Water, Flow, Temperatures, Trout
Four dams were recently removed from the Prairie River in Wisconsin. Check out this page from the City of Merrill’s website, with lots of pictures. At first, dam removal was controversial in their community; but now that the dams are gone you can see that the City is extremely proud of their beautiful river.
The two impoundments (Lakes George and Louise) are shallow and slow. They warm up the river water in the summer, and cool the water down in the winter. This means that the lower river has larger temperature extremes than the upper river.
The water temps of the Kinni have been extensively studied (20 years of temperature records), and a summary of the data can be downloaded from our Library page. Water temperatures in Lakes George and Louise can reach 80° (City data), which is fatal to brown and brook trout.
If the dams are removed, then the river temperatures downstream will be less extreme (water not so hot in the summer and not so cold in the winter) — and this is better for trout.
In the summer, 20 years of data show that the average temperature just upstream of the dams (Division Street) is 61° F (~ 16° C) and the temperature just downstream of the lower dam is about 66° F (~ 19° C). So, as the river goes through town and the two impoundments it warms up about 5°.
66°F is considered a “threshold” temperature for trout. Above the dams this temp was exceeded on only 9 days in summer 2012; but below the dams this river temp was hotter than 66°F on 39 days. This is a more accurate indication of the temperature impact of the dams because it is the extreme temps that threaten trout, not the average temps. (For example, 6 hours of 85° water will kill trout, but that sort of short event will barely change the 20-year average temps.)
There are 91 days in ‘meteorological summer,’ and on 39 of those days (43%) the temps were higher than the threshold temperature. This is a significant impact, and possible risk. More detailed information about river temperatures is on our Library page.
No. Every gallon that enters the impoundments must leave the impoundments at the same rate. So, if the dams are removed, the amount of water downstream does not change.
No. Our two dams are operated so that the impoundments are always full (this is called “instantaneous run of the river”). Since the impoundments are always full, they can’t catch and hold water during periods of high runoff. Some really big dams can be operated in a way to prevent or delay floods by drawing down their reservoirs and creating space to capture flood waters. Our dams can’t do that.
No, not a constant flow. The flow above the dams and the flow below the dams is not altered by the dams. The two impoundments are always full, and water is released through the turbines at the same rate that water enters the impoundments. This is called “run of the river” operation, and is required by the current FERC license.
During spring melt, or high water caused by rains, the extra flow spills over the tops of the dams. The dams do not moderate the flow, or provide a constant flow to the lower river. The impoundments do alter temperature, but not flow, to the lower river.
Not if the dams are drained down and recovered properly. There must be engineered plans that we all have a chance to review and comment on. We can avoid erosion problems by doing this right — draining down at the correct time of year, and seeding new grasses when they will sprout quickly to hold the soil. It will take time to prepare a good plan.
The Kinni dams are not “tailwater” fisheries. Tailwater dams are typically big dams with huge, deep reservoirs. Large tailwater dams catch and store snow-melt and spring-runoff and then release water at other times of the year. In contrast, the Kinni impoundments are extremely shallow.
The Kinni dams are much too small to store water for later release; and they do not ‘stratify’ water the way that tailwater fishery dams do. Water temperatures in Lakes George and Louise can reach 80° (City data), and this is a fatal temperature for brown and brook trout. Trout populations on the Kinni above the dams have been measured at more than 10,000 per mile; below the dams, trout population is less than half this size.
The birds that are present here today should continue to inhabit the area with the dams removed. In fact the increased amount of wetlands and parkland that would replace the lakes could potentially attract more birds and wildlife. Geese and ducks actually already use the wetlands and the river along the entire length of the Kinni throughout the year, we just think of them on the lakes because we see them there in town every day but we don’t get out on the upper/lower Kinni every day to witness the wildlife there. On our facebook page there is a picture of a pair of swans that reside on the upper Kinni all summer long. You can also see a photo of these trumpeter swans on our website Photos page.
The Lake George Recovery Plan adopted by the City includes new wetland areas that should be good waterfowl habitat. We could have a Lake Louise Recovery Plan that also provides wetland areas. Geese, ducks, and trumpeter swans also use the natural, flowing parts of the Kinni, of course. See photo of trumpeter swans on our Photos page.
The DNR tells us that if the Powell Falls dam is removed, the existing waste water discharge permit would not need to be amended.
