Paiute cutthroat trout.  The strategy was largely successful in slowing the rate of hybridization, with most populations exhibiting minimal rainbow trout genetic influence.  There were, however, consequences associated with these recovery actions.  While the threat of hybridization was greatly reduced, re-introduced Little Kern golden trout populations exhibited very low levels of genetic diversity. Genetic diversity is important because it enables species to adapt to changes in their environment.  If sufficient diversity does not exist, adapting to change becomes a difficult task and the potential for extinction increases.  While resource managers were able to greatly reduce the threat of hybridization in Little Kern golden trout, a new threat of low genetic diversity emerged.


Figure 1: Conceptual model of threat evolution. Dotted lines indicate indirect effects. Positive sign indicates a positive effect or the amelioration of initial threat. Negative sign indicates a negative effect or the creation of a new threat (Lusardi et al. 2015)

In describing the conservation history of the Little Kern golden trout, Lusardi et al. (2015) introduces the term ‘threat evolution’ and defines it as fixing an initial threat (hybridization) through management action, but in so doing creating a secondary threat (low genetic diversity). A review of the literature suggests that the phenomenon has occurred in numerous other western inland trout species.  This points to an inherent difficulty in salmonid recovery.  Immediate action is often required to slow further demise, but those actions might produce new threats which could equally compromise long-term persistence.  This is why adaptive management is an important tool to assist in species recovery.  Management strategies must be flexible in their approach, understanding that different actions can elicit different responses that operate at diverse time scales.


Photo by Mike Wier.

Improving Little Kern golden trout genetic diversity will not be easy.  Defining the entire genetic landscape of the Little Kern Basin appears to be a logical first step.  Resource managers can then focus on removing remaining hybridized populations and promoting connections between isolated unhybridized populations.  In some cases, this may mean altering barriers to promote connectivity or moving fish from one population to another in an effort to improve genetic diversity.  There are risks associated with these types of management actions, but if approached cautiously and within a scientific framework, there are also potentially great benefits.  Establishing Little Kern golden trout refuge populations outside of the basin should also be considered.  Low genetic diversity and small population sizes that currently plague the Little Kern golden trout suggest that the fish is more vulnerable to random events such as disease, wildfire, drought, or further introductions of non-native fish.  Establishing refuge populations would provide insurance against the potential future loss of salmonid biodiversity.

Numerous inland trout populations are threatened by the introduction of non-native rainbow trout.  Recovery of inland trout populations is a difficult task and is, at times, uncertain.  Uncertainty, however, should not mean inaction.  New tools such as structured decision making allow managers to weigh the relative risks and benefits of particular recovery actions and identify uncertainty.  Key to all of this is understanding that the recovery of inland trout populations will take time.  Adaptive management and using the best available science to guide recovery provides the best path forward.

Dr. Lusardi is the UC Davis-California Trout Wild and Coldwater Fish Scientist.  The original article appeared in the September issue of Reviews in Fish Biology and Fisheries.

Further Reading

Lusardi RA, Stephens MR, Moyle PB, McGuire CL, and Hull JM. 2015. Threat evolution: negative feedbacks between management actions and species recovery in threatened trout (Salmonidae). Reviews in Fish Biology and Fisheries 25: 521-535.


Posted in Fish, Planning and Management | Tagged | 1 Comment

California’s Delta-Groundwater Nexus: Delta Effects of Ending Central Valley Overdraft?

By Timothy Nelson, Heidi Chou, Prudentia Zikalala, Jay Lund, Rui Hui, and Josué Medellín–Azuara

Surface water and groundwater management are often tightly linked, even when linkage is not intended or expected. This link has special importance in drier regions, such as California. A recent paper examines the economic and water management effects of ending long-term overdraft in California’s Central Valley, the state’s largest aquifer system.  These effects include changes in regional and statewide surface water diversions, groundwater pumping, groundwater recharge, water scarcity, and resulting operating and water scarcity costs.

The analysis used a hydro-economic optimization model for California’s water resource system (CALVIN) that suggests operational changes to minimize net system costs for a given set of conditions, such as ending long-term overdraft. Based on model results, ending overdraft could induce some major statewide operational changes, including significantly greater demand for Delta exports, more intensive conjunctive-use operations to increase artificial and in-lieu groundwater recharge, and greater water scarcity for Central Valley agriculture. Figure 1 summarizes these changes.


Figure 1 Average annual changes to accommodate ending groundwater overdraft of 1.2 million acre-ft in California’s Central Valley

Ending overdraft in the Central Valley increases economic demands for additional Delta exports, additional groundwater recharge, and additional water market sales, but these are not enough to prevent increased water scarcity to agriculture.

The statewide costs of ending roughly 1.2 maf/yr of groundwater overdraft in the Central Valley are probably at least $50 million per year from additional direct water shortage and additional operating costs. The costs of ending Central Valley overdraft could be much higher, perhaps comparable to the recent economic effects of drought ($1.5 billion/year) (Medellín-Azuara et al. 2015; Howitt et al. 2014).  There is, of course, some uncertainty on both the quantity of Central Valley overdraft and how agencies will manage without it.

Driven by recent state legislation to improve groundwater sustainability, ending groundwater overdraft will have statewide implications for water use and management.  In particular, these implications extend to the Sacramento–San Joaquin Delta, where ending Central Valley overdraft amplifies economic pressure to increase Delta water exports rather than reduce water exports.  California’s largest water management problems are often tied together.

Delta exports and groundwater overdraft in the southern Central Valley have a long intertwined history.  Both the federal Central Valley Project and the State Water Project were developed in part to alleviate groundwater overdraft in the southern Central Valley and improve the sustainability of the region’s agriculture.  The fundamentals of California’s geography, hydrology, and economy of water uses continue to challenge and bind the state and individual regions to balance limited water supplies.

