Southwest Hydrology: The Resource of Semi-Arid Hydrology Volume 4 Number 2

Home Browse Search

How Low ?, continued from page 28 levels continue to decline, the "minimum power pool," the level at which water can no longer flow to the turbines, could be reached. At Glen Canyon Dam, the minimum power pool is just 71 feet below the current elevation. Even at that level, the lake would contain nearly 4 million acre -feet of water that could be delivered downstream through the outlet works. At Hoover Dam, water can be drawn into the turbines down to an elevation of 895 feet, at which point the remaining water could not be extracted by gravity flow. This water level is termed the "dead pool," and the nearly 2 million acre -feet of water remaining in the lake at this level is not included in reported reservoir storage. Even though water can reach the turbines down to the dead pool elevation, their design does not permit operation at that level. The costs and benefits of changing out the turbines at Hoover Dam as water levels rise and fall are being researched. Declining reservoir levels have also affected recreation. The Hite Bay Marina at Lake Powell became inoperable in 2003. At I �a Lake Mead, three public launch ramps have been closed and approximately $10 million has been spent to keep the remaining seven ramps open. Relocation of the Las Vegas Boat Harbor and Lake Mead Ferry Service is estimated to exceed $5 million. Further investments are anticipated to revamp water supply and wastewater systems. Where Do We Go from Here 9 Despite the precipitation seen in early 2005, it is unclear if this drought is nearing its end. History tells us it is not unusual to have wet years during an extended drought. Although the forecasted inflow into Lake Powell for the April through July runoff season is 98 percent of average at the time of this writing (Colorado River Basin Forecast Center, 2005), a similar forecast last year was radically altered when an abnormally dry and warm March vaporized the snowpack basin -wide. Although six consecutive years of below- average inflow has not occurred in the past 100 years, we should not bet on a turn- around. More likely, storage will continue to decline in the near -term and the system will take longer to recover than it did after previous droughts — largely because of greater M R 5 E 3 161 R ` HANDHELD OR LAPTO The AquiStar' PT2X Smart Sensor — ideal for all your level and temperature monitoring needs — wells, tanks, surface waters... -Integrated datalogger/ sensor -Measures and records • Pressure, Temperature. Time • Digital Accuracy -Real-Time Monitoring -Easy Export Easy -to -Use Software With INW's powerful software, create test sessions, examine data, and monitor real time readings from either a laptop or a handheld. Instrumentation Northwest, Inc. Protecting our water resources since 1982 1 -800- 776 -9355 / www. inwusa.com / info@inwusa.com 28 • March /April 2005 • Southwest Hydrology demands today. These increasing demands, including more use by the Upper Basin states as they develop their allocated shares of the river, will mean less water in storage, on average, than seen in the past, regardless of how long the current drought lasts. In recognition of this fact, the Department of Interior has actively encouraged the seven basin states to develop consensus management strategies to address water needs in the coming years. In December, the department announced plans to develop and institute formal shortage guidelines for the Lower Basin before 2008. Technical studies to examine possible shortage strategies for the Lower Basin were initiated last year. All management options examined to date deal with the impacts and tradeoffs that will be required to maintain certain water levels at Lake Powell and Lake Mead. For example, given the current demands on the system, if no particular elevations are protected and the current drought continues, the lakes could be nearing their "dead pools" as early as 2008. Drawing the reservoirs down to those low levels is likely to further impact power production, recreation, and fish and wildlife resources. To protect the minimum power pools, water deliveries would have to be curtailed in the Lower Basin as soon as 2007 if the current drought continues. These are only examples of the potential trade -offs that will be considered when shortage guidelines are developed. Despite the obvious difficulties in reaching these decisions, we must remain focused on the long -term picture of water management in the Colorado River Basin. We must prepare now to meet our water resource needs in the future. Contact Terry Fulp at tfulp @lc.usbrgov. References ........ ............................... Colorado Basin River Forecast Center, 2005. www. cbrfc.noaa.gov. Griles, J.S., 2004. "Building on Success, Facing the Challenges Ahead," Speech to the Colorado River Water Users Association, Dec. 2004; available at www usbrgov. Southern Nevada Water Authority, 2005. www.snwa. cam. U.S. Bureau of Reclamation, 2005. wwwusbrgov/!e/ region.