The Niobrara Formation as a challenge to water quality in the Arkansas River, Colorado, USA

Journal of Hydrology: Regional Studies
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Abstract

Study region

Arkansas River, east of the Rocky Mountains.

Study focus

Cretaceous sedimentary rocks in the western United States generally pose challenges to water quality, often through mobilization of salts and trace metals by irrigation. However, in the Arkansas River Basin of Colorado, patchy exposure of multiple Cretaceous formations has made it difficult to identify which formations are most problematic. This paper examines water quality in surface-water inflows along a 26-km reach of the Arkansas River relative to the presence or absence of the Cretaceous Niobrara Formation within the watershed.

New hydrological insights for the region

Principal component analysis (PCA) shows Niobrara-influenced inflows have distinctive geochemistry, particularly with respect to Na, Mg, SO42βˆ’, and Se. Uranium concentrations are also greater in Niobrara-influenced inflows. During the irrigation season, median dissolved solids, Se, and U concentrations in Niobrara-influenced inflows were 83%, 646%, and 55%, respectively, greater than medians where Niobrara Formation surface exposures were absent. During the non-irrigation season, which better reflects geologic influence, the differences were more striking. Median dissolved solids, Se, and U concentrations in Niobrara-influenced inflows were 288%, 863%, and 155%, respectively, greater than median concentrations where the Niobrara Formation was absent. Identification of the Niobrara Formation as a disproportionate source for dissolved solids, Se, and U will allow for more targeted studies and management, particularly where exposures underlie irrigated agriculture.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The Niobrara Formation as a challenge to water quality in the Arkansas River, Colorado, USA
Series title Journal of Hydrology: Regional Studies
DOI 10.1016/j.ejrh.2017.05.001
Volume 12
Year Published 2017
Language English
Publisher Elsevier
Contributing office(s) Colorado Water Science Center
Description 15 p.
First page 181
Last page 195
Country United States
State Colorado
Other Geospatial Arkansas River