Greater demands for Delta water exports from ending overdraft will probably further complicate potential solutions to Delta problems.  Conversely, the great and perhaps insurmountable difficulties to increasing Delta exports are likely to hinder ending groundwater overdraft in the Central Valley (and increase its costs).  While solving local and regional problems, connections to the statewide system will remain important.  Integrated modeling studies can provide useful insights for these problems, and sometimes insights for solutions.

The authors were or are affiliated with the Department of Civil and Environmental Engineering at the University of California – Davis for this work.  Many have moved on, but some have stayed behind.

Further reading

Nelson, T., H. Chou, P. Zikalala, J. Lund, R. Hui, and J. Medellín–Azuara (2016), Economic and Water Supply Effects of Ending Groundwater Overdraft in California’s Central Valley, San Francisco Estuary and Watershed Science, Volume 14, Issue 1, Article 7,

Hanak, E., J. Lund, A. Dinar, B. Gray, R. Howitt, J. Mount, P. Moyle, and B. Thompson, Managing California’s Water:  From Conflict to Reconciliation, Public Policy Institute of California, San Francisco, CA, 500 pp., February 2011.

Medellín-Azuara, J., D. MacEwan, R.E. Howitt, G. Koruakos, E.C. Dogrul, C.F. Brush, T.N. Kadir, T. Harter, F. Melton, J.R. Lund,” Hydro-economic analysis of groundwater pumping for California’s Central Valley irrigated agriculture,” Hydrogeology Journal, Vol. 23, Issue 6, pp 1205-1216, 2015.

Howitt, R.E., Medellin-Azuara, J., MacEwan, D., Lund, J.R. and Sumner, D.A. Economic Analysis of the 2014 Drought for California Agriculture. Center for Watershed Sciences, University of California, Davis, CA, 28pp., July 28, 2014.

Posted in Uncategorized | 8 Comments

Sailing the Seas of Data Discovery

by Megan Nguyen

Which display is more engaging to you? The table or the map?


Crop Economics Web Map displaying information at the hydrologic region.

This table shows the total water use of each hydrologic region in California measured in Thousand Acre Feet.

Do you remember a time when you really needed to find something in your room that you know you for certain have but can’t remember where you placed it? And so then you have to search every nook and cranny of your room by hand? That’s what searching for online data feels like.

Data is the currency of science exchange and it is everywhere. As scientists, we deal with data constantly and are either collecting our own or searching for it. Government agencies produce a wealth of data and statistics collected from sensors, gauges, or sometimes simulated by models. However, finding this information is an arduous task as it is often buried deep within a website.

The data diggers are on a quest to find information! After traversing the many links on a website, we finally uncover the coveted data chest. We open it, expecting treasures, only to find ourselves presented with a library of zip files. These files have a secret code of numbers and letters and we are left to unlock their meaning with no cipher. But we can’t give up our search here! We must carry on with our mission. After many attempts, we manage to discover a common pattern between the file names and have unlocked their mystery. We manage to scavenge through the data chest and download what we need. After we process the raw data and refine our analysis, how do we share our data riches to the world? In other words, how do we display our data in a visually appealing manner?

The most common method used to display data is in static forms such as tables, graphs, and charts. Although widely used, a list of numbers in a table is not always the best way to get a message across. Dynamic displays that include color, graphics, or an interactive component can tell a story beyond a simple table or graph. One innovative method of dynamically displaying useful information in an engaging and attractive way is the use of interactive web maps. Web maps invite the user to take action in an interactive framework and explore the data on their own terms.

Our data voyage begins with an investigation into California’s irrigated agricultural use of land and water and its gross value. This information can be found on the California Department of Water Resources website. In its most basic form, the data is a set of excel spreadsheets which contain crop statistics as measured by the California DWR. This data set is consistent and well organized across years and spatial areas, which greatly facilitates translating it into a visual form. Instead of displaying these numbers in a table, Josué Medellin-Azura, Lawrence Li, and myself at the Center for Watershed Sciences recently published online the California Crop Economics Interactive Web Map. We chose to use a web map as an engaging display and invite users to freely explore the information.


Total water use of California at the detailed analysis unit level. Low to high values range from light to dark.

With one glance, a lot can be interpreted from this web map. By combining statistical data to GIS spatial data, we can associate statistics to the location they are related to on a map. As a result, the first thing that immediately stands out is the color gradient which shows the concentration of water usage or crop area based on color intensity. For example, in the map to the left you can see that the Central Valley has the highest total water usage which, makes sense as the Valley is a major hub of agricultural activity.

There are seven variables in the map: total water use, total irrigated crop area, applied water per acre, evapotranspiration of applied water per acre, total revenue, revenue per acre, and revenue per applied water. Each variable (except revenue variables which can only be viewed for revenue regions) can be viewed for different spatial analysis units (consistent with California Water Plan Update) that include, from largest to smallest: hydrologic region, planning area, detailed analysis unit, and revenue regions. The dataset only contains data for California from the years 1998-2010, and can be expanded to include years beyond 2010 when that data becomes available.

The web map has an user friendly interface that features toggle buttons for changing the analysis unit or variable shown as well as a slider to change years. Included in the map are text summary pop ups of each region and a gradient legend. By organizing data in an easily understandable and interactive graphic, a broader audience is able to engage with information in a way that makes it more meaningful, and increases general scientific literacy.

Explore the California Crop Economics Interactive Web Map for yourself!

Megan Nguyen is a GIS researcher at the Center for Watershed Sciences. Her work and interests  revolve around a variety of topics such as drought impacts, flood mitigation, environmental policy, and education outreach.

Posted in Agriculture, Drought, Tools, Uncategorized | Tagged | 6 Comments

ENSO the Wet Season Ends (almost) – March 31, 2016

By Jay Lund

Summary of conditions

March 2016 has been unusually wet, and quite a contrast to February.  The “Godzilla” El Nino this year has been a bit “Gonzo”, but overall has brought a welcome above average precipitation for northern California, after four solid drought years.  The unevenness of the precipitation is some concern, and the depth of remaining surface and subsurface storage drawdown from the drought remains sizable.

