PUB00047

• Year: 2000
• Title: SECWD/Arkansas Basin Preferred Storage Options Plan Final Draft Report
• Author: GEI Consultants, Inc
• Description: SECWD/Arkansas Basin Preferred Storage Options Plan Final Draft Report
• Publications - Doc Type: Water Resource Studies

Final Draft - Pr.eferred Storage Options Plan
Southeastern Colorado Water Conservancy District
June 8, 2000

. Storage efficiency (projects with low evaporation and conveyance losses are more
efficient)

The Turquoise Lake enlargement and the Pueblo Reservoir enlargement were judged to have the
best performance in terms of the above-noted factors. Re-operation would provide similar
benefits in comparison to the Turquoise and Pueblo enlargements; however, re-operation does
not provide firm storage space. Turquoise Lake is located high in the basin; therefore, it can
effectively serve a large number of potential users and is subject to lesser rates of evaporation.
Although lower in the Basin, the Pueblo Reservoir enlargement provides significant operational
flexibility and better storage efficiency than all other options except the Turquoise Lake
enlargement. Storage in gravel lakes provides flexibility and fairly good storage efficiency;
however, individual gravel lakes projects are small (probably less than 3,000 at) and will not
provide significant operational flexibility for meeting regional water management objectives.
The lowest ranking storage options, in terms of water supply performance, are the Lake Meredith
enlargement and Williams Creek Reservoir. The primary drawbacks to the Lake Meredith
enlargement are relatively higher rates of evaporation and potentially high conveyance losses
which decreased storage efficiency. The location of Williams Creek limits the reservoir filling
opportunities and effectiveness in meeting the water storage objectives of entities other than
CSU.

4.2 Stream Flow and Water Quality Impacts

Projected changes to stream flows at key locations on the Arkansas River for various alternative
project developments are documented in Section 3.4. In general, each alternative would have
about the same effect on historic stream flows with increased average flow during the months
of May, June, and July and, depending on locations along the river, somewhat higher flows to-
somewhat lower flows in the August through April period. At the Wellsville gage, the average
flow in June may increase by up to 250 cfs. The modified flows will, on average, exceed the
minimum stream flows recommended by the Colorado Department of Natural Resources (250
cfs throughout the year and 700 cfs from July I through August 15). As described in detail in
the Modeling Report, a significant amount of stream flow data have been generated for various
gaging station locations. These data are available to the resource agencies and interested public,
so that changes in stream flow from historic levels can be examined by month for a model
simulation period from 1966 to 1995.

Preliminary assessments were made of potential water quality impacts that may be expected with
implementation of the storage options and the alternatives described in Section 3. Qualitative
assessments were made relative to lake eutrophication, lake stratification, salinity, nutrients, and
metal loadings in the reservoirs and Upper Arkansas River. A simplified mass-balance model
of the Lower Arkansas River was used to assess potential salinity and selenium impacts.

m GEl Consultants, Inc.

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