ill.; Includes bibliographical references (leaves 6-8)
ABSTRACT Orifice temperatures, specific conductance, and flow have been measured for springs in the vicinity of Crater Lake ranging in elevation from 1266 to 2182 m. Spring temperatures generally decrease with increasing elevation. Air temperatures from weather stations in an area surrounding Crater Lake decrease by 4.6°C/km of elevation with an intercept of 13.2°C at sea level. Ground temperatures obtained by extrapolating temperature/depth data for seven drill holes back to the surface show a variation with elevation generally similar to that found for air temperatures. Comparison of spring and air temperatures versus elevation shows that spring temperatures are generally cooler (1.9°±1°C) than air temperatures except for a group of springs in the eastern Wood River Valley. Some of the springs in the eastern Wood River Valley are as much as 4°C higher in temperature than other springs at the same elevation. A chloride inventory of the springs in the eastern Wood River Valley shows an anomalous discharge larger than the inflow to Crater Lake. Though not warm enough to qualify as thermal springs, the springs in the eastern part of the Wood River Valley represent a significant thermal and chemical anomaly. INTRODUCTION The chemistry of springs in the vicinity of Crater Lake, Oregon, has been discussed by Thompson and others (1990) and by Nathenson and Thompson (1990). The purpose of this study is to extend those works by using careful measurements of spring temperatures to relate spring temperature to air and ground temperatures and by using these data to explore the notions of thermal, nonthermal, and cold springs. The temperatures of springs involve a complex relationship between circulation path, flow rate, average annual air temperature, and local climate effects. A special class of springs known as thermal springs are ones "whose water has a temperature appreciably above the mean annual temperature of the atmosphere in the vicinity of the spring (Meinzer, 1923, p. 54.)." Meinzer does not define appreciable. Meinzer (p. 55) goes on to state that: "Nonthermal springs may be divided into (1) those whose waters have temperatures approximating the mean annual temperatures of the atmosphere in the localities in which they exist, and (2) those whose waters are appreciably colder." The second group of nonthermal springs are cold springs. Waring (1965, p. 4) agrees with Meinzer that any spring that "is noticeably above the mean annual temperature of the air at the same locality may be classed as thermal" but uses 15°F (8.3°C) above mean annual temperature of the auto define thermal springs in the United States. Reed (1983, p.2) in the U.S. Geological Survey's assessment of low-temperature geothermal resources of the United States uses a minimum temperature function that is 10°C above the mean annual temperature at the surface and increases with depth by 25°C/km to define low-temperature geothermal resources. Muffler (1987) in a letter to the Director of the National Park Service concerning "Significant Thermal Features" proposes that 10°C above mean annual air temperature be used to define thermal. In most situations, the question of using a numerical temperature criterion for thermal springs is not important, because measured temperatures are sufficiently anomalous. In the Cascade Range, however, large quantities of cold ground water can mix with thermal water making the magnitude of the temperature anomaly very small.
ABSTRACT Orifice temperatures, specific conductance, and flow have been measured for springs in the vicinity of Crater Lake ranging in elevation from 1266 to 2182 m. Spring temperatures generally decrease with increasing elevation. Air temperatures from weather stations in an area surrounding Crater Lake decrease by 4.6°C/km of elevation with an intercept of 13.2°C at sea level. Ground temperatures obtained by extrapolating temperature/depth data for seven drill holes back to the surface show a variation with elevation generally similar to that found for air temperatures. Comparison of spring and air temperatures versus elevation shows that spring temperatures are generally cooler (1.9°±1°C) than air temperatures except for a group of springs in the eastern Wood River Valley. Some of the springs in the eastern Wood River Valley are as much as 4°C higher in temperature than other springs at the same elevation. A chloride inventory of the springs in the eastern Wood River Valley shows an anomalous discharge larger than the inflow to Crater Lake. Though not warm enough to qualify as thermal springs, the springs in the eastern part of the Wood River Valley represent a significant thermal and chemical anomaly. INTRODUCTION The chemistry of springs in the vicinity of Crater Lake, Oregon, has been discussed by Thompson and others (1990) and by Nathenson and Thompson (1990). The purpose of this study is to extend those works by using careful measurements of spring temperatures to relate spring temperature to air and ground temperatures and by using these data to explore the notions of thermal, nonthermal, and cold springs. The temperatures of springs involve a complex relationship between circulation path, flow rate, average annual air temperature, and local climate effects. A special class of springs known as thermal springs are ones "whose water has a temperature appreciably above the mean annual temperature of the atmosphere in the vicinity of the spring (Meinzer, 1923, p. 54.)." Meinzer does not define appreciable. Meinzer (p. 55) goes on to state that: "Nonthermal springs may be divided into (1) those whose waters have temperatures approximating the mean annual temperatures of the atmosphere in the localities in which they exist, and (2) those whose waters are appreciably colder." The second group of nonthermal springs are cold springs. Waring (1965, p. 4) agrees with Meinzer that any spring that "is noticeably above the mean annual temperature of the air at the same locality may be classed as thermal" but uses 15°F (8.3°C) above mean annual temperature of the auto define thermal springs in the United States. Reed (1983, p.2) in the U.S. Geological Survey's assessment of low-temperature geothermal resources of the United States uses a minimum temperature function that is 10°C above the mean annual temperature at the surface and increases with depth by 25°C/km to define low-temperature geothermal resources. Muffler (1987) in a letter to the Director of the National Park Service concerning "Significant Thermal Features" proposes that 10°C above mean annual air temperature be used to define thermal. In most situations, the question of using a numerical temperature criterion for thermal springs is not important, because measured temperatures are sufficiently anomalous. In the Cascade Range, however, large quantities of cold ground water can mix with thermal water making the magnitude of the temperature anomaly very small.