Summer water warming of the Pigeon River caused by the Golden Lotus Inc. dam and impoundment.

Andrew J. Nuhfer

David J. Borgeson

and

Kurt Newman

Michigan Department of Natural Resources

June 2009
Abstract

Impoundment of water by the Golden Lotus Inc Dam causes substantial warming of the Pigeon River during summer months. Water released from Golden Lotus Dam during the summer is sometimes more than 5⁰F warmer than at sites located upstream of the impoundment. Summer warming caused by the dam severely reduces thermal habitat suitability for trout in many miles of the river downstream. Removal of the dam would reduce summer heating by the impoundment thereby expanding the length of the Pigeon River with optimal thermal habitat for trout by up to 16 miles.

Introduction

It is common knowledge that in Michigan dams and their impoundments increase the temperature of waters during summer such that waters downstream of the dams on coldwater streams are often too warm to sustain thriving coldwater fish communities. Adverse effects of dams on aquatic habitat have been documented in watersheds throughout northern Michigan such as the Muskegon River watershed, the Manistee River watershed, and the Au Sable River watershed (O’Neal 1997, Rozich 1998, Sendek and Zorn 2001). Objectives of this report are to document summer water warming of the Pigeon River caused by the Golden Lotus dam and impoundment and to project how much additional riverine habitat could be improved for coldwater aquatic communities if the dam was removed.

Methods

Water temperatures in the Pigeon River at sites located above and below the dam were recorded electronically in various years between 1998 and 2008 (Figure 1). In 1998, Ryan™ Tempmentors were used to record water temperatures at 15-minute intervals at Old Vanderbilt road (3 miles upstream of the dam) and immediately downstream of the dam from 1-July through 21-August. In other years electronic thermometers manufactured by Onset Computer Corporation were used to collect temperature data. Water temperatures were almost always collected at 1-hour intervals during these later years so that thermometers could be deployed for longer periods of time. The manufacturers of the thermometers report that the expected accuracy of the units is about ±0.33⁰C.

Water temperature data were summarized in a variety of ways including computation of; daily minimum, mean, and maximum temperature, monthly minimum, mean, and maximum temperature, and the averages of daily minimum and daily maximum temperature readings by month. Heating or cooling rates per mile of river for different segments of the river were computed by dividing the change in mean monthly temperatures between upstream and downstream sites by the number of miles of river in the segment.

Results

Water warming in the impoundment created by the Golden Lotus Inc. Dam increases average summer water temperatures in the river downstream of the dam up to 5⁰F as compared to temperatures at river sites upstream of the dam (Table 1). The specific amount of warming varies among years depending upon air temperature and other factors. During hot summers, warming in the impoundment may reduce the miles of river with good thermal habitat for trout by up to 16 miles.

In 1998, mean July water temperature immediately below the dam was 5.1⁰F warmer than in the river at Old Vanderbilt Road, located about 3 miles upstream of the dam (Figure 1). Maximum daily water temperatures upstream of the dam rarely exceeded 70⁰F in July 1998, whereas downstream of the dam they approached 80⁰F on hotter days of the month (Figure 2).

Summer water temperatures increased substantially between sites upstream of the dam and sites downstream of the dam in all years that thermometers were deployed (Table 1). In 1998, average daily minimum, mean, and maximum temperatures each increased about 5⁰F between Old Vanderbilt Road and the site immediately below the dam (Table 1). The average of June water temperatures collected during 4 years downstream of the dam were 3.7⁰F warmer than temperatures in the river upstream of the impoundment. The average July warming due to the impoundment for the 5 years data were collected was 3.5⁰F, while August warming averaged 3.0⁰F (Table 1).

The impoundment caused even greater increases in daily maximum water temperatures during some months. For example, average June daily maximum water temperatures were 5.5⁰F warmer downstream of the dam in 1998 and nearly 6⁰F warmer in 2007 (Table 1). July daily maximum water temperatures downstream of the dam averaged 4.3⁰F warmer than the river upstream during the 5 years temperature data were available (Table 1).

