Jarina Waterfowl Production Area 



Climatic setting. The net annual precipitation for the Jarina WPA 

 site (from the MAPS database) is -9 inches, making Jarina the least 

 evaporative of sample sites within it's classification. Note, 

 however, that the Jarina site is in an area of very steep 

 precipitation gradients which may not be represented well by the 

 MAPS cell averages. Monthly average precipitation for the 

 Blackleaf Canyon climatic station shows a relatively strong May- 

 June peak with wide ranges between monthly minimum and maximum 

 values. Annual totals for the 44 year period of record at the 

 Blackleaf site show an apparent periodicity in precipitation with 

 a wavelength of 5 to 7 years (shown by the 3-year running average). 

 Precipitation for 1993, the year prior to the sample collection, 

 exceeded the average for the period of record by approximately 8 

 inches. 



Geologic setting. The Jarina WPA and surrounding areas are 

 underlain by calcareous till deposited by an alpine glacier or 

 glaciers terminating on the western edge of the plains. Shoreline 

 areas display variable sediment character, apparently controlled 

 by prevailing wind directions; the sample site proper is on the 

 westerly (upwind) shore, and is underlain by fine-grained organic - 

 rich sediments. Easterly (downwind) shores of the sample site and 

 nearby lakes tend to be underlain by coarse sand and gravel. 



Bedrock in the area is sandstone and mudstone from unspecified Late 

 Cretaceous formations. The overlying till is thin to absent in 

 places, exposing occasional sandstone outcrops, some of which 

 appear to be associated with ground-water seeps. 



Hydrologic type. The Jarina WPA site is a glacial depression 

 lacking surface drainage at current water levels. Strandlines of 

 unknown age indicate periods in the past when water levels have 

 been controlled by drainage to the southeast (to Sheep Creek) . 

 During such times, water depths were 3 to 4 feet greater than those 

 measured in 1994 and lake volume may have been greater by as much 

 as a factor of 5(?). 



Basin characteristics. The Jarina WPA site has a relatively small 

 surface catchment with respect to wetland area and volume. The 

 basin is shallow throughout, with a maximum measured depth in 

 August 1994 of 2.8 feet and an average depth of about 2 feet or 

 less. The cluster of numerous small lakes and wetlands surrounding 

 the sample site display highly disjunct water chemistry; surveyed 

 water bodies within a 2 square mile area ranged from 452 to >50,000 

 microsiemens/cm in specific conductance. More saline sites are 

 typically underlain by unidentified evaporitic minerals; some 

 lakes were desiccated in 1994. Construction of the berm supporting 

 the Birch Creek road isolated the northernmost end of the basin 

 from the remainder of the sample site. However, the presence of 

 a high-water outlet at the opposite (southeastern) end of the basin 

 effectively prevents the road from exerting a major influence on 

 water budgets of the sample site. 



