difficult to estimate. Table 4 compares nutrient loads and concentrations for Station 9 

 (near mouth) and the mainstem of the Clark Fork River utilizing 1999 water data for Lost 

 Creek and Clark Fork and data collected by the DEQ between 1989-1990. 



In all years, Lost Creek contribution of SRP and TP is insignificant in terms of 

 Clark Fork River concentrations, and mean concentrations for most sites on Lost Creek 

 fall well below the VNRP target of 20 ppb (Figures 3 and 4). Similarly, mean 

 phosphorus loads (Fig. 5) were typically low (< 1 kg/day) and results indicated only slight 

 differences between sites. A maximum daily load of 0.7 kg/day was recorded at Station 9 

 near the mouth. Mean loading at the mouth (0.3 kg/day) was only 1% of the Clark Fork 

 river load of 28 kg/day. Station 2 exhibited the highest concentrations of TP in Lost 

 Creek ranging from 14-53 ppb with a summer mean of 24 ppb. The area upstream from 

 this station contains the greatest concentration of unsewered residential development in 

 the basin and may be the source of most of the Total P load to Lost Creek. 



Nitrate/nitrite levels (Fig. 6) were lowest at the 4 upstream stations; below these 

 stations nitrate/nitrite were much higher. Station 5 results are based on only two sample 

 dates in May where access to the channel was permitted, and mean value is highly 

 variable. Dutchman Creek (Station 6) exhibited the highest mean values and the highest 

 peak value of 720 ppm. Stations downstream from this area exhibited a gradual decrease 

 in mean nitrate/nitrite concentrations ending with a mean value of 179 ppb at Station 9, 

 considerably higher than most upstream stations. 



Nitrogen, particularly nitrate, shows the greatest increases in concentrations and 

 loads in the middle and lower reaches of Lost Creek. Like the 3 upstream stations, 

 station 4 (located below the overwintering and calving area) exhibited low nutrient levels 

 during the sampling period (May-August). Although this area is a likely source of 

 nutrients, its effect on nutrient levels would occur earlier in the spring when low 

 elevation snow melt would deliver nutrients from animal waste to the creek. The area 

 including Stations 5-7 all exhibit high mean levels of nitrate relative to upstream values. 

 Likely explanations for these high levels vary from site to site. Station 5 is located above 

 the Dutchman reservoir and high levels of nitrate may be influenced by subsurface return 

 of irrigation from the land application of wastewater to fields occupying the ridge north 

 of this station. Upstream from Station 5 are several wet meadow complexes that form 

 against the base of this ridge where a number of seeps have formed. Station 6 on 

 Dutchman Creek drains the southern portion of the basin, which includes the site of the 

 wastewater storage ponds and the groundwater infiltration basins that receive excess 

 wastewater 2-3 months of the year depending on supply and demand. Groundwater 

 nitrate data is scant yet one sample obtained from the Montana Department of 

 Environmental Quality Groundwater Section from 1995 indicates that levels are 

 significant (9.38 mg/1) from a sample taken from a well just east (down gradient) from 

 storage ponds. 



Station 7 is located below the outfall of the Dutchman reservoir, and Lost Creek 

 nitrate levels here may be affected by the water table fluctuations caused by the filling 



