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BASIN ASSESSMENTS
<br /> South Platte
<br /> The SWSI value +0.3 is an improvement from May 1, 1990. The basinwide
<br /> runoff forecast is 85% of average ranging from 70% for the upper South Platte
<br /> River to 103% for the Big Thompson River. The runoff is developing as
<br /> expected and should peak by early to mid June. Flow at the key index gaging
<br /> station, South Platte River near Kersey, measured 939 cfs on May 1, 1990, and
<br /> 3267 cfs on June 1, 1990. Reservoir storage is slightly improved over storage
<br /> measured on June 1, 1989. Soil moisture is classified as being near normal .
<br /> Water supply availability for the irrigation season is expected to meet demand.
<br /> Arkansas
<br /> The SWSI value of -0.7 is basically unchanged from the previous month.
<br /> Although, the streamflow component was significantly below average, this was
<br /> due to cooler than normal conditions for the month, reducing runoff.
<br /> Reservoir storage, although only 78% of storage measured on June 1, 1989, is
<br /> still above the historic average as a result of significant carryover storage
<br /> from the wet decade of the 1980's. Pueblo Reservoir had 131,511 acre-feet in
<br /> storage on June 1, 1990, compared to 190,753 acre-feet in storage on June 1,
<br /> 1989, and 242,750 acre-feet in storage on June 1, 1988. John Martin Reservoir
<br /> had 56,677 acre-feet in storage on June 1, 1990, compared to 84,220 acre-feet
<br /> on June 1, 1989, and 212,000 acre-feet on June 1, 1988. The basinwide runoff
<br /> is forecast to be 69% of average ranging from 34% for the Purgatoire River
<br /> below Trinidad to 85% for the Cucharas River above La Veta. The runoff is
<br /> expected to peak by mid to late June. Flow at the key index gaging station,
<br /> Arkansas River near Portland, measured 335 cfs on May 1, 1990, and 998 cfs on
<br /> June 1, 1990. Irrigation demands are expected to draw down reservoir supplies
<br /> significantly by mid July.
<br /> Rio Grande
<br /> The SWSI value of -1.7 indicates that water supplies are declining. The
<br /> Division 3 Engineer's office suggests that conditions are even worse than the
<br /> SWSI value indicates. Warmer than normal conditions during the month of May,
<br /> resulted in an early runoff. As reservoir storage in this basin is limited,
<br /> it is beneficial to have a late runoff when demand is generally greatest. The
<br /> basinwide runoff forecast is 66% of average ranging from 28% for the San
<br /> Antonio River at Ortiz to 86% for Culebra Creek at San Luis. Flow at the key
<br /> index gaging station, Rio Grande near Del Norte, measured 692 cfs on May 1,
<br /> 1990, and 2793 cfs on June 1, 1990. Junior water rights are expected to be
<br /> severely curtailed if precipitation conditions are normal to below normal
<br /> during the irrigation season.
<br /> Gunnison
<br /> The SWSI value of -1.4 is unchanged from May 1, 1990. The streamflow
<br /> component was significantly below normal for the month of May. This was
<br /> partially due to below normal temperatures for the month, however, the
<br /> snowpack on June 1, 1990 was only 36% of normal . The basinwide runoff
<br /> forecast is only 45% of average ranging from 31% for the Gunnison River at
<br /> Grand Junction to 51% for the Uncompahgre River above Ridgway Reservoir. Flow
<br /> at the key index gaging station, Uncompahgre River above Ridgway Reservoir,
<br /> measured 113 cfs on May 1, 1990, and 244 cfs on June 1, 1990. Storage in Blue
<br /> Mesa Reservoir was 679,460 acre-feet on June 1, 1990 as compared to 727,400
<br /> acre-feet on June 1, 1989. It is expected that a minimum of 300 cfs will be
<br /> maintained in the Gunnison River in the Black Canyon.
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