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| EDWARDS EAGLE RIVER RESTORATION PROJECT -- WATER QUALITY |
| River Temperature and Dissolved Oxygen Content |
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| A specific goal of the Restoration Project is to convert the river from a wide, relatively slow flowing waterway into one that flows more swiftly and is narrower. Narrowing the river deepens the water course and at the same time helps to keep the temperature lower, which is a condition more healthy for trout. Also, intrinsic to a successful restoration project is the creation of riffle zones where the water rushes across rocks, thus mixing air and water which increases oxygen concentrations. |
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| The saturated concentration of oxygen in water has an inverse relationship to temperature. That is, a lower amount of oxygen will dissolve in warm water than cool water. For example, water that is 90° F (32°C ) can only hold 7.4 mg/L (milligrams per liter) of dissolved oxygen (DO) at saturation, whereas water that is 45° F (7.2° C) can hold 11.9 mg/L DO at saturation. (Saturation is the maximum theoretical amount that will dissolve at a given temperature.) Typically, the mountain waters along the Eagle River between the Tigiwon Road and the Waste Water Treatment Plant below Edwards will run between 8 - 9.4 mg/L in the temperature range of 2 to 13°C (35.6 - 55.4°F). |
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| A concentration of 5 mg/L DO is a viable concentration to maintain healthy fish. Sensitivity to low levels of dissolved oxygen varies with fish species; but most species of fish are distressed when the DO falls to the 2-4 mg/L level. Death usually occurs at oxygen concentrations of less than 2 mg/L. The inverse relation between temperature and oxygen saturation puts a fish in double jeopardy because at high water temperatures its metabolic rate increases which in turn, increases its physiologic demand for oxygen. |
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| The restoration process will include the construction of new cobble and rock bars in the river. As noted above, this will narrow the channel, which will create faster flowing water and lower temperatures in the summer months. Extensive planting of vegetation along the river banks is also part of the overall plan. Vegetation that grows over the river creates shade, which both cools the river and provides cover for fish during the hot hours of the day. |
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| The Watershed Council purchased 8 temperature loggers and a dissolved oxygen meter to track the temperature and dissolved oxygen content respectively of the river to determine if differences could be detected before and after the restoration. The temperature loggers record the temperature once an hour; these data are retained in the logger until downloaded into a computer. The data can then be moved into a spreadsheet, analyzed, and graphed. |
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| The graph below displays the river temperature over a period of 19 days in October -- a small time slice of the overall period that the loggers were in the river. |
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| (October 2008 Data) |
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| Over the days shown, it is obvious that the trend (the black line) shows a steady temperature decline (0.25°C/day) as the weather cools with the approach of winter. Each day, the temperature swings about 4 -6°C with the coolest river temperature occuring at 7 - 8 am and the high at 4pm. |
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| Interestingly, the river temperature also gives an indication of weather -- the small temperature rise on the 4th of October probably indicates a cloudy day with possible snow or rain. The strong dips of the 9th and 14th may indicate the passage of a cold front followed by a warming trend. |
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| The oxygen meter is a hand-held device with an attached probe which is dropped into the river. Water temperature is recorded as well as the oxygen level (mg/l) and the percent saturation with respect to the recorded temperature. The oxygen values that were recorded at the time of logger placement in mid-July of 2009 is shown below: |
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| Station |
River Temperature (ºC) |
River Temperature (ºF) |
Dissolved
Oxygen
(mg/L) |
PercentSaturation(%) |
| 1 |
11.2 |
52.2 |
8.68 |
78.2 |
| 2 |
11.2 |
52.2 |
9.00 |
82.2 |
| 3 |
11.5 |
52.7 |
8.73 |
80.1 |
| 4 |
12.6 |
54.7 |
7.84 |
73.3 |
| 5 |
12.1 |
53.8 |
8.64 |
80.9 |
| 6 |
13.3 |
55.9 |
9.10 |
86.9 |
| 7 |
12.0 |
53.6 |
8.94 |
83.1 |
| 8 |
13.0 |
55.4 |
9.44 |
89.7 |
(July 2009 Data)
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| The values shown here are well above the 5 mg/L level desired to maintain a healthy fish stock. |
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| Further measurements were made on Saturday, 22-Aug-09 in the afternoon. Five of the loggers were directly observed; number six was out of the water and was relocated about 6 feet further into the river. The remaining 3 were not directly observed because either the logger was directly across the point of measurement or in the middle of the river (number 7). The dissolved oxygen levels for the 22nd of August are shown below: |
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| Station |
River Temperature (ºC) |
River Temperature (ºF) |
Dissolved
Oxygen
(mg/L) |
PercentSaturation(%) |
| 1 |
17.8 |
64.0 |
7.48 |
79.1 |
| 2 |
18.4 |
65.1 |
6.95 |
73.7 |
| 3 |
18.2 |
64.8 |
7.34 |
77.6 |
| 4 |
19.8 |
67.6 |
6.86 |
75.2 |
| 5 |
19.5 |
67.1 |
5.20* |
56.4 |
| 6 |
18.1 |
64.6 |
8.60 |
91.7 |
| 7 |
18.3 |
64.9 |
8.81 |
93.6 |
| 8 |
19.3 |
66.7 |
6.92 |
74.7 |
(August 2009 Data)
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| *) The logger could not be placed without it partially sinking into the silt in this section of the river. Hence, this is possibly the reason for the relatively low oxygen levels. |
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(Note ruler for size reference) |
Photo One
A Typical Temperature Logging System
A) A heavy metal anchor; in this case, a railroad tie-to-rail connector.
B) Logger Housing. 2" PVC pie with end caps. Holes are systematically drilled in the pipe to allow good water contact with the logger.
C) Plastic coated steel wire connector cable.
D. The actual logger ( Tidbit v2 Temp (UTBI-001).
E. Stainless steel wire fastening the Tidbit to the logger case cap.
F. Logger case cap (note that the cap has a hole drilled in it to accommodate the wire. The wire is wrapped around a stainless steel bolt and pinched by a stainless steel lock nut. |
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Photo Two
The Loggers were delivered to their respective sites via boat. The river pilot was Joe Macy, who is also in the photo. The eight loggers placed in the river are at his feet. It was a beautiful day to be on the river. |
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Photo Three
The Loggers were placed in river at 8 different locations and anchored to a rebar hammered into the river bed. Joe is hammering in a bar at this location. A nylon rope tethers the railroad anchor to the bar. |
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Photo Four
Some photos from the trip down the river. A couple of geese enjoying the pleasant day. |
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Photo Five
A huge beaver lodge. |
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Photo Six
In the "old" days auto bodies were placed along the shore to stabilize the banks. The banks were typically eroded by cattle. Hopefully, this old car will be removed during the restoration effort. |
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| The loggers went in, but they also came out when the river began to freeze in mid-October. |
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Photo Seven
The river appears to be a bit icy. "Hey, it can be kinda difficult to find the loggers under the ice!" |
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Photo Eight
Got this one back without falling in, but, "gosh, these things are heavy. And I have to lug it about a quarter of a mile back to my truck," says Timm. |
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