18c (2) - Laserfiche WebLink

Home Browse Search

Discussion The following information is provided by the USGS, and may be considered as a draft justification and Scope of Work for this project: Numerous entities have expressed concerns about a wide range of water-quality issues in the Arkansas River Basin in Colorado. In the Upper Arkansas River Basin, water-quality concerns generally are residual metal contamination from historical mining practices, fish and biological integrity issues, or concerns about potential affects associated with storage and movement of water. In the Lower Arkansas River Basin, water-quality concerns are associated with awide- variety of environmental stressors including point and non-point source contamination, population growth, storm-water flows, and future changes in land and water use. As population within the basin increases, demands on the limited water supplies also will increase. Changes in water storage, water releases, and/or transfer of water within or outside of the Arkansas River Basin are likely to occur to accommodate the growing population. These changes in water use and reservoir operations have the potential to affect water quality within the basin by affecting such things as the dilution of chemicals and sediment transport. In addition to changes in water use, water quality within the basin can be affected by land-use changes associated with urbanization and agricultural practices. Urbanization and agricultural practices can increase contaminant loading to ground and surface waters and change ground-water recharge and streamflow characteristics. As the result of continuing water-quality concerns and recognition of the importance of understanding potential affects of changes in land and water uses throughout the Arkansas River Basin, the U.S. Geological Survey (USGS) has been asked by the Southeastern Colorado Water Conservancy District to assess the 'state of knowledge' of water quality throughout the Arkansas River Basin and develop a comprehensive basin-wide strategy to address multiple water-quality concerns. To date this assessment indicates numerous existing data gaps. Additional data are needed to adequately quantify various contaminant sources, as well as the physical, biochemical, and geochemical processes that adversely affect water quality. Rou hg samplin~lan/rationale: - In the upper Basin, samples would be collected in a Lagragian manner (essentially sampling the same water parcel as it flows through the upper basin. - Between Canon City and Pueblo Reservoir, an important issue is to better understand the decay rates and assimilation of nutrients and carbon. To assess this, again we would use a Lagragian approach coupled with the use of auto samplers, and then sub-sample various aliquots of individual samples, then analyze 'a flow-weighted sample' which would provide us an integrated concentration over several hours. - In the lower Basin, given all the diversions - it is very difficult to successfully collect a single sample in a Lagragian manner that provides data that can be used to assess various processes and sources that affect water quality. Frequently, instantaneous samples used to compute loads do not provide a reasonable mass balance (can't balance inflows/outflows or loads even for conservative constituents). Therefore, during irrigation season or when flows are highly variable, we would plan to utilize several auto samplers that would collect about 8 samples per day for 3 days. We would then sub-sample to obtain 3 daily flow-weighted samples. These data would then provide the necessary data to identify the dominant sources/source areas and assess the physical, biochemical and geochemical processes that occur and affect the water quality. Rough methods and costs: New continuous WQ stations -- probably 2 upstream from John Martin Reservoir, maybe 1 below JMR Temporary/interim stations -- about 65 surface water stations, and about 100 wells 2