Attachment	Water Quality

This section analyzes water quality in the study area, defined as lands in both the Sargent and the Farwell Irrigation Districts. Analysis was made of groundwater and surface water for physiochemical constituents, pesticides, and trace elements.

Affected Environment

Both groundwater and surface water quality in the study area are generally good, with the exception of elevated selenium levels in some areas.

Groundwater

Groundwater was analyzed in both the Sargent and Farwell Irrigation Districts. Because no water quality problems were detected in the Sargent Irrigation District, all the discussion below applies only to the Farwell Irrigation District.

Groundwater is not a major source of Farwell Unit irrigation water. There is minor irrigation from wells for a small amount of irrigated acreage confined to the river valley near St. Paul, Nebraska. Data on the chemical quality of groundwater in the Farwell Unit have been collected since 1949. Based on water quality data, there is little likelihood of a salt problem developing on project lands if groundwater were used for irrigation. Groundwater sources used for municipal supplies in the area are moderately hard.

Table E-1 displays the groundwater quality from Geological Survey (USGS) wells in and adjacent to the project areas. The well near St. Paul exhibits a relatively high nitrate concentration, but it is well below the drinking water standard. Samples collected from the other wells show little seasonal variation.

Based on data presented in table E-1, local groundwater has greater mineral content than either the Middle Loup River or Sherman Reservoir. This is typical since the Middle Loup River originates in the sandhills, which are underlain by groundwater of low mineralization. The irrigation district lands are situated in the loess hills underlain by water of greater mineralization. The water quality data simply reflects the local geology of the two aquifers.

Surface Water

Surface water was analyzed in both the Sargent and Farwell Irrigation Districts. Because no water quality problems were detected in the Sargent Irrigation District, all the discussion below applies only to the Farwell Irrigation District.

As stated in the Special Report Farwell Unit Water Conservation Study (Bureau of Reclamation [Reclamation], 1992), the overall quality of water in the Middle Loup River is well within Nebraska standards for uses such as agricultural supply and fish and wildlife.

Three types of studies were conducted on surface water. These studies looked at pesticides, physiochemical constituents, and trace elements. No pesticides were found in elevated concentrations. One physiochemical constituent, fecal coliform, was found in elevated concentrations. One trace element, selenium, appeared in elevated concentrations sufficient to warrant further study. Study results for both these elements are described in more detail below.

Physiochemical Constituents.-- Table E-2 illustrates that water quality of the mainstem Middle Loup River and the outflow from Sherman Reservoir is generally very good from a physicochemical standpoint.

As displayed in table E-2, the major water quality problem in the Middle Loup River basin is excessive bacteria levels (fecal coliform). The elevated bacteria concentrations are a concern only for recreational uses involving partial or full body contact. The high concentrations of bacteria are attributed to a combination of inadequate wastewater disinfection and uncontrolled runoff from pastures, rangeland, and confined animal feedlots. None of these activities is directly related to Farwell Unit operation; therefore, activities resulting from the project title transfer would not change the bacterial loadings to the river. The USGS has also collected water quality data on several streams that drain the Farwell Irrigation District. These data are summarized in table E-3 and include two stations each on Oak Creek and Turkey Creek and one station each on Deer and Dry Creeks.

The Oak Creek stations indicate water quality similar to groundwater. The Deer, Turkey, and Dry Creek stations suggest that those waters contain a combination of groundwater discharge and subsurface irrigation return flows. Irrigation return flow data collected from district subsurface drains show results similar to those for the tributaries draining the district.

In addition, table E-2 contains a summary of water quality data gathered by the USGS at the St. Paul gage in the project area. The St. Paul gage is located downstream from the mouths of all the tributaries shown in table E-3. The concentrations of principal constituents shown in table E-2 increase by about 35 percent between Arcadia and St. Paul. Several factors--such as the addition of more highly mineralized water from the South Loup River, discharge of more highly mineralized groundwater from the loess hills, and project irrigation return flow--contribute to the change in water quality as it is monitored upstream to the St. Paul gage. This gage is upstream of the confluence of the North Loup River and is generally considered the endpoint water quality indicator of the Sargent and Farwell Project service areas.

It is important to understand that operation of the Sargent and Farwell Irrigation Districts comprises only 10.38 percent of the basin's irrigated acreage in proportion to the total of Middle Loup Basin irrigated lands. Therefore, the irrigation return flow contribution to the basin's overall water quality conditions is very minor.

