What a Difference 20 Years Make

Climate changes in the Pacific Ocean determine wet and dry cycles

LeRoy W. Hooton, Jr.

March 7, 2002

At this time in 1983, snowpack measurements were far above normal.  Ultimately a delayed spring melt, along with above normal snowpack, would lead to widespread flooding affecting much of the western United States. High water flows would gush down from the Colorado River watersheds. In late May, the inflow into Lake Powell increased from 36,000 cubic feet per second to about 90,000 cubic feet per second. High releases from Glen Canyon and Hoover dams caused flooding along the Colorado River in Arizona and California.

Thousands of acres of farmland were flooded in northern California when the San Joaquin River burst a levee near Vernalis.  On the east side of the Sierra Nevada mountain range flooding occurred on the Truckee River near Reno, Nevada.  The Truckee River flow reached 2,000 cubic feet per second, nearly three times its normal flow.

The May 2, 1983 issue of Time Magazine described the period as the "wild, wet West."  According to the news article, the wet cycle was contributed to warmer than usual El Nino currents from the Pacific, the jet stream pulling down cold air from Canada, and major volcanic activity in Mexico and Hawaii.” 

In Salt Lake City flood flows released from Mt. Dell Reservoir would result in a man-made dike being constructed along 1300 South, and City Creek turned State Street into a river.  The water volume from the six Wasatch Canyon streams located east of Salt Lake City produced over 306,000 acre-feet of water, the largest volume of water measured over 81 years of record. The record 207 percent volume eclipsed the previous 1921 record of 238,000 acre-feet by 29 percent.

The flooding spurred on the ultimate construction of Little Dell Dam and Lake and extensive flood control work throughout Salt Lake County

Proving that Mother Nature is fickle, historic data shows that there are wide variations of precipitation. Twenty years ago we were in a wet cycle that lasted from 1983 to 1986. Today we are in a dry cycle starting in 1999. The cause of the drought has been attributed to three years of La-Nina conditions with the cooling of the eastern Pacific Ocean.  This past year there has been a change towards an El Nina regime, which may signal the end of the drought.

Whereas twenty years ago the Colorado River experienced enormous run-off flows, the flows this past year were at record lows. Declining water levels behind Glen Canyon and Hoover dams show the effects of the drought on the Upper Colorado River Basin watersheds.

The current Salt Lake City drought has not been as severe as the benchmark drought of 1930-1935, which included the driest year on record in 1934.  Only 54,500 acre-feet of water was produced from the Wasatch Canyon streams that year. The lowest volume of water produced from the canyon streams during the current drought thus far is 94,000 acre-feet in the year 2001, ranking that year as the ninth lowest volume on record. 

The 2002-03 winter snowpack is currently about 60 percent of normal within the Provo River -Utah Lake - Jordan River drainage.  A key snow course is Trial Lake.  For the third consecutive year the snowpack is substantially lower than normal at this critical watershed area. Unless extraordinary spring snowstorms increase the amount of water in the basin watersheds, the water supply for the coming year again will be less than normal.  Preliminary projections indicate that there will only be a 50 percent allotment in Deer Creek Reservoir, and the water supply from the canyon streams will be about 65 percent of normal.

Drought and wet cycles have in the past and will continue in the future, to be a fact of life. Some years there is too much water and other years not enough. What determines this is the water temperature in the eastern Pacific Ocean.