Draining Lake Powell - the Water Supply Effects
(The EDF Study - Water Issues)
This page is dedicated to providing information on a study that was conducted and has received some media attention.
A report was prepared in September 1997, prior to the Congressional Joint Hearing of the Subcommittees on National Parks & Public Lands, and on Water & Power, concerning the Sierra Club's Proposal to Drain Lake Powell or Reduce its Water Storage Capability.
The report was titled "The Effect of Draining Lake Powell on Water Supply and Electricity Production". The author was Spreck Rosekrans of the Environmental Defense Fund (EDF). The effect on electrical production is addressed on another web page on this site.
(click here for electrical production information)
In this report a paragraph in the "Summary" does a good job of summarizing Mr. Rosekrans' study results concerning the water issues.
It states that "The delivery of water to the Upper Basin States does not change between the two scenarios ["with Lake Powell" and "without Lake Powell"]. Average annual deliveries to the Lower Basin States are 91 thousand acre-ft less than under Current Operations .... only a little over 1% of the average annual delivery....."
For the "study" the Bureau of Reclamation's computer program CRSSEZ was used. Experts within the Bureau do not feel that the program is capable of adequately assessing the Colorado River system without Lake Powell. The fact that the "study" does not show a significant difference between the two scenarios (with or without Lake Powell) is the result of three facts:
- The program does not require a minimum of 75 MAF over a ten year period to be delivered by the Upper Basin (as required by the Colorado River Compact).
- The "study" used the years 1997-2050 even though the Bureau computer model had the data through the year 2060.
- The program can only calculate annual values (versus monthly values) for flows and reservoir contents, which does not provide a true picture of the results of as significant of a change as draining Lake Powell. The Bureau's more powerful computer model "Riverware" cannot provide this type of information either.The Bureau will not spend the time and effort developing the tools adequate to analyze what the Clinton Administration and Congress consider to be an "unrealistic" proposal.
(For a letter from the Clinton Administration stating their official position on draining Lake Powell - click here)
I obtained a copy of the Bureau's CRSSEZ computer program, and though I don't pretend to be the expert on river hydrology that Mr. Rosekrans is, I am a registered professional engineer and have experience with computer models and how the models can be manipulated.
NOTE: A statement needs to be made at his point; for the shortages to occur to the Lower Basin rather than the Upper Basin the Colorado River Compact would have to be renegotiated (it would be no small task to get the seven states involved - and very dependent on the water - to go back to the bargaining table). But for the sake of the discussion the following does show that there would definitely would be significant shortages.
The computer model uses historical flow data from 1906 through 1995, then applies it in a rotational basis to a data base that varies the Upper Basin consumptive uses. What this results in, is a set of 90 "traces" of the years 1998-2060. The EDF study used the overall averages for the total number of years 1997-2050. Since years of high or low precipitation/runoff occur over several years (not a high flow year followed by a low flow year or vice-versa), and since the traces increase the projected Upper Basin Consumptive use, a more practical way (and more statistically valid method) to view the data is looking at the traces as individual occurrences.
First off, ignoring the years 2050-2060 would provide an inaccurate conclusion. In correspondence with Mr. Rosekrans he stated that he was not aware that the last ten years data was in the data base (the time period of the highest projected Upper Basin Consumptive Use) until after the report was made public.
Just looking at the average numbers, in the year 2060 there is a 61% probability of a "Shortage" being declared.
Of more significance, looking at the 62 year long traces (90 total) there are the following major differences (a major point is that the Southern Nevada Water Authority cannot obtain water from Lake Mead with an elevation below 1050' and the SNWA -including Las Vegas - currently receives 85% of its water from Lake Mead):
Scenario with Lake Powell - Only one of the 90 traces (each 62 years long) predicted a lack of water to SNWA (for only one year), and no years with Lake Mead drained (this is assuming that Lake Powell would be drawn on to protect the SNWA water).
Scenario w/o Lake Powell - 89 of the 90 traces (each 62 years long) predicted a lack of water to SNWA (on average six years) , and with 24 of 90 traces predicting Lake Mead drained during at least one year (the average was 3 years).
Steven Hannon, author of the book "Glen Canyon" has referred to the use of the SNWA water as "to enrich an equally few individuals in Las Vegas who make their very comfortable livings [comparing them with the Lower Basin agriculture users] exploiting one of mankinds most tragic addictions." Denver Post 12/28/97.
This is probably a common feeling among those who are the ardent supporters of draining Lake Powell. What I don't understand is why they just don't say:
"Las Vegas won't have water but those people deserve to dry up and blow away." (Maybe that would be a little too harsh for the politically correct PR they need to maintain.)
For further discussion of the water issues considering data from the 1800's click here
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