Release of Colorado River Basin Study

Background

The Colorado River Basin (“the Basin”) spans parts of seven western states: Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming.  The Basin currently provides water to around 40 million people and 4 million acres of irrigated agricultural land, making it one of most important watersheds in the western United States.  Beginning in January of 2010 and lasting for three years, the Department of the Interior funded a supply and demand study of water use in the Basin through the Bureau of Reclamation and its WaterSMART program.  Completed in December 2012, the published full report of the Colorado River Basin Water Supply and Demand Study (“Study”) can be found in the links provided below.

 

The Study

The Study evaluated future imbalances in the watershed over the next 50 years, up to year 2060.  The Study, however, did not result in any decision on how exactly the future imbalances will be addressed.  Performed in four phases, the Study (1) assessed the water supply of the watershed; (2) assessed the demands for water within the basin; (3) analyzed the reliability of the computer models; and (4) developed and evaluated strategies to decrease the imbalance. The Study found the average imbalance between supply and demand for water would be more than 3.2 million acre-feet.  Most of this imbalance is due to an increase in demand from municipal and industrial users because of an estimated doubling of the population within the Basin.  The study estimated that by 2060 the population could be approximately 76.5 million people.

 

It is important to note that any future water supply and demand scenarios predicted within the watershed are highly uncertain because an infinite number of possibilities exist.  While no study will be exact, the Bureau of Reclamation analyzed four different scenarios for both supply and demand.  On the supply side, four scenarios exist: (1) an Observed Resample scenario that looked at water tends over the past 100 years; (2) a Paleo Resampled scenario that looked at water trends over the past 1,250 years; (3) a Paleo Conditioned scenario that looked at water trends over the past 1,250 years but conditioned on the water values observed over the past 100 years; and (4) a Downscaled GCM Projected scenario estimating that the climate will continue to warm substantially over the next few decades.  This last scenario estimated that the natural water flow within the basin will decrease by approximately 9% over the next 50 years.  On the demand side, four scenarios also exist: (1) a Current Projected Growth model; (2) a Slow Growth model; (3) a Rapid Growth model; and (4) an Enhanced Environment Growth model accounting for enhanced environmental stewardship.  All the scenarios were then run in different combinations through the Colorado River Simulation System in RiverWare software, obtaining a range of potential future system conditions.

 

The Study next evaluated more than 150 options and strategies on how to resolve imbalances in the watershed.  The options and strategies can be generally organized into four groups.  The first group included options that increase water supply such as reuse, desalination, and importation.  The second group included options that reduce water demand from both M&L and agricultural conservation.  The third group included options that modify operations such as transfers & exchanges and water banking.  Finally the last group included options that focus on governance and implementation of water such as stakeholder committees, population control, and reallocation.

 

Finally, the Study listed ten general areas of options and strategies seeking to resolve water imbalances that are realistic to implement within the watershed: water conservation and reuse; water banks; watershed management; augmentation; water transfers; tribal water; environmental flows; data and tool development; climate science research; and partnerships.  The Bureau of Reclamation closed public comments on the Colorado River Basin Water Supply and Demand Study on April 19, 2013, and all comments will be summarized and considered in planning activities.

 

Brief Comments on the Study

The best solution laid out in the Study is water conservation.  Because irrigated agriculture is responsible for approximately 70% of watershed water use, conservation is this sphere could result in significant savings.  Effective conservation can also occur in cities by reducing water use in outdoor landscapes because half of all city water use is involved in such endeavors.  With desalination technology rapidly evolving, it could become another very attractive option.  Desalination projects do occur in other countries, but the energy cost and cost of recovery are still very high.


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