WSP09132 - Laserfiche WebLink

Home Browse Search

watershed area. Approximately 400 are used for irrigation and 100 for drinking, livestock, and other uses. Studies have been done showing high nitrate levels in the upper 2 feet of the soil in many areas. Other studies show that high nitrate levels have resulted in reduced nodulation in alfalfa plants. This in turn forces the alfalfa growers to apply additional nitrogen to obtain high alfalfa yields. The diverted water from the Arkansas used to irrigate in the watershed also has a high level of nitrates. Nutrient levels are high due to not only commercial fertilizer application, but also from manure application. Approximately 40 cattle feeders are in the watershed. Management of the combination of nutrient sources is necessary to ensure that the nutrient level applied is at the correct proportions. The Department of the Interior has studied an area consisting of the Middle Arkansas River Valley from Pueblo Reservoir in Colorado, to Garden City, Kansas, and includes the Highline Breaks area. Although the area is semiarid, the predominant land use is agricultural. Extensive acreage is irrigated, primarily along the Arkansas River and its tributaries and near off-channel reservoirs. Some irrigated soils are derived from outcrops of marine shale formations, that under current climatic conditions, can result in accumulation of selenium and other toxic trace elements in soils and groundwaters.2 Selenium is an element that deforms and kills fish, wildlife, sheep, and horses. Eating too much contaminated fish or fowl, or drinking contaminated water could be hazardous to human health. A number of plants take up selenium which when eaten is toxic to Iivestock.3 The predominant uses of surfacewater in the Middle Arkansas River Basin are for irrigation and recreation. Reservoirs in the basin are among the most popular in Colorado for boating and fishing. Ground water in the alluvium of the rivervalley s used for domestic supply by several towns in the basin. The Arkansas River also provides recharge water to the Ogallala Formation, which provides domestic supplies at Garden City, Kansas, and other towns downstream from the study area. According to an Interior study, selenium was found at elevated concentrations in water, bottom sediment, and biota of the Arkansas River. Selenium concentrations in . surface water was 1 microgram/liter in Pueblo Reservoir upstream of the project area. Data indicates that the stretch of the Arkansas River from the Highland Canal diversion (Nepesta gauge) to the water quality gauge at La Junta, which is affected by the Highline Breaks area, has a significant change in selenium concentrations. Samples taken at these gauges (Nepesta and La Junta) show that the average total selenium concentration increases from 8 micrograms/liter to 17 micrograms/liter between the gages. EPA data shows similar increases. The mean concentration is close to The Colorado Department of Public Health and Environment standard and the US Environmental Protection Agency maximum contaminant level for the dissolved selenium in the water supply for agriculture- 2 ReconnaissllIlce investigation of water quality, Bottom sediment, lIIId Biota Associated with Inigation drainage in the Middle Arkansas River Basin. Colorado lIIId Kansas. 1988-1989. 3 Selenium in Agriculture, Agricultural Handbook No. 200, 1961 19