Fundamental Physics of Great Plains Drought
The U.S. Great Plains experienced a severe drought in 2012, symptoms of which included severe rainfall deficits and record setting high temperatures. An outstanding question is the relationship between regional precipitation deficits and heat waves, and further their mutual effects on soil moisture conditions. Land surface model simulations were conducted to quantify the combined and separate effects of rainfall deficits and air temperature on soil moisture--indicating an approximate 3:1 ratio of precipitation versus temperature control on soil drying. The plot on the left shows agreement in monthly anomalies (2002-2013) among independent estimates of terrestrial water anomalies from the GRACE satellite and two land surface models, ULM, and VIC (left ordinate axis) as well as observed precipitation (right ordinate axis) averaged over the Great Plains domain. A further question addressed in this work is the role of human-induced climate change on future Great Plains drought. Combining an understanding of the fundamental physics of drought with plausible future temperature and precipitation changes, the risks for unprecedented future drought are assessed and deemed to be unlikely.
This project is a collaboration with the National Oceanic and Atmospheric Administration, Physical Sciences Division.
Extreme Streamflow Events in the Upper Missouri River Basin
Extreme streamflow in the upper Missouri River Basin has become more prevalent in recent decades. Since 1975, 9 out of the 10 most extreme streamflow years on the Missouri River Basin since 1898 have occurred. Making use of naturalized flow data for the upper Missouri River Basin and 6 sub-basin catchments, trends in streamflow will be analyzed and compared to the main flow drivers of precipitation and snowmelt. It was previously found (NOAA Climate Assessment Report – 2011 Missouri River Basin Flooding, 2013) that streamflow is becoming more extreme and variable, while the precipitation levels are remaining relatively constant in both mean and variability. Through the use of the Variable Infiltration Capacity (VIC) model, an understanding of the drivers of these extreme flow events are being analyzed. Sensitivity experiment focusing on precipitation frequency and intensity are being performed to determine what role precipitation specifically has as a driver to these extreme events. This project is currently in the preliminary stages, with initial findings soon to come.
Sediment Modeling in the Colorado Front Range
Soil erosion adds constituents to streams, altering water chemistry and streambed morphology. This can adversely affect aquatic life, water resource infrastructure and regulation due to increased contaminants and sediment buildup above reservoirs. The effects of drought and wildfire on sedimentation will pose a critical challenge in the future and physically-based modeling offers a potential framework for mitigation. Through a model ensemble, this project will compare the output of empirical, conceptual and physically-based sediment models over three large catchments (>1000 square km) in the Colorado Front Range in order to simulate suspended sediment concentrations throughout time. This project is currently in the prliminary stages, with initial findings soon to come.