The continued presence of the dam and impoundment causes a dramatic increase in the rate of warming of the Pigeon River, i.e. temperature increases per mile (Figure 3). In 2005, mean July temperature increased by 0.59⁰F per mile between Old Vanderbilt Road and Sturgeon Valley Road, the section of the Pigeon River that contains the Golden Lotus Pond. By contrast, mean July temperatures increased an average of only 0.22⁰F per mile between Sturgeon Valley Road and highway M-68 (Figure 3, upper panel). More refined estimates of the warming that occurs in the impoundment were obtained in 2008 by placing thermometers in the river immediately above and below the impoundment. In 2008, water temperatures increased 4.3⁰F as water traversed the 1-mile distance between the thermometer in the river upstream of the impoundment and the thermometer located immediately downstream of the dam (Figure 3, lower panel). In 2008, DNR found that groundwater entering the river between Old Vanderbilt Road and the thermometer in the river upstream of the impoundment actually reduced mean July water temperature in this 1.75-mile section of river (Figure 3 and Figure 4, lower panels). Hence, estimates of heating due to the impoundment based on comparisons of temperature data from electronic thermometers placed at easily accessible road crossings located further away from the dam and impoundment during other years were probably large under-estimates of the actual amount of heating that occurred.

Discussion

Water warming caused by Golden Lotus Dam and impoundment decreases thermal habitat suitability of downstream reaches of the Pigeon River for trout species. Michigan has developed a river classification system based on average July water temperatures and average variation in daily water temperatures. Streams classified as “cold”, and thermally optimal for trout are those having mean July water temperatures less than 19⁰C (66.2⁰F) (Wehrly et al. 1999, 2003). Wild, naturally-reproducing trout are rarely abundant in Lower Michigan streams having mean July water temperatures higher than 68 ⁰F. Zorn et al. (in press) examined brown trout and brook trout density at a large number of Michigan stream sites relative to July water temperatures and found that the maximum potential density of trout fell to near zero as mean July temperatures approached 70 ⁰F.

Water warming that occurs in the impoundment above the dam increases summer water temperatures in the river downstream thereby permanently reducing the miles of river that would otherwise be thermally optimal for trout during summer. Average July water temperatures in the Pigeon River during the warm summer of 2005 reached 66.8 ⁰F at Tin Bridge and 68 ⁰F at Webb Road. During hot summers such as 2005, the Pigeon River has excellent thermal habitat for trout only in about the first 9 miles of river between the dam and Tin Bridge (Figure 4, top panel). During cooler summers such as 2008, water temperatures were good for trout down to at least Webb Road, 14 miles downstream from the dam, and were only about 1⁰F above optimum down to M-68, about 25 miles downstream from the dam (Figure 4, lower panel).

Just a few degrees of water cooling accomplished by removal of dams can dramatically increase the potential of a stream section to support a thriving trout population. At Webb Road and sites further downstream summer water temperatures are above optimum during hot summers. If the Golden Lotus dam was removed, thermally optimal habitat for trout might be restored as far downstream as M-68, an increase of up to 16 miles of optimal thermal habitat. Removal of the dam could result in a 3⁰F reduction of mean July water temperature resulting in temperatures at highway M-68 that are similar to those presently recorded at Tin Bridge during hot summers (Figure 5). Even if dam removal does not generate a full 3⁰F reduction in mean July water temperatures all the way downstream to highway M-68, it is clearly evident that optimal water temperatures for trout could be created in a very long section of the lower Pigeon River via removal of the Golden Lotus Dam.

References

O’Neal, R. P. 1997. Muskegon River Watershed Assessment. Michigan Department of Natural Resources, Fisheries Division, Special Report Number 19. Ann Arbor, Michigan.

Rozich, T. J. 1998. Manistee River Assessment. Michigan Department of Natural Resources, Fisheries Division, Special Report Number 21. Ann Arbor, Michigan.

Wehrly, K.E., M.J. Wiley, and P.W. Seelbach. 1999. A thermal habitat classification for lower Michigan rivers. Michigan Department of Natural Resources, Fisheries Research Report 2038, Ann Arbor.

