WSP02066

• File Number: 8220.125.A
• Description: San Juan-Chama Project
• State: NM
• Basin: San Juan/Dolores
• Date: 3/1/1999
• Title: San Juan-Chama Project: Excerpted from 1998 Report to the Rio Grande Compact Commission
• Water Supply Pro - Doc Type: Report/Study

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1998 report to the Rio Grande Compact Commission

Bureau of Reclamation

on October 27 at elevation 6,809.57 ft (1,183 af). As a result of the reservoir's cyclical
operation, Pojoaque Tributary unit's 1998 depletion of 1,234 af exceeded the 1,030 af
stored at Heron Reservoir to offset the depletion. San Juan-Chama replacement water
was released in June, July, August, and October to offset the depletions for Nambe
Falls operations in the amount of 1,248 af (equivalent release from Heron). Nambe
Falls Reservoir ended 1998 at elevation 6,820.19 ft (1,671 af). A summary of the
reservoir operation is shown on Table 5, and the return flow credits are accounted for in
Table 6.

Under the Technical Assistance to States Program, Reclamation performed a sediment
survey at Nambe Falls Reservoir in July 1997. New area-capacity tables were
generated by Reclamation and are available.

As part of Reclamation's Native American Program, a water measurement device will
be installed on the Rio Nambe upstream of Nambe Reservoir. The device will provide
for a more accurate measurement of the inflow into reservoir.

U.S. Army Corps of Engineers' Reservoirs Sediment Surveys and Related
Operations Review.

In the latter half of 1998, the Corps of Engineers performed sediment surveys on
Abiquiu Reservoir, Cochiti Lake, and Jemez Canyon Reservoir, yielding sediment
volumes accumulated since the last surveys, and new Area-Capacity tables; The new
tableswere put into use beginning January 1, 1999 in Reclamation's daily programs.
The surveys showed the current daily program equations overestimated sediment
accumulations by 5,207 af (651 af/year) in Abiquiu, 3,725 af (532 af/year) in Cochiti,
and 2,047 af (292 af/year) in Jemez since the last surveys were completed and
implemented in 1991 and 1992. Reclamation has scheduled the re-working of the
equations to obtain more accurate sedimentation rates for the last quarter of 1999. At
the request of the Engineer Advisers, once the revised equations are in the daily
programs, Reclamation will rerun the entire 1999 year retroactively sathe results ofthe
new equations are used in finalizing the 1999 water accounting. .

At Abiquiu Reservoir, Public Law 97-140 authorizes storage of up to 200,000 af of SJ-C
Project water. Adjustments for sediment reduced the available storage allocations to
180,231 af in 1998. See Table 7 for Abiquiu Reservoir operations. .

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At Cochiti Lake, the SJ-C pool was adjusted monthly to compensate for displacement of
SJ-C content by deposited sediment. The maximum allowable surface acreage
(including wetlands) of the SJ-C pool is 1,200 acres.

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San Juan-Chama deliveries to replace losses from the Cochiti Lake's permanent
recreation pool are usually performed in accordance with the recommendations made
in the Cochiti Lake Re-regulation Interagency Biological Report issued June 30, 1993.
There was a year-end under-delivery of 2,851 af. Most of this requirement will be met
prior to the 1999 spring runoff.

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