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<br />. <br /> <br />. <br /> <br />. <br /> <br />tlfttrTZlr' <br /> <br />USGS Accomplishments <br /> <br />Detailed Investigations of Irrigation Drainage in the San Juan River Area, San Juan <br />County, Northwestern New Mexico <br /> <br />A detailed investigation, which is a cooperative study by the U,S, Geological Survey, Fish and <br />Wildlife Service, Bureau of Indian Affairs, and Bureau of Reclamation is complete through the <br />data collection phase in fiscal year 1994. The overall objectives of the detailed study are to: <br />(1) identify the sources, distribution and movement of selenium and other potentially toxic <br />chemical constituents in water, sediment and biota associated with irrigation drainage and <br />fishery waters, and (2) identify the processes and pathways leading to elevated levels of <br />selenium and other selected potentially toxic chemical constituents in the San Juan River study <br />area, <br /> <br />A reconnaissance investigation was conducted previously in the same general area as the <br />detailed investigation, The final report, "Reconnaissance investigation of water-quality, <br />bottom sediment, and biota associated with irrigation drainage in the San Juan River area, San <br />Juan County, northwestern New Mexico, 1990-91" by Paul 1. Blanchard and others, was <br />released as W.J.er Resources Investigations Report 93-4065, Based on findings of the <br />reconnaissance investigation, the detailed study of selected irrigation projects in the San Juan <br />River area was begun in fiscal year 1993. <br /> <br />Utah <br /> <br />Aneth Ground-Water Salinity Study <br /> <br />This study investigates the elevated and possibly increasing salinity in the water of the Navajo <br />and other sandstone aquifers in the Aneth area, San Juan County, Utah, Over the last 25 <br />years, specific-conductance measurements of water from selected wells tapping the Navajo and <br />Entrada Sandstones apparently have increased, A field investigation conducted in fiscal year <br />1989 confirmed salinity increases on the order of 2,000 mg/L in selected wells, Water wells <br />with the largest dissolved-solids concentrations are within or adjacent to the perimeter of the <br />Greater Aneth and Ismay-Flodine Park petroleum fields, <br /> <br />Specific objectives are: (1) to identify conservative and nonconservative inorganic and isotopic <br />geochemical constituents that can be used to define the source(s) and path(s) of the saline water <br />invasion-of freshwater aquifers; and (2) to utilize the newly developed chemometrics software <br />PIROUETIE to identify, classify, and quantify source solutions throughout the intruded <br />freshwater aquifer, <br /> <br />Data collection continued during fiscal year 94 and included sampling additional wells <br />completed in the Navajo, Upper Paleozoic, and alluvial aquifers, as well as co-mingled <br />injection brines and recharge water in the form of early spring snowpack, Additional pressure <br />head, water level, and discharge data were collected at selected Navajo wells, Data collection <br />concluded in September 1994, <br /> <br />16 <br /> <br />