The City has a DNR permit to discharge treated waste water to Lake Louise (a “warm water” impoundment). But the standards in the permit, and the standards that our treatment plant already meet, are the DNR’s more stringent cold water standards, not the warm water standards.
It might be desirable to discharge our treated waste water to a restored wetland area that is created when the Lake Louise impoundment is recovered, but this is probably optional. Our waste water treatment plant discharges about 1.2 cubic feet per second of treated water (at about 69°). Because this is a small volume of water compared to the Kinni’s average flow, and because the removal of the upper dam will decrease average river temperatures, the DNR has told us that it does not think that discharging directly to the Kinni would be a problem. For more information, please see the DNR memo in our Library .
There have been dams on the Kinni since the 1850’s. Only two dams now remain— many dams failed or were removed. The first settler to our area, Joel Foster, reported in 1848 that the brook trout fishing in the lower river was fantastic.
The Wisconsin DNR take fish surveys in the Kinni every few years—it’s like a census of what is living in our river. There are redhorse (a fish) in the Kinni below the dams—they have lived there for years. Fish surveys have found no redhorse anywhere in the South Fork. If redhorse cannot swim or jump up the small step-cascades of the South Fork (there is no dam on the South Fork), then how could they jump the vertical 8- to 12-foot falls of Junction Falls?
We believe that Junction Falls are a natural barrier that redhorse and common carp cannot get past. We also think this is very important, and must get more study.
The fisheries survey found common carp in the Kinni below the dams. The South Fork was surveyed (4 locations), and no carp were found. Carp have not swum up the small-stepped cascades of the South Fork.
Fishermen report there have caught carp and green sunfish in Lake George for years. But those fish have not been found upstream–even though there are no physical barriers at all to their migrating that way. The cold upstream water probably makes it unattractive to warm-water fish.
And, by the way, suckers and sticklebacks live throughout the Kinni watershed, and always have — they are native fish of the Kinni.
The US Geological Survey has a stream gage in the Kinni that measures flow every few minutes. This gage has been operating for years, and the data is available easily online here: USGS
Note that the gage measures in decimal feet. So, for example, between March 11 and 18, 2014 the maximum variation in river height was less than 2″ (it varied from 10.42 to 10.54 feet — and that is a 2″ difference).
Money, Power, Green Energy
So, we have lost out on potential profits of $274,520 since 1988 by generating hydroelectricity!
This raises further questions about the costs the City has had and can reasonably expect to have over the coming 30 years for repairs to aging infrastructure, major maintenance, new equipment, required upgrades, and so forth. These costs must be made a part of the discussion on whether our hydroelectric facilities are profitable over the long term.
We will need detailed cost estimates before dam removal is considered.
Two dams were removed from the Willow River not long ago. The Mounds Dam was removed in 1998 for $170,000 (the pre-removal cost estimate was $1,100,000, so the final cost was 84% less than quoted). The Willow Falls Dam was removed in 1992 for $450,000 (the cost estimate was $622,000, final cost was 27% less than quoted). Both of the Willow dams were much larger than our dams. Willow Falls dam created a 100 acre impoundment, and Mounds dam impounded 57 acres.
On the Kinni, our dams each impound a 16 acre lake. Mounds and Willow Falls dams were both more than 58 feet tall. Our dams are about 24 feet tall. For more comparisons, click on the “About Our Dams” link above.
Our hydroelectric dams produce renewable energy, but they do not meet the Environmental Protection Agency definition of a “green” energy source. Our dams catch sediment and silt, and they affect water temperatures downstream which is bad for the natural cold-water Kinni ecosystem. Our impoundments (some call them “lakes”) turn green with algae blooms.
Hydro-generation is often believed to have a smaller carbon impact than, say, coal-generation. However, new research is showing that hydroelectric facilities actually release a significant amount of methane gas into the atmosphere. If the dams are removed, we support efforts to locally generate truly green power, and continued efficiency improvements to reduce our City’s carbon footprint. We are doing research with experts on what that might look like, because like you we are concerned about our planet.
The RFMU has award-winning conservation efforts and solar-generation projects, and we know they want even more successes. Through conservation, the City reports that 1 million Kwh have been saved each year. We think there are opportunities to bring our local embrace of truly green energy to a new level.