Trace Elements.--Initial data indicate that selenium has been found in the five repre-sentative return flow sampling locations in the basin. The three irrigation return flow drain samples in the Farwell Unit ranged from 5.1 to 12.1 micrograms per liter (µg/L). The two Sargent Unit irrigation return flow drain samples were 1.5 and 1.8 µg/L. Table E-4 and Table E-5 display trace element test results.

Significant geology investigations by the USGS indicate that the principal source of selenium in Nebraska is the uppermost bedrock of Cretaceous age which underlies about one-fourth of Nebraska. The Niobrara formation and Pierre Shale also contain significant amounts of selenium, as does the Mobridge Member of the Pierre Shale. Little information on the selenium content of the Niobrara and of the lower and upper parts of the Pierre Shale (below and above the Mobridge Member, respectively) in Nebraska is available, but significant amounts of selenium may be present in each of these units. The other stratigraphic units of Cretaceous age are reported to contain insignificant amounts of selenium.

In most places where there are outcrops of Niobrara, it forms bluffs and is not an aerially extensive parent material for soils. The Pierre Shale is thicker and crops out much more extensively, and most of the soil material in the outcrop area is residual produced by weathering of the shale. Soils in the outcrop area are likely to be seleniferous if the parent rock material contained significant amounts of selenium.

Unconsolidated deposits of Quaternary age form the surface of a large part of Nebraska. Three important components of these deposits are glacial drift, loess, and alluvium, all of which incorporate, at least in some places, fragments derived from seleniferous Cretaceous rocks: these deposits can be a source of selenium to groundwater that comes into contact with them. Beds of volcanic ash in the Quaternary sequence are another possible source of selenium in groundwater. These unconsolidated deposits are present in the Sargent and Farwell Irrigation Units. Another source of the elevated selenium in the Farwell Unit might be selenium leached from the loess by infiltrating groundwater in areas where the loess has become saturated as a result of the rising water table, which has possibly occurred during the 40 years of project operation.

Summary of Selenium Effects.-- The Environmental Protection Agency has established a "water quality criterion" of 5 µg/L to protect freshwater aquatic life from chronic levels of selenium. This means selenium concentrations at or below 5 µg/L in water are not considered harmful, but higher levels of selenium can cause birth defects, reproductive failures, and death in fish, wildlife, and livestock. However, selenium is also an essential trace nutrient for animals, and it serves beneficial metabolic functions (Arthur and Beckett, 1994). Thus, selenium deficiency as well as toxicity can cause adverse effects for fish and wildlife (Oldfield, 1990). Interestingly, both deficiency and toxicity cause similar effects--reproductive depression, anemia, weight loss, and immune dysfunction (Koller and Exon, 1986). The known effects of selenium exposure to various classes of organisms are summarized in table E-7 (Department of the Interior, 1998).

Concentrations above 5 µg/L in water may occur naturally from the weathering process of marine shales containing selenium and/or may result from human activities (such as irrigation) accelerating the process of leaching, which naturally occurs. Preliminary results from a limited number of sample locations seem to indicate the occurrence of selenium-bearing soils, and concentration in irrigation return flows may be greater in lands irrigated in the Farwell Unit than the Sargent Unit. There are numerous variables that may account for the difference in selenium concentration between lands in the two irrigation units.

Reclamation is concerned about the levels of selenium concentrations and believes further studies are warranted. A combination of significant selenium uptake and bioaccumulation in indicator macroinvertebrates, plants, fish, and wildlife would need to be conclusively proven before mitigative activities would be considered, evaluated, and implemented. Table E-6 and Table E-7 display results of bottom sediment testing for saturated extract and acid digest, respectively.

In May and June of 1997, personnel from Reclamation, the Fish and Wildlife Service, and the Nebraska Game and Parks Commission harvested fish and macroinvertebrate samples (of various species) from the Middle Loup River located in Nebraska. The samples were frozen and sent to the Environmental and Contaminants Research Center (ECRC), USGS, Columbia, Missouri, to be tested for selenium concentrations.

The samples were prepared for testing using standard procedures. Large fish specimens were tested individually, while small fish species were ground up and made into a composite sample.

