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WSU/Pend Oreille Extension introduced the Sense of Place series in 1999, with a focus on local landscape and natural history of Pend Oreille County, Washington. A partnership with the Kalispel Tribe of Indians Natural Resources Department has allowed us to expand this program through EPA funding to include more classes, a newsletter and this website.

Forecasting Water Supply

by Mark Simpson
adapted from http://www.wcc/nrcs.usda.gov/snotel

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.

Most of the usable water in the western states originates as mountain snowfall. This snowfall accumulates during winter and spring, several months before the snow melts and appears as streamflow. Since the runoff from precipitation as snow is delayed, estimates of snowmelt runoff can be made well in advance of its occurrence. The forecasts of natural runoff are based principally on measurements of precipitation, snow water equivalent, and antecedent runoff. Forecasts become more accurate as more of the data affecting runoff are measured, and as the season progresses.

The Natural Resources Conservation Service (NRCS) installs, operates, and maintains an extensive, automated system to collect snowpack and related climatic data in the Western United States called SNOTEL (for SNOwpack TELemetry). The system evolved from NRCS's Congressional mandate in the mid-1930's "to measure snowpack in the mountains of the West and forecast the water supply." Climate studies, air and water quality investigations, and resource management concerns are all served by the modern SNOTEL network. The high-elevation watershed locations and the broad coverage of the network provide important data collection opportunities to researchers, water managers, and emergency managers for natural disasters such as floods.

There are 90 sites in Pend Oreille Watershed stretching from Bunchgrass Meadows east to mantana where most of our watershed is located. the Bunchgrass Meadows site is located at 5000 feet in elevation on Monumental Mountain, near the headwaters of LeClerc and Harvey Creek. At most SNOTEL sites, precipitation and temperature data are automatically recorded and continuously relayed to NRCS data processing offices. a pillow measures the weight of the snow by how much it is displaced. Thanks to the internet, musch of the data transmitteed from these sites can now be viewed easily on the web. Some of the information can even be seen on an hourly basis. See the Washington SNOTEL web site at http://www.wcc.nrcs.usda.gov/snotel

SNOW WATER EQUIVALENT measurements in the Pend Oreille River Watershed

Based on Mountain Data from NRCS SNOTEL Sites as of February 13, 2005

(Snow water equivalent is reported as basin wide “percent of average” which compares it to the average for the date measured over a 30-year period. A report of 50% means there is only half as much snow water availabel as we woudl find in an "average" year. Data for individual sites witin each basin are also available at ftp://ftp.wcc.nrcs.usda.gov/data/snow/update/columbia.txt

KOOTENAI RIVER IN MONTANA Basin wide percent of average 62

FLATHEAD RIVER BASIN Basin wide percent of average 63

UPPER CLARK FORK RIVER BASIN Basin wide percent of average 59

BITTERROOT Basin wide percent of average 56.61

LOWER CLARK FORK RIVER BASIN Basin wide percent of average 51

IDAHO PANHANDLE REGION Basin wide percent of average 53.81

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