Annual precipitation and snowpack are now about average overall for California.  The largest reservoirs in northern California are in good shape, with sizable, about average, snowpacks waiting to trickle down in spring.  Overall, total surface storage in California is about 2.7 million acre-ft below average for this time of year (improved from an 8 maf surface storage deficit in October).  Groundwater will be recharging, as it should this time of year in most places, but groundwater is likely to remain drawn down in much of the southern Central Valley.

California remains in a drought, a bit.  So far, the much-hyped El Nino has brought us largely average precipitation and snowpack.  A huge improvement over the last few years, but not an excuse to forget the lessons of the drought so far.  And who knows what next year will bring.

Here are recent highlights, with links to the California Department of Water Resources’ California Data Exchange Center (CDEC) at

Reservoir and Groundwater Storage Conditions

Major reservoirs in northern California are mostly healthy this year, but substantially emptier south of the Delta.

California’s total reservoir storage remains about 2.7 maf (about 2.7 full Folsom reservoirs) less than average for this time of year.  This is a nice improvement from being 8 maf below average in October.  Groundwater statewide will be making some recovery but will be a long way from recovering from drought in many drier areas south of the Delta.

The drought by 2015 depleted total storage in California by about 22 maf cumulatively or nearly a year’s worth of water use in agriculture.  Storage is recovering during this wet season, but still has a good bit to go, probably 12-16 maf of drought storage drawdown remains, mostly from groundwater.


Precipitation and Snowpack


Northern Sierra 8 Station Precipitation Index (inches) (tiny totals, compared to average, in yellow)

Precipitation in most of California is far superior to the last four years of drought.  But we have had some very dry months (February) and some very wet months (March and January).  Southern parts of California, south of the Delta, have had a smaller share of relative water bounty, but are in much better shape than last year.


Precipitation: – Sacramento Valley – San Joaquin Valley – Tulare Basin

ns_precip SJ_Precip tulare_precip

Concluding thought

Much better than the last four years, but still a bit of drought. A very wet March, and fairly wet December and January, has helped recover from a dry February and four years of drought. Northern California is in mostly good shape for the coming year.  More southern parts of California are more stressed, but still far better off than the previous four years. Lingering drought effects will continue.  A “Godzilla” El Nino is no guarantee of a drought-buster.

It is unclear if the next year will be a return to drought conditions, but the forecast for April so far seems mostly dry.

UC Davis’ drought seminar series videos are now available at:

Jay Lund is Director of the UC Davis Center for Watershed Sciences and Professor of Civil and Environmental Engineering at UC Davis. 

Further Reading

Paul Ullrich (Video): Drought in California: A climatological look at water in a semi-arid landscape. UC Davis School of Law and Center for Watershed Sciences Water Policy Seminar Series, January 13, 2016

Jay Lund (Video): Drought and Water Management in California. UC Davis School of Law and Center for Watershed Sciences Water Policy Seminar Series, January 6, 2016

Peter Moyle and Jay Zeigler (Video): Drought Impacts and Management for Ecosystems. UC Davis School of Law and Center for Watershed Sciences Water Policy Seminar Series, February 1, 2016

Thad Bettner and Robert Roscoe (Video): Local Responses to California’s Drought. UC Davis School of Law and Center for Watershed Sciences Water Policy Seminar Series, February 8, 2016

Posted in California Water, Drought, El Niño, Uncategorized | Tagged | 4 Comments

Water managers drop the ball on Hetch Hetchy

Hetch Hetchy Reservoir has been covered with floating black balls to reduce evaporation and protect water quality

By Nan W. Frobish

Visitors to Yosemite’s iconic Hetch Hetchy reservoir are doing a double-take. Instead of seeing the majestic backdrop of the Sierra Nevada reflected in the pristine mountain water, they are now greeted by millions of black balls that cover the surface.

After four years of record-setting drought and statewide low reservoir levels, concerns developed about evaporation losses and the drought’s effect on water quality for San Francisco’s premier water source. Plans to protect the drinking supply and reduce reservoir evaporation began in 2014, when another year of dry conditions was predicted with no end to the drought in sight.

Inspired by similar measures taken at Ivanhoe Reservoir and the Los Angeles Reservoir in Southern California, 96 million black balls were poured into Hetch Hetchy to limit sunlight penetrating the water surface. Limiting sunlight on the reservoir will reduce both evaporation and the growth of potential contaminants. Given the emergency measures required to mitigate the drought’s effects on municipal water supplies, covering the reservoir was deemed more cost-effective and easier to achieve than constructing additional treatment facilities or implementing additional water conservation actions.

Milly Pore, a spokesperson from the San Francisco PEC, explained, “We are facing long-term concerns about water quality and water supply reliability and estimated that we could save a lot of water and water quality this way.”

“It’s an eye-sore,” said Louie Swan, a recent visitor to the reservoir. “It looks like an oil slick. If this is the best we can come up with to fix water quality, we might as well take the dam down altogether.”

Average 2100 deliveries, scarcity, and scarcity cost associated with O'Shaughnessy Dam removal

Average 2100 deliveries, scarcity, and scarcity cost associated with O’Shaughnessy Dam removal. Null and Lund (2006)

Previous research suggests that dam removal may be a contentious idea whose time has come for the politically charged reservoir. Dr. Sarah Null, a former researcher at the Center for Watershed Sciences, published a study of the effects of dam removal on San Francisco’s water supply. The findings suggest that the dam could be removed with little loss to water supply, but would require additional water treatment costs.

With more and prolonged droughts predicted due to climate change, those water treatment costs are becoming a reality. As water managers and conservationists are becoming aware of the “new normal” for water quality in Hetch Hetchy, dam removal is quietly being revisited.

