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Section 6 Site-Specific Opportunities and Limitations ^ There are opportunities in the basin to improve water quality and crop yield from agricultural conservation measures if water rights and compact concerns are adequately addressed. Rio Grande The Conejos River and the Rio Grande are subject to the Rio Grande Compact. The Conejos River and Rio Grande have separate delivery obligations to the Compact. Terms and conditions of the Compact provide that as flows increase the Conejos River and the Rio Grande must deliver an increased percentage of the total flows respectively for Compact purposes. Return flows from irrigation of certain lands in the basin return to the river above the Lobatos gage and help meet compact delivery requirements. Implementation of conservation measures in this area could reduce return flows that are used to meet compact obligations. Many agricultural lands in the closed basin of the Rio Grande have been converted from irrigation of spring grain with an average of 18 inches CU to full season alfalfa at an average of 30 inches CU. This contributed to the decline in water levels in the unconfined aquifer of the closed basin as supplies decreased and consumptive use increased. ^ The proposed groundwater management subdistricts are examn>u1g measures to reduce consumptive use in certain areas pumping groundwater. Gunnison The Upper Gunnison Basin has some irrigated areas with very low application efficiencies. Some of this irrigation water application may he needed to build up the water table to allow for sub-irrigation. The quantity of irrigation water that is lost to consumptive use from the raised water table and free standing water on fields has not been evaluated. ^ The low irrigation efficiencies in the Upper Gunnison result in delayed return flow s that help sustain late season streamflows. Along the Uncompahgre River system return flows are reused several times within its system, but there is still a significant return flow leaving the system with a degradation of water qualit~~. There is a potential for water quality improvement if the irrigation of the Mancos shale soils on the east side were irrigated more efficiently and return flows minimized. This would have to be done in a manner to protect the water rights of the Uncompahgre Water Users and prevent buildup of salts in the soil. Uncompahgre water users diverting from the Gunnison River also have senior rights and at ti_ntes call out Upper Guruuson basin water rights. Water conservation measures in the Uncompahgre area resulting in less need for water could help upper basin users. The Uncompahgre water users have stated that any water conserved through these improvements is for the benefit of its users. Possible win- DRAFT 6-2