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Section 6 <br />Site-Specific Opportunities and Limitations <br />^ There are opportunities in the basin to improve water quality and cro~ yield from <br />agricultural conservation measures if water rights and compact concerns are <br />adequately addressed. <br />Rio Grande <br />The Conejos River and the Rio Grande are subject to the Rio Grande Compact. The <br />Conejos River and Rio Grande have separate delivery obligations to the Compact. <br />Terms and conditions of the Conlpact provide that as flows increase the Conejos <br />River and t11e Rio Grande nlust deliver an increased percentage of the total flows <br />respectively for Conlpact purposes. Peturn flows fronl irrigation of certauz lands in <br />fl1e basin return to t11e river above the Lobatos gage and 11e1p nleet conlpact <br />delivery requirements. Iinplementation of conservation nleasures u1 this area could <br />reduce return flows that are used to nleet conlpact obligations. <br />Many agricultural lands in the closed basin of the Rio Grande have been converted <br />fronl irrigation of spring grain with an average of 18 inches CU to full season alfalfa <br />at an average of 30 inches CU. T11is contributed to the decline in water levels u1 the <br />unconfuled aquifer of the closed basul as supplies decreased and consunlptive use <br />increased. <br />The proposed groundwater nlanagenlent subdistricts are exan1u1u1g nleasures to <br />reduce consunlptive use in certain areas punlping groundwater. <br />Gunnison <br />T11e Upper Gunnison Basin has sonle irrigated areas with very low application <br />efficiencies. Some of this irrigation water application nlay be needed to build up the <br />water table to allow for sub-irrigation. Tl1e quantity of irrigation water tllat is lost to <br />consumptive use from the raised water table and free standing water on fields has <br />not beeil evaluated. <br />^ The low irrigation efficiencies u1 the Upper Gunnison result in delayed return flows <br />that help sustain late season streanlflows. <br />Along the Uncoinpallgre River system return flows are reused several times within <br />its system, but there is still a significant return flow leaving the system with a <br />degradation of water quality. There is a potential for water quality improvenlent if <br />fl1e irrigation of t11e Mancos sllale soils on t11e east side were irrigated nlore <br />efficiently and return flows nlinimized. This would have to be done in a nlanner to <br />protect the water rights of the Unconlpahb e Water Users and prevent buildup of <br />salts uz the soil. <br />Uncompahgre water users divertuzg fronl flze Gwznison Piver also have senior <br />rights and at tinles call out Upper Gunnison basuz water rights. Water conservation <br />ineasures in the Uncompahgre area resulting in less need for water could 11e1p <br />upper basul users. The Uncompallgre water users have stated fllat any water <br />conserved through these inlprovenlents is for tlle benefit of its users. Possible win- <br />DRAFT 6-2 <br />