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levels of irrigation and pumping activities in the study region. Pressure transducers equipped <br />assembled with thermistors and data loggers will be installed in 5 to 10 observation wells for <br />continuous monitoring of water levels. Periodically, water samples will be collected and <br />analyzed in the laboratory to determine correlation of EC to TDS and to specific salt ions. <br />Periodic samples also will be gathered from a subset of 10 to 15 of the wells up to three times per <br />year for analysis of TDS, specific salt ions, dissolved Se, dissolved U, and perhaps other <br />minerals, using CWQCD-approved protocols. <br />Task 2c: Estimation of Hydraulic Conductivity in Alluvial Aquifer of the UARB <br />Slug tests will be conducted in as many as possible of the observation wells drilled within the <br />study region of the UARB to estimate horizontal hydraulic conductivity of the alluvial aquifer. <br />These tests are conducted by evacuating water from the well using a battery-powered <br />submersible pump, measuring the subsequent rate of rise of the water table in the well (and the <br />associated time-varying hydraulic gradient) with a pressure transducer, and calculating the <br />approximate depth-averaged horizontal hydraulic conductivity around the annulus of the well. <br />Task 3: Measurement of River Flow and Water Quality <br />Another key element of the proposed project is the simultaneous characterization of river flow <br />rates and water quality characteristics. In both the UARB and the LARB, the river has complex <br />interactions with the alluvial aquifer and the associated ground water resources. This interaction <br />has important implications not only for the pathways of water through the system but also for the <br />mobilization and transport of salt, Se, U, and other constituents. This project will compile, <br />assess, and supplement river flow and water quality measurements that are available from <br />multiple resources. Data on flow rates in the main stem of the Arkansas River, in gauged <br />tributaries, and in diversions from the river will be gathered from the USGS and the Colorado <br />Division of Water Resources (CDWR). Water levels and flow rates and, in some cases, EC are <br />measured periodically at a few selected sites along the Arkansas River by the USGS Subdistrict <br />Office in Pueblo and the District 2 Office of the CDWR. The project proposed herein will <br />cooperate with these agencies to obtain and assess the available data. <br />Task 3a: River Water Quality Sampling in the LARB <br />Under support from this project EC, temperature, pH, DO, and ORP will be measured monthly to <br />bi-monthly at 5 to 10 existing locations along the river in the Upstream Study Region and at 3 to <br />6 existing locations along the river in the Downstream Study Region of the LARB. <br />Simultaneous flow measurements will only be made occasionally at some of these sites under the <br />support of this project. Instead, flow rates at the times that EC, temperature, pH, DO, and ORP <br />measurements are made will be estimated from nearby existing USGS and CDWR gauging sites. <br />Water samples will be gathered from a subset of 3 to5 locations once or twice annually and <br />analyzed in the laboratory to determine correlation of EC to TDS and to specific salt ions. Plans <br />are underway to conduct more frequent surface water measurements in the LARB, subj ect to <br />7