Authors: Saïd Majdi, Thomas Manaugh
Systems thinking leads to a plan to keep Hoover Dam as viable source of clean water and energy.
Hoover Dam, built during the Great Depression, should be preserved as (a) a powerful and lasting historic symbol of resilience and determination of Americans and (b) a sustainable source of clean hydroelectric power and water. Unfortunately, Hoover Dam’s capacity to generate and transmit electricity has been reduced because drought has reduced water that is available to turn its turbines.
To bolster the viability of the Hoover Dam system as a source of clean energy and water and to tap underutilized transmission capacity, we propose installing a floating solar photovoltaic (PV) farm on Lake Mead, Hoover Dam’s reservoir, to generate electric power. These floating platforms, covered with solar PV panels, would provide shade for lake water, thus reducing loss of water from evaporation. Less evaporation means more water available both for generating electricity and for meeting water demand from consumers and businesses in Arizona, California, and Nevada.
Energy from this floating solar PV farm could be used for a large variety of purposes. We propose to use this green and renewable power source to power desalination plants on the California Coast to support a water exchange program between Nevada and California. Thus, this proposed project uses systems thinking to identify novel and cooperative ways to put underutilized resources to work to produce clean energy and water.
What actions do you propose?
In proposing actions to deal with water scarcity in the Western United States, we recognize Hoover Dam as a nexus of water and energy, and an historic icon that testifies to the industry, bold vision, and resilience of Americans. It was miraculously constructed in a few short years during the middle of the Great Depression. Americans are deeply proud of what Hoover Dam represents.
However, if Hoover Dam were not already built, would it be a project that would get approved for construction today? Unfortunately, the answer is probably “No” because water flow in the Colorado River is too low to allow the dam to sustain full capacity of hydroelectric power generation. It now operates at far below its expected output if Lake Mead were at full height.
If Lake Mead were at full height, that would allow Hoover Dam’s generators to generate closer to their “nameplate” (i.e., maximum sustainable) generation capacity. Operating 24 hours per day and 365 days per year, the generators could theoretically produce 18.2 terawatt-hours (TWh) annually. The closest to that theoretical maximum occurred in 1984 when 10.4 TWh were generated. An average in recent years has been 4.2 TWh.  Expected generation in 2015 is 3.7 TWh. 
If the height of Lake Mead continues to fall, output lower than 3.7 TWh can be predicted in coming years. There is no doubt that if electricity could be generated at the 1984 output level, when Lake Mead was at a high level, the clean and inexpensive electricity generated would be more than welcome on the electricity market. On the other hand, great disruption would occur if Lake Mead were to fall to such a low level that no electricity could be generated. One observer commented: “Hoover goes nowhere without taking down a significant piece of the economic and electric portfolio of California.” Similar sentiments have been expressed by observers in Arizona and Nevada. 
Here, systems thinking is used to design a large, bold, and novel proposal for actions to help Hoover Dam continue to serve its historic function as an important source of both clean electricity and clean water for consumers in California, Arizona, and Nevada.
Water scarcity has become ever more dire in Southwestern United States and has led to the following actions:
- Restrictions on water availability to consumers in California. 
- A groundwater pumping plan in Nevada that is advancing toward realization in spite of opposition from environmental activists. 
- Construction of new desalination facilities to make potable water from seawater taken from the Pacific Ocean. [6, 7]
- Funding by the U.S. Bureau of Reclamation, Arizona, California, and Nevada of pilot studies aimed at identifying new ways to conserve water in the Colorado River system. 
The authors recently traveled to Nevada and California to talk to water officials and to citizens concerned about water scarcity in the southwest.  The impetus for that trip was a proposal developed by the authors into a 2014 MIT Climate CoLab entry, entitled “Stop Groundwater Plan – Save $8 Billion.”  The 2014 entry, for which the authors received an award, proposed a plan called the Desalination Plan. Under that plan, California would accept locally produced desalinated water from the Pacific Ocean in exchange for foregoing some of its allotment of water from the Colorado River. That water from California’s allotment would be directed to Las Vegas. In exchange, Nevada pays for the desalination plant and the solar power plant to power it—all at a price tag less than half the price tag of the Groundwater Plan.
The Groundwater Plan  was adopted by the Southern Nevada Water Authority (SNWA). It calls for constructing the largest groundwater pumping project in U.S. history. It will consist of pumping groundwater from the eastern region of Nevada and transporting it to Las Vegas over sections of pipeline that total 263 miles in length. Experts and concerned civic groups believe that the Groundwater Plan, if implemented, will be environmentally destructive and costly at a price tag that could exceed $15 Billion, according to some estimates.
