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• Board Meeting Date: 5/21/2008
• Description: IWMD Section - Presentation of Agricultural Water Conservation Paper
• Board Meetings - Doc Type: Memo

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 f or 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 f ull season alf alf a
at an average of 30 inches CU. This contributed to the decline in water levels in the
unconfined aquif er of the closed basin as supplies decreased and consumptive use
increased.
The proposed groundwater management subdistricts are examining 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 be 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 f lows
that help sustain late season streamf lows.
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 quality. There is a potential f or 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 f rom the Gunnison River also have senior
rights and at times call out Upper Gunnison basin water rights. Water conservation
measures in the Uncompahgre area resulting in less need f or water could help
upper basin users. The Uncompahgre water users have stated that any water
conserved through these improvements is f or the benefit of its users. Possible win-
DRAFT 6-2