WSP11390

• File Number: 8040.970
• Description: Basin Outlook Reports
• State: CO
• Date: 1/1/2000
• Author: USDOA
• Title: Colorado Basin Outlook Report
• Water Supply Pro - Doc Type: Publication

Reservoir Storage

One of the blightest highlights of the 2000 water year continues to be abundant storage in the state's
reservoirs. Statewide, storage increased slightly again during February. and is now 142% of average.
This volume amounts to slightly more than 1.3 million acre-feet above the average mark for March I,
and is 10% more than last year's storage. All basins continue to report above average volumes, with
the highest percent of average in the Arkansas Basin, at 256%. Storage in the Rio Grande Basin is also
well above average at 160%. Reservoirs in the Colorado and Yampa basins are storing just slightly
less than last year's volumes, with the remainder of the basins reporting volumes above those of a year
ago.

Streamflow

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While the additional snowfall during February helped to improve the prospects for runoff across the
state, below average volumes are forecast for most of the state's rivers. The highest forecasts are
located across the northern basins. Near average volumes are forecast along the Front Range
tributaries of the South Platte, the North Platte and Yampa, and most of the Colorado River Basin.
Below average runoff is forecast in the Arkansas, Gunnison, San Miguel, and Animas basins. Volumes
of only 50% to 70% of average are forecast in the Rio Grande, San Juan, and extending nOl1hward to
the upper reaches of Ihe Arkansas and South Platte rivers. Extremely low runoff volumes, of only 30%
to 35% of average are forecast on some of the smaller tributaries of the Rio Grande with originate
along the southern San Juan Mountains.

SURFACE WATER SUPPLY INDEX
MARCH 1, 2000

Abundant Supply

NelrNorml1

Moderlle Drought

Severe Drought

Extreme Drought

The Surface Water Supply Index (SWSI) is a weighted value derived for each major basin which generally
expresses the potential availability of the forthcoming season's water supply. The components used in
computing the index are reservoir storage, snowpack water equivalent, and precipitation. The SWSI number
for each basin ranges from d -4.0 (prospective water supplies extremely poor) to a +4.0 (prospective water
supplies plentiful). The SWSI number is only a general indicator of surface water supply condition.
Further data analysis may be required in specific situations to more fully understand the impacts of
abnormally dry or wet conditions suggested by the SWSI. Development of the SWSI has been a cooperative
effort between the Colorado State Engineer's Office and the Natural Resources Conservation Service.