It makes basic sense for California to accept desalinated water from a plant on its Pacific Ocean coast instead of Colorado River water that must be transported hundreds of miles from a location on the border between Arizona and California. The desalination approach would make California’s water supply more secure and virtually increase its allotment from the Colorado River—transporting water over long distances requires energy and results in loss from evaporation (up to 20%), leakage and seepage. Moreover, desalination offers many direct and indirect benefits, including better quality water and reduced demand on groundwater resources. 
Based on that prior work, this proposal is designed to support and facilitate efforts to make clean water and energy available to citizens of western states in a way that (a) is cost-effective because it makes good use of underutilized resources, (b) is environmentally responsible, and (c) helps to avoid unintended consequences that typically result from solutions that increase supply to satisfy increasing demand. Specifically, we propose the following:
- Solar photovoltaic (PV) panel arrays on floating platforms in Lake Mead will generate and deliver electricity through Hoover Dam’s currently underutilized transmission network and to the grid that services Southern California. That same grid is used to deliver electricity needed by desalination plants on the California Coast. Thus, solar power from Lake Mead will benefit California by providing clean power that is used to produce clean water. Mounting solar panels on floating platforms is a proven technology that is being used in Japan and Brazil. [13, 14]
- Shade from the installed solar panels will decrease evaporation, thus conserving water in the Colorado River system. Southern Nevada is dependent on the Colorado River for 90% of its potable water, so it especially will benefit from any conservation effort. All the three states of the Colorado River Lower Basin (Arizona, Nevada and California) will benefit if water is conserved in Lake Mead. If water in Lake Mead falls below a certain level, all three states will suffer a decrease in their water allotments. 
- Water in Lake Mead will be available to keep solar panels at an optimal temperature for converting solar radiation to electricity in an efficient manner.
Floating Solar PV Structure
Figure 1 depicts an installed floating solar PV farm in Kato City, Hyogo Prefecture, Japan. At least two other floating solar PV farms have been installed in Japan with more floating solar PV farms in the planning phase.
Figure 2 shows a schematic diagram of floating modules with specification provided by the French manufacturer Ciel & Terre. The floating modules are connected to form a platform for mounting solar PV panels. The connected floating modules are engineered to withstand extreme physical stress, including typhoon conditions with winds up to 118 mph. They are made of high-density polyethylene (HDPE). This material is 100% recyclable, UV and corrosion resistant, and drinking-water compliant.
For safety reasons, the installation will include a security cordon and standard maritime traffic signage to alert and keep away nearby boat traffic.
Breaking the Vicious Cycle
Bringing clean water to the end user requires energy for extraction, conveyance, and treatment. Similarly, converting conventional energy into electric power results in water utilization and water consumption. So, an increase in water supply results in an increase in energy demand, which results in an increase in water demand, which in turn results in increased water scarcity, further leading to the need of greater water supply. This interrelationship between water and energy is illustrated in Figure 3, which depicts a causal loop diagram. When reading the diagram, keep in mind that an arrow links a cause to its resulting effect. A plus sign (+) on the arrow means that the cause and effect move in the same direction; i.e., an increase in the cause results in an increase in the effect and a decrease in the cause results in a decrease in the effect. A minus (-) sign on the arrow means the cause and effect move in opposite directions; i.e., an increase in the cause results in a decrease in the effect and a decrease in the cause results in an increase in the effect. While increasing water supply seems to fix the problem of water scarcity (small, balancing (B) feedback loop), there is an unintended consequence that results in increased water scarcity (large, reinforcing (R) feedback loop). In system dynamics, this phenomenon is typically called “fixes that can backfire”. Our proposal breaks the reinforcing feedback loop by relying on a source of energy that requires no water, or minimal amounts of water, for its conversion into electric power. Thus, systems thinking leads to a solution that solves the problem of water scarcity without causing unintended negative consequences.
Who will take these actions?
Lake Mead is within the boundaries of the Lake Mead National Recreation Area, which is federal land under the jurisdiction of the National Park Service (NPS) of the U.S. Department of the Interior. The NPS would therefore be the governmental entity to make decisions and conduct the National Environmental Policy Act (NEPA) analysis (environmental impact statements, etc.) that would be necessary to site the floating solar PV farm. The Department of the Interior and its Bureau of Reclamation have a long history of efforts to deliver both water and energy to people, businesses and farms in the U.S.