Hetch Hetchy Reservoir, before black balls were used to cover the water surface

Hetch Hetchy Reservoir, before being black balled

Hetch Hetchy Valley, before O'Shaughnessy Dam was constructed

Hetch Hetchy Valley, before O’Shaughnessy Dam

“It’s a sensitive issue,” said one state agency representative with knowledge of the dam removal talks. “Frankly, we never thought the barriers to dam removal would [be eliminated] by natural conditions. But now that they are, it gives dam removal advocates a stronger position.”

As awareness grows of the recent management activities, local San Francisco residents are voicing additional concerns.

“What are the balls made out of, anyway?” asked Matthew McPhee, a long-time Bay Area resident who was attracted to the city because of its environmental consciousness. “Are they BPA-free? Will sunlight degrade their material? We’re just trading one water quality issue for another.”

The materials used in each black balls are causing some Bay Area residents to question their net effect on water quality

The materials used in each black balls are causing some Bay Area residents to question their net effect on water quality. Photo credit: Irfan Khan, Los Angeles Times

As well as addressing water quality issues, the ‘shade balls’ are also a pilot project to address broader goals set by Governor Brown to reduce evaporation in all of California’s reservoirs.

“Following last year’s 25% reduction in urban water use, we considered requiring that all reservoirs be covered to further save water,” says Rex Kransrose of the Governor’s office. “This year’s wetter conditions delayed this move, but we are glad to see San Francisco leading the way on this.”

“Water supply losses due to evaporation are a major issue,” says Dr. Mollie Luna, a researcher at the Center for Watershed Sciences. “We have enough storage, it’s preventing loss that’s the issue. We’re not sure how effective these shade balls might be, but the drought has shown us that we need to proactively consider many different approaches to secure our water supply.”

Recreational activities bump up against the black ball approach. Image source:

Recreational activities bump up against the black ball approach. Photo credit: Gerd Ludwig, National Geographic

Balancing the ‘shade balls’ with recreational uses is another concern. One option is to phase out municipal supply from reservoirs with the poorest water quality, and gradually transition to solely recreational purposes. The experiment on Hetch Hetchy will provide guidance on whether the ‘shade ball’ approach can be effective for California’s extensive reservoir system.



Nan W. Frobish is an occasional contributor to the California Waterblog and director of life enrichment for the UC Davis Center for Watershed Sciences.

Further reading

A reservoir goes undercover. Los Angeles Times. June 10, 2008

Why Did L.A. Drop 96 Million ‘Shade Balls’ Into Its Water? National Geographic. August 12, 2015

Magin, G.B. and L.E. Randall (1960), Review of Literature on Evaporation Suppression, US Geological Survey, Professional Paper 272-C, U.S. Govt. Printing Office, Washington, DC.

Null SE and Lund JR. 2006. Reassembling Hetch Hetchy: Water supply without O’Shaughnessy Dam. Journal of the American Water Resources Association, Vol. 42, No. 4, pp. 395 – 408, April 2006.

Null, Sarah E., 2016. Water Supply Reliability Tradeoffs between Removing Reservoir Storage and Improving Water Conveyance in California. Journal of the American Water Resources Association (JAWRA) 1-17. DOI:10.1111/1752-1688.12391.

Posted in April Fools' Day, Uncategorized | 20 Comments

“Toilet to tap”: A potential high quality water source for California

Tap closeup with dreaping waterdrop. Water leaking, economy concBy Nathaniel Homan

Reusing water is not a new concept to many Californians. Many municipalities across California have facilities that treat wastewater to high standards, which allows it to be reused for agricultural irrigation, landscape irrigation, and industrial use. Other municipalities, such as the Orange County Water District, treat wastewater even further using advanced technologies, and use the treated wastewater to supplement drinking water supplies by injecting it into underground aquifers. In this manner, they practice indirect potable reuse, or IPR.

However, there is a third method of reusing wastewater that is not currently practiced in California: direct potable reuse, or DPR. DPR is an emerging water supply option which can provide a significant amount of drought resistant, high quality water in arid regions such as California.

In direct potable reuse, advanced treated wastewater is directly introduced into the drinking water system either upstream or downstream of a drinking water treatment plant (see Figure 1). The distinction between indirect and direct potable reuse is that IPR systems include an environmental buffer between wastewater treatment and potable reuse, whereas DPR systems do not.


Figure 1: Comparison of potable reuse schemes (Leverenz, Tchobanoglous, & Asano, 2011)

Environmental buffers are uncontrolled hydraulic systems such as a groundwater aquifers, rivers, lakes, and artificial reservoirs. Historically, environmental buffers were thought to provide additional treatment of recycled wastewater through natural environmental processes. While the concept of additional treatment may have been true in the past, as treatment technologies have matured, the quality of water produced by advanced wastewater treatment has improved. Now, treated wastewater is often of higher quality than the water in the environmental storage buffer. Rather than providing additional treatment, environmental storage buffers can actually degrade the quality of advanced treated wastewater.

Environmental buffers also increase the time between treatment of wastewater and the intake of the treated wastewater to the drinking water system. Use of a buffer allows wastewater treatment plant operators time to respond to monitoring results and prevent water that does not meet treatment standards from entering the potable water system. Some DPR projects include an engineered storage buffer to provide additional residence time for the treated wastewater.

In many situations DPR is a less costly and more efficient reuse scheme than IPR. Many communities may not have access to a large surface reservoir to use as an environmental buffer, or if there is one, the treated wastewater may have to be pumped long distances to reach the reservoir. In IPR systems that use a groundwater aquifer as an environmental buffer, the treated wastewater must be injected underground and later pumped back out. This two-stage process consumes energy and requires the construction of injection wells. For many communities, DPR is a more feasible and cost effective water management strategy.

