Influence of multi-decadal land use, irrigation practices and climate on riparian corridors across the Upper Missouri River Headwaters Basin, Montana

Hydrology and Earth System Sciences
By: , and 

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Abstract

The Upper Missouri River Headwaters Basin (36,400 km2) depends on its river corridors to support irrigated agriculture and world-class trout fisheries. We evaluated trends (1984-2016) in riparian wetness, an indicator of riparian condition, in peak irrigation months (June, July, August) for 158 km2 of riparian area across the basin using the Landsat Normalized Difference Wetness Index (NDWI). We found that 8 of the 19 riparian reaches across the basin showed a significant drying trend over this period, including all three basin outlet reaches along the Jefferson, Madison and Gallatin Rivers. The influence of upstream climate was quantified using per reach random forest regressions. Much of the interannual variability in the NDWI was explained by climate, especially by drought indices and annual precipitation, but the significant temporal drying trends persisted in the NDWI-climate model residuals, indicating that trends were not entirely attributable to climate. Over the same period we documented a basin-wide shift from 9% of agriculture irrigated with center pivot irrigation to 50% irrigated with center pivot irrigation. Riparian reaches with a drying trend had a greater increase in the total area with center pivot irrigation (within-reach and upstream from the reach) relative to riparian reaches without such a trend (p<0.05). The drying trend, however, did not extend to river discharge. Over the same period, stream gages (n=7) showed a positive correlation with riparian wetness (p<0.05), but no trend in summer river discharge, suggesting that riparian areas may be more sensitive to changes in irrigation return flows, relative to river discharge. Identifying trends in riparian vegetation is a critical precursor to enhancing the resiliency of river systems and associated riparian corridors.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Influence of multi-decadal land use, irrigation practices and climate on riparian corridors across the Upper Missouri River Headwaters Basin, Montana
Series title Hydrology and Earth System Sciences
DOI 10.5194/hess-23-4269-2019
Volume 23
Issue 10
Year Published 2019
Language English
Publisher Copernicus Publications
Contributing office(s) Geosciences and Environmental Change Science Center
Description 24 p.
First page 4269
Last page 4292
Country United States
State Montana
Other Geospatial Upper Missouri River headwaters basin
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