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Drought Update 11 Aug 2008
South Dakota Drought Update
4-11-2008
Dr. Dennis Todey
State Climatologist
Summary
Several recent major snow storms have extended the winter conditions into the spring across much of state. These storms came on the heels of a very dry winter over nearly the whole state and have therefore eased some short-term moisture conditions across eastern parts of the state. Most of the heavy snow events have been over areas east of the river. Snow in the western part of the state has been welcomed, but had done little to adjust the longer term dryness conditions.
An above average snow pack over the Black Hills should alleviate some of the short lake level conditions in and around the Black Hills. The final result is still pending as melt-off has been slow to start. Most of the Plains areas saw little snow pack during the winter and are going to be very dependent on spring precipitation.
The Missouri River has improved since this time last year, mainly due heavier downstream precipitation, which has forced holding back water in the reservoirs. Snow pack in the mountains has generally been above average this winter. But the lack of winter snow pack in the Plains will reduce the impact of the snow melt.
Drought Status
The most recent US Drought Monitor for South Dakota (Fig. 1) indicates continuing D1 and D2 drought conditions west of the river because of dry late summer through winter over most of West-River as well as on-going issues from the 7-8 years of extended dryness. Most of the D0 area exists because of the winter dryness. Areas of D0 have been reduced because of the snows over the last several weeks. More will likely be removed in the next map issued April 17.
Changes in the Drought Monitor are included in Figure 2. The degradation over the west and short term improvement over the east are shown.
Soil moisture conditions continue to lag. Most water bodies, including lakes, ponds and dug-outs are below average over the western part of the state. The lack of water issues are a continuing impact of the long term dryness for water supplies, irrigation, and cattle watering. Several county extension people are reporting concerns about having to move water to cattle through the summer and the added impact of fuel prices on this activity.
Fig. 1 Most recent US Drought Monitor.
Fig. 2 Drought Monitor changes from 1 week to six months.
Figures 3 and 4 indicate the overall moisture situation in the state over the last 30 days and since last fall. The heaviest precipitation out of the last several snow storms has occurred in the northeastern part of the state. At a few locations this has brought their totals up near average since October 1. Areas of the southeast that were wet through the winter have dried recently, but should still be OK for soil moisture going in to the spring.
Of more concern is the northwest where event some recent snow still leaves the area well below average. The station near Maurine in northern Meade County is still below 50% of average since October.
Balancing these precipitation differences at different time scales creates difficulties in determining exact impacts of the drought situation. But it is clear that moisture is still lacking at various time scales across the state.
Fig. 3 Percent of average precipitation over the last 30 days.
Fig. 4 Percent of average precipitation since October 1. Note that the recent snow in the northeast still leaves the area below average over the last six months in a few locations.
Impact
Specific impacts are limited currently and will only start to be seen as warmer temperatures occur. Potential impacts for the summer will be continued stress on rangeland, if spring precipitation is limited. The refill of lakes around the Black Hills is still pending the snow melt-off. Angostura still looks like it will be the worst off with more limited recharge. More complete effects will become apparent as the spring continues.
Outlook
The spring and summer outlook is a very interesting question currently. With the on-going La Nina, there is some additional risk of drier than average conditions for the late spring into summer. Much of this is dependent on how long the current La Nina lasts. Outlooks right now indicate a weakening but continuation of La Nina into at least early summer.
The Drought Monitor outlook map (Fig. 5) shows some improvement likely over the northwest and west central parts of the state, while drought conditions will continue unabated in the southwest part of the state. The limited improvement indicated is expected because of spring rains.
Fig. 5 Drought Monitor Outlook
One more piece of information… if you have a specific drought impact, you can report to us at the state climate office or directly to the Drought Monitor Impact Reporter at:
http://droughtreporter.unl.edu/
We welcome hearing about drought impacts at our office, also to track current conditions and on-ground changes across the state. Email to dennis.todey@sdstate.edu
Dennis Todey
State Climatologist