Drought, dams and dirt tied
together in South Dakota
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.”
![](images/images_02_10_2022/pic2.jpg)
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.
The overall
Missouri River Basin system of dams and reservoir storage is well
below the base of flood control.
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.
Millions per acre (MAF) storage
line comparisons
Existing is the storage in the
system as of Feb. 8
The base of flood control is the standard.
The top flood control is the most during flood control.
![](images/images_02_10_2022/pic3.jpg)
The MAF storage was under 50 as of Feb.
8.
According to the Army Corps, the MAF
55.2, on July 1, 2021, when it implemented conservation measures.
The MAF base of flood control is 56.5 MAF.
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.
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