Colorado River Supply - NCSE-NASA
This curriculum module looks at climate change impacts that affect us locally right now. We will study the data, the possible consequences to various user groups, and suggest solutions to adapt to and mitigate these changes.
Your first part of the assignment is to become acquainted with the Colorado River watershed as shown in this image. The source of the water is in the snowpack of regional mountain ranges (mostly the Rockies). It then flows southwest through the red desert of Glen Canyon National Park on through the Grand Canyon in Arizona, forming Lake Mead on the middle left side of the image, down through the agricultural lands on the California, Arizona and Mexico border. Look at where the water is coming from and the vast deserts it must travel through before reaching its destination in the Gulf of California. Who is using the water and for what purpose?
This module will help you explore the following questions: Where is the water coming from and where it is going (most will be diverted without actually reaching the ocean)? For what purposes is the water being used? Will climate change impact the use of this water? How many people will be impacted by a change in the amount and availability of this water sources?
To begin this module we will look at a data set that shows the percent of average snowpack found in Colorado that feeds into the Colorado River. Look at the data and answer the following questions. Updated data sets can be found at here (make sure you scroll down to the Colorado basin).
Table 1. Monthly percentages of average snowpack in Colorado for the Colorado River watershed for years 1968-2009.
What are the units on the graph?
When was the maximum amount of snowpack? When was the minimum amount of snow pack?
Do these max/mins validate or disprove that climate change is occurring? Are max/mins an example of a region’s climate or weather? Explain.
Pick a month (not January or June since they do not have complete data sets) and find the average from 1968 to 1988 and then find the average for 1989 to 2009. When did we get more snow and when did we get less snow?
Is this data set long enough to establish whether climate change is occurring? Explain your answer. If there is less snowpack in the Colorado Rockies, what do you think that will mean for the amount of water available to the watershed?
What will happen to the level of Lake Mead?Click here to download Part One with data up through 2010 as a PDF
From your results, you can see that a decrease in snowpack in the Colorado Rockies means less water in the river system.
The Colorado has over a dozen different dams that help to regulate and store the flow of water, but the law of the river dictates how much each dam must release to users downstream.
Less water in the system means less water coming into the reservoirs despite the fact that there are mandates on how much must be released. The result is lower water levels.
Less snow in Colorado means drops in lake levels.
Seeing that the water stored for our use is dropping, we need to next look at how that water is being used. The Colorado watershed covers 7 states and all seven are allocated a share of the water through the 1922 compact. The upper and lower basins get equal shares of the water, 7.5 MAFY each. Due to the decreased amount of water available a temporary agreement was reached in 2007. This 2007 interim drought agreement has it limited to 7.05 MAFY per basin until 2026. This assumes that the drought is a temporary condition or that a new agreement can be reached for the allocation of the water if this is in fact a new drier climate the region is now experiencing. The boundary between the basins is at Lee Ferry just below Glen Canyon Dam.
The table to the right shows each state’s allocations. Each state’s share of water reflects their state of development in 1922 when the original compact was negotiated. Notice that Nevada gets a mere fraction of the water. All of Nevada’s allocation goes to the Las Vegas Valley for the municipal water supply. California gets the largest allocation for their agriculture and city centers and has been using over their allocated share (5 MAFY). Federal authorities have told California to come up with alternative sources to supplement their water supply to bring them back in compliance. Native American tribes are eligible for up to 1 MAFY but not all have claimed them, so others use their allotment. The Mexico allocation is part of an international treaty, so they do get their portion of the water; however, the water quality is degraded by the time it reaches the end of the river.
Table 2. Water Allocation from the Colorado River
Million Acre Feet Per Year (MAFY)
One of the primary uses of the Colorado River in the arid west is for agriculture. 63% of water used in Upper Basin is for agriculture. 80% of Arizona’s allocation is used for irrigating agriculture, and almost California’s entire portion is for growing crops in the Imperial Valley. The Imperial Valley and the Coachella Valley are some of the most productive agriculture areas in the world with nearly 500,000 acres being irrigated producing nearly $1 billion in crops annually. One out of every three jobs in the valley is dependent on the agriculture industry. You can see in this true color image the contrast between the irrigated crops and the desolate desert surrounding them. Water diverted from the Colorado River is entirely responsible for this landscape. Even the Salton Sea is a historical artifact filled with flows from the river. Notice the change in vegetation that occurs at the border.
Since 1942, the valley has received its water through the 82-mile long All-American Canal that carries water from the Colorado River in Arizona along the Mexico-California border to the California agricultural valleys.
Notice that the All American Canal is mostly an earthen canal that is uncovered and flowing through a sandy desert. The inefficiencies of the canal mean that it loses water to high evaporation rates as well as seepage through the sandy soil. Mexican farmers would take advantage of this recharge to the groundwater system and pump it up to water their own crops on the Mexico side of the region. However, California noticed the amount of water they were losing and has since decided to line portions of the canal, effectively conserving that water available to them and decreasing the amount available to Mexican farmers.
