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Can Drought be Predicted?

Posted May 1, 2002

Drought, in relation to forage production, is defined as "slow plant growth when fast growth is expected" or "no growth when slow growth is expected."Drought can occur seasonally (within a given year), annually (for an entire year), or for extended periods of time (such as 1995 through 2001).

We can even experience drought during above average rainfall years. Take 2000 and 2001, for example. The total annual precipitation in Ardmore was 45.89 inches and 45.37 inches, respectively, compared to the average annual precipitation of 37.5 inches. However, the rain did not come at the right time, causing seasonal drought to occur. The precise year or season drought will occur cannot be predicted with tremendous accuracy, but perhaps long-term weather forecasts are becoming more dependable.

I believe that drought is cyclical much like markets but predicting it with precision does not appear feasible just yet. However, drought is a regular occurrence and should be expected. Furthermore, proactive managers should have a plan to overcome at least a short-term seasonal drought.

I thought it would be interesting to look at Ardmore's monthly rainfall totals compared to the averages from 1995 to the present. Looking back, 1995 was the beginning of an extended drought cycle.

In 1995, we had a good spring followed by a dry fall, which drastically limited winter pasture production. 1996 brought a dry spring and summer, followed by a wet fall. Any time precipitation is below average in April and May, a substantial reduction in forage growth in May and June can be expected. Even if there is average rainfall in June and July following a dry May, forage production will not be at normal levels due to limited subsoil moisture early in the season.

The spring of 1997 was good, but it was followed by a dry summer. Then, in 1998, we experienced one of the worst years in history. Average annual precipitation was 33 inches (only 4.5 inches below normal), but most of it fell in January, March and October, with limited moisture in between.

In 1999, there was a fairly normal precipitation pattern with most of the rainfall occurring from March to May and in September and October. The overall amount was below normal, however. This reduced rainfall was greatly magnified due the severity of the previous year's drought.

2000 was similar to 1996, with a dry May that limited summer growth. Total rainfall was 45.86 inches, a little more than 8 inches above normal. However, most of the rain fell from October through December, which helped fill ponds and replenish watersheds but did little to promote plant growth.

2001 was also 8 inches above normal for the year, but below normal in March, April and June through August, with nearly 11 inches falling in September. 2002 started off dry in January and February, but March and April seem to have pulled us out of the ditch. (Note: April 2002 totals are through April 22.)

As a result of the extended drought we have experienced since 1995, many pastures are in poor shape and desperately need some tender loving care. Please remember to give your pastures some much-needed rest and time to recover during the upcoming growing seasons. That means you will need to defer from grazing while the plants are actively growing.

Can drought be predicted? I don't think so, but I will say this if May is a dry month, the probability of drought this summer greatly increases.

Generally speaking, most farmers and ranchers are eternal optimists. So let's hope we see the reality of our optimism and remember 2002 as the year the drought was broken.

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