History and Future of Wyoming Droughts

The Great Basin of North America and Wyoming specifically, is known for its arid and semi-arid environment, as well as prolonged and sometimes severe droughts. Drought is the prolonged and abnormal deficiency of moisture with the concomitant decline in runoff to a level significantly lower than usual (Guldin 1989). The history of droughts in Wyoming has been uncertain in the past, but recent studies of tree rings in the Big Horn Basin of Wyoming have given insight to droughts as far back as 1260A.D. (Gray et al. 2004). Looking at tree ring records in Douglas fir (Pseudotsuga menziesii) and limber pine (Pinus flexilis) trees, Stephen Gray and his colleagues discovered that droughts which have been experienced in Wyoming since the 1750's, are weak in severity and length when compared to those since. The most severe drought period in Wyoming’s history occurred from 1262 to 1281. The droughts of the 1930’s and 1950’s, which have been used as benchmarks for all other droughts in the United States in recent times (Woodhouse et al. 2002), are ranked 149th and 28th respectively in comparison (Gray et al. 2004). The five top ranking droughts for 10, 15, and 20 year periods are all prior to the 1800’s, with the four driest single years being 1263, 1274, 1278, and 1280 (Gray et al. 2004). This indicates a change in precipitation patterns in the Big Horn Basin area of Wyoming since the 18th century, as all recent droughts have been mild when compared to those of Wyoming’s past.

Droughts in Wyoming’s future are unpredictable and uncertain; however, Richard Guldin of the Rocky Mountain Forest and Range Experiment Station in Fort Collins, Colorado, has made some predictions for the water situation in the United States as far ahead as 2040. According to Guldin, 526,600 million gallons of freshwater will be withdrawn per day in the year 2040 versus the 385,200 million gallons used in the year 2000 (Guldin 1989). These estimates account for use of groundwater, surface water, and wastewater by thermoelectric steam cooling, irrigation, municipal central supply, industrial self-supply, domestic self-supply, and livestock watering purposes, with the greatest user being thermoelectric steam cooling followed by irrigation. Guldin also divided the freshwater usage by region with the Rocky Mountains using a total of 48,631 million gallons in 2040 (Guldin 1989). Along with water usage estimates, Guldin also forecasts the effects lack of water will have on land usage, stating that “agricultural operations that are dependant upon irrigation will either change to dry-land farming or cropland will revert to native vegetation” (Guldin 1989). He projects that nearly 160 million acres of cropland will be idled by 2030 due to lack of water resources.

Another cause for lack of water in the intermountain West is due to the heightened levels of immigration from Pacific coast states such as California, as well as others. The majority of those immigrating are doing so for more preferable climate in the drier environments, yet they are landscaping the municipalities in the same manner as their original communities. This large-scale landscaping, and maintenance of that landscaping, requires large quantities of water from an already dry ecosystem.

Droughts have various effects on the water resource, rangeland, and animal populations in Wyoming. Another study, which looks at tree-ring records, suggests that a small, severe, and persistent drought from 1845 to 1856 may have played a large role in the disappearance of the North American bison (bison bison) from the Great Plains (Woodhouse et al. 2002). Other studies in the 1930's and 1950's found that grass in the shortgrass uplands was reduced, in some cases from 90% to 20%, even in ungrazed areas during the drought of the mid-nineteenth century (Woodhouse et al. 2002). Yet another study conducted in Yellowstone National Park, found that the drought experienced in 1988 reduced some warm-season grasses by as much as 50% of normal (Singer et al. 1989). Yellowstone Park staff stated that 60% of the Northern herd of elk in Yellowstone died off in the winter of 1919-1920, which followed the drought of 1919 (Singer et al. 1989).

The history of Wyoming’s droughts has been extremely variable and unpredictable over time with the longest and most severe droughts occurring prior to the eighteenth century. Droughts have been experienced since that time, but have been much less pronounced and shorter. Future droughts are hard to predict, but are guaranteed to occur as the area is noted for its arid characteristics. Droughts in Wyoming’s future will have a more devastating effect due to the increased need for water in the dry environment, caused by the immigration from more populous states, and higher populations in general. Drought also has pronounced effects on the rangeland and ecosystem as a whole, which is evidenced by the contribution it made to the disappearance of the buffalo from the Great Plains, the winterkill of the Northern herd of elk in Yellowstone National Park following the 1919 drought, and the large reduction of forage production associated with drought. Wyoming is assured to have droughts in the future and they will continue to be costly on an ecological and economical level.

REFERENCES

Gray et al. 2004. Tree-Ring-Based Reconstruction of Precipitation in the

Impacts and Implications. Bulletin of American Meteorological Society. Vol. 83: 1485-1492.

Yellowstone Fire 1988

David Delancey- Researcher

Lucas Line- Writer

Morgan Wolvington- Programmer