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Physical and chemical water quality of the Spokane River outlet reach of Lake Coeur d'Alene, Kootenai County, Idaho 1990 and 1991 Item Info

The University of Idaho conducted a water quality study on the Spokane River outlet arm of Lake Coeur d'Alene from June, 1990 through September, 1991. The project was sponsored by the Idaho Division of Environmental Quality (Coeur d'Alene office). Objectives of the study were to: 1) Characterize baseline river water quality; 2) determine seasonal river water quality variation; 3) assess diel temperature and dissolved oxygen changes for indications of aquatic ecosystem stress; and 4) provide a cursory view of the effects of existing and proposed wastewater discharges on river water quality, to the extent that river water quality data and WWTP data will allow. The study updated earlier work by the University of Idaho and USEPA in 1980 and 1988. The study area covered the 8.1-mile reach of the Spokane River from the outlet of Lake Coeur d'Alene at River Mile 108.8 downstream to just below Post Falls Dam at River Mile 100.7. This reach is typified by swift water currents and cobble bottom channel in the upper section merging to deeper, slower lacustrine conditions in the lower section where channel cobbles yield to fine sediments in lateral embayments. Water depths ranged from 2 to 18 m through the reach. Water flows in the 16-month study ranged from high flows of 31,750 cfs in May, 1990 to low flows of 340 cfs in September, 1990. Retention times of the study reach varied from 4.3 hours at annual high flows in 1990 and 1991, respectively, to 12.7 days at annual low flows in 1990 and 1991. Surface water temperatures peaked at 25.7 and 26.1 C in 1990 and 1991. Vertical thermal stratification was minimal, always less than 3.0 C from surface to bottom. Slight summer temperature increases were noted downstream through the reach. Sample site mean summer dissolved oxygen was always greater than 7.0 mg/1; one sample occurrence was recorded of 5.4 mg/1. Electrical conductivity generally ranged from 30 to 55 umhos. Median pH was slightly on the acid side (5.7 to 7.8) throughout the reach. Secchi depth ranged from 2.4 to 6.5 m with a study average of 4.0 m. High flows coincided with low secchi depths, as a result of suspended sediments and an extended spring algae pulse. Mean year-round chlorophyll a averaged 2.5 and 4.2 mg/m3 at the upper and lower sections of this river reach for an average 73% increase over the 7.6 mile reach. Mean summer chlorophyll a of the lower sections averaged 6.0 mg/m3 in 1990 but only 3.3 mg/m3 in 1991 (= 45% reduction) following 1) a very large spring algae bloom, and 2) 80% phosphorus removal from the Coeur d'Alene WWTP. The 1990 and 1991 chlorophyll a levels place the Spokane River in mesotrophic and meso-oligotrophic productivity ranges, rexi spectively. Mean Kjeldahl nitrogen was 0.18 mg/1 and generally increased >20% below the Coeur d'Alene WWTP at low flows. There was a general trend of TKN increasing downstream through the study reach. The WWTPs contributed 25 to 50% of the TKN load to the Spokane River at low flows. Nitrate nitrogen was typically less than 0.05 mg/1 through summer months with fall-winter maxima of 0.50 mg/1. At low flows, WWTPs supplied 40% of the total nitrate load to the river. Mean total ammonia in the Spokane River arm of Lake Coeur d'Alene was 0.14 mg/1. From RM 111.1 to 108.8, there typically was an average 75% increase of total ammonia in the River, but less than one third of that increase was from the Coeur d'Alene WWTP. However, 30% of the average summer ammonia load to the river was from the Coeur d'Alene WWTP (up to 60% of the total ammonia load in September, 1991 at 340 cfs river flow). Total phosphorus ranged from 0.007 to 0.025 mg/1 with a study mean of 0.014 mg/1 (in the mesotrophic range). Total phosphorus increased 70% between RM 111.1 and 108.8over the entire study. Summer total phosphorus increased 87% between RM 111.1 and 108.8 over the entire study, 187% in 1991, but showed a 30% decline in 1991 after phosphorus