&EPA
San Juan Watershed:
Water Quality and Agriculture
Under the, Clean Water Act (CWA), EPA regulates the quality of and discharges of pollutants into our nation's surface
waters. States: and tribes regularly monitor and assess surface water quality, communicate water quality conditions
to the public, and work to address natural and human-caused water quality issues. The San Juan Watershed in the
southwestern United States comprises: the San Juan and Animas Rivers and their tributaries. The headwaters of the:
Animas River lie in a naturally ore-rich mineral belt that was the site of significant historical mining activity. While some
metals in the waters of the upper Animas River are naturally occurring, many come from acid mine drainage and
runoff from mining disposal piles.
The lower Animas River is diluted by incoming waters with lower levels of metals as the Animas flows southward
through Durango, CO to Farmington, NM where: it joins the San Juan Rivet: The Animas is the largest free-flowing
perennial tributary to the San Juan and can have an important influence on San Juan water quality.
The San Juan River is a source of water and power for over 4 million people. The river crosses diverse landscapes
and receives waters from multiple tributaries before it reaches Lake Powell and converges with the Colorado River.
STATE AND TRIBAL ASSESSMENTS1
Animas River
Lake Powell
- .
San Juan River
armington
Waterbody Status
| Not Supporting Agricultural Use
Fully Supporting Agricultural Use
| Other Assessment Status
Note: Agricultural use includes irrigation, livestock watering, and other uses depending on the state.
N
I
Data Sources: EPA ATTAINS, USGS, Esri
This map presents state and tribal assessments of water quality relative to the standards they established under the
CWA for agricultural uses. These standards protect livestock that drink the water and crops that are irrigated with
the water. Green segments are meeting standards for agricultural uses. Red segments are not meeting standards for
agricultural uses. Blue segments were not assessed or not reported or are in the process of being assessed.
' This map diOes.;not include information for Ute Mountain Utfi: or Southern UtQ Indian Tribes. The'Southern Ute was authorized, as treatment in a
¦similar manner as a slate (TAS) for CWA Section 303(e); and aisf July 2020, is in the process of preparing tfieirwatenquality standards package
for EPA review and approval The Ute Mountain U{8 hay? trlpally-adopted and federally-apprqsed water quality standards and are in tire process;
of developing an assessment methodology Thetribsgcan be contacted directly with any questions related to water quality.

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&EPA
San Juan Watershed:
Water Quality and Agriculture
KEY POINTS
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EPA, states, tribes and other federal, non-profit, and local entities have: conducted extensive monitoring to
evaluate watershed condition.
The states and tribes in the watershed have assessed surface water quality based on their respective
standards under the CWA. Assessments are, updated periodically in accordance with established state and
tribal assessment cycles.
According to CWA reporting for 2020, Colorado determined that waters assessed in thfe upper and lower
Animas River are meeting established state standards for agricultural uses.
According to: CWA reporting for 2018 to 2020, New Mexico determined that the lower Animas River and
upper San Juan River in New Mexico were meeting state Surface water quality standards for agricultural
uses, including for livestock watering and irrigation.
According to CWA reporting for 2011 to 2017 Navajo Nation determined that waters assessed in the San
Juan River and certain tributaries to the San Juan River were not meeting established tribal standards for
agricultural use due toJevels of certain metals in the water.
According to CWA reporting for 2016, Utah determined that waters assessed in the lower San Juan River
and Lake Powell were meeting-established state standards for agricultural uses, Utah determined that an
assessed tributary to the lower San Juan River was not meeting standards for agricultural use due to levels
of metals and salts.
From 2018 through 2021, EPA is working in collaboration with states and tribes to collect water quality and
Sediment samples at 39 locations across the watershed. These samples are analyzed for metals and other
parameters.
• Results to date showed sporadic excursions above EPA's national water quality recommendations for
concentrations of metals that protect livestock and crops,
SomS metals, including nickel and copper, are prevalent in higher concentrations in the upper Animas due
to mining activities, but diminish further downstream.
All available data from these monitoring efforts can be found on EPA's San Juan Watershed website.
EPA 840-F-20-003
August 2020
https://www.epa.gov/san-iuan-watershed

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