Laserfiche WebLink
<br />O~:1552 <br /> <br />(irrigation and livestock, 20 micro grams/liter). Numerous samples exceeded the <br />standards. Selenium is an element which is subject to bioaccumlation in the food <br />chain and is concentrated in green plants as they take up water. As drains within the <br />irrigation system pick up water, selenium concentrations become very high. The <br />water from these drains is reused for irrigation throughout the watershed and <br />downstream. <br /> <br />Five species of fish in the Arkansas River and the John Martin Reservoir had selenium <br />concentrations ranging from 2.1 to 18.5 micro grams/gram with samples of 20 micro <br />grams/gram. All but 3 of the 59 total fish samples exceeded the 85th-percentile <br />national baseline for selenium in fish (2.45 micro grams/gram dry weight), and 21 of <br />the samples had concentrations exceeding the range associated with reproductive <br />failure in blue gill.2 About one-half of the samples had selenium concentrations that <br />exceeded the dietary concentration known to increase the rate of mortalities and <br />deformities in mallard embryos.4 <br /> <br />Investigations found that selenium levels in aquatic plants exceeded acceptable <br />dietary limits of avion species. No evidence of deformity or reproductive failure was <br />observed for any bird or fish species. The study was not designed to assess <br />reproduction or to determine the extent of embryonic deformities.2 <br /> <br />The Colorado Department of Public Health and Environment standard for aquatic life, <br />which pertains to both Class I and Class II streams, is 17 micrograms/liter dissolved <br />selenium. The EPA Storet data set had 24 values collected from 1990 through 1992 <br />for the Fowler location. The mean value was 10.6 micrograms/liter with some <br />readings approaching the state standards. The data shows the levels of dissolved <br />selenium are high, and on occasion, are exceeding the aquatic life standard. This <br />could adversely affect substantial wildlife habitat of the area. The increase in <br />dissolved selenium is similar to total selenium concentration trends. <br /> <br />Salinity is another serious problem for water quality in the Arkansas Valley. There are <br />three important factors in the salinity problem: salt pick up and concentration and the <br />management of water, soils, and crops. This project is not formulated to reduce <br />salinity since no standards exist; however, it is desirable to control salt loading. High <br />salt levels will remain as long as the water is used. The greatest potential for reducing <br />salinity is by more effective use water throughout the valley. <br /> <br />Irrigation water diverted at Nepesta has a mean Total Dissolved Solids (TDS) of 600 <br />milligrams/liter (obtained from USGS records). The mean TDS in the Arkansas River <br />at La Junta, which is just below the project area, is 807 milligrams/liter for the <br />Arkansas River. The TDS levels are therefore increasing downstream due to <br />concentrations of salt in the remaining water. No TDS standards have been set for <br />Colorado; however, TDS levels of 500 is deemed desirable and below 1,000 is <br />acceptable for agricultural purposes. It is anticipated that total TDS will be lowered <br />through project action. <br /> <br />20p.sit. <br />4Aquatic cycling of Selenium:, United States Department of the Interior, USFWS Leaflet 12. 1987 <br />2op.sit. <br /> <br />20 <br />