| |||||||||||||||||||
|
| ||||||||||||||||||||||||||||
Weather outlook depends on definition of "normal"By Randy Buhler Colorado State University Cooperative Extension Logan County Agent (Agronomy) Where did all our water go? That was a question recently received at the Extension office. How can a bright outlook for water suddenly go bad? The answer is it depends on the concept of normal. In Colorado, we are dependent on winter snowfall accumulation to provide most of our growing season water. Everyone relies on this water to provide for our needs. Agriculture is the largest user of this water on a volume basis. Agricultural irrigation water is converting to municipal and industrial uses as our population grows and our economy creates more businesses. The water accumulation from snowfall occurs during the period of October to May. Over the past years, the U.S. Department of Agriculture has measured depth of snow on specific tracts or courses. The long-time average is the normal accumulation. Each month has its own normal amount. Throughout a seven-month season, each month should accumulate additional depth of snowpack. As the snowpack melts, we receive runoff in our streams and rivers. The runoff season is the period of April through September. Streamflow is measured at specific gauging stations. The amount passing the gauging device is recorded. The longtime average flow measurement is our normal flow rate. During the period of October through May, we have a reservoir filling cycle. Occasionally, excess summer time flows are diverted to refill some reservoirs. The amount of water contained in our reservoirs is recorded and expressed as a longtime average or normal. Several agencies are involved with measuring and recording these flow and accumulation records. That information is provided to our state engineer. The state engineer uses the numbers to manage the river flows to meet international, interstate, and local water supply agreements. The problem with some of these agreements is that they were reached during a period of above normal runoff. Using a high runoff volume as the base creates additional hardship on Colorado during the dry years. Because the agreements specify a volume and not a percent of flow, it creates a disproportional hardship to Colorado. We have to watch the water flow by without being able to use it. For our South Platte Basin, we have to run 120 cubic foot seconds past the gauging station at the Nebraska state line to meet our obligation. After out-of-state obligations are filled, the engineer must provide each in-state water user his proportionate share of the remainder. These shares are meted out according to water right ownership. The ownership is dated and receives its specified amount according to the date the water right was perfected in water court. Most wells have a much more junior, or later date, water right than surface water users. This means wells can be shut down during a period of water shortage. The big rub is that wells are drilled in order to have water when surface water is not available. The circumstance of ground water and surface water being intimately connected in the South Platte Basin creates a seemingly illogical process. Our months for snowpack accumulation were great in October, November and December. We were running 130 to 140 percent of normal. Then we saw January at about 90 percent, February at less than 70 percent, March at 95 percent and April at about 50 percent of normal accumulation for each month. This created a year-to-date water accumulation that dropped to just 74 percent of normal. Some early melt out further eroded the snowpack accumulation. This left predicted runoff flows at 65 percent of average for the South Platte at the South Platte gauging station. This sudden change in the numbers created the emergency for the state engineer. It was unexpected and a significant departure from the trend line for the water equivalent yield of the snowpack. Last week saw field bindweed and buffalo grass blooming. This is two or three weeks or more ahead of our usual date. Grass pastures are green, but have not grown any forage that would be considered excess available for grazing. Hackberry trees were hit by a late freeze and lost their leaves again this year. These unusual occurrences point out how variable our weather has become. We need to rethink our usual actions and adjust to new circumstances in response to our climate situation. Do not make the mistake of doing the usual, just because that is how you have always done it. Nature will treat us as it will. How our man-made rules limit or restrict us in responding to those circumstances will have a greater play on the outcome of this season. The answer to the question of where did our water go is that it never came. Numbers can be misleading unless we know what they represent. Percentages are especially troublesome. Date: 5/24/06
Copyright/Privacy
Copyright 1995-2008. High Plains Publishers, Inc. All rights reserved. Any republishing of these pages, including electronic reproduction of the editorial archives or classified advertising, is strictly prohibited. If you have questions or comments you can reach us at High Plains Journal 1500 E. Wyatt Earp Blvd., P.O. Box 760, Dodge City, KS 67801 or call 1-800-452-7171. Email: webmaster@hpj.com |
| ||||||||||||||||||||||
