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

Abstract: The Colorado River Basin is an essential freshwater resource
for the southern Rocky Mountains and southwestern U.S. The majority of
water originates in the headwaters region and hence changes to this
region will largely control downstream water availability.
Understanding the role of climatic change and land cover disturbances
on hydrology is of growing importance for water managers in light of
steady increases in demand. Numerous studies have identified
appreciable inter-annual variability in historical precipitation,
which in combination with warming temperatures could have severe
implications on future water supply. More recently, the northern
headwaters region has suffered widespread tree kills due to Mountain
Pine Beetle (MPB) infestation across a range of forest types,
elevation, and latitude. Additionally, the incidence and severity of
desert dust-on-snow events have risen in the past decade, causing
increased radiative transfer and snowmelt rates within headwaters
snowpacks, shifting peak snowmelt runoff earlier in the year. In this
presentation, I will first explore hydrologic impacts of the latter
two disturbance factors in a hydrologic modeling framework. Next, I
will discuss issues associated with separating these impacts from
climatic factors and present some relevant results. The Distributed
Hydrology Soil Vegetation Model (DHSVM) was selected to simulate
hydrologic conditions over a set of 4 candidate catchments within the
headwaters region that offer a gradient in MPB impacts, dust-on-snow
severity, elevation, and forest coverage. The observational data sets
include meteorological forcings of precipitation, maximum and minimum
temperature, time series maps of leaf area index (LAI), as well as
other forest cover properties derived from MODIS forest phenology and
aerial survey data. Experiments are focused on examining the impacts
of changing LAI and phenology cycles (from MPB), and snow surface
albedo properties (from dust-on-snow events) on streamflow and
hydrologic fluxes, such as snow water equivalent. It is expected that
these results will lead to a clearer understanding of current and
future drivers for change in hydrologic response and identify key
issues going forward.

About the presenter
Ben Livneh, Ph.D.

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Date and time: 
Wednesday, January 16, 2013 - 3:00pm