WSP08926 - Laserfiche WebLink

Home Browse Search

00ln~7 . . National Park Service Studies to Support Quantification of Reserved Water Rights at Black Canyon of the Gunnison National Monument Sediment Tran~rt Sediment supplied to the river from side drainages and canyon walls is transported through the canyon by water. As water energy levels and the volume of material exposed to moving water are reduced, the volume of sediment moved through the canyon is reduced, resulting in a build-up of sediment particles. The National Park Service (NPS) has contracted scientists from the US Geological Survey to determine the magnitude of streamflow necessary to entrain and transport existing sediment. Data collection occurred in 1994 and again in 1995 following the spring peak: of nearly 10,000 cubic feet per second (cfs). Final report is expected in 1997. Riparian Vee:etation The presence and areal extent of woody riparian vegetation is believed to have increased since construction of the Aspinall Unit reservoirs. The elimination or reduction of scouring flows has increased the occurrence and stability of depositional features (e.g., sediment bars, debris fans). These features serve as ideal germination and establishment sites for many plant species. Consequently, vegetation establishment is occurring in areas that in the past would not have supponed vegetation. The NPS has contracted with scientists from the US National Biological Service (NBS) to examine the relationship between streamflow and riparian vegetation composition. Vegetation sampling was initially conducted in 1990, repeated and expanded in 1994, and repeated again in 1995 following the unusually high spring runoff. A preliminary report was produced in 1991. Final report is expected in 1997. Visual Ouali ty and Aesthetics As mentioned above, prior to construction of the Aspinall Unit, strearnbanks along the mainstem Gunnison River were relatively devoid of vegetation. These rugged, barren shorelines and banks were clearly visible from both the canyon rim and floor. The river and river channel were often described as raging, turbulent, and roaring - characteristics which were also easily discernable from the canyon rim, especially at high flows. In 1990, the NPS contracted scientists from Colorado State University (CSU) to identify discharge-sensitive aesthetic resource attributes and to evaluate the probable impacts of hypothetically altered now regimes on visual quality within the canyon. A preliminary report for this study was submitted in 1992. Final analysis of potential impacts to aesthetic resources will be completed once the NBS' vegetation study has concluded.