Status and Trends of Resources Below Glen Canyon Dam Update 2009

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Update of key dommolro m natural, cultural, and recreational resew= affected by Glen Carryon Dam, surunarizicg data publisliedd raogh April 2111K [The goals presented were established by the Glen Canyon Dam Adaptive Management Program (GCDAMP; httpJtwww.usbr govtu AmVamplstrategic -plan html). Predictions are drawn from the 1995 Operation of Glen Canyon Final Environmental Impact Statement ( EIS) on how key resources would respond to the selected flow alternative] Resource and GCDAMP Goal 0i' Summary Natural resources Water quality (water temperature) No effect Since 2003, downstream water temperatures have increased (Goal: Establish water temperature, in response to drought conditions (see http: //pubs.usgs.gov / quality, and flow dynamics to achieve ds/2007/251/). GCDAMP ecosystem goals) Specific conductance (salinity) No effect Drought conditions, prevalent since 1999, generally result in increases in specific conductance (see http://pubs usgs gov /ds/3W. Sediment (sandbars and related physical Modest improvement Sandbars erode during periods between high flows. Increases in habitats) (Goal: Maintain or attain total sandbar area and volume are only possible when high -flow levels of sediment storage within the releases follow large tributary floods that enrich sand supplies main channel and along shorelines) in the main channel (see http : // pubs.usgs.gov/fs/2007/3020/). Aquatic food web (Goal: Protect or Potential major increase Increases were apparent in Glen Canyon Dam tailwater reach, but the improve the aquatic food base) trend is unclear along downstream reaches. Unlikely that quagga mussels (Dmissena bugensis) will become well established in the mamstem Colorado River below Lees Ferry or its trr'butanes (see httpJ)pubs usgs.gov/og2007/lW- Native fish (humpback chub) (Goal: Potential minor increase The population of adult humpback chub (Gila cypha) decreased Maintain or attain viable populations between 1989 and 2001; however, adult abundance has of existing native fish) increased more than 50% since 2001 (see http: / /pubs.usgs.gov/ of/2009/1075/). Trout (Goal: Maintain a naturally Increased growth potential, Rainbow trout (Oncorhynchus mykiss) numbers have decreased in reproducing population of rainbow dependent on stocking the Lees Ferry reach. trout above the Paria River) Riparian vegetation (Goal: Protect Modest increase Native and nonnative woody vegetation continues to expand in or improve the biotic riparian and the river corridor. Nonnative tamarisk (Tamanx ramosissima) is spring communities) the dominant species, making up 24% of vegetation (see http: // pubs.usgs.gov/oV2008/12161). Kanab ambersnail (Goal: Maintain or Some incidental take Snail habitat increased since 1998 (see chapter 6 at http: / /www. attain viable populations of Kanab gcmrc.gov /products/score12005n. ambersnail) Cultural resources Archeological sites affected (Goal: Preserve, protect, manage, and treat cultural resources) Traditional cultural resources affected (Goal: Preserve, protect, manage, and treat cultural resources) Recreation resources Moderate degradation Archeological site condition continues to decline because of (less than 157 sites affected) a combination of factors including erosion, gravity, visitor impacts, and insufficient sediment (see chapter 11 at http:// www. gcmrc.gov /productstscoret2005/). Increased protection. Tribes have developed protocols for monitoring the condition of cultural resources in accordance with tribal values. Whitewater boating camping beaches Minor increase (average area at normal peak stage) (Goal: Maintain or improve the quality of recreational experiences) Areas suitable for camping have decreased on average 15% per year between 1998 and 2003 (see chapter 12 at htipJ /www.gcmrc. gov /products /score/2005/).