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United States

San Juan Watershed Monitoring

Watershed Monitoring Challenges

Water resources in the San Juan Watershed are essential for recreational, agricultural, cultural, and residential uses. Potential contamination sources within the watershed include historic mining activities that disturbed the land and exacerbated naturally occurring mineralization of mining process residuals in the watershed’s aquatic environment. As part of the EPA’s San Juan Watershed Monitoring Program, in collaboration with the jurisdictions of Arizona, Colorado, New Mexico, Utah, Navajo Nation, Southern Ute and Ute Mountain Ute, TRC was tasked with designing a consistent approach to data collection and assessment of the water quality conditions in the San Juan Watershed and encompassing rivers.

Watershed Monitoring Solutions

The TRC project team conducted this water resource analysis from 2018 to 2021. Watershed impact studies and sampling rounds were taken during the 4 primary hydrologic regime events of spring runoff, summer base flow, fall monsoons and winter low-flow conditions at 39 defined site locations within the Watershed. The seasonal flow variability had to be carefully considered in the field program as well as the final analysis of findings and conclusion. Streamflow and water quality conditions found in each watershed and sub watersheds have material effects on the overall health and vitality of the surrounding terrestrial ecosystem and its relative value to the natural resiliency of the watershed as studied over time.

Fieldwork and laboratory work focused on characterizing water and sediment quality conditions and interactions in the contributing rivers and watershed by collecting
samples of each at every station location over time. TRC also assessed the watershed’s physical habitat values and collected fish and stream flow measurements using water flow measuring devices. Data and findings on water quality conditions in the Watershed that would lead to prudent watershed resource sustainability and management planning were also shared with stakeholder groups and the general public.


In June 2019, TRC water resource scientists presented findings of the data collection and analysis at the Animas and San Juan Watersheds Conference in New Mexico, where researchers and the general public meet, learn from and share the results of ongoing water quality research. An abundance of mayflies and stoneflies were observed at each site location, which are good indicators that the watershed seems to be recovering over time with improved water quality conditions that support wildlife and fisheries sustainability.

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