Effects of Human Influences and Natural Persistence on Low Streamflow Changes in the United States
Abstract
Accurate assessment of low streamflows is important to the management of water supply, ecological conditions in streams, and protection of water quality. This study compares observed trends in low streamflow across the conterminous U.S. at near-natural (Hydroclimatic Data Network-2009) stream gages to trends at stream gages which have experienced substantial basin alteration (Agricultural, Regulated, and Urban), while accounting for the natural persistence present in low-flow time series. This work provides insight into regional climate-related trends in low streamflows and changes driven, in part, by human activities. Trends were tested for low 1-, 3-, and 7-day streamflows, number of zero-flow days, and annual deficit metrics at 2,482 U.S. Geological Survey stream gages across the conterminous U.S. For all time periods tested (50, 75, and 100 years through 2015), higher low streamflows over time were consistently observed throughout much of the northeastern quadrant of the conterminous U.S., as were lower flows in the southeastern and northwestern U.S. Reference gages with minimal human impacts generally indicated lower low-flow conditions over time for much of the U.S. In agricultural basins, trends predominantly indicated higher low-flow conditions over time which may be associated with increased precipitation and activities related to annual row crop cultivation. Trends in regulated basins were generally toward higher low flows, lower annual deficits, and fewer days of zero flow, though results were less regionally coherent. Geographic distributions of trends at urban gages were very similar to those for the reference gages but generally had a greater percentage of significant upward trends in low streamflows, fewer days of zero flow, and decreases in annual deficits which may be attributed to urban landscape features and patterns of water use and waste-water discharge that can increase base flow.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H51L1456D
- Keywords:
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- 1817 Extreme events;
- HYDROLOGYDE: 1821 Floods;
- HYDROLOGYDE: 1833 Hydroclimatology;
- HYDROLOGYDE: 1860 Streamflow;
- HYDROLOGY