Watershed Response to Hydrologic Disturbances: Local, Regional, and National Perspectives
This presentation will explore several aspects of land cover change and climate impacts on hydrology. We’ll start by 
addressing the question: What makes watersheds sensitive to forest disturbance? Despite a long appreciation of the 
significance of forests to water supplies, watershed sensitivity to forest disturbances remains difficult to 
predict. Yet, forested watersheds supply water to more than 180 million people in the US. An analysis of a 
national-scale watershed database together with high-resolution forest disturbance imagery demonstrated that 
disturbance has caused significant changes (both increases and decreases) in water yield and streamflow timing. 
Watersheds exhibiting post-disturbance increases or decreases in water yield were found to be distinct from each 
other (p<0.05) and regional patterns of sensitivity appear to be driven largely by differences in edaphic (soil) 
characteristics. 
The second part of this presentation offers a land-surface perspective on both flooding and sediment transport in 
the Upper Missouri River Basin and Colorado Front Range. Gauge records reveal a sharp increase in the Upper Missouri 
River Basin’s year-to-year streamflow variability since about 1970 with the coefficient of variation of annual 
streamflow in the 20-year period 1993-2012 having roughly doubled relative to the 20th century. Yet commensurate 
changes in the variability of precipitation and temperature have not been observed. Here we attempt to diagnose the 
causes of the streamflow changes, focusing on the relationship between land surface physics and the evolving 
characteristics of the meteorological forcings. Model calibration issues will be discussed, followed by a 
description of several experiments including an ensemble streamflow experiment designed to isolate the role of 
initial conditions versus meteorological forcing in the three largest events in recent decades. Outcomes of this 
research are relevant for recent concerns over intensification of the hydrological cycle. The last part of the 
presentation will explore hydrologic uncertainties on the Colorado Front Range. In particular, the development of a 
sediment modeling system sensitive to changes in climate and land cover. Future uncertainties in hydrological 
extremes challenge drinking water utilities’ ability to treat water to meet regulatory and public health protection 
goals. This work is part of a larger project linking water treatment, decision support and hydrologic extremes, with 
the goal of aiding in water treatment facilities amidst challenges posed by climate change.