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Orifice temperatures, specific conductance, and flow have been measured for springs in the vicinity of Crater Lake ranging in elevation from 1266 to 2182 ra 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. The definitions for thermal spring use mean annual air temperature, because there are abundant data available from weather stations. Conceptually, a more appropriate quantity for comparison to spring temperatures would be the average ground temperature at the surface. Although a small number of weather stations do measure ground temperatures, many more ground-temperature values can be calculated by projecting temperature versus depth data obtained in drill holes back to the surface. An advantage of this method is that it provides an integrated measure that is less sensitive to small-scale variations in soil properties. Bodell and Chapman (1982) used this method to study part of the Colorado Plateau. They found that ground temperatures had a lapse rate of -6.9°C/km over an elevation interval of 1100 to 2900 m. The U.S. Standard Atmosphere (U.S. Committee on Extension to the Standard Atmosphere, 1976) assumes a lapse rate for air temperatures of -6.5°C/km from 0 to 11 km altitude, agreeing with the slope found by Bodell and Chapman (1982). Powell and others (1988) added mean annual air temperatures from weather stations to the data set of Bodell and Chapman and found that both had a lapse rate of about -7°C/km. Ground temperatures averaged approximately 3°C warmer than air temperatures. Delisle (1988) gives a general rule that ground temperatures have a lapse rate of -7 °C/km in dry climates and -4 °C/km in wet climates, and values cited in Birch (1950, Table 5) generally agree. Thus ground temperatures are not necessarily the same as air temperatures. AIR AND GROUND TEMPERATURES Air temperatures for weather stations in an area of 3° longitude by 2° latitude are given in Table 1. Locations of the weather stations are shown on Figure 1, and temperatures are plotted versus elevation in Figure 2. These values are for a 30 year period and should be relatively stable. The area covered by these stations is relatively large, ranging from the Coast Range through the Cascade Range and into the Basin and Range. Stations from a large area are necessary to get an adequate range of elevations. Figure 2 shows that at each elevation there is a significant range of average annual temperatures, but it appears reasonable to fit a best straight line to the data. Using temperature as the dependent coordinate, the line has a slope of -4.6±0.4°C/km and an intercept of 13.2±0.5°C at sea level elevation (± values are standard error). The value for lapse rate is smaller in absolute value than that found by Bodell and Chapman (1982) for the Colorado Plateau but is similar to the ground temperature lapse rate given by Delisle (1988) for wet climates. A search was made to find drill hole data for calculating average ground temperatures for the same area. Data from many drill holes indicate either hydrologic disturbances or near-surface disturbances that are not easily understood. Data from seven drill holes were found to be used easily for extrapolation, and the results are given in Table 2 and plotted on Figures 1 and 2. The ground temperature data are more restricted areally and in elevation range because of the significant influence of hydrology on near-surface temperatures in the higher elevations of the Cascades (e.g. Black and others, 1983a). Unlike the results for the Colorado Plateau, the distribution of ground temperatures is generally similar to that for air temperatures (Figure 2). More data might show that this is somehow a biased sample; however, the larger data set of Powell and others (1988) has no ground temperatures cooler than mean annual air temperatures whereas 3 out of 7 in Figure 2 are cooler than the air temperature best fit line. It seems likely that the difference reflects a difference in climate between the Cascade Range and the Colorado Plateau and is not an artifact of the data set SPRING TEMPERATURES AND OTHER CHARACTERISTICS Measurements of temperature, specific conductance, and flow have been made for many of the springs in the vicinity of Crater Lake (Figure 3 and Table 3). Temperatures were measured using a thermocouple thermometer (Omega Engineering Model 871) with 0.1 °C electronic digital readout Temperatures from the thermocouple and readout device were compared to a 0.1 °C mercury-in-glass thermometer in a well-stirred beaker of water and found to be within 0.2°C over the range 1° to 15°C, both before and after the field trip. Spring temperatures were measured by placing the thermocouple in the orifice. Specific conductance was measured using a digital conductivity meter (Whatman CDM 300) with automatic temperature compensation of 2% per °C. Comparison to standard solutions at 74 and 718 M-S/cm showed the meter and cell to agree to the standard solutions to within 3 %. Specific conductance was measured either in the spring orifice or slightly downstream. Elevations were obtained from 1:24,000 topographic maps to the nearest contour (40,20, 5, or 1 foot depending on the map). Spring flows were obtained by measuring a representative depth (in a few cases several depths were measured) and a representative width to obtain a cross-sectional area and measuring speeds by timing the passage of a floating object over a measured distance. This method of measuring flows is inherently limited in accuracy and precision, and flows are probably only known within ±50 %. Figure 4 shows the measured temperatures plotted versus elevation. It has previously been established that the source of the Wood River and other springs in the eastern Wood River Valley are anomalous in chemical constituents compared to the water in other springs (Nathenson and Thompson, 1990). Data for these springs are shown using special symbols in Figures 3 and 4 and will be discussed as the Wood River group. Springs in the western Wood River Valley along with Cedar Spring provide a useful comparison to the Wood River group and are combined as the Cedar Springs group. Except for about half the data for the Wood River group, nearly all of the spring temperatures in Figure 4 plot below the best-fit air line and even below the lowest air temperature measured. Spring temperatures, like air temperatures, increase with decreasing elevation. Most of these springs probably fit Meinzer's definition of a cold spring. Excluding the Wood River group, spring temperatures average 1.9±1.0°C cooler than the air temperature line. Some of the temperatures that have been obtained in this study are significantly cooler than those published by Thompson and others (

Temperatures of springs in the vicinity of Crater Lake, Oregon, in relation to air and ground temperatures