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Discussion in 'Archives - Yahoo Canyons Group' started by adkramoo, Jul 26, 2006.

  1. adkramoo

    adkramoo Guest

    I apolgize for my continuing to root for drought, but it seems that they won't let it fall like years past. 110' down last year, it will be hard pressed to get that low again. There be great canyons just under that water. Sigh! R


    July 11, 2006

    Glen Canyon Dam Operations

    Releases from Glen Canyon Dam in July 2006 will average 13,400 cubic feet per second (cfs) with a total of 822,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in July, daily release fluctuations due to load following will likely vary between a low of 9,500 cfs (during late evening and early morning off-peak hours) to a high of 17,500 cfs (during daylight and early evening on-peak hours). On Saturdays, release fluctuations will likely vary between a low of 9,500 cfs to a high of 17,000 cfs. On Sundays, the range will likely vary from 9,500 cfs to 15,000 cfs.

    Releases in August will likely be very similar to releases in July.

    Releases from Glen Canyon Dam are scheduled to be 822,000 acre-feet in August 2006 (an average of 13,400 cfs). Releases in September 2006 will be lower. The volume of release scheduled in September is 550,000 acre-feet (an average of 9,200 cfs).

    Upper Colorado River Basin Hydrology

    Inflow projections to Lake Powell have been reduced in response to warm and dry spring conditions in the Colorado River Basin. Precipitation in the Upper Colorado River Basin in April, May, and June 2006 was approximately 65, 35, and 50 percent of average, respectively. The July final inflow forecast, issued by the National Weather Service on July 5, 2006, is now projecting April through July unregulated inflow to Lake Powell for 2006 to be 5.25 million acre-feet, only 66 percent of average. Inflow projections earlier in the year were significantly higher (the April inflow forecast, for instance, projected Lake Powell inflow to be 97 percent of average). It is now almost a certainty that inflow to Lake Powell will be below average in 2006.

    Thus far, inflow to Lake Powell in water year 2006 (which began on October 1, 2005) has been about 77 percent of average. Summer 2006 inflow is expected to be below average and projected inflow for the entire water year of 2006 is projected to be 73 percent of average. Unregulated inflow in April 2006 was 103 percent of average and unregulated inflow in May was 89 percent of average. However, inflow in June was only 53 percent of average. The snow melt runoff occurred earlier than normal in 2006. Peak inflow to Lake Powell in 2006 was 41,700 cfs and occurred on May 29, 2006.

    The water surface elevation of Lake Powell reached a seasonal low on April 7, 2006, at elevation 3,588.7 (111.3 feet from full pool). The water surface increased from April 7, 2006, until June 22, 2006, when Lake Powell reached a seasonal peak of 3,610.9 (89.1 feet from full pool). Since that time (June 22nd), the elevation of Lake Powell has been decreasing. The current (July 10, 2006) elevation of Lake Powell is 3,609.3 feet (90.7 feet from full pool). Current storage is 12.6 million acre-feet (52 percent of live capacity).

    The water surface elevation of Lake Powell will likely continue to decrease through the summer, fall, and winter of 2006 until April 2007, when anticipated snowmelt runoff will cause the water surface level to increase once more. The projected elevation of Lake Powell on January 1, 2007, is about 3,599 feet.

    Upper Colorado River Basin Drought

    The Upper Colorado River Basin experienced five consecutive years of extreme drought from September 1999 through September 2004. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity. Inflow volumes for five consecutive water years were significantly below average. Total unregulated inflow in water years 2000, 2001, 2002, 2003, and 2004 was 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year drought, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.

    Hydrologic conditions improved in water year 2005 in the Upper Colorado River Basin. Lake Powell increased by 2.77 million acre- feet (31 feet in elevation) during water year 2005. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.

    Inflow to Lake Powell is almost certain to be below average in 2006. The current projection for inflow to Lake Powell in water year 2006 is 73 percent of average. Over the past 7 years (2000 through 2006, inclusive) inflow to Lake Powell will have been below average in all but one year (2005). While drought conditions eased in 2005, and the inflow in 2006 is not expected to be as extremely low as what occurred in 2000 through 2004, the drought in the Colorado River Basin may not be over. Historical droughts show that it is common to have 1 or 2 above average or above average years during sustained multi-year droughts.

    The effects of multiple years of low inflow remain visible at Lake Powell where reservoir storage has been reduced. Lake Powell storage is currently 52 percent of capacity.

    This release courtesy Tom Ryan, Bureau of Reclamation.

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