One such community is Windhoek, Namibia, where DPR has been practiced for over 40 years. Windhoek is located in one of the most arid regions of the world, and it relies on the New Goreangab Water Reclamation Plant to treat wastewater and provide nearly a quarter of its 15 million gallon per day demand for water. More recently, several municipalities in the United States have implemented DPR. The city of Big Springs, Texas, Wichita Falls, Texas, and Cloudcroft, New Mexico, have all implemented DPR projects, while other cities, such as El Paso, Texas, have DPR projects planned in their future. So far, all of the DPR projects in the U.S blend the advanced treated water with raw water before passing the blended water through a conventional drinking water treatment plant. The New Goreangab plant is the only DPR project in the world which introduces the advanced treated water directly into the potable distribution system.

There are many benefits to implementing DPR in California and other arid regions:

  • DPR can increase the amount of available water in California by reusing wastewater that would otherwise be discharged to the ocean. The amount of additional water recoverable in this manner is estimated at 1.2 million acre feet per year – more than the entire storage capacity of Folsom Lake.
  • DPR can increase water supply reliability, as wastewater is not as subject to seasonal and annual variations as other water sources.
  • DPR can increase the quality of drinking water. Because the effluent produced by DPR is of such high quality, if blended with the traditional source water ahead of a drinking water treatment plant, it can improve the quality of drinking water distributed to users.
  • DPR can reduce energy consumption by providing a local source of water for municipalities. A large portion of the cost of water in arid regions comes from the energy required to transport it long distances. While the treatment technologies used for DPR are energy intensive, in areas such as Southern California, the energy required to produce water with DPR is less than that required to transport water from the State Water Project to users (Figure 2).

Figure 2: Power required to supply water to Southern California. It is assumed that power consumption for supply and conveyance of DPR will be close to zero. Adapted from Shroeder et al. (2012).

Many who are opposed to the concept of DPR label it as “toilet to tap,” or “drinking wastewater.” There are several reasons why the perception of DPR as “drinking wastewater” is misleading. First, the treatment technologies used to treat water for IPR and DPR projects produces an effluent which is typically of higher quality than that of the drinking water source (whether groundwater or surface water) for a given municipality. Second, many large municipal areas that would benefit most from DPR projects, such as Los Angeles County, have source water which has already been used by upstream users several times before it reaches the intake to their drinking water treatment plant. In essence, Los Angeles residents are unknowingly practicing “toilet to tap,” but without the careful engineering and safety measures that a real DPR project would incorporate.

While DPR is not yet legal in California, authorities in California have begun investigating DPR as a legitimate water reuse strategy. The California Water Code section 13563 mandates that the State Water Resources Control Board report on the feasibility of developing criteria for DPR by the end of 2016. To accomplish this goal, the SWRCB established an expert advisory committee to hold hearings and gather data in 2014. Progress of the committee can be found here. While legalization of DPR in California is still a ways off, many speculate that it is inevitable.  The acceptance of DPR in Texas and New Mexico, California’s search for new water sources in the current drought, and California’s push towards sustainable technologies are all factors which indicate that DPR will have a future in California.

Nathaniel Homan is earning his Masters degree in Environmental Engineering at UC Davis. He is working with Dr. Peter Green and Dr. Thomas Young to minimize waste from strong base anion exchange systems used to remove hexavalent chromium from drinking water.

Further Reading

Crook, J. (2010). “Regulatory Aspects of Direct Potable Reuse in California.” National Water Research Institute.

Du Pisani, P. L. (2006). “Direct reclamation of potable water at Windhoek’s Goreangab reclamation plant.” Desalination, 188(1-3), 79-88.

Gerrity, D., Pecson, B., Trussell, R. S., and Trussell, R. R. (2013). “Potable reuse treatment trains throughout the world.” Journal of Water Supply Research and Technology-Aqua, 62(6), 321-338.

Harris-Lovett, S. R., Binz, C., Sedlak, D. L., Kiparsky, M., and Truffer, B. (2015). “Beyond User Acceptance: A Legitimacy Framework for Potable Water Reuse in California.” Environmental Science & Technology, 49(13), 7552-7561.

Leverenz, H. L., Tchobanoglous, G., and Asano, T. (2011). “Direct potable reuse: a future imperative.” Journal of Water Reuse and Desalination, 1(1), 2-10.

Shroeder, E., Tchobanoglous, G., Leverenz, H. L., and Asano, T. (2012). “Direct Potable Reuse: Benefits for Public Water Supplies, Agriculture, the Environment, and Energy Conservation.” National Water Research Institute.

Tchobanoglous, G., Cotruvo, J., Crook, J., McDonald, E., Olivieri, A., Salveson, A., and Trussell, S. R. (2015). “Framework for Direct Potable Reuse.” J. J. Mosher, and G. M. Vartanian, eds., WateReuse Research Foundation.

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Floods, farms, fowl, and fish: a confluence of successful management

By Eric Holmes


Figure 1: Map of the Yolo Bypass, courtesy of Amber Manfree.

The floodplain smorgasbord is open! Wrapping up a successful fifth season, the Knaggs Nigiri  project, partnered with California Trout and the California Department of Water Resources, places fall run juvenile Chinook salmon in inundated rice fields during a six week period in February and early March, the non-rice-growing season.  The project has implications for improving the condition of the fish and the chances of survival by giving them access to floodplain habitat.

Historically, large areas of floodplain habitat in the Central Valley were available to salmon during the winter and spring months.  Regulation of river flows combined with alteration of river channel geometry by construction of levees and channelization have vastly reduced the amount of floodplain habitat.  California’s water infrastructure is designed for flood control and water supply during the dry summer months, but has inadvertently cut off a valuable habitat for rearing juvenile salmon.

How do we reconcile these seemingly competing interests?  The answer is simple: use our existing infrastructure, with some minor modifications, to create “surrogate” floodplains in rice fields during the non-growing season.


Figure 2: Zooplankton from the Nigiri project fields at Knaggs Ranch. Photos by Miranda Tilcock.

