WSP08819

• File Number: 8583
• Description: Rio Grande Decision Support System
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 3/1/1996
• Author: Dept of the Interior
• Title: 1996 Calendar Year Report to the Rio Grande Compact Commission
• Water Supply Pro - Doc Type: Report/Study

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1996 Report to the Rio Grande Compact Commission

Bureau of Reclamation

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Channel development work in the Elephant Butte Reservoir headwater area continued
through 1996. A total of 20,000 cy of fill material was placed to raise the San
Marcial levee. A total. of 30,000 cy of material was excavated in a pilot channel from
the south boundary of the Bosque Del Apache National Wildlife Refuge to an area north
of Black Mesa. The excavation was performed through a 4-mile long sediment plug.

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Minimal inflow to the reservoir was experienced during the spring runoff of 1996
resulting in a lowering of the reservoir at the headwaters of Elephant Butte. The
resultant change in reservoir pool content from 1995 to 1996 was a decrease 0.1
approximately 300,000 af. Excavation of a new temporary channel into Elephant
Butte commenced in January of 1 997. The work Will involve construction of a'
temporary berm and excavation of a new channel alignment to the reservoir pool.
Approximately 20,000 cy of fill material will be used to construct the temporary berm.
The temporary channel will involve approximately 100,000 cy of excavation.

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In the river channel between Elephant Butte Dam and Caballo Dam approximately
30,000cy of sediment material deposited by tributaries was removed from the river
channel. ThEi material removal was necessary to maintain a channel delivery capacity
of 5,000 cfs. Approximately 300 cy of riprap material was placed for bank
stabilization of private property along the river channel.

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Endangered Species

Rio Grande Silvery Minnow

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The U,S. Fish and Wildlife Service listed the Rio Grande silvery minnow as
endangered in 1 994. The silvery minnow is currently found in about .1 70 miles of the
Rio Grande in central New Mexico, from Cochiti Dam to the headwaters of Elephant
Butte Reservoir. This reach of the river, commonly referred to as the middle Rio
Grande, comprises less than 10-percent of the silvery minnow's historic range.
Proposed critical habitat was designated as the reach of the middle Rio Grande from
the State Highway 22 bridge below Cochiti Dam downstream to the railroad bridge
crossing near San Marcial, New Mexico. Final designation of critical habitat has been
postponed, Reclamation projects that potentially affect both the river flow and the
channel of the middle Rio Grande are largely defined by the Middle Rio Grande and San
Juan-Chama Projects.

The Rio Grande experienced an extremely low runoff in the spring of 1996. In April
1996, water diversions for irrigation needs resulted in the dewatering of a reach of the
Rio Grande below San Acacia Diversion Dam and above Elephant Butte Reservoir.

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