How dry is it in South Dakota? 02/10/2022

SIOUX FALLS, S.D. (KELO) — There is an intricate relationship between snowfall in the state and in mountain ranges west of South Dakota, the dry soil and rivers and reservoirs in the state.

Rivers and reservoirs in South Dakota aren’t as deep these days and the soil is dry.

Typically run-off from snowmelt runs into rivers and tributaries that feed the Missouri River. It’s the same with most rain. But just how much of that melting snow and rain reaches the Missouri and six dams along it in South Dakota, North Dakota, and Montana can depend in large part on the condition of the soil.

“We look at our soil moisture. And the soil is very dry,” said Eileen Williamson of the Army Corps of Engineers in Missouri River Basin. The Missouri River Basin is part of the northwestern division.

“When there is dry soil…the soil acts like a sponge and soaks up (the moisture),” Williamson said. “Any slow snowmelt goes into the soil instead of the reservoirs and rivers. Even if there is a deluge of rain, it still gets into the soil. But the ability of the soil to absorb all that moisture is somewhat compromised.”

The year 2021 was not a banner year for moisture in South Dakota. This year has started very slow as well.

“…we’ve seen near to zero measurable moisture in Sioux Falls, Pierre and Aberdeen this month so far. Rapid City has 0.1″ of measurable water this month. The overall pattern has kept storm systems with appreciable moisture well to our south and east,” said KELOLAND meteorologist Adam Rutt.

Williamson said the base of flood control is the standard for water storage in the system. The million-acre feet (MAF) shows how much water is stored in the system. It’s broken into the base of flood control which means flooding is not likely. The base of exclusive flood control would trigger responses to flooding. The top exclusive flood control is the top few feet of storage.

The chart below compares the MAF of Feb. 8 with the other base flood control measures.

The base of flood control is the standard. The top flood control is the most during flood control.

According to the Army Corps, the MAF 55.2, on July 1, 2021, when it implemented conservation measures.

The three largest storage sites are the Fort Peck dam in Montana, the Garrison dam in North Dakota and the Oahe Dam in South Dakota. The water level is called elevation.

The Garrison elevation was 1,830 feet as of Feb. 8. The average base of flood control is about 1,840 feet.

The Oahe elevation was 1,595 feet. The average base of flood control is just over 1,605 feet.

At Fort Peck, the elevation was 2,225 feet. The average base of flood control is just under 2,325 feet.

Reservoir and river users may notice boat ramps that are now in shallow water but municipalities are still getting their water, Williamson said.

Reductions in the release of water could mean less water for barge traffic during the navigation season.

On July 8, 2021, the Corps reduced barge traffic from a full-service level because of drought conditions.

As of Feb. 3, 78% of South Dakota was in abnormally dry conditions, according to NOAA. About 43% of the state was in a moderate drought and 14.3% was in an extreme drought.

Most of Montana was in an exceptional, extreme or severe drought as of Feb. 3, according to NOAA.

While a chunk of southeastern North Dakota is not dry, the rest of the state ranges from abnormally dry to extreme drought as you move from east to west across the state.

It’s been a dry February so far but the states do get snow and rain in February and March.

Rutt divided the state into the four cities of Sioux Falls, Aberdeen, Pierre and Rapid City to show average snowfall and precipitation amounts for February and March. Snowfall does not translate directly into precipitation because moisture content can differ from the actual snowfall amount.

Sioux Falls averages: 0.6″ precipitation, 6.9″ of snow for February, 1.76″ of precipitation, 8.4″ of snow for March. Aberdeen averages: 0.62″ precipitation, 8.6″ of snow for February, 0.89″ of precipitation, 6.3″ of snow for March. Pierre averages: 0.74″ of precipitation, 8.0″ of snow for February, 0.96″ of precipitation,5.0″ of snow for March. Rapid City averages: 0.53″ of precipitation, 9.1″ of snow for February, 0.94″ of precipitation, 10.4″ of snow for March.

Drought, dams and dirt tied together in South Dakota

Millions per acre (MAF) storage line comparisons

Existing is the storage in the system as of Feb. 8