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<br />Section 9 <br />Options for Meeting Future Water Needs <br />'.IlL <br /> <br />. Fewer risks of contamination and disruption of supply. <br />Being far below the surface insulates the supply from <br />contamination and since aquifer supplies would <br />typically be extracted using multiple wells there is <br />redundancy built into the system. <br /> <br />. Significant volumes of potential aquifer storage are <br />available. Most of the major bedrock aquifers in <br />Colorado have significant volumes of storage. <br /> <br />Issues and conflicts with implementation of bedrock <br />aquifer conjunctive use include: <br /> <br />. Surface water supplies must be available for <br />recharge. <br /> <br />. The surface water diverted for recharge to a bedrock <br />aquifer must be treated both to potable water quality <br />and must be chemically compatible with the native <br />aquifer groundwater so that dissolved constituents do <br />not precipitate and clog the aquifer. <br /> <br />. All of the recharged water may not be recoverable. <br /> <br />. Recharge rates for non-tributary aquifers often are <br />low. <br /> <br />. High energy costs are incurred for aquifer recharge <br />and pumping. <br /> <br />. May require the construction of specialized wells or <br />refitting of existing wells that can be used to both <br />inject and pump water. Such wells are referred to as <br />aquifer storage recovery wells, or ASR wells. <br /> <br />. There may be a need for additional infrastructure <br />(wells, surface water storage, and water treatment) <br />constructed to meet peak demands. <br /> <br />. Additional surface storage may be needed to capture <br />peak surface water flows that would be used later to <br />recharge the aquifer. Surplus supplies are normally <br />available during peak runoff periods, which can be <br />when water demands are highest and existing wells <br />will not be available for recharge. <br /> <br />9.2.4.2 Alluvial Aquifer Conjunctive Use <br /> <br />Alluvial aquifer conjunctive use involves diverting surplus <br />surface water supplies and recharging the alluvial <br />aquifer. Recharging is typically accomplished by canal <br />infiltration or spreading basins, and then pumping the <br />groundwater when needed as a source of supply or <br />when the timing of accretions to the river system is <br />needed to meet demands (for example, stream depletion <br />requirements or streamflow enhancements). The benefits <br />of alluvial aquifer conjunctive use include: <br /> <br />CONI <br /> <br />9-14 <br /> <br />. Maintains high groundwater levels, benefiting <br />wetlands, nearby streams and other nearby surface <br />water features. <br /> <br />. Evaporation is minimized. Once the water has been <br />recharged, there is no additional evaporation as <br />compared to surface water storage. <br /> <br />. There may be fewer environmental impacts than for <br />surface reservoir storage. <br /> <br />. Often requires less land for water storage. <br /> <br />. The permitting process is simpler than developing <br />surface water storage. <br /> <br />. Streamflows can be diverted and recharged without <br />additional treatment costs. <br /> <br />. Existing structures can often be used for recharge, <br />such as river diversion structures and canals. <br /> <br />. Recharge can occur with low capital and operating <br />costs since the recharge can occur through ditch or <br />pond seepage as opposed to pumped injection. <br /> <br />. Tributary aquifers usually have a high recharge rate. <br /> <br />. Significant volumes of potential aquifer storage are <br />available. <br /> <br />. Can be used to regulate streamflows for <br />environmental enhancements. Timing the stream <br />accretions from alluvial recharge can occur so that <br />the water is accreted to the stream to benefit the <br />environment <br /> <br />. Can be used to augment agricultural well pumping. <br />Timing the accretions from alluvial recharge can <br />occur so that the water reaches the stream to match <br />and augment depletions from agricultural well <br />pumping. <br /> <br />Issues and conflicts with implementation of alluvial <br />aquifer conjunctive use and storage and recovery <br />include: <br /> <br />. Surface water supplies must be available for <br />recharge. <br /> <br />. May lead to high water table conditions, which could <br />reduce infiltration rates and be potentially damaging <br />to nearby structures. <br /> <br />. The water quality may be degraded during recharge <br />as additional salts and minerals may be leached <br />during the infiltration. <br /> <br />. Advanced water treatment may be required if the <br />recovered water is used for potable purposes. Alluvial <br /> <br />S:\1177\Basin Reports\North Platte\S9_North Platte.doc <br />