Deciphering the impacts of competing hydrologic disturbance factors in the Upper Colorado River Basin

Abstract: The Colorado River Basin is an essential freshwater resourcefor the southern Rocky Mountains and southwestern U.S. The majority ofwater originates in the headwaters region and hence changes to thisregion will largely control downstream water availability.Understanding the role of climatic change and land cover disturbanceson hydrology is of growing importance for water managers in light ofsteady increases in demand. Numerous studies have identifiedappreciable inter-annual variability in historical precipitation,which in combination with warming temperatures could have severeimplications on future water supply. More recently, the northernheadwaters region has suffered widespread tree kills due to MountainPine Beetle (MPB) infestation across a range of forest types,elevation, and latitude. Additionally, the incidence and severity ofdesert dust-on-snow events have risen in the past decade, causingincreased radiative transfer and snowmelt rates within headwaterssnowpacks, shifting peak snowmelt runoff earlier in the year. In thispresentation, I will first explore hydrologic impacts of the lattertwo disturbance factors in a hydrologic modeling framework. Next, Iwill discuss issues associated with separating these impacts fromclimatic factors and present some relevant results. The DistributedHydrology Soil Vegetation Model (DHSVM) was selected to simulatehydrologic conditions over a set of 4 candidate catchments within theheadwaters region that offer a gradient in MPB impacts, dust-on-snowseverity, elevation, and forest coverage. The observational data setsinclude meteorological forcings of precipitation, maximum and minimumtemperature, time series maps of leaf area index (LAI), as well asother forest cover properties derived from MODIS forest phenology andaerial survey data. Experiments are focused on examining the impactsof changing LAI and phenology cycles (from MPB), and snow surfacealbedo properties (from dust-on-snow events) on streamflow andhydrologic fluxes, such as snow water equivalent. It is expected thatthese results will lead to a clearer understanding of current andfuture drivers for change in hydrologic response and identify keyissues going forward.


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Wednesday, January 16, 2013 - 3:00pm