These surrogate floodplains serve as engines of productivity when the water is spread out by increasing the solar influx and driving production of a robust food web.  Fish are provided a rich diet of large zooplankton (figure 2).  At times the water is so full of large zooplankton that the fish appear to be swimming in a “Zoop-Soup.”  The fish respond by gaining weight and length at rates that far surpass growth rates of fish confined to the channelized river.

Eventually, modification of our existing infrastructure includes plans for an operable structure in Fremont Weir, which will allow salmon and river water access to the productive habitats of the Yolo Bypass even at relatively low flows.  Modified operable weirs in the Bypass itself will allow water to be impounded, providing floodplain habitat to wild-origin salmon migrating out to the ocean.  This impoundment will allow for robust floodplain food webs to establish, giving these fish access to better food resources than in the main river.  Access to the Yolo Bypass also has the potential to give the juvenile salmon a better migration corridor and a more direct route to the Pacific Ocean.  The modified system will be capable of providing floodplain habitat during drought conditions


Figure 3: Comparison of juvenile salmon, one confined to the river (top) and one with access to a surrogate floodplain for 3 weeks (bottom). Otholith (ear bone) analysis showed that the two fish in the photo are only 4 days difference in age. Photo by Carson Jeffres.

when it can have the most profound impact.

Reconciling our needs for water supply, agricultural food production, and flood control with the needs of fish and other ecological needs for birds is not impossible.  With some creative thinking and engineering modifications to our existing infrastructure we will be able to have a productive system that takes into account floods, farms, feathers, and fish!

Eric Holmes is researcher at the Center for Watershed Sciences. His work focuses on salmonid restoration and research projects in California’s complex ecosystems.

Further reading

Ryan Sabalow. “Salmon Experiment Gets New Twist in Yolo Bypass.” Sacramento Bee. Feb. 19, 2016.

“Project Nigiri Celebrates Five Years on the Floodplain.” UC Davis Center for Watershed Sciences.

“A Sweet Spot for Farms and Fish on a Floodplain.” California Water Blog.

“Reconciling Fish and Fowl with Floods and Farming.” California Water Blog.

“Innovations in Floodplain Modeling a Test Drive on the Yolo Bypass.” California Water Blog.

Posted in Uncategorized | 4 Comments

Using Game Theory To Encourage Cooperation in Levee System Planning

Delta Island Flooding

A fragile levee system threatens to flood Delta islands. Credit: USACE, Sacramento District

By Rui Hui, Jay Lund and Kaveh Madani

Levees protect land from floods, but not perfectly. Different levees on a river often are controlled by different agencies or groups. A landowner on one riverbank sees the levee system differently from a landowner on the opposite bank or downstream. Each landowner, or elected levee board, is likely to make levee planning decisions considering only local benefits and costs, and not those to other levee districts. Collaborating with the other levee owners might provide system-wide benefits, perhaps sometimes sacrificing a little local benefit for larger gains elsewhere.

Our study, recently published in Water Resources Research, applies game theory to this levee system problem with risk-based analysis of individual and collaborative levee decisions. As expected, it finds that collaborative planning can be economically best for the overall system. But, collaboration among many levee authorities often is impractical without more centralized authority or appropriate compensation to some local areas. Rational and self-interested landowners on opposite riversides can be myopic and independently optimize their own levees, resulting in a less efficient system (a “tragedy of commons”). Game theory can provide solutions to encourage cooperation.

Flood protection with levees

Levees can increase channel capacity to protect adjacent areas from floods, but they can fail by overtopping and other causes (Figure 1). Flood risk to economic activity is the likelihood of flooding times the magnitude of losses, and usually is measured by economic impacts. Levees decrease, but cannot eliminate the likelihood of flooding and flood risk.

Alternative levee plans distribute flood risks differently. Flooding in a leveed river system depends largely on levee heights. A symmetric levee system has identical levees (and failure probabilities) on opposite riversides (Figure 2(a)), while an asymmetric levee system has a lower levee more likely to fail (Levee 1 in Figure 2(b), Levee 2 in Figure 2(c)). Total flood risk could be lowered by transferring risk from a high-cost urban side to a lower-valued rural side with a higher urban levee, which can increase rural costs. So better system-wide solutions are not necessarily acceptable for all stakeholders, and compensation might be required. Various transaction costs and legal and political barriers often prevent such compensation.


Figure 2. Profile view of (a) symmetric levees with the same height, (b) asymmetric levees with lower Levee1, and (c) asymmetric levees with lower Levee2

Historic non-cooperation in levee systems

In flood-prone river basins, individual landholders sometimes lack incentives to cooperate in levee planning with other landholders upstream, downstream, or across the river. Historically, non-cooperation often causes damaging outcomes and conflicts.

In California, levees have been used since the mid-1800s. From 1867 to 1880, levee districts along the Sacramento River raced one another to build higher levees on each riverside. Flood-prone landholders raised their levees to force floodwater onto their neighbors. The resulting escalation of levees in the Sacramento Valley became ineffective and economically inefficient, and ultimately led to violence as it became less expensive to demolish the opposing levee than to strengthen one’s own (Kelley 1989).

Similar levee battles have occurred elsewhere. During a major flood, flood risk transfer through lower levees also can occur by breaching the levee on the lower-valued side or raising the levee on the opposite riverside. Such a “levee battle” happened in the Mississippi floodplain during the post-Civil War boom near New Orleans. Due to many breaks in adjoining areas (Plaquemines Parish), rumors gradually arose that levees were purposefully weakened to save more valuable city property on the opposite river bank. A worse unexpected situation appeared after the 1849 flood on the Mississippi River that broke the levee at River Ridge, where uptown residents thought of strengthening the levee on their side, but those living on the opposite side threatened to prevent this by armed force.

