Ha If breed Leike 



Climatic setting. The net annual precipitation balance for 

 Half breed Lake (from the MAPS database) is -28 inches, placing it 

 among the most strongly evaporative of the sample sites. Average 

 monthly precipitation for the Rapelje climatic station shows a 

 strong May-June peak. The 3-year running average of total annual 

 precipitation shows apparent periodicity, with 6 to 9 years between 

 peaks. Between the early 1970s and 1992, the 3-year average 

 remained mainly above the average for the period of record. Data 

 for 1993 and 1994 were not recovered for this station. 



Geologic setting. Halfbreed Lake lies near the intersection of the 

 Lake Basin fault zone and the trend of the Lake Basin anticline. 

 Upland areas adjacent to the lake are scattered with noncalcareous 

 sandstone float of an uncertain formation (Lennep Sandstone?) 



The site is underlain by fine-grained, calcareous, plastic lake 

 sediments with accumulations of organic debris at higher shoreline 

 elevations. 



Hydrologic type. Halfbreed Lake is a structurally controlled(?) 

 depression, modified by ditching and impoundment, with controlled 

 outflow. 



Basin characteristics. Halfbreed Lake has a relatively high 

 catchment to wetland ratio in comparison to hydrologically similar 

 sample sites. At low water levels, the northeastern basin of the 

 irregularly shaped lake is separated from the main basin, allowing 

 distinct salinity to develop. A distinct "full pool" shoreline is 

 developed at an elevation approximately 2 . 3 feet above the lake 

 stage at the time of sampling, and approximately 1.7 feet above 

 lake stage at the time of follow-up observations in October 1994. 

 This shoreline feature may be controlled by the lake's outlet 

 structure . 



Water chemistry. At the time of sampling, Halfbreed Lake contained 

 "mesosaline" sodium sulfate water. Eguilibrium calculations 

 indicate substantial oversaturation with carbonate species and 

 slight undersaturation with gypsum. [Estimated calcium/magnesium 

 ratios and uncertain carbonate and bicarbonate concentrations 

 reduce the usefulness of these indices.] 



Nutrient concentrations were unremarkable in comparison to 

 hydrologically similar sites. Along with other sample sites in the 

 region, Halfbreed Lake water contained copper, chromium and nickel 

 concentrations at or near upper end of the sampled range. 



Chemical history. No water chemistry data prior to the April 1993 

 DHES sampling are known from Halfbreed Lake. In October 1994, 

 specific conductance at the WET25 site was only 37% of the 

 conductance at the time of the 1993 sampling, probably reflecting 

 flushing during the wet spring and summer of 1993. Historic water 