Your assignment for this part of the module is to learn about what is grown using Colorado River water. Search the internet, look at the produce and labels in your store, and research agricultural periodicals. What crops are grown in the Imperial Valley and other regions using the river’s water? Who eats those crops or where are they shipped? Can you find these crops at your local store? How many people are fed with this water? You may not be able to find all the answers to these questions, but you should get an idea of the river’s contribution to people as a food supply and an industry. How will a change in the amount of water available make a difference to you or other people? Once you understand the extent of the impact, identify adaptation measures that can be taken to sustain agriculture in a drier climate. How is adapting to climate change different from mitigation climate change? Are any of the adaptation measures you identified also mitigation strategies?
The last section demonstrated the importance of the Colorado River water for agriculture. The amount of food produced and people employed because of the river cannot be understated. However, there are other users that compete with farmers for their share of the river water. As less water flows down the river, competition becomes fiercer. Is there anything more important than guaranteeing water for our food supply?
Urban Growth in the Southwest
The Southwest has been one of the fastest growing regions in the United States over the past decade. Las Vegas and Phoenix have both experienced unprecedented growth. Other cities that are dependent on the river’s water include Tucson, San Diego, and Denver – all of which are still growing.
In Colorado, 80% of the water is deposited on the west side of the Rockies, but 80% of the state’s population is on the east side of the continental divide. This means that 22% of the Upper Basin water is moved over the divide to where the majority of the state’s population resides. The competition over water between urban centers and agriculture is explained in the water supply video by the Colorado River District at http://www.crwcd.org/page_315.
Western water law is governed by the Law of Prior Appropriation. Another way of putting it is first in time, first in right or first come, first served. The history of the country is told by its farmers. The landscape was a checkerboard of crops before big urban centers were built with their exploded suburbs. This means that the first water rights in the area belonged to the farmers and are still held as part of grower’s cooperatives. The fact that the municipal claims for water are newer means that in case of drought, they are susceptible to having their water cut off in order to assure that the farmers’ claims are met. Realistically, the number of people in modern cities lends them more political clout should a legal battle over water rights ensue.
However, even without a legal battle, the competition between urban use and agricultural use has had impacts in other ways. The City of Los Angeles has taken to leasing water rights from farmers during drought years. They pay the farmers to not grow food, so that the city can use the water. There are also water speculation markets that are emerging. In anticipation of a demand for a bedroom community, developers will go around and buy up the water rights from farmers and then pay to pipe that water to a new location where they will build a new master community. Another way cities impact the demand for water is through their increased use of energy.
Water’s Role in Energy Production
More urban centers mean more of a demand for electricity. For the Upper Basin, that means more water used in extracting oil from the ground to be used for gas for cars or burned in plants for electricity. Most power plants use water as a coolant. The steam from the water is then pressurized and pushed through a turbine, which creates electricity. Whether it is a nuclear power, coal, oil, natural gas, or even thermal solar power plant, they all need water as part of the energy production process.
Coal plants also use water as part of the process to scrub pollutants out of the emissions. The water reacts with the particle in the smoke stacks and takes a percentage of nitrogen oxides and sulfur oxides out of the air. The plants can do this process without water, but it is more costly and less efficient. Coal plants are provide a feedback loop in the process. Since the coal plants also emit a lot of carbon dioxide in the smoke stacks, they are increasing the global temperature thus decreasing the snowpack of the Rockies and the water supply that they draw from in order to produce electricity from burning coal.
In the 2000’s there were over 3800 MW of electricity production from burning coal that were planned as part of several different coal plants in Nevada, which already gets 50% of its power from in state coal plants. A 500 megawatt coal plant uses 2.2 billion gallons of water a year. Colorado currently receives 70% of its power from coal burning plants and has proposals for over 2000 MW of coal produced electricity planned to be built soon. New Mexico gets 90% of its power from coal and has plans for 1800 MW more. Utah gets 95% of its energy from coal-fired plants with plans for 750 MW more and Wyoming gets 96% of its power from coal with plans for 1400 MW more.
Alternatives to coal power production in the area include hydroelectric, solar thermal and photovoltaic arrays. While these are clean sources of power production that do not increase the impact of climate change in the area, both hydroelectric and solar thermal power plants have an ongoing demand for water.
Look up growth rates for urban centers in the Southwest. What have been the recent growth rates and the projected growth rates for Phoenix, Las Vegas, Denver, San Diego, others? What has been the growth rate and projected growth for energy demand for those areas? Identify mitigation strategies that can help keep the impacts of climate change to a minimum while still providing for the energy demands of these urban centers? Can these strategies also be considered adaptation strategies for climate change as well? Explain your answer.
Figure 13. (Source)
Figure 14. (Source)
The first sections of this module have illustrated the competition for water between farmers and urbanites. Now we will look closer at whom else we share the water with. 1.5 Million Acre Feet per Year are delivered to Mexico. However, the quality of the water is drastically different than what is used further up river. As the water flows over and through rocks, salts and minerals are eroded and added to the water. The concentrations of these then build up the further down river you go. Since lakes lose more water to evaporation than rivers do, the salinity of the water continues to increase after every dam. Salty water means salty soils for farmers and a common method for overcoming the salt is to add more water to try and dilute the salts in the soil. However, if the additional water evaporates out, it leaves more salt behind; there by adding to the problem it was meant to diminish. Saline soils means a decline in crop production.