Game theory analysis

Game theory, which examines how independent and self-interested individuals interact, can help in analyzing each landholder’s levee strategy. Non-cooperative game theory helps examine short-sighted decision-making and potential ways to guarantee a better system-wide solution. Each landholder would decide its own levee height, without considering the system-wide economic costs and impacts on others. Payoffs for game outcomes are the total average annual cost for each landholder, including average annual damage and annualized construction cost. These payoffs of individual decisions drive decisions and individual strategy.

An example illustrates game theory application to levee system planning for various institutional conditions. Both riversides are assumed rural areas for the symmetric river channel system, while Riverside 1 is rural and Riverside 2 is urban for the asymmetric system.

Table 1 summarizes different institutional and flood damage cases and results.


The system-wide least-cost plan has the minimum total of levee construction cost and overall average flood damage. However, without interference (e.g. authority or compensation) to support collaboration, economically inefficient plans are likely (a “tragedy of commons”). A rational landholder may have no equilibrium best strategy, get stuck in cycling best response decisions (Figure 3) or accept inferior converged stable heights. A farsighted landholder who foresees inferior end results may take the “strategic loss” to reduce conflict and attain better long-term benefits. A system-wide decision-maker/regulator that understands the effects of short-sightedness can design mechanisms to create an overlap between stability and optimality.


Figure 3. Best response (BR) curves of levee heights and changing trends for each landowner in response to the other’s previous height decision, in the multiple-shot leveed river system planning where decisions are reversible

A cooperative game can determine how to allocate the benefit from cooperation, where appropriate compensation or authority can incentivize or force collaboration among players. Institutions and compensation schemes should give all parties the greatest support for joining a grand coalition supporting the best overall solution.

By examining game outcomes representing different institutional arrangements, decision-makers, funders, and regulators can better assess how to lead and organize river system plans for better and more stable overall outcomes, which usually require cooperation.

Dr. Rui Hui is an analyst in the Program Management Office in California ISO and recently completed her dissertation on levee system risk analysis and game theory.  Jay Lund is a Professor of Civil and Environmental Engineering at the University of California – Davis.  Kaveh Madani is a Senior Lecturer in Environmental Policy at Imperial College, London.

Further reading

Hui, R., J. R. Lund, and K. Madani (2015), Game theory and risk-based leveed river system planning with noncooperation, Water Resour. Res., 51, doi:10.1002/2015WR017707.

Barry, J. M. (1997). Rising tide: The great Mississippi flood of 1927 and how it changed America. Simon and Schuster. TOUCHSTONE, Rockefeller Center, 1230 Avenue of the Americas, New York, NY 10020.

Croghan, L. (2013). Economic Model for Optimal Flood Risk Transfer. Master’s Thesis. Civil and Environmental Engineering Department, UC Davis.

Gordon, H. S. (1954). The Economic Theory of a Common-Property Resource: The Fishery. Journal of Political Economy, 62, 124-142

Hanak, E., Lund, J., Dinar, A., Gray, B., Howitt, R., Mount, J., Moyle, P., & Thompson, B. (2011). Managing California’s water: From conflict to reconciliation. Public Policy Instit. of CA.

Kelley, R. (1989). Battling the Inland Sea: Floods, Public Policy and the Sacramento River. Univ. of Cal. Press: Berkeley, CA.

Madani, K. (2010). Game theory and water resources. Journal of Hydrology, 381(3), 225-238.

Madani, K., & Hipel, K. W. (2012). Non-cooperative stability definitions for strategic analysis of generic water resources conflicts. Water Resources Management, 25(8), 1949-1977.

Pinter, N., Huthoff, F., Dierauer, J., Remo, J. W., & Damptz, A. (2016). Modeling residual flood risk behind levees, Upper Mississippi River, USA. Environmental Science & Policy, 58, 131-140.

Read, L., Madani, K., & Inanloo, B. (2014). Optimality versus stability in water resource allocation. Journal of environmental management, 133, 343-354.

Posted in Planning and Management, Uncategorized | Tagged , , , , | 1 Comment

Let people pay what water is worth – Sell your conserved water


By Jay Lund

During dry years, water becomes scarcer, and, economically, people should pay more for it. But most urban residents do not pay directly for water scarcity. We only pay the financial cost of providing water through pipes, pumping, treatment plants, and reservoirs. We do not pay for the lost value that water would have had for environmental or agricultural uses outside our communities or the value of that water to other water users in our community.

These scarcity costs are real and including scarcity costs in water rates would appropriately increase incentives for water conservation. But Proposition 218, enacted by the voters in 1996 as an amendment to California’s Constitution, bars retail water agencies from charging water rates that exceed their financial cost of providing water service to each parcel within their service area. Proposition 218 also makes it difficult for retail water agencies to adopt conservation or lifeline rate structures.

One idea to improve conservation incentives for urban water users, consistent with Proposition 218, is to have a two-part water bill. The first part of the bill would cover the financial cost of water service (pipes, pumping, treatment, water acquisition, and other utility operations), and the second part would include the scarcity value of water used.

The water scarcity (second) part of the bill could be set using an internal water market. Here, each customer could have a fixed share of the water available to the community or water utility, which could be sold or bought by each customer depending on their amount of water conservation. The share could be set by any of various methods. This approach can provide equity, incentives for conservation, and flexibility to accommodate the many different types of households and customers in urban areas. You are paid if you use less than your share and pay more if you use more than your share.

This is illustrated in an example monthly bill below.


Explaining your new water bill

With your new water bill, you pay more to use more, depending on the scarcity of water, and pay less when you use less.

Each billing period, each customer has a share of the community’s available water. If you use more than your share, you must purchase additional water conserved by others at a market rate. If you use less than your share, you can sell your water for a rebate on your bill or donate it to environmental or other charitable causes. (Some people conserve for money, and some conserve for the environment or could conserve for charity.)


