Tooley Lake 



Climatic setting. The net annual precipitation balance for Tooley 

 Lake (from the MAPS database) is -14 inches, at the more 

 evaporatively intense extreme of the range shown by Rocky Mountain 

 sites. Mean monthly precipitation at the Eureka Ranger Station 

 climatic station shows a relatively even distribution throughout 

 the year with a maximum in June. Annual totals for the Eureka 

 station show the short-term (3-year) moving average at or above the 

 average for the period of record from 1981 through 1993. In 1993 

 (the year prior to sampling) the total precipitation exceeded the 

 mean by about 5 inches . 



Geologic setting. Tooley Lake occupies a depression of uncertain 

 origin along the margin of a thick sequence of glaciolacustrine 

 sediments deposited during late Pleistocene impoundment of the 

 Kootenai River. The glaciolacustrine sediments are described as 

 predominantly fine sand and silt with only a minor clay fraction. 

 The permeability of these sands and silts appears to be higher than 

 for many lacustrine deposits; ground-water flow is shown by 

 reported behavior during well drilling and by spring discharges 

 from the sediments. Upslope areas within the lake catchment are 

 underlain by drumlinoid till described as bouldery in texture. 



Bedrock outcrops within the lake catchment are composed of 

 formations of the mainly argillitic Ravalli Group of the 

 Proterozoic Belt series. Adjacent drainages expose areas of the 

 calcareous and pyritic Siyeh Formation of the Belt series. 



Hydrologic type. Tooley Lake has intermittent(?) surface water 

 inflow but lacks surface water outflow. Relatively dilute water 

 chemistry in this setting appears to imply significant ground-water 

 outflow from the lake to moderate the accumulation of solutes 

 contributed by lake inflow. Tooley Lake is also in a topographic 

 position suggesting the likelihood of ground-water inflow along 

 it's western shore. 



Basin characteristics. The catchment to wetland area ratio ranks 

 mid-range with respect to other Rocky Mountain sites. The depth 

 of Tooley Lake is unknown. Ground-water outflow rates may have 

 been altered by the filling of Lake Koocanusa, artificially raising 

 the local hydrologic base level. Road construction along the 

 eastern shore may have altered shoreline characteristics. 



Water chemistry- The WET68 sample was moderately dilute, 

 calciura/magnesium-bicarbonate/carbonate in composition, and only 

 slightly basic in the field. Mineral equilibria indicate 

 approximate saturation with calcite and aragonite under field 

 conditions. The pH measured in the lab, however, was 9.3, 

 indicating that the sample was not in equilibrium with the surface 

 environment. The one other known pH measurement from Tooley Lake 

 was also above 9. A probable explanation is that ground-water 

 enters the lake along the western shore, increasing in pH as inflow 



