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Predicting Drought in the US

By Jeannine Swindell

The inability to make a reliable prediction of drought hampers our ability to be proactive toward management for dry spells. In this part of the world, drought affects range livestock agriculture in two important ways. First is the effect that winter drought has upon snowpack and resultant stream flows. Many streams in the states are very susceptible to water shortages as a result of low snowpack. There are ways to predict the stream flow supplies. The United States Geological Survey, Natural Resources Conservation Service (NRCS) have excellent data gathering and analysis programs that are readily available.

When the NRCS Snotel surveys alert us to critical shortfalls in snowpack, we know that irrigation water supplies will be critically short. Without water, haylands are non-productive as our ranching industry is extremely reliant on the ability to produce winter feed stores from those haylands. We can see this problem coming and hopefully make proactive decisions to help get through this drought challenge.

The second way that drought can affect the ranch industry is in rangeland grass production. Without adequate soil moisture during the growing season, range grasses just don’t produce and the forage base for the following months is compromised. In this instance, predicting this element of drought, and its degree of severity is much more difficult. There are a number of factors that contribute to summer range drought and its severity. Among them are the amount of soil moisture we had going into the Fall, the amount of wind, temperatures, summer rains, timing and amount of Spring rainfall. Of all factors, the timing and amount of spring rains is probably most important.

Predicting an annual forage yield early in the forage production and grazing season is essential for effective livestock management planning. A fourteen-year study in the in the Saratoga area of Wyoming shows a high correlation exists between forage production and moisture timing.

The point is that range plants have critical growth periods in which adequate moisture is extremely important to the amount of production the range ultimately produces. It is wise to factor spring rains, or lack thereof, into your management decisions.

These are but a few of the known causes of drought in the U.S. To further our understanding of the factors that lead to drought in a region, an extensive collection of environmental data spanning back into history is required. For two-thirds of the world, collection of this data is critically needed.

References:

http://drought.unl.edu/whatis/predict.htm

http://test1.icrisat.org/Vasat1/learning_resources/drought/html/m3l2/resources/2573.html

http://www.wyorange.net/Drought/predrout.html

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