SDSU climatologist says drought’s end is hard to call
June 30, 2008
South Dakota’s current debate about whether the long drought in the state has ended underscores the difficulty climatologists face in making the same call, a South Dakota State University scientist said.
“With drought it’s very difficult to define beginning and ending, unlike a flood, hurricane, tornado, or similar weather event,” SDSU Extension State Climatologist Dennis Todey said. “Drought differs in definition across the range of people affected.”
The main national determination of drought currently is the U.S. Drought Monitor, online at http://www.drought.unl.edu/dm. This weekly map uses short-term and long-term measurements of precipitation, combined with soil moisture assessments, and subjective input to determine a single drought level for all locations in the country.
“Combining all effects into one number is easy for most people to understand, but also loses some of the complexity of drought, too, by minimizing some pieces of information,” Todey said.
Most people in South Dakota’s East River counties wouldn’t consider themselves in drought currently because the short-term issues they have been dealing with include wet fields and some flooding.
“West River is a little more difficult to handle. This is where the drought definition comes in again,” Todey said.
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Most West River locations have been quite wet this spring and early summer, allowing rangeland to start to recover. The precipitation has replenished surface water in ponds and dugouts in some places. However, all West River reservoirs except for Belle Fourche are still well below longer-term average levels, Todey said.
Todey said because of this period of wetness, the U.S. Drought Monitor map from June 17 includes only the far southwest corner of South Dakota in any category of drought. The rest of the state shows no category of drought using the U.S. Drought Monitor categorization, since most measures of precipitation are well above average.
“But even with our wet conditions, we have not been able to overcome all the drought issues accumulated over the past seven or eight years. And this is the Plains. Without more precipitation during the rest of the summer, we could start seeing those impacts return,” Todey said. “While most people don’t think of us being in drought conditions, the lingering effects are there.”