Multi-jurisdictional projects pose great challenges. However, states in the Western U.S. have made a tremendous amount of progress toward establishing a unified front in dealing with the impact of climate change. One of the channels to facilitate such productive interaction is the Western Governors’ Association (WGA). The WGA represents the Governors of 19 western states and 3 U.S.-flag islands who use the association for bipartisan policy development, information exchange and collective action to deal with critical issues in the Western U.S.
The authors of this proposal have created a nonprofit organization, Integral Scientific Institute, which is dedicated to the idea of identifying and advocating for environmentally responsible solutions to complicated social and economic problems. Following publication of this proposal, the authors will continue their advocacy for implementing an approach to problems like water scarcity where underutilized natural and renewable resources can be tapped to solve problems in ways that are both environmentally responsible and cost-effective. Thus, we are committed to presenting public officials and interested citizens with creative alternatives to costly and environmentally damaging ways of doing “business as usual.” Clearly, alternatives are needed that involve more cooperation, more long-term planning, and better use of resources.
Where will these actions be taken?
The proposed project will be located on Lake Mead in the vicinity of Hoover Dam. Lake Mead acts as a reservoir for Hoover Dam. Nearby Las Vegas and Boulder City, Nevada, will serve as likely hubs for activities related to project construction and operation.
Lake Mead is a very large body of water, even though it currently holds only 37% of the volume of water it once had. It used to be the largest reservoir in the United States; now it is ranked fourth. It stretches for about 110 miles north and east from Hoover Dam to the point where it receives water from the Colorado River. Its surface area is 248 square miles when at full capacity. A small fraction—less than one square mile—of Lake Mead surface area would be required for the proposed project.
How will these actions have a high impact in addressing climate change?
This project will have very significant implications for coping with climate change. Here are the most salient:
- It will be climate friendly. Use of solar PV panels will help to meet energy needs in the southwest with no significant release of greenhouse gases. It is estimated that reduction in use of fossil fuels to produce electricity will reduce CO2 emissions by 222,000 tons per year.
- Providing clean energy to desalinate water in Southern California will be a benefit to California, which now is (a) in a severe drought and (b) producing significant amounts of greenhouse gases in association with transporting water from other areas of the state.
- Because this project leads to less water evaporation and more use of desalinated water, all states in the southwest will benefit from reducing the demand for water from the Colorado River. Every state will suffer a diminished allotment of water from the Colorado River if Lake Mead water levels fall too low. 
What are other key benefits?
Some other key benefits are:
- Underutilized resources for electric power transmission will be put to use.
- Hoover Dam releases water to generate electricity even during times when demand for electricity is not at its highest. Because power from the floating solar farm will often be available to satisfy demand during non-peak-demand times, Hoover Dam will become better able to preserve water for release during peak demand times. Thus, Hoover Dam and the floating solar farm, working together, will save water for generating peaker power and thereby reduce the need for using peaker power plants that burn fossil fuels.
- Project construction and operation will stimulate the economy in the area of Hoover Dam and Lake Mead.
- Cooperation between states for implementing the project will serve as both (a) a benefit for coping with water scarcity in the southwest and (b) a model for cooperation among other states and nations as they attempt to cope with the impact of climate change.
What are the proposal’s costs?
The proposed amount of water to be exchanged between Nevada and California is 200 million gallons per day (MGD). The desalination plant to be built in California will use reverse osmosis (RO) technology. Usually, producing 200 MGD requires 3 gigawatt-hours (GWh) per day of electricity. However, the integration of an energy recovery system will yield energy savings of 40%. So, the energy requirement for producing 200 MGD of potable water will only be 1.8 GWh per day.
Lake Mead receives 6.45 hours of average daily solar irradiance. This means that the floating solar PV farm needs to have a capacity of 279 megawatts (MW).
Installed cost for commercial solar PV projects is between $3 and $7 per watt. Considering that this is a very large project, with economies of scale and decreasing PV panel costs, the low end of $3 per watt is a good estimate. This yields a total cost of $837 million. Surcharges that are traditionally associated with work on water in off-shore projects do not apply in the case of this project. Indeed, none of the specialized equipment and additional effort required for off-shore installations is needed for deploying the floating solar PV farm on Lake Mead.
The cost of a similar installation in Japan for a 92-MW solar PV plant is $290 million (2015). Extrapolating, without taking into account economies of scale, yields $879 million for a 279-MW solar PV plant. So, $837 million is a reasonable estimate.
