Prairie Pothole Region waterbody extent and chemistry

This image shows a portion of the Prairie Pothole Region (see location map). The figure illustrates the variability of lake chemistry—red dots are lakes for which sulfate increased between the 1970’s and 2012-2013, whereas the blue dots show water bodies with a sulfate decrease over this time period. The lakes are shown by Landsat satellite imagery in two colors reflecting their extent in 1973 (light blue) and 2011 (dark blue). May of these were dry in 1973. The base of the figure is surface geology. The water bodies with decreasing sulfate over time are larger and associated with sandy portions of the landscape, whereas those with sulfate increase over time are associated with clay-rich portions of the landscape. Image credit: Martin Goldhaber, USGS

Dec 14, 2015 • Martin Goldhaber is a Research Chemist with the U.S. Geological Survey. Today at the 2015 AGU Fall Meeting, Dr. Goldhaber gave a talk about how climate change will impact the hydrochemistry of wetlands in an immensely important ecosystem known as the Prairie Pothole Region. Landsat data helped Goldhaber track how the size of the waterbodies in his study area changed between 1973 and 2011. Here’s what Dr. Goldhaber shared with us about his research.

Presentation Title:
Impact of Climate Variability on the Hydrogeochemistry of Ecologically Important Prairie Wetlands and Lakes

Background:
The Prairie Pothole Region of the north-central U.S. and south central Canada, which occupies 750,000 square kilometers, is one of the most important ecosystem complexes on the continent. It’s millions of ponds and lakes support the majority of the continent’s waterfowl. Water chemistry here is 1) highly variable, and 2) unusually rich in sulfate.

Approach:
To characterize how climate variability impacts wetland chemistry in time and space, we chemically analyzed 167 water bodies in a 10,000 square kilometer during 2012-2013, following a time of extreme precipitation. These same water bodies had been studied in the 1960’s and 70’s during a time of mild drought

Results:
Using a geochemical modeling approach, we determined that for most water bodies, their chemical evolution was due to addition of rainwater and overland flow. However, for a significant minority (~40%), their chemical evolution was more complex and required inputs of saline groundwater. The first group was larger and their surface area changed less over time than the second group. The first group also was associated with more permeable underlying sediments (sand) than the second group (clay).

Landsat data was used to evaluate both the surface area change over time (1973- 2011) and to derive a statistical measure of water permanence both of which could be tied to the chemical evolution of the water bodies.

These results will help establish which portions of the Prairie Pothole Region are most susceptible to climate variability and change and guide management decisions as to where conservation efforts should be placed.

Co-authors:
Christopher Mills
USGS Central Region Office

David Mushet
USGS

Craig Stricker
USGS-Denver Federal Center

Jennifer Rover
USGS

Anyone can freely download Landsat data from the USGS EarthExplorer or LandsatLook.

Further Reading:
+ Martin Goldhaber’s USGS Profile
+ Landsat at #AGU15