Wehrly, K. E., M. J. Wiley, and P. W. Seelbach. 2003. Classifying regional variation in thermal regime based on stream fish community patterns. Transactions of the American Fisheries Society 132:18-38.

Zorn, T. G. and S. P. Sendek. 2001. Au Sable River Assessment. Michigan Department of Natural Resources, Fisheries Division, Special Report 26, Ann Arbor, Michigan.

Zorn, T. G., P.W. Seelbach, and M.J. Wiley. In press. Relationships between habitat and fish density in Michigan streams. Michigan Department of Natural Resources, Fisheries Research Report, Ann Arbor.

Table 1 – Average daily minimum, mean, and maximum summer water temperatures (⁰F) at sites upstream and downstream of Golden Lotus Dam on the Pigeon River. The upstream site was at Old Vanderbilt Road in all years except 2008. In 2008 the upstream thermometer was placed in the river upstream of the impoundment at coordinates N45.13458 W84.47906. The downstream thermometer site was at Sturgeon Valley Road in 2005-2007. In 1998 and 2008 the downstream thermometers were deployed just downstream of the dam. Min. denotes the average of daily minimum temperatures in the month. Max. denotes the average of maximum daily temperatures in the month.

		Upstream			Downstream			Heating
Year	Month	Min.	Mean	Max.	Min.	Mean	Max.	Min.	Mean	Max.
1998	July	58.7	62.4	65.9	64.2	67.5	71.4	5.5	5.1	5.5
	August^1	58.3	61.3	64.0	63.5	66.1	69.0	5.2	4.8	5.0
2005	June	58.6	62.1	65.8	62.1	65.2	68.6	3.5	3.1	2.8
	July	59.4	62.7	66.3	62.3	65.1	68.1	2.9	2.4	1.8
	August	58.1	60.8	63.4	60.3	63.1	66.3	2.2	2.4	2.9
2006	June	55.7	59.4	63.1	59.3	63.9	68.8	3.6	4.4	5.7
	July	59.9	63.5	67.0	61.9	66.5	71.1	2.0	3.0	4.1
	August	57.6	60.6	63.7	57.2	62.3	67.1	-0.4	1.7	3.4
2007	June^2	58.5	62.5	66.2	62.0	67.0	72.1	3.5	4.5	5.9
	July	57.5	61.1	64.8	59.4	64.2	68.8	1.9	3.0	4.0
	August	58.2	61.2	63.9	59.2	63.8	68.1	1.1	2.5	4.1
2008	June	56.6	57.9	59.8	58.7	60.7	63.7	2.1	2.8	3.9
	July	59.7	60.5	61.6	62.4	64.7	67.7	2.7	4.2	6.1
	August	59.0	59.5	60.2	60.7	63.2	66.0	1.7	3.7	5.8

¹Data only for August 1-21, 1998.

²Thermometers were deployed on June 11, 2007.

Figure 1─Map showing locations where electronic thermometers were deployed. 1 – Old Vanderbilt Road, 2 – Upstream of pond, 3 – Downstream of Pond, 4 – Sturgeon Valley Road, 5 – Elk Hill, 6 – Tin Bridge, 7 – Webb Road, 8 – Highway M-68.

Figure 2 – Daily maximum and minimum water temperatures in the Pigeon River upstream of Golden Lotus Dam at Old Vanderbilt Road and immediately downstream of the dam during July 1998. Mean July water temperature downstream of the dam (67.5 ⁰F) was 5.1 ⁰F warmer than at Old Vanderbilt Road (62.4 ⁰F).

Figure 3 – Change in mean July water temperature (⁰F) per mile in 2005 and 2008. In 2008 electronic thermometers were placed in the Pigeon River immediately upstream and downstream from Golden Lotus Pond whereas in 2005 thermometers were placed at road crossings above and below the dam. Segments on the X axis are arranged from upstream (left side) to downstream (right side).

Figure 4 – Mean, maximum, and minimum water temperatures ( ⁰F) at sites on the Pigeon River in July of 2005 and 2007. The vertical bars indicate the range of temperatures recorded and the horizontal tick marks are monthly mean temperatures. