National Irrigation Water Quality Program Research Articles

Commentary: selenium study on endangered razorback sucker is flawed

The razorback sucker ( Xyrauchen texanus) is listed as federally endangered throughout its range. A massive recovery effort by the Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin has focused its efforts in the upper Colorado River. The upper Colorado River basin also has two locations that have been identified by the National Irrigation Water Quality Program as having substantial selenium contamination. Selenium is toxic to fishes, affecting reproductive success. Thus, there is concern about potential effects of selenium on the endangered razorback sucker. Two sets of studies have investigated the effects of selenium on razorback suckers, but study results are conflicting. This commentary evaluates studies that claim selenium is not a problem for razorback sucker. We find that study bias was so pervasive that purported conclusions were unwarranted. Contaminated control water, older life stages of fish tested, lack of methodology for analysis of selenium in water, diet, or fish, use of rotifer food, low feeding rates, low growth rates of fish, and improper storage of site waters resulted in an apparent erroneous linkage of high selenium in whole-body residues with no adverse effects.

Selenium in Irrigated Agricultural Areas of the Western United States

A logistic regression model was developed to predict the likelihood that Se exceeds the USEPA chronic criterion for aquatic life (5 µg/L) in irrigated agricultural areas of the western USA. Preliminary analysis of explanatory variables used in the model indicated that surface-water Se concentration increased with increasing dissolved solids (DS) concentration and with the presence of Upper Cretaceous, mainly marine sediment. The presence or absence of Cretaceous sediment was the major variable affecting Se concentration in surfacewater samples from the National Irrigation Water Quality Program. Median Se concentration was 14 µg/L in samples from areas underlain by Cretaceous sediments and <1 µg/L in samples from areas underlain by non-Cretaceous sediments. Wilcoxon rank sum tests indicated that elevated Se concentrations in samples from areas with Cretaceous sediments, irrigated areas, and from closed lakes and ponds were statistically significant. Spearman correlations indicated that Se was positively correlated with a binary geology variable (0.64) and DS (0.45). Logistic regression models indicated that the concentration of Se in surface water was almost certain to exceed the Environmental Protection Agency aquatic-life chronic criterion of 5 µg/L when DS was greater than 3000 mg/L in areas with Cretaceous sediments. The “best” logistic regression model correctly predicted Se exceedances and nonexceedances 84.4% of the time, and model sensitivity was 80.7%. A regional map of Cretaceous sediment showed the location of potential problem areas. The map and logistic regression model are tools that can be used to determine the potential for Se contamination of irrigated agricultural areas in the western USA.

SYNTHESIS OF DATA FROM STUDIES BY THE NATIONAL IRRIGATION WATER‐QUALITY PROGRAM1

ABSTRACT: From 1986 to 1993, the National Irrigation Water‐Quality Program (NIWQP) of the U.S. Department of the Interior studied whether contamination was induced by irrigation drainage in 26 areas of the Western United States. In 1992, a study to evaluate and synthesize data collected during these 26 investigations began. Selenium, boron, and molybdenum are the trace elements and DDT the pesticide most commonly found in surface water at concentrations exceeding chronic criteria for the protection of aquatic life. In six of the areas, the median selenium concentration exceeded the criterion. Aquatic‐life criteria have not been developed for uranium, but the median uranium concentration exceeded the proposed Maximum Contaminant Level for drinking water in seven areas. A principal components analysis indicates that severity of selenium contamination is not related to the severity of contamination by boron, molybdenum, and arsenic. Arsenic, boron, molybdenum, and selenium concentrations are nearly the same in both filtered and unfiltered samples, which indicates that contaminant concentrations in filtered samples can be directly compared with biological‐effects data developed using unfiltered samples. At a given site, selenium concentrations in surface water can change by an order of magnitude during the course of a year and from one year to another.

Pattern recognition analysis and classification modeling of selenium-producing areas

Established chemometric and geochemical techniques were applied to water quality data from 23 National Irrigation Water Quality Program (NIWQP) study areas in the Western United States. These techniques were applied to the NIWQP data set to identify common geochemical processes responsible for mobilization of selenium and to develop a classification model that uses major-ion concentrations to identify areas that contain elevated selenium concentrations in water that could pose a hazard to water fowl. Pattern recognition modeling of the simple-salt data computed with the SNORM geochemical program indicate three principal components that explain 95% of the total variance. A three-dimensional plot of PC 1, 2 and 3 scores shows three distinct clusters that correspond to distinct hydrochemical facies denoted as facies 1, 2 and 3. Facies 1 samples are distinguished by water samples without the CaCO 3 simple salt and elevated concentrations of NaCI, CaSO 4 , MgSO 4 and Na 2 SO 4 simple salts relative to water samples in facies 2 and 3. Water samples in facies 2 are distinguished from facies 1 by the absence of the MgSO4 simple salt and the presence of the CaCO 3 simple salt. Water samples in facies 3 are similar to samples in facies 2, with the absence of both MgSO 4 and CaSO 4 simple salts. Water samples in facies 1 have the largest selenium concentration (10 μg 1 -1 ), compared to a median concentration of 2.0 μg 1 -1 and less than 1.0 μg 1 -1 for samples in facies 2 and 3. A classification model using the soft independent modeling by class analogy (SIMCA) algorithm was constructed with data from the NIWQP study areas. The classification model was successful in identifying water samples with a selenium concentration that is hazardous to some species of water-fowl from a test data set comprised of 2,060 water samples from throughout Utah and Wyoming. Application of chemometric and geochemical techniques during data synthesis analysis of multivariate environmental databases from other national-scale environmental programs such as the NIWQP could also provide useful insights for addressing 'real world' environmental problems.

Prognosis on Managing Trace Elements

Concern over the potentially toxic effects of trace elements in agricultural drainage waters has been aroused by the discovery of selenium poisoning of wildlife at Kesterson Reservoir, California, and was heightened further through discovery of elevated levels of selenium in shallow ground water underlying extensive areas of San Joaquin Valley's west side. Recent investigations by the U.S. Department of the Interior's National Irrigation Water Quality Program (NIWQP) revealed that similar trace‐element problems exist in several other western states including Nevada, Utah, Wyoming, and Colorado, as well as the Tulare Lake Bed and Salton Sea in California. Management options assessed for trace elements discharged from irrigated lands include source control, drain‐water reuse, drain‐water treatment, and removal of contaminants, disposal, and institutional and jurisdictional control measures. A combination of source control and other drainage‐water‐management options has the potential to reduce the toxic‐elem...

Concentrations, Distribution, and Sources of Selenium from Irrigated Lands in Western United States

Concentrations, distribution, and sources of selenium from irrigated lands were studied between 1986 and 1990 at 20 reconnaissance project areas in 17 western states under the Department of Interior's National Irrigation Water Quality Program. Samples of water, bottom sediment, whole‐body fish, and bird livers for analysis of selenium concentrations were collected before, during, and after irrigation season from streams, canals, lakes, and ground water in each project area. Selenium concentrations in water ranged from less than the detection limit of 1 μg/L in 42% of the 586 samples collected to 4,800 μg/L from a well in the Pine River Area, in southern Colorado. Selenium concentrations in 223 samples of bottom sediment ranged from less than the detection limit of 0.1 μg/g to 85 μg/g in a sample from the Middle Green River Basin, in Utah. Selenium concentrations in whole‐body fish (all species) ranged from 0.1 μg to 50 μg per gram dry weight, with the maximum concentration observed in a carp from the Gunnison River Basin, in western Colorado. Selenium concentrations in bird livers (all species) ranged from less than 0.32 μg to 170 μg per gram dry weight with the maximum concentration observed in the liver of an avocet from the Kendrick Reclamation Project, in Wyoming. Cretaceous‐age marine shales probably are the original sources for selenium in 16 of the 20 areas studied. In several areas, evaporative concentration of applied irrigation water and drainage of this water to wetlands, canals, streams, and lakes appears to be responsible for elevated concentrations of selenium.