Your bill has two parts. The first part of the bill is your share of the cost of water utility operations (piping, pumping, water treatment, and acquiring the community’s water supply). This utility financial cost must comply with the provisions of Proposition 218. The second part of the bill is for water you buy or sell from others’ shares of the community’s resource, including revenues you made from sharing your lower water use with others in the community.

Benefits and Challenges

This approach has some desirable features:

  • Encourages water conservation. People receive direct credit for conservation. Conserving more than their share allows them to dedicate conserved use to environmental or other purposes, or this conserved water can be sold, perhaps to finance the customer’s water conservation activities, such as landscaping or plumbing improvements.
  • Conservation incentives increase with greater water scarcity. In places and times when water is scarce, water prices rise automatically, without need for additional rate hearings.
  • Flexibility to use more water if customers pay for it, and incentives to use less. If someone values water so much, probably we should allow them to buy additional water from willing sellers (conservers) from their shares. Given the diversity of urban users and uses, there is economic and social value in such flexibility.
  • Pricing includes opportunity cost, and not just utility financial cost. The customer’s cost of water now includes its opportunity cost of the water to customers and can better include some of the opportunity cost of water use to the environmental.
  • Proposition 218 compliance. Although it certainly would be challenged in court, inclusion of a water scarcity charge should comply with Proposition 218 for one of two reasons.
    1. First, if the purpose of Proposition 218 is to regulate both financial and economic charges for service, the scarcity part of the bill represents the economic (as opposed to financial) cost of serving water to a parcel arising from the additional cost that parcel’s water use imposes on other water users (in the form of additional scarcity costs). This scarcity cost would be appropriately set by the internal water market among customers.
    2. Second, if the purpose of Proposition 218 is to regulate only financial charges by the water utility, the scarcity charge is not a charge for the utility’s financial cost of retail water service to each parcel and is not paid to the utility, but to other customers – the utility is only the accountant and market steward for the scarcity charge. Rather, the scarcity charge assigns to each customer a share of the water available to the retail agency for distribution and use each year or billing period, which each customer may dispose of however the customer chooses. If the customer uses the water, he or she must pay the cost of that additional water service financially to the utility and to other customers in terms of scarcity. If the customer chooses to sell the water, then he or she is paid for the conservation and sale by other customers.
  • Water utility and customers learn customers’ actual willingness to pay for additional water. If acquiring additional water costs more than what customers are willing to pay, then perhaps expansion is a less attractive than the remaining scarcity cost to customers. In a dry place like California, some scarcity is economical and good. The cost of eliminating all scarcity is likely to exceed its value.   This value information supports better balance and integration across the portfolio of water supply and demand management actions.
  • Social equity. Social equity is enhanced by this water billing system, as each household has a share of community water use, which it can sell if it conserves sufficiently. Also, larger water users which often drive water capacity expansions would pay more for any expansion costs. (Some care might be needed to discourage desperate residents from selling their shares of water availability in perpetuity for some small capitalized sum.)
  • Ability to dedicate conserved water to the environment. Customers can directly dedicate their conserved water to the environment, rather than having this water become available for other purposes. This might require a formal contract whereby the utility water right or contract holder sells or transfers this water nominally to an environmental agent.

A main challenge is that this is a new approach, making it hard for many to understand. Another challenge would be selecting a method of allocating shares of a community’s available water. Allocations could be similar to the “water budget” rates common in some California districts, allocated equally among all service connections, by a proportion of previous water use, or any other means. Allocation of annual amounts across monthly or seasonal billing periods and among customer classes are some other community implementation decisions. Any means would bring similar conservation incentives, but perform differently in terms of social equity. Allowing customers to “bank” some conserved water from month to month might be useful. Soliciting customers’ selling prices for conserved water also is a challenge, perhaps with a default pricing policy set by the utility.  There would be  many implementation issues, but the idea seems worth considering and some are already considering it.

Financial incentives to conserve water that provide market information to customers and utilities might be especially useful in moving beyond plumbing and building codes for urban conservation to making behavioral changes among diverse urban customers.  Such incentives and willingness to pay information also would aid integration of supply and demand management decisions across sectors and uses.

Jay Lund is Director of the Center for Watershed Sciences and Professor of Civil and Environmental Engineering at the University of California – Davis.

Further readings

Baerenklau, K.A., K.A. Schwabe and A. Dinar. 2014. “Allocation-Based Water Pricing Promotes Conservation while Keeping User Costs Low.” Agricultural and Resource Economics Update 17(6): Jul/Aug.

Baerenklau, K.A., K.A. Schwabe, and A. Dinar. 2014. “Residential Water Demand Effect of Increasing Block Rate Water Budgets.” Land Economics 90(4): 683-699.

Gray, B., D. Misczynski, E. Hanak, A. Fahlund, J. Lund, D. Mitchell, and J. Nachbau, “Paying for Water in California: The Legal Framework,” Hastings Law Journal, Vol. 65, pp. 1603-1663, 2014.

Hanak, E., B. Gray, J. Lund, D. Mitchell, C. Chappelle, A. Fahland, K. Jessoe, J. Medellin-Azuara, D. Misczynski, J. Nachbaur, and R. Suddeth, Paying for Water in California, Public Policy Institute of California, San Francisco, CA, 78 pp., March 2014.

Lund, J.R. and R.U. Reed, “Drought Water Rationing and Transferable Rations,” Journal of Water Resources Planning and Management, ASCE, Vol. 31, No. 6, pp. 429-437, November 1995.

Lund J. “New environmentalism needed for California water“. CaliforniaWaterBlog. Dec. 9, 2014

Lund J. “Water conservation for the birds “. CaliforniaWaterBlog. October 6, 2015

Muelrath, D. (2015), “Enabling Customers to Buy and Sell Conserved Water”, Powerpoint presentation, Valley of the Moon Water District, Water Smart Innovations conference, October.

Schwabe, K.A., K.A. Baerenklau and A. Dinar. 2014. “Coping with Water Scarcity.” Policy Matters 6(1).

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