The amount of selenium in fish and invertebrates was determined by flow injection hydride generation atomic spectroscopy. The ECRC forwarded the results to Reclamation personnel in the Great Plains Regional Office for analysis.

Environmental Consequences.-- Certain fish species bioaccumulate selenium in greater concentrations than other fish species. This may be attributed to, but not limited to, feeding habits, genetics, physiology, and/or location.

Geographic Locations of Fish and Invertebrate Samples.--Data were gathered at the following sample locations:

(1) Sherman Reservoir
(2) Loup River Basin tributaries: Deer, Oak, and Turkey Creeks
(3) Drains: Daylight point of buried pipe drain
(4) Middle Loup River: Milburn Diversion Dam, Rockville, and St. Paul
(5) Wetlands: West of St. Paul, northeast of Boelus

The data do not take into consideration individual fish or invertebrate species. Each data point represents one fish or invertebrate sample. There are 118 fish and 22 invertebrate samples, of which 50 fish samples (42 percent) and 20 invertebrate samples (91 percent) are greater than the Lemly threshold (4 micrograms per gram [µg/g] and 3 µg/g, respectively). Certain sample locations tend to contain fish species with higher selenium concentrations than the fish species in other sample locations. The sample location codes are as follows:

A total of 29 bottom sediment samples were collected at the above locations, and 17 of those samples (59 percent) exceed the selenium biotic toxicity threshold of 2 µg/g (dry weight). Water samples at the three irrigation return flow drain locations were collected in June and September 1996. Results of the water analysis indicate that selenium concentrations at all drain sites (except the September Turkey Creek location) exceed the biotic toxicity threshold for selenium in water. The two open ditch drain water sampling locations (representing land form, geology, soils, and cropping pattern of the Sargent Irrigation District's 13,922 acres) were below the biotic toxicity threshold on both sampling events. It was determined additional sediment and biota samples would not be collected for the Sargent Unit based on the initial drain water screening investigation.

Figure C-1, Figure C-2, Figure C-3, Figure C-4, Figure C-5, Figure C-6, Figure C-7, Figure C-8, and Figure C-9

Conclusions.-- The data collected for this investigation of selenium in water, sediments, macroinvertebrates, and fish eggs provide a straightforward, consistent approach to evaluate the aquatic hazard of selenium using a set of data from contaminant monitoring. Hazard is characterized from sensitive endpoints linked to important biological effects. The hazard profiles are based on a large body of field and research data on selenium cycling and toxicity. The Farwell Unit selenium investigation utilized data results from four ecosystem components, with the objective of determining the potential for food-chain bioaccumulation and reproductive impairment in fish, which are sensitive biological receptors for estimating impacts of selenium contamination. Four degrees of selenium hazard are possible. Based on the separate numerical score for water, sediment, fish, and benthic macroinvertebrates, a final hazard characterization is determined by adding individual scores and comparing the total to the evaluation criteria. The final hazard characterization for Farwell Unit is as follows:

The final aquatic hazard assessment of selenium in the Farwell Unit of the Middle Loup Basin is determined to be a high hazard and reflects a range of geographic locations reflecting differences in waterborne selenium concentrations and associated influences on the sediment food pathway and dietary exposure of fish. Corrective actions may be prescribed and implemented at the high hazard sites such as irrigation return flow drainways and the Farwell North wetland. The selenium hazard protocol can be utilized to evaluate the success of mitigating action in reducing selenium hazards.

Environmental Consequences

Environmental impacts of the alternatives on water quality are described by topic below.

Groundwater

There are no groundwater problems currently in the study area. Because title transfer would not change project water supply or operations, impacts on water quality under the Title Transfer Alternative would be the same as under the No Action Alternative.

Surface Water

Based on review of prior water quality data, it is apparent that Middle Loup River water can be continued to be used for irrigation of the existing crops in the project area with little likelihood that a soil salinity hazard or harmful levels of exchangeable sodium will develop. Normal irrigation practices and rainfall will provide adequate leaching of any salts that develop. No negative environmental impacts are expected under any alternative regarding physiochemical constituents and pesticides.

Selenium concentrations will not be affected by title transfer; therefore, impacts would be the same as under the No Action Alternative. Under the No Action Alternative, Reclamation would coordinate with the State to address these issues. Under title transfer, the Loup Basin Reclamation District would coordinate with the State to address these issues.