removal in the Coeur d'Alene WWTP. WWTPs contributed -50% of the total phosphorus load to the reach at low flows. Upgrading the Coeur d'Alene WWTP in June, 1991 resulted in an effluent TP decline of 79%. Total N:total P ratios indicate phosphorus limitation most of the time with the exception of summer-fall 1990. BODs levels in the Spokane River were moderately high, averaging 3.4 mg/1 over all sites and dates. WWTP BODs levels from the Coeur d'Alene and Post Falls plants averaged 81.2 and 13.2 mg/1, respectively. Mean BODs increased 14% in the lower four river sites compared to the two upstream sites. Ultimate BOD in the Spokane River averaged 10.7 mg/1. WWTP ultimate BOD levels from the Coeur d'Alene and Post Falls plants averaged 644.7 and 371 mg/1, respectively. Mean ultimate BOD increased 11% in the lowest river site compared to the uppermost site. Median fecal coliform bacteria in the Spokane River were -1 colony/100 ml except for immediately below the WWTPs. Median fecal coliform bacteria were 30 and 24 colonies/100 ml in the Coeur d'Alene and Post Falls WWTPs, respectively. Median fecal coliform bacteria increased -30-fold from above to immediately below the Coeur d'Alene WWTP. River fecal coliform levels dropped to background concentrations within two river miles. Median fecal coliform bacteria increased -2-fold from above to immediately below the Post Falls WWTP. The diel study in August, 1991 showed insignificant stratification of either temperature or oxygen and little day-to-night fluctuation of either temperature or oxygen.

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Title:
Physical and chemical water quality of the Spokane River outlet reach of Lake Coeur d'Alene, Kootenai County, Idaho 1990 and 1991
Authors:
Falter, C. Michael; Riggers, B.; Carlson, J. W.
Date Created (ISO Standard):
1992-03
Description:
The University of Idaho conducted a water quality study on the Spokane River outlet arm of Lake Coeur d'Alene from June, 1990 through September, 1991. The project was sponsored by the Idaho Division of Environmental Quality (Coeur d'Alene office). Objectives of the study were to: 1) Characterize baseline river water quality; 2) determine seasonal river water quality variation; 3) assess diel temperature and dissolved oxygen changes for indications of aquatic ecosystem stress; and 4) provide a cursory view of the effects of existing and proposed wastewater discharges on river water quality, to the extent that river water quality data and WWTP data will allow. The study updated earlier work by the University of Idaho and USEPA in 1980 and 1988. The study area covered the 8.1-mile reach of the Spokane River from the outlet of Lake Coeur d'Alene at River Mile 108.8 downstream to just below Post Falls Dam at River Mile 100.7. This reach is typified by swift water currents and cobble bottom channel in the upper section merging to deeper, slower lacustrine conditions in the lower section where channel cobbles yield to fine sediments in lateral embayments. Water depths ranged from 2 to 18 m through the reach. Water flows in the 16-month study ranged from high flows of 31,750 cfs in May, 1990 to low flows of 340 cfs in September, 1990. Retention times of the study reach varied from 4.3 hours at annual high flows in 1990 and 1991, respectively, to 12.7 days at annual low flows in 1990 and 1991. Surface water temperatures peaked at 25.7 and 26.1 C in 1990 and 1991. Vertical thermal stratification was minimal, always less than 3.0 C from surface to bottom. Slight summer temperature increases were noted downstream through the reach. Sample site mean summer dissolved oxygen was always greater than 7.0 mg/1; one sample occurrence was recorded of 5.4 mg/1. Electrical conductivity generally ranged from 30 to 55 umhos. Median pH was slightly on the acid side (5.7 to 7.8) throughout the reach. Secchi depth ranged from 2.4 to 6.5 m with a study average of 4.0 m. High flows coincided with low secchi depths, as a result of suspended sediments and an extended spring algae pulse. Mean year-round chlorophyll a averaged 2.5 and 4.2 mg/m3 at the upper and lower sections of this river reach for an average 73% increase over the 7.6 mile reach. Mean summer chlorophyll a of the lower sections averaged 6.0 mg/m3 in 1990 but only 3.3 mg/m3 in 1991 (= 45% reduction) following 1) a very large spring algae bloom, and 2) 80% phosphorus removal from the Coeur d'Alene WWTP. The 1990 and 1991 chlorophyll a levels place the Spokane River in mesotrophic and meso-oligotrophic productivity ranges, rexi spectively. Mean Kjeldahl nitrogen was 0.18 mg/1 and generally increased >20% below the Coeur d'Alene WWTP at low flows. There was a general trend of TKN increasing downstream through the study reach. The WWTPs contributed 25 to 50% of the TKN load to the Spokane River at low flows. Nitrate nitrogen was typically less than 0.05 mg/1 through summer months with fall-winter maxima of 0.50 mg/1. At low flows, WWTPs supplied 40% of the total nitrate load to the river. Mean total ammonia in the Spokane River arm of Lake Coeur d'Alene was 0.14 mg/1. From RM 111.1 to 108.8, there typically was an average 75% increase of total ammonia in the River, but less than one third of that increase was from the Coeur d'Alene WWTP. However, 30% of the average summer ammonia load to the river was from the Coeur d'Alene WWTP (up to 60% of the total ammonia load in September, 1991 at 340 cfs river flow). Total phosphorus ranged from 0.007 to 0.025 mg/1 with a study mean of 0.014 mg/1 (in the mesotrophic range). Total phosphorus increased 70% between RM 111.1 and 108.8over the entire study. Summer total phosphorus increased 87% between RM 111.1 and 108.8 over the entire study, 187% in 1991, but showed a 30% decline in 1991 after phosphorus removal in the Coeur d'Alene WWTP. WWTPs contributed -50% of the total phosphorus load to the reach at low flows. Upgrading the Coeur d'Alene WWTP in June, 1991 resulted in an effluent TP decline of 79%. Total N:total P ratios indicate phosphorus limitation most of the time with the exception of summer-fall 1990. BODs levels in the Spokane River were moderately high, averaging 3.4 mg/1 over all sites and dates. WWTP BODs levels from the Coeur d'Alene and Post Falls plants averaged 81.2 and 13.2 mg/1, respectively. Mean BODs increased 14% in the lower four river sites compared to the two upstream sites. Ultimate BOD in the Spokane River averaged 10.7 mg/1. WWTP ultimate BOD levels from the Coeur d'Alene and Post Falls plants averaged 644.7 and 371 mg/1, respectively. Mean ultimate BOD increased 11% in the lowest river site compared to the uppermost site. Median fecal coliform bacteria in the Spokane River were -1 colony/100 ml except for immediately below the WWTPs. Median fecal coliform bacteria were 30 and 24 colonies/100 ml in the Coeur d'Alene and Post Falls WWTPs, respectively. Median fecal coliform bacteria increased -30-fold from above to immediately below the Coeur d'Alene WWTP. River fecal coliform levels dropped to background concentrations within two river miles. Median fecal coliform bacteria increased -2-fold from above to immediately below the Post Falls WWTP. The diel study in August, 1991 showed insignificant stratification of either temperature or oxygen and little day-to-night fluctuation of either temperature or oxygen.
Subjects:
water quality flow chemical composition bacteria (coliform)
Location:
Spokane River; Lake Coeur d'Alene
Latitude:
47.69
Longitude:
-116.81
Collection:
Coeur d'Alene Basin
Series:
Water for Idaho
IWRRI number:
199207
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
Publisher:
University of Idaho
Contributing Institution:
University of Idaho
Type:
Text
Format:
application/pdf
Cataloger:
wbv
Date Digitized:
2012

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Preferred Citation:
"Physical and chemical water quality of the Spokane River outlet reach of Lake Coeur d'Alene, Kootenai County, Idaho 1990 and 1991", Idaho Waters Digital Library, University of Idaho Library Digital Collections, https://www.lib.uidaho.edu/digital/iwdl/items/iwdl-cda_falter_1992.html
Rights
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
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