Water Supply Forecasting |
Water supply forecasting is the science and art of predicting the volume of water that will flow past a given point on a stream during a specific period of time. The Natural Resources Conservation Service (NRCS), in cooperation with the National Weather Service (NWS), provides seasonal water supply forecasts for over 600 points in the Western United States. Wise use of these forecasts can provide a critical advantage to irrigators and water managers in the West.
Seasonal water supply forecasts are generated monthly from January through June for most areas. At the current time, data availability and user service generally limit the update interval to one month. In some basins, mid-month (or more frequent) forecasts are generated at the request of specific water users. The main reason forecasts are updated during the month is to account for changes in weather and hydrologic conditions.
================================================================================ LOWER COLUMBIA BASIN Streamflow Forecasts - April 1, 1997 ================================================================================ | <=== Drier === Future Conditions === Wetter ===> | | | Forecast Pt | ============== Chance of Exceeding * ============== | Forecast | 90% 70% | 50% (Most Prob) | 30% 10% | 30 Yr Avg Period |(1000AF) (1000AF)|(1000AF) (% AVG.)|(1000AF) (1000AF)| (1000AF) ================================================================================ COLUMBIA R. at The Dalles (2) APR-JUL 101763 108454 113000 133 117546 124237 84760 APR-SEP 119900 127700 133000 134 138300 146100 98982 SANDY RIVER near Marmot APR-JUL 378 417 443 138 469 508 321 APR-SEP 446 487 515 138 543 584 373 ================================================================================ * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow will exceed the volumes in the table.The average is computed for the 1961-1990 base period.
B A S I N W I D E R E S E R V O I R S U M M A R Y FOR THE END OF MARCH 1997 BASIN AREA CURRENT AS LAST YR AS AVERAGE AS CURRENT AS CURRENT AS RESERVIOR % CAPACITY % CAPACITY % CAPACITY % AVERAGE % LAST YR -------------------------------------------------------------------------------- ARIZONA RESERVOIR STORAGE (8 RESERVOIRS) LAKE PLEASANT 52 52 8 659 100 SAN CARLOS 22 50 44 51 45 SALT RIVER RES SYSTEM 57 68 79 72 84 VERDE RIVER RES SYSTEM 46 35 59 79 132 TOTAL OF 4 RESERVOIRS 47 57 50 93 82 Raw AF Totals: Current=1901.7 Last Year=2306.2 Average=2035.1 Capacity= 4055.0
Water Supply Forecasting |