| Hayden Lake Water Quality Report – 2005
Summary: Based on Mid-Lake, Bervin Bay and Northern Arm sampling stations the water quality of Hayden Lake remains good. Lake clarity, total phosphorous, chlorophyll, and dissolved oxygen measurements provided values in the range of high water quality. However, total phosphorous has increased from values measured in 2004 and remains above the goal of the Hayden Lake Management Plan and federally required levels determined to fully protect water quality. The Forest Service and DEQ are working jointly to measure the amount of phosphorous entering the lake from its primary tributary, Hayden Creek. For the first time this year, continuous real-time data were collected along transects between the open lake and selected bays. As these measurements are made in subsequent years and compared, a more sensitive measure of the overall health of the lake should emerge.
Introduction: Assessment of Hayden Lake’s water quality is based on three separate approaches. The water quality is assessed at three stations on the lake: Mid-Lake (279), Bervin Bay (283), and the Northern Arm’s deep area (282) (Figure 1). Water quality is assessed at these stations based on four measurements. Clarity is the depth to which a fixed object can be seen in the water column. Total phosphorous is the key plant growth nutrient that can cause algae to multiply in the water column. Chlorophyll is a measure of the relative amount of algae growing in the water column. Dissolved oxygen is required by fish and other aquatic life to survive. An increase in phosphorous can cause increasing algae growth, resulting in reduction of the clarity of the water. Dissolved oxygen concentration declines as the algae decay. The second approach is the measurement of the load of total phosphorous entering the lake through its primary tributary, Hayden Creek. The final approach is to assess the key indicator of algae growth (chlorophyll) across transects from the open mid-lake waters into key bays where algal growth is known to occur naturally at higher levels. The change in the chlorophyll concentrations over the years and the nature of that change is the most sensitive measure of the lake’s health.
Techniques: Water quality data were collected at the three stations five times during the period from late May to late October. Physical measurements (clarity, temperature dissolved oxygen) were completed on site, while samples from the upper water column (upper 45 feet) were collected and integrated for analysis of total phosphorous and chlorophyll. The Forest Service measured the discharge of water into the lake from Hayden Creek at a stream gage located near Forest Road 206 Bridge. The DEQ measured total phosphorous at a nearby gage. The total phosphorous load entering the lake from its largest tributary can be calculated in pounds per unit time from these data. The level of chlorophyll was measured in real time based on fluorescence of chlorophyll during early September, when the water column of the lake is most stable. Transect measurements were recorded between the mid-lake area and the upper end of the northern arm (Sportsman’s Access) and from the mid-lake into Bervin Bay. All measurements were linked to global position for the most exact comparison to subsequent transects collected in the coming years. Water samples were collected at specific transect locations for chlorophyll analysis to calibrate results.
Figure 1: Approximate locations of Mid-Lake (279), Bervin Bay (283) and Northern Arm (282) water quality sampling stations on Hayden Lake.
Note: Adapted from Soltero et.al. 1986. Water Quality Assessment of Hayden Lake, Idaho. Eastern Washington University, Department of Biology, Cheney WA 99004. p.10.
2005 Results: The average, maximum and minimum values for clarity, total phosphorous, chlorophyll and dissolved oxygen for the three stations are provided in Table 1.
Table 1: Average, maximum and minimum clarity, total phosphorous, chlorophyll a and dissolved oxygen for the Mid-Lake, Bervin Bay and Northern Arm Stations of Hayden Lake.
Note: ug/L – micrograms per liter of water or parts per billion; mg/L – milligrams per liter of water or parts per million; * – near bottom, because station too shallow for stratified upper, warm water and lower cold water.
The averages for the three key measurements, clarity, total phosphorous and chlorophyll for the mid –lake station are plotted with averages from previous years in figures 2 – 4.
Figure 2: Average, maximum and minimum clarity measured as Secchi depth in meters from 1985 to 2005
Note: 1 meter equals 3.28 feet.
Figure 3: Average, maximum and minimum total phosphorous measured as micrograms per liter (parts per billion) from 1985 to 2005
Water quality monitoring of Hayden Lake is a joint effort of the Idaho Department of Environmental Quality’s Citizen Volunteer Monitoring Program and the Hayden Lake Watershed Association. The program loans the equipment and pays for laboratory analysis. Association members collect physical data and sample for analysis from their privately owned boats. The result of the joint effort is a twenty-year record of lake water quality and continuing vigilance to detect any changes in Hayden Lake’s water quality.