Tracking the Source of Metals to the San Juan River

Fact Sheet 2021-3029
Prepared in cooperation with the Navajo Nation Environmental Protection Agency
By: , and 



The San Juan River is a major water source for communities in the Four Corners Region of the United States (Colorado, Arizona, New Mexico, Utah) and is a vital source of water for the Navajo Nation. The Navajo Nation Environmental Protection Agency (NNEPA) periodically samples surface water on the Navajo Nation and has found that some elements exceed NNEPA surface water standards (the upper limits of an element for consumption or other use of water). Constituents of concern are substances that could be harmful if present in sufficient quantities, and it is important to keep track of the concentrations of these substances in the environment. In the San Juan River, constituents of concern include metals detected in river water, such as arsenic, lead, and aluminum. These metals can come from natural sources or can result from human activities (anthropogenic) and can affect the health of people, plants, and animals. The Animas River is one natural source of metals to the San Juan River because of the types of rock through which the Animas River flows and because of hard rock mining at the headwaters. Other potential sources of metals are oil and gas development, coal mining, coal-fired power plants, urban areas, illegal trash dumping, abandoned uranium mines and mills, overgrazed areas, natural geology, and leaching from subsurface agricultural return flows. Determining how much each of these sources contributes and the relative effect of each source on San Juan River water will help the Navajo Nation in their efforts to protect human health and the environment along the San Juan River.

The U.S. Geological Survey (USGS) is working with the NNEPA to identify sources of metals and trace elements entering the San Juan River from tributaries in the reach flowing through the Navajo Nation and to quantify the contribution from each natural and human-caused source. The USGS and NNEPA worked with local community members to locate tributaries where sampling equipment was installed. The 3-year source-tracking project, starting in spring 2021, will identify where metals at concentrations above safe surface water standards might be entering the river by evaluating the chemical signatures of water in the major tributaries of the San Juan River. Results will provide valuable information to the Navajo Nation, public drinking-water managers, irrigation districts, other stakeholders, scientists, and the public.

Suggested Citation

Blake, J.M., Chavarria, S.B., and Matherne, A.M., 2021, Tracking the source of metals to the San Juan River (ver. 1.1, July 2021): U.S. Geological Survey Fact Sheet 2021–3029, 4 p.,

ISSN: 2327-6932 (online)

ISSN: 2327-6916 (print)

Study Area

Table of Contents

  • Introduction
  • Approach and Tools
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Tracking the source of metals to the San Juan River
Series title Fact Sheet
Series number 2021-3029
DOI 10.3133/fs20213029
Edition Version 1.0: June 3, 2021; Version 1.1: July 2, 2021
Year Published 2021
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New Mexico Water Science Center
Description 4 p.
Country United States
State Colorado, Arizona, New Mexico, Utah
Other Geospatial San Juan River
Online Only (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details