**National Irrigation Water Quality Program**\
U.S. Department of the Interior

Irrigation Drainage Studies of the Angostura Reclamation Unit and the
Belle Fourche Reclamation Project, Western South Dakota: Results of 1994
Sampling and Comparisons with 1988 Data. U.S. Geological Survey
Water-Resources Investigations Report 01-4103, 65p.

Sando, S.K., Williamson, J.E., Dickerson, K.K., Wesolowski, E.A.

ABSTRACT

The U.S. Department of the Interior started the National Irrigation
Water Quality Program in 1985 to identify the nature and extent of
irrigation-induced water-quality problems that might exist in the
western U.S. The Angostura Reclamation Unit (ARU) and Belle Fourche
Reclamation Project (BFRP) in western South Dakota were included as part
of this program. The ARU and BFRP reconnaissance studies were initiated
in 1988, during below-normal streamflow conditions in both study areas.
Surface water, bottom sediment, and fish were resampled in 1994 at
selected sites in both study areas during generally near-normal
streamflow conditions to compare with 1988 study results.

Concentrations of major ions in water for both the ARU and BFRP study
areas are high relative to national baseline levels. Major-ion
concentrations for both areas generally are lower for 1994 than for
1988, when low-flow conditions prevailed, but ionic proportions are
similar between years. For ARU, dissolved-solids concentrations probably
increase slightly downstream from Angostura Reservoir; however, the
available data sets are insufficient to confidently discern effects of
ARU operations on dissolved-solids loading. For BFRP, dissolved-solids
concentrations are slightly higher at sites that are affected by
irrigation drainage; again, however, the data are inconclusive to
determine whether BFRP operations increase dissolved-solids loading.

Most trace-element concentrations in water samples for both study areas
are similar between 1988 and 1994, and do not show strong relations with
discharge. ARU operations probably are not contributing discernible
additional loads of trace elements to the Cheyenne River. For BFRP,
concentrations of some trace elements are slightly higher at sites
downstream from irrigation operations than at a site upstream from
irrigation operations. BFRP operations might contribute to trace-element
concentrations in the Belle Fourche River, but available data are
insufficient to quantify increases. For both study areas, concentrations
of several trace elements occasionally exceed National Irrigation Water
Quality Program guidelines. Selenium routinely occurs in concentrations
that could be problematic at sites upstream and downstream from both
study areas. Elevated selenium concentrations at sites upstream from
irrigation operations indicate that naturally occurring selenium
concentrations are relatively high in and near the study areas. While
ARU operations probably do not contribute discernible additional loads
of selenium to the Cheyenne River, BFRP operations might contribute
additional selenium loads to the Belle Fourche River.

Concentrations of most trace elements in bottom sediment, except arsenic
and selenium, are similar to typical concentrations for western U.S.
soils for both study areas. Bottom-sediment arsenic and selenium (1988)
concentrations in both study areas can reach levels that might be of
concern; however, there is insufficient information to determine whether
irrigation operations contribute to these elevated concentrations.

Concentrations of most trace elements in fish in both study areas are
less than values known to adversely affect fish or birds, although there
are occasional exceedances of established criteria. However, selenium
concentrations in fish samples routinely are within the National
Irrigation Water Quality Program level of concern, and also commonly
exceed the dietary guideline for avian consumers for both study areas.
Selenium concentrations in fish samples generally are higher at sites
downstream from irrigation operations. For BFRP, arsenic and mercury
concentrations are elevated in fish samples from site B-18, which is
influenced by mine tailings.