| OCR Text |
Show 41 Pan evaporation for the October- April period averages 53.9 inches at the Bear River Refuge near the mouth of the Bear River compared to 72.7 inches for the same period as measured at the Saltair Salt Plant on the southern shores of the Lake. Evaporation from Great Salt Lake itself has been the subject of several studies and the average evaporation is not certain. Early studies estimated an average of 37.7 inches while later studies indicate approximately 40 inches per year. If the higher estimates are correct, total evaporation is approximately 3 million acre- feet per year ( or about 4150 cubic feet per second), which is about 20 percent of the total volume of the Lake. Considering that average annual surface inflow is about 1- 1/ 2 million acre- feet per year, it appears that if upstream water developments increase significantly and climatic conditions remain stable, drastic reductions in Lake volume could occur in 10- 20 years. Increase in surface elevation of the Lake decreases the salinity of the water, increasing the rate of evaporation. At levels of approximately 4196 mean sea level and lower, the Lake is nearly saturated and the evaporation rate is only about 70 percent that of fresh water. Evaporation rates are also influenced by variations in density throughout the Lake at any one time. Fresh water may be dominant near the mouths of large rivers during certain times of the year. These density variations in the Lake can be observed from the air. Observations of evaporation pans containing fresh and brine water on the southern slopes of Great Salt Lake have shown that condensation ( gain of water to the Lake) can occur while fresh water is losing volume by evaporation. It has been hypothesized by some scientists ( Richardson, 1974) |