Therefore the proposed floating solar PV farm on Lake Mead will have the following specification:
- 279 MW solar PV power plant
- Generation capacity per year: 657,000 MWh
- Generation capacity per day: 1,800 MWh
- Area: 0.63 square mile
- Water evaporation reduction capacity per year: 2,620 acre-feet or 854 million gallons (Evaporation rate at Lake Mead: 6.5 feet per year) 
- CO2 reduction per year: 222,000 tons (370,000 tons if reduction from using the RO energy recovery system is included)
- Cost: $837 million
The projected time needed to implement the proposed project is five years. That short suggested timeline is possible because the project might need relatively little lead time to implement a pilot project, secure funding, complete construction, and begin operations.
Favorable circumstances for allowing relatively quick implementation are as follows:
- Conservation pilot studies are already being cooperatively funded by the U.S. Bureau of Reclamation in Nevada, California, and Arizona.
- Bipartisan support would be achievable because the significant benefits from the project would inure both to the environment and to the state’s economic interests.
- Southern Nevada Water Authority has pushed forward on a groundwater pumping and transfer project that has been estimated to cost upward of $15 billion. That suggests that funding would be available to any well-conceived project that would enhance water security for Nevada and surrounding states.
- Siting a project is usually a lengthy and contentious task. In this case, the proposed site is under the exclusive jurisdiction of the federal government, so siting could be expedited because fewer local, state, and regional agencies would be required to approve siting plans. Given that Hoover Dam is in danger of becoming obsolete because of its declining power-generating capacity, it is reasonable to hope that the federal government would act in an expeditious manner.
All Internet references retrieved on 6/8/15.
- Capacity factor. Wikipedia, at https://en.wikipedia.org/wiki/Capacity_factor.
- Operation Plan for Colorado River System Reservoirs May 2015 24-Month Study, U.S. Bureau of Reclamation, at http://www.usbr.gov/lc/region/g4000/24mo.pdf.
- B. Walton, Low water may halt Hoover Dam’s power. Circle of Blue, at http://www.circleofblue.org/waternews/2010/world/low-water-may-still-hoover-dam’s-power/.
- NPR: The Two-Way, California Regulators Adopt Unprecedented Water Restrictions, at http://www.npr.org/sections/thetwo-way/2015/05/06/404630607/california-regulators-adopt-unprecedented-water-restrictions.
- R. Kearn, Giant Nevada water transfer for Las Vegas under fire. CourthouseNews Service, at http://www.courthousenews.com/2014/02/18/65413.htm.
- The Carlsbad Desalination Project, at http://carlsbaddesal.com.
- Municipal Water District of Orange County, Doheny Desalination Project, at http://www.mwdoc.com/services/dohenydesalhome.
- Commissioner’s Office, U.S. Department of the Interior and Western municipal water suppliers reach landmark collaborative agreement, at http://www.usbr.gov/newsroom/newsrelease/detail.cfm?RecordID=47587.
- S. Majdi and T. Manaugh, Trip Report – Water Scarcity in the US Western Region. Integral Scientific Institute, Dallas, Texas, March 2015.
- S. Majdi and T. Manaugh, Proposal for Adaptation to Climate Change, 2014 MIT Climate CoLab Contest, at https://www.climatecolab.org/web/guest/plans/-/plans/contestId/1300208/planId/1309211.
- Southern Nevada Water Authority. Clark, Lincoln, and White Pine Counties Groundwater Development Project Conceptual Plan of Development, November 2012, at http://www.snwa.com/assets/pdf/ws_gdp_copd.pdf.
- G. Minter and M. Bird, Top 10 myths about desalination. Water Conditioning & Purification, November, 2014.
- Kyocera, Kyocera TCL Solar Completes Construction of Third Floating Solar Power Plant in Hyogo Prefecture, Japan, news release at http://global.kyocera.com/news/2015/0503_khfp.html.
- A. Upadhyay, Brazil Announces Huge 350 MW Floating Solar Power Plant. CleanTechnica, at http://cleantechnica.com/2015/04/06/brazil-announces-huge-350-mw-floating-solar-power-plant.
- K. Thompson, Last straw: How the fortunes of Las Vegas will rise or fall with Lake Mead. Popular Science, at http://www.popsci.com/article/science/last-straw-how-fortunes-las-vegas-will-rise-or-fall-lake-mead.
- U.S. Department of the Interior, Record of Decision: Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead, at http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf.
- M. Moreo, et al, Evaporation from Lake Mead, Nevada and Arizona, March 2010 through February 2012: U.S. Geological Survey Scientific Investigations Report 2013–5229, at http://dx.doi.org/10.3133/sir20135229.