C150042 Report

• Contract/PO #: C150042
• Contractor Name: Rio Grande Restoration Project Enterprise
• Contract Type: Grant
• Loan Projects - Doc Type: Report

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One of the primary resources that can be managed to allow better utilization of surface water
supplies are the underground aquifers in the San Luis Valley. By storage of surface water rights
in the aquifers, the aquifers can function as under ground water storage reservoirs. The filling of
the aquifers has historically occurred, but in an unplanned manner that has resulted in overfilling
in some areas and under-filling in other areas. One of the objectives of this project was to assist
in developing a better understanding of the dynamics of ground water recharge in the San Luis
Valley and to convey this information to water users and managers to facilitate maximum water
utilization and conservation.
Since elimination of the Rio Grande Compact debt, over delivery to the Compact has occurred in
several individual years. These over deliveries result in credits that may be used to reduce
Compact deliveries in subsequent years. However, the credits are subject to evaporation losses
in Elephant Butte Reservoir. It may be possible to reduce these over deliveries and efficiently
store more water in the aquifers of the San Luis Valley. This may be accomplished by means of
better managed irrigation season diversions and maximizing winter ground water recharge. In
many years the potential for Compact over deliveries do not become apparent until October or
November which is near the end of the accounting year for the Compact. It is also near the time
when ditches can be frozen shut by cold weather. During wet years and in the late fall or early
winter, the aquifers could be partially refilled, thereby supplying the ground water to be
withdrawn by wells during dry years.
Recharge of ground water has been difficult during November and December due to the forming
of ice in diversion structures and canal laterals. Additionally, changes in irrigation practices
from flood irrigation to significant numbers of center-pivot sprinkler systems that require less
volume of water has made it difficult for irrigators to use large wet year flows that can occur in
the spring. One of the objectives of this project was to construct a significant recharge structure
specifically designed to overcome much of the icing problems and provide additional capacity to
allow large diversions from the river during flood conditions.
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