Long Lake 



Climatic setting. The net annual precipitation balance for the 

 Long Lake site (from the MAPS database) is -26 inches, placing the 

 site near the mid-range of evaporative intensity for hydrologically 

 similar sites. Monthly average precipitation for the Sunburst 8E 

 climatic station show a broad summer peak with a maximum in June. 

 Since the mid-1970 's, the 3-year running average of annual 

 precipitation for the Sunburst station was mainly at or above the 

 mean for the period of record. Data for 1993 and 1994 were not 

 recovered for this station; regionally, 1993 totals were well above 

 average and 1994 totals were below average. 



Geologic setting. The Willshaw Flats basin is underlain by 

 lacustrine and paludal sediments (including chemical precipitates) 

 with calcareous glacial till forming the immediately adjacent 

 upland slopes. The Willshaw Flats topographic depression has been 

 interpreted as a south flowing ice-marginal drainage during late 

 Pleistocene time. If this interpretation is correct, it is 

 possible that glaciof luvial sediments underlie Holocene lacustrine 

 deposits beneath the wetland complex. 



Surf icial deposits are underlain by shale and sandstone of the 

 Colorado Group. 



Hydrologic type. Long Lake is a depression (glacial drainage?) 

 lacking surface outflow. (Although it lies within the limits of 

 Pleistocene glaciation and is developed in glacial deposits, the 

 basin is not thought to be the direct result of the action of ice, 

 as are most sites with which Long Lake is classified.) The extent 

 of flooded area in Willshaw Flats is unusually transient with 

 respect to the set of sample sites. Surface water outflow would 

 require major changes in the Willshaw Flats water budget. 



Basin Characteristics. The Willshaw Flats basin is an extensive 

 complex of playa surface and vegetated wetland receiving runoff 

 from upland areas to the east. Topographic gradients within the 

 basin are very low and observed water depths were on the order of 

 1 foot near the center of the sampled wetland; raising the stage 

 the 10 feet or more needed to allow surface outflow would require 

 storing a very large volume of water within the basin. No 

 abandoned shorelines which might correlate to outflow-controlled 

 stage were observed. It seems probable that the basin has been 

 internally drained throughout the Holocene. Water storage in 

 Beaupre Coulee, the major drainage contributing runoff to the 

 Willshaw Flats Basin, may have reduced the runoff received by the 

 wetland complex during recent historic times. Wetland extent and 

 shoreline position are unusually transient. 



Water chemistry. At the time of sampling. Long Lake contained 

 mixed-cation/sulfate "oligosaline" water with specific conductance 

 of 4840 microsiemens/cm. Equilibrium calculations indicate 

 moderate supersaturation with carbonate species and undersaturation 



