How Has Discharge Been Changing over the U.S. Midwest During the Last Fifty Years?
Abstract
Potential changes in discharge distribution and frequency of flood events over the U.S. Midwest could have very large economic and social repercussions (e.g., fatalities, agricultural losses, flood losses, water quality issues). It is therefore of paramount importance to detect these changes. Long-term historical records are key to understand our past and provide valuable information about possible future changes. Streamflow time series from 509 USGS stream gage stations over the U.S. Midwest (North Dakota, South Dakota, Nebraska, Kansas, Missouri, Iowa, Minnesota, Wisconsin, Illinois) are used to (1) investigate the presence of abrupt and gradual change in different parts of the discharge distribution (from low to high quantiles), and (2) evaluate changes in the frequency of flood events. All stream gage records have at least 50 years of data and ending no earlier than 2011. Non-parametric tests are used to examine the presence of changes in the discharge distribution. The results of this work indicate that the number of stations with statistically significant changes in low to moderate quantiles is higher than the changes in high quantiles. These findings will be interpreted in light of human modifications of the catchments and climate variability. The examination of changes in the frequency of flood events is based on Poisson regression. For any given year, we count the number of flood peaks exceeding a high threshold (the threshold is set to give, on average, two flood events per year). Results indicate that the frequency of flood events has been increasing over large areas of our domain, with the most noticeable exceptions being Nebraska and Kansas. We discuss the interpretation of these changes in terms of possible physical mechanisms (e.g., climate, construction of dams, changes in agricultural practices).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.H33G1471M
- Keywords:
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- 1807 HYDROLOGY Climate impacts;
- 1869 HYDROLOGY Stochastic hydrology;
- 1632 GLOBAL CHANGE Land cover change