C21D-05
Hydrologic impacts of land cover disturbances in the Upper Colorado River Basin.
Tuesday, 15 December 2015: 09:00
3002 (Moscone West)
Ben Livneh1, Jeffrey S Deems2, Brian Buma3, Joseph J Barsugli4, Dominik Schneider5, Noah P Molotch5, Carol Adele Wessman6 and Klaus Wolter7, (1)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (2)National Snow and Ice Data Center, Boulder, CO, United States, (3)University of Alaska Southeast, Forest Ecosystem Ecology, Juneau, AK, United States, (4)CIRES, Boulder, CO, United States, (5)University of Colorado at Boulder, Geography / INSTAAR, Boulder, CO, United States, (6)University of Colorado at Boulder, EBIO, Boulder, CO, United States, (7)University of Colorado at Boulder, CIRES, Boulder, CO, United States
Abstract:
The U.S. Southwest and surrounding areas rely on the Colorado River Basin for water supply across a range of applications. The majority of water originates as snowfall in the headwaters region, which has experienced both episodic disturbance from deposition of dust from regional dryland sources on mountain snowpacks, as well as widespread forest mortality due to bark beetle infestation across a range of forest types, elevation, and latitude. In this work, the relative impacts of competing streamflow drivers are explored through assessing system sensitivities to individual and combined disturbances. This analysis begins at the catchment-scale by parameterizing the Distributed Hydrology and Vegetation Model (DHSVM) over a historical period for a set of 4 catchments that offer a gradient in dust-deposition, bark beetle impacts, elevation, and forest coverage. Observational estimates of disturbance are used to parameterized the model, including satellite inferences of dust-on-snow radiative loading, aerial survey forest disturbance data, ecological indices derived from MODIS forest phenology products, as well as plot-scale disturbance and in situ dust radiative loading information. Sensitivities from the catchment analysis presented, then compared with hydrologic simulations over the entire headwaters region using a meso-scale hydrologic model. Experiments are aimed at quantifying the system sensitivity and hydrologic impacts of changing LAI (from forest disturbance) and reduced snowpack albedo (from dust deposition and forest litter) on streamflow and hydrologic states. Results suggest beetle kill-induced canopy loss leads to an overall increase in water yield (i.e. streamflow) on the order of 8 - 13%, depending on disturbance severity and extent. Dust-on-snow exerts a primary control on the timing and rate of melt, with earlier and more rapid melt rates associated with more extreme dust deposition and with relatively limited interaction among components. Differences in model sensitivity across scale present a compelling case for additional research.
