Chemical Quality of Water Deliveries to Stillwater National Wildlife Refuge, Nevada Active

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The wetlands of Lahontan Valley, including those in Stillwater National Wildlife Refuge (SNWR) are critical feeding and resting habitat for thousands of migratory birds that follow the Pacific Flyway. However, water demands for agriculture, public supplies, and endangered and threatened fisheries have reduced the quantity and quality of water that had once supported more than 150,000 acres of Lahontan Valley wetlands. Recognizing the decline in this critical habitat, Congress included provisions in the 1990 Truckee-Carson-Pyramid Lake Water Rights Settlement Act (Title II of Public law 101-618; the Act) to assist with restoration and maintenance of wetland ecosystems in Lahontan Valley. The Secretary of the Interior was authorized to purchase water rights from willing sellers to support a long-term average of 25,000 acres of wetland habitat in Lahontan Valley, including 14,000 acres on SNWR. The Act also required the closure of agricultural drains from the Newlands Reclamation Project documented to deliver contaminated water to wetlands, and initiated studies of the feasibility of using treated municipal wastewater to improve or create wetlands.

Acquired water rights benefit SNWR by ensuring that wetland habitat is available in non-drought years and by improving water quality compared to when irrigation drainage was the dominant water source. However, the program’s goal of 70,000 acre-feet/year of water is far less than the 270,000 acre-feet/year estimated to have flowed into Stillwater Marsh during average years before construction of Lahontan Dam. Information about how the chemical quality of water and bottom sediment is affected by the water rights acquisition program is needed for science based management of SNWR.

To support decisions about the water delivered to SNWR for wetland enhancement, the USGS Nevada Water Science Center has Implemented a monitoring program to establish a baseline of chemical quality conditions for a network of the primary surface water inflows to SNWR. Sites can be revisited over time to document effects of future water- or land-use changes.

Four sets of water samples were collected as metrics of contributions from

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• irrigation drainage,
• feedlot runoff,
• treated wastewater effluent, and
• water from geothermal power generation.

These water-quality samples were sent to the laboratory for determination of

• major ions,
• selected species of nitrogen and phosphorus,
• selected trace elements, and
• trace organic compounds. 

Two sets of bottom sediment samples were collected for laboratory determination of selected trace elements. The water-quality and bottom sediment data are being reviewed and evaluated in terms of regulatory standards, criteria for the protection of aquatic life (see table 1 below), and for comparisons to data that were collected prior to the water acquisition program. 

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Extended drought during the data collection phase of this study resulted in fewer samples collected than originally planned.

DATA COLLECTION SITES

Water-quality samples were collected at the following sites. Map number corresponds to the numbered locations on the monitoring sites map. Data for each site is available by clicking on the site name below.

1  10312190         Lower Diagonal Drain at Highway 50 near Fallon

2  1031220130     Harmon Reservoir Outflow near Fallon

3  103122155       Stillwater Point Reservoir Bypass Canal near Stillwater

4  1031221902     S-Line Diversion Canal near Stillwater

5  10312220         Stillwater Slough Cutoff Drain near Stillwater

6  10312277         Paiute Drain below TJ Drain near Stillwater

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Table 1. Aquatic life criteria established for designated water of the State of Nevada (1994) and guidelines compiled by the U.S. Environmental Protection Agency (2014)

Chemical                              Aquatic Life Criteria                                 National Recommended Water Quality Criteria
Constituent                     (Nevada State Environmental                           (U.S. Environmental Protection Agency 2014)
                                             Commission, 1994)                                 

                                 1-hour Average       96-hour Average                     Criteria Maximum  Criterion Continuous

Aluminum                          --                             --                                              750                          87

Arsenic                              340^a                        180^a                                           340                         150

Boron                                550                          550                                              --                            --

Cadmium                            8^b                            2^b                                                2                           0.25

Chromium                   15^c/1,500^{b, d}            10^c/180^{b, d}                                 16^c/570^d                  11^c/74^d

Copper                               15^b                          10^{b                                               e                                      e}

Iron                                 1,000                       1,000                                              --                          1,000

Lead                                  41^b                           1^b                                                65                          2.5

Mercury                             2.0                         0.012                                             1.4                           0.77

Molybdenum                      19                            19                                                --                            --

Nickel                             1,200^b                       130^b                                             470                           52

Selenium                            20                             5                                                   ^f                             5^f

Zinc                                   99^b                          90^b                                              120                          120

pH                                     --                             --                                                --                           6.5-9

footnotes

^a Criterion is for As (III), the least abundant species of arsenic in typical surface water.
^b Criterion is hardness dependent; value shown is valid for hardness of 100 milligrams per liter CaCO_3.
^c Criterion is for chromium (III).
^d Criterion is for chromium (VI).
^e Criterion is calculated with the Biotic Ligand Model and 10 water quality constituents.
^f Criterion is being updated based on the latest scientific information.