Comeirtoifn Preserve 



Climatic setting. The net annual precipitation balance for the 

 Comertown Preserve site (from the MAPS database) is -20 inches, 

 ranking the site toward the less evaporative end of the range shown 

 for this classification. Mean monthly precipitation for the Westby 

 climatic station shows a pronounced June maximum. Annual total 

 precipitation records are incomplete through the 1980s for the 

 Westby station. For the years available during the 1980s, 3-year 

 averages of the annual total were well below the average for the 

 period of record. Regional trends during the missing years (1985- 

 87) indicate precipitation was above average in 1986 and below 

 average in 1985 and 1987. The 3-year average was near or above the 

 long term average in the early 1990s. 



Geologic setting. The Comertown Preserve is underlain calcareous 

 till of late Pleistocene age. Geologic mapping shows isolated 

 deposits of stratified glacial drift in the general vicinity of 

 the preserve, but the site lies well to the west of the known 

 distribution of regional gravel aquifers. The till and other 

 surficial deposits are underlain by the early Tertiary Fort Union 

 Formation. 



Hydrologic type. The Comertown Preserve site is a glacial 

 depression (kettle) lacking surface outflow under most(?) 

 conditions. During moist periods, the pond may be joined with 

 adjacent intermittently flooded depressions. The comparatively 

 dilute water chemistry observed at the site suggests ground-water 

 outflow may be significant to the site's water and solute budgets. 



Basin cheuracteristics . Based on available topographic mapping, the 

 Comertown Preserve appears to have only a minimal surface catchment 

 beyond the wetland itself. However, the fine scale knob-and-kettle 

 topography characterizing the area makes it difficult to be sure 

 of the true position of local drainage divides. Overflow from 

 adjacent, apparently separate basins, may occur. 



Water chemistry. At the time of sampling, Comertown Preserve held 

 alkaline, "oligosaline" water lacking dominant ionic composition. 

 Equilibrium calculations indicate substantial oversaturation with 

 carbonate phases. Ammonium, orthophosphorous and total organic 

 carbon concentrations ranked this site ranked this site toward the 

 upper end of it's classification. Most trace elements were below 

 detection limits in the water column. Reported arsenic and boron 

 concentrations ranked the site toward the lower end of it's class, 

 while zinc and copper concentrations ranked in the upper half 

 within the site's classification. 



Chemical history. No other chemical data for this site are known. 



Sediments. Arsenic, boron, copper and zinc concentrations rank 

 this site toward the middle or lower end of it's classification. 

 Chromium, nickel, selenium, and vanadium concentrations ranked 



