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<br />-{rf-? 0 ~4--- <br /> <br />.' <br /> <br />To limit the salinity of the Colorado River and in response to the Federal <br />Water Pollution Control Act and its amendments, the seven Colorado River <br />Basin States adopted and the Environmental Protection Agency (EPA) <br />approved salinity standards to meet numeric criteria listed below. <br /> <br />Table S-2.-Numeric Criteria for the Lower Colorado River <br /> <br />Annual flow-weighted <br />concentration (mgIL) <br /> <br />Below Hoover Dam <br />Below Parker Dam <br />At Imperial Dam <br /> <br />723 <br />747 <br />879 <br /> <br />Decreased water quality in the Colorado River Basin results from two <br />, general causes-salt loading and salt concentration, as noted above. <br />Specifically, salt loading is the addition of salt to the river from such <br />sources as salt dissolving from saline geologic fonnations, irrigation return <br />flows, and saline springs and seeps. Salt concentration results from <br />reducing the volume of water through consumptive use3 without reducing <br />the total salt carried. <br /> <br />Both salt loading and salt concentration occur on the Hammond Project, <br />which was originally designed as an earth-lined system. Mter the Project <br />was completed in the early 1960's, several sections of the system were <br />concrete-lined to reduce canal water loss (seepage) and for operation and <br />maintenance (O&M) reasons. Sections that have not been lined show <br />significant deterioration of the canal prism. Conveyance and operation <br />losses currently average appro:ximately 50 percent of the diversions into the <br />Hammond distribution system, and canal seepage is a substantial part of <br />this loss. Salt pickup results from canal seepage water and excess irrigation <br />deep percolation flowing through the underlying shales high in salt content <br />and returning to the river. <br /> <br />Salt concentration occurs on the Hammond Project because of consumptive <br />use by the irrigated crops and by evapotranspiration in wetlands created by <br />operational waste and conveyance losses. <br /> <br />Results of preliminary river salt budgets indicate a total salt pickup to the <br />San Juan River of 98,000 tons unaccounted-for per year between the <br />U.S. Geological Survey (USGS) gauges at Archuleta and Farmington, <br />New Mexico, shown on the frontispiece location map. Hydrosalinity studies <br />on the Hammond Project show that an estimated canal and lateral loss of, <br /> <br />3 Consumptive use is a water use resulting in s loss to the atmosphere by evaporation <br />and/or transpiration (the process by which plants give off water vapor through their <br />leaves). <br /> <br />S-3 <br />