capacity; at the beginning of 1994 (the year of the DHES sampling) 

 the lake was at approximately 69% of "management capacity". This 

 represented a slight gain in storage over the previous year. I 

 midsummer of 1993, runoff in Big Muddy Creek allowed for diversion 

 of several hundred cfs, raising the lake level almost two feet in 

 a matter of a few days. This kind of rapid episodic fill and lake 

 level rise, followed by periods of progressive water-level decline, 

 is probably characteristic of the management of Medicine Lake. 



Water chemistry. At the time of sampling, the WET49 site exhibited 

 "oligosaline" sodium-sulfate water with near-neutral pH and low 

 dissolved oxygen concentration. Substantial calcium and carbonate 

 remained in solution, and mineral equilibria indicate moderate 

 oversaturation with respect to carbonate phases. The ammonium and 

 total phosphorous concentrations were high in comparison to the 

 sample sites in this class; orthophosphate and total organic carbon 

 concentrations ranked mid-range within the site classification. 



Concentrations of arsenic, boron and iron ranked low among sites 

 of this class; most other trace element concentrations were below 

 reporting limits. 



Chenical history. Occasional measurements of field water quality 

 parameters ar available since 1984, with quantitative water 

 chemistry from one Medicine Lake site in 1990. Beginning in 1994, 

 the U.S. Fish and Wildlife Service has measured limited field 

 parameters (specific conductance, dissolved oxygen and temperature) 

 on an approximately monthly basis from five sites in Medicine Lake, 

 including one relatively near the DHES site WET49. These data 

 demonstrate substantial spatial gradients in salinity within the 

 lake, as well as temporal variability in water quality within 

 regions of the lake basin. 



In September of 1984, measurements of specific conductance at ten 

 different points along the lake shoreline yielded a mean of 2060 

 microsiemens/cm, with a minimum of 1590 and a maximum of 3053 

 microsiemens/cm. Eight specific conductance measurements in August 

 of 1990 ranged from 650 (at the Muddy Creek diversion inflow?) to 

 4760 microsiemens/cm, with a mean of 4034. A DHES survey of 4 

 shoreline sites in May of 1993 yielded a mean of 5555 

 microsiemens/cm and a range from 3460 to 6410 microsiemens/cm. In 

 all cases where sites near WET49 were measured they were the least 

 saline within the lake at that time, with the exception of the 

 August 1990 low reading of 650 microsiemens/cm, which may have been 

 collected from the Muddy Creek inlet itself rather than from the 

 lake. This is consistent with the presence of ground-water inflow 

 to Lake Creek and to the eastern (upgradient) end of Medicine Lake; 

 surface runoff from the Lake Creek catchment, when it occurs, will 

 further dilute water at the WET49 site relative to other parts of 

 the lake basin. 



The pH and dissolved oxygen concentrations are both relatively low 

 in the WET49 sample. The 1990 analysis, conducted on a sample 