The figure on the left shows the California-Mexico border. The image is shown using near infrared bands of the electromagnetic spectrum to highlight the green vegetation (crops), which show up as bright red in the image. Notice the drastic change that occurs at the Mexican border. At any given point in time, only about half of the arable land in the Mexicali Valley is cultivated due to a lack of sufficient water. Due to the salinity of the water, crops are currently experiencing a 10-15% decline in production.
The figure to the right is an image using different color bands and shows the lower half of the Mexicali Valley. The Colorado River is the dark blue patch at the top central part of the picture. Urban sprawl and irrigation siphon off most of the river before it reaches Mexico. In fact, only about 10% of all the river water makes it to the Mexican border, and that is then used before it reaches the delta where it would historically flow into the Gulf of California. The purplish flow from the gulf is where the ocean water is actually flowing up the river channel. The grey areas to either side of the delta are the historic sediment deposits from when the river carried sediments in its raging current to be deposited here at the mouth of the river. Now most of the sediments are trapped by large dams and the river sinks into the sand before it reaches the coast.
This upset in the natural flow of the water and the disruption of the balance of sediment erosion and deposition has changed the ecology of the river delta. Not only has it left coastal villages dry, but it has caused several species to struggle for existence as well. Birds, marine life, and creatures adapted to the salt water marshes of the delta are all left struggling as the environment changes from the one they adapted to into something different. When we divide up a resource among different states and communities, we need to remember that it is not just humans who use these resources. Can we afford to live at the expense of other living creatures?
Should Lake Mead fall to 1,075 ft above sea level, the federal government would cut the water to seven states that depend on the Colorado River, according to an agreement they all signed in 2007. If that happens, the states would likely renegotiate the 1922 pact that establishes how the water is to be allocated. The current lake level is 1,129 feet. The database, located here, is updated once per month with Lake Mead's level. An automatically updated graphic can be found here that gives an easy-to-interpret picture of Lake Mead water levels since 1935.
Your final assignment is to discuss what that renegotiated compact should include. How much will we have to share? Who will we share it with? For what purpose should the water be used? Will it be sustainable in the face of growing populations and uncertain climate? How can we make our water use sustainable? Are there any conditions that need to be met before different user groups can use the water? The original pact for the river was made in 1922. What changes have occurred that would support changes in the pact today? Remember that the river is a system where all the water is allocated and there is less water available as a whole. Giving more water to any one area or user group means less water available for everyone else.
TEACHING NOTES / CONTEXT FOR USE
This module has been used as part of an on-line course as well as a lecture style class. Students have demonstrated that they are not very good at interpreting graphs, so it is recommended that if the first section is not done in class, a follow up should be done with the students to go over the data, the trends that can be identified, and their significance to climate change. There is a 20 year trend that can be identified showing less snowpack the last couple decades. Managing that trend as a drought or as climate change has long lasting impacts. Adaptation and mitigation are not explicitly defined in the module. The module also requires students to do their own research on what strategies can be used by different user groups. It is expected that this module is a part of larger course that has introduced some of these examples and definitions.
- Climate change initiatives at the NCSE
- Colorado River Commission of Nevada
- Colorado River District
- Colorado River System Consumptive Uses and Losses Report: (Provisional) 2006-2010 (Upper Basin)
- Colorado River Water Users Association
- Gelt, Joe. 1997. “Sharing Colorado River Water: History, Public Policy and the Colorado River Comapct” Uof A Water Resources Research Center.
- Drought Monitor
- Earth Observatory (NASA) - lower lake mead levels image
- Earth Observatory (NASA) - mexicali border in infrared
- Earth Observatory (NASA) - las vegas growth
- Earth Observatory (NASA) – river delta
- Earth Observatory (NASA) – lower basin image
- Earth Observatory (NASA) – salton sea
- Earth Observatory (NASA) – Page, AZ
- Earth Observatory (NASA) – infra red bands of Lake Mead
- Earth Observatory (NASA) - Lake Powell image
- Navajo Generating Station Site
- Union of Concerned Scientists - How Coal Works
- Imperial Irrigation District
- Lippert, John. 2009. “Las Vegas Running Out of Water Means Dimming Los Angeles Lights.”
- McDade, Sharon. 1995. “Case Study Pedagogy to Advance Critical Thinking.” Teaching of psychology [0098-6283] vol:22 iss:1
- Miller, Paul W. and Thomas C. Piechota. 2008. “Regional Analysis of Trend and Step Changes Observed in Hydroclimatic Variables around the Colorado River Basin.” Journal of Hydrometeorology. Vol 9 pp. 1020-1034.
- National Resource Conservation Service Colorado Historical Snow Data and Graphs
- Southern Nevada Water Authority. Water Resources. Apportionment of Colorado River
- The Essential Principles of Climate Science
- Western Resource Advocates