Scientific Investigations Report 2008–5168
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2008–5168
Table 4. Nutrient load budgets and errors, Coeur d’Alene Lake, Idaho, calendar years 1991–92 and water years 2004–06.
[Sampling locations are shown in figure 1. Sampling locations on the St. Joe and Spokane Rivers changed between the 1991–92 and 2004–06 studies. For comparability, data are normalized to the following stations: St. Joe River: USGS gaging station 12415140, St. Joe River near Chatcolet; Spokane River, USGS gaging station 12417598, Spokane River at Lake Outlet at Coeur d’Alene. Sampling location on the Coeur d’Alene River for both studies was at USGS gaging station 12413860, Coeur d’Alene River near Harrison. Load and error estimates for ungaged tributaries and other surface-water inflow in 1991 and 1992 are from Woods and Beckwith (1997). Loads for ungaged tributaries and other surface-water inflow in 2004–06 were estimated using a relation between 1991–92 load data and annual flow in closest gaged tributary (see text for full explanation). Load and error estimates for nearshore wastewater and precipitation in 1991 and 1992 are from Woods and Beckwith (1997). Assumed nearshore wastewater and precipitation loads and errors were constant for 2004–06 study as no recent data were available. Actual error unknown for loads from ungaged tributaries, surface-water inflow, ground-water outflow, and lake storage change in 2004–06 study. Errors for 2004–06 were estimated by applying the average percent error in loads from the 1991–92 study (see text for full explanation). Loads and errors are in kilograms per year. Streamflows are in cubic hectometers per year. Abbreviations: USGS, U.S. Geological Survey; NA, not applicable]
Variable | Budget component | Calendar year | Water year | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
1991 | 1992 | 2004 | 2005 | 2006 | ||||||||
Streamflow | St. Joe River | 3,350 | 1,660 | 1,940 | 2,140 | 2,720 | ||||||
Coeur d’Alene River | 2,610 | 1,280 | 1,700 | 1,910 | 2,550 | |||||||
Spokane River | 6,270 | 3,140 | 4,120 | 4,230 | 5,870 | |||||||
Load | Error | Load | Error | Load | Error | Load | Error | Load | Error | |||
Total nitrogen | ||||||||||||
Inflow | St. Joe River | 991,000 | 98,000 | 343,000 | 26,100 | 62,700 | 18,500 | 48,500 | 16,600 | 84,600 | 28,600 | |
Coeur d’Alene River | 819,000 | 93,600 | 402,000 | 36,800 | 117,000 | 11,600 | 107,000 | 12,800 | 87,900 | 12,000 | ||
Ungaged tributaries and other surface-water inflow | 225,000 | 46,400 | 128,000 | 28,500 | 148,000 | 31,100 | 164,000 | 34,400 | 214,000 | 44,900 | ||
Nearshore wastewater | 4,900 | 1,220 | 4,900 | 1,220 | 4,900 | 1,220 | 4,900 | 1,220 | 4,900 | 1,220 | ||
Precipitation | 75,000 | 11,500 | 75,000 | 11,000 | 75,000 | 11,200 | 75,000 | 11,200 | 75,000 | 11,200 | ||
Outflow | Spokane River | 1,670,000 | 107,000 | 709,000 | 38,300 | 217,000 | 54,300 | 181,000 | 45,200 | 597,000 | 253,000 | |
Ground-water outflow to Rathdrum Prairie | 71,500 | 17,900 | 54,300 | 13,600 | 33,300 | 8,320 | 28,700 | 7,180 | 40,500 | 10,100 | ||
Lake storage change | 9,710 | 850 | 11,500 | 860 | 2,320 | 190 | 3,640 | 290 | 1,540 | 120 | ||
Total phosphorus | ||||||||||||
Inflow | St. Joe River | 40,100 | 11,100 | 14,800 | 3,400 | 35,300 | 3,670 | 45,100 | 5,150 | 71,600 | 8,690 | |
Coeur d’Alene River | 33,600 | 6,480 | 10,900 | 1,600 | 25,700 | 4,060 | 38,200 | 7,260 | 54,200 | 9,860 | ||
Ungaged tributaries and other surface-water inflow | 12,200 | 2,340 | 6,850 | 1,570 | 7,960 | 1,670 | 8,860 | 1,860 | 11,500 | 2,420 | ||
Nearshore wastewater | 390 | 100 | 390 | 100 | 390 | 100 | 390 | 100 | 390 | 100 | ||
Precipitation | 6,460 | 1,000 | 6,460 | 1,100 | 6,460 | 1,050 | 6,460 | 1,050 | 6,460 | 1,050 | ||
Outflow | Spokane River | 46,600 | 7,320 | 24,800 | 3,360 | 32,200 | 4,480 | 31,500 | 4,040 | 52,000 | 9,120 | |
Ground-water outflow to Rathdrum Prairie | 1,000 | 250 | 510 | 130 | 990 | 250 | 1,190 | 300 | 3,250 | 810 | ||
Lake storage change | 180 | 10 | 130 | 30 | 180 | 20 | 180 | 20 | 80 | 20 | ||
Summary | ||||||||||||
Constituent load | Calendar year | Water year | 1991 | 1992 | 2004 | 2005 | 2006 | |||||
Total nitrogen | ||||||||||||
Total inflow | 2,110,000 | 953,000 | 408,000 | 399,000 | 466,000 | |||||||
Total outflow | 1,750,000 | 775,000 | 253,000 | 213,000 | 639,000 | |||||||
Residual (outflow- inflow) | -360,000 | -178,000 | -155,000 | -186,000 | 173,000 | |||||||
Residual (percentage of inflow) | 17 | 19 | 38 | 47 | NA | |||||||
Overall error | 180,000 | 68,000 | 67,700 | 62,000 | 259,000 | |||||||
Total phosphorus | ||||||||||||
Total inflow | 92,800 | 39,400 | 75,800 | 99,000 | 144,000 | |||||||
Total outflow | 47,800 | 25,400 | 33,400 | 32,900 | 55,300 | |||||||
Residual (outflow- inflow) | -45,000 | -14,000 | -42,400 | -66,100 | -88,700 | |||||||
Residual (percentage of inflow) | 48 | 36 | 56 | 67 | 62 | |||||||
Overall error | 15,000 | 5,400 | 7,350 | 10,000 | 16,200 |