From: Jan Curtis, Chairman of Drought Monitoring Sub-group
Subject: 22 April 2002 Lander, WY minutes
23, April 2002
The following was presented to the Governor's Drought Task Force with the Governor of Wyoming in attendance.As of 22 April, various drought indicators were reviewed and as summarized below:
SWE: Significant improvements during the past week are noted across most of the state except in the extreme NE and SE basins. The Wind River experienced a 10% increase in snow-water equivalent and the extreme NW part of the state is now above the 90% of average level. The Black Hills have lost 2/3 of their snowpack in the past 2 weeks and the rivers in that area are flowing clear, indicating that much of the moisture is being absorbed into the ground and not running into the streams. Despite some positive news, snow levels would need to be running 130% of normal west of the continental divide and up to 160% in the eastern plains for the drought to end. Odds for adequate precipitation during the next 6 months to end the drought are less than 20% throughout the state. However, the latest national forecast is for improving conditions over the eastern plains with some improvement through the rest of the state due to possible enhancement of summer monsoons. With increase thunderstorm activity, increased likelihood of range and forest fires is possible.
Streamflow forecast through September indicates between a 70 and 90 percent of normal flow in the western part of Wyoming decreasing eastward to less than 50 percent over the eastern regions of the state. Current and 7 day average streamflow is running about 20 percent below normal. However, since snowpack appears to have peaked two weeks earlier than normal, streamflows are about as high as they will get this spring. Because of this developing scenario, streamflow this summer appears reasonably accurate but might be a bit optimistic. Steamflow on the lower Platte, the upper North Platte, and Wind River will be a problem.
The reservoir levels are seriously low at Boysen, Bull Lake, and Wheatland #2. Jackson lake is expected to make a slow recovery from near record low levels. Generally, the 13 Bureau of Rec managed reservoirs are running nearly half useable capacity as of 1 April.
Ground water (wells) appears to be holding up during this drought. Soil moisture improved slightly from last week's 79 percent short to very short to 70 percent this week.
The precipitation forecast shows mixed signals during the next 6 to 9 months as a result of problems determining the timing and strengthen of El Nino. Long term statistics show only 2 out of 3 strong El Nino's impact Wyoming with increased summer precipitation and decreased winter precipitation. The state climatologist feels El Nino will occur later in the year and will be weaker than the previous one in 1997-98. As a result, precipitation is expected to be near normal through next winter. The statewide drought should end by this time next year with water surplus in 2004. Statewide droughts since 1895 have only occurred 6 times and never lasting more than 3 years. There are no reasons to believe other atmospheric patterns such as the Pacific Decadal Oscillation and solar index will prevent the drought from ending in the next year.