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IN REPLY REFER TO, GRAND CANYON MONITORING AND RESEARCH CENTER 2255 N. GEMINI DR., MS-5000 FLAGSTAFF, ARIZONA 86001 REC~" .--;~. .. _1.. i ~ ~ ~ r, ~ 11 ~ ". i:1 . ., United States Department of the Interior ~ ,. FEB 12 2001 GCMR -700 ADM -1.10 r:;; G Z 2011 CoIomdo "'. .", ' .JI", - .. " ...... '.' "~"I"", I,'. ,.,,- ~. MEMORANDUM ,.. .. f,1 , '!. TO: Glen Canyon Darn Adaptive Management and Technical Group Representatives, GCMRC Cooperating Scientists Ted S. Melis. Physical Science Program Manage~ Final LSSF Sediment Resources Fact Sheet t >. ., ,., " ::. ~. ~ .. ,. FROM: SUBJ: The attached Northern Arizona University Fact Sheet, entitled Monitoring the Effects of the Spring 2000 Habitat Maintenance Flow on Colorado River Ecosystem Sand Bars, is the first of several reports on the physical responses measured during last summer's Low Summer Steady Flow test (LSSF). The fact sheet is intended to convey system-wide sand-bar changes that occurred as a result of the May 2000, peak power- plant spike flow (31,500 cfs for 96 hours), relative to long-term monitoring data collected since 1991. f ~, k r t, f l ~. ~- ~. ~." :>'. I believe that this fact sheet provides an efficient and accurate overview of the state of sand bar resources below Glen Canyon Darn up to the onset of 8,000 cfs steady flows released during summer 2000. Additional integrated physical resource reports are anticipated during 2001, that report responses for the entire range of experimental flow treatments released as part of the LSSF design. ~ t ~, One key hypothesis tested as part of the LSSF experiment was to determine if sand bar restoration responses to a Habitat Maintenance Flow (31,500 cfs) would be significantly increased following a low-flow period which tended to limit downstream export of newly input sand. Because most sand is introduced to critical reaches during summer flash floods, the LSSF design turned out to be nearly optimal for testing this hypothesis. The next fact sheet from the NAU team shall provide a comparison of the May versus September 2000, spike flow results; data that are vital to testing this hypothesis. . '. ;: Please contact me at (520) 556-7282, or through e-mail at tmelis@usgS.20V with any questions you have regarding these monitoring data, or conclusions and interpretations published in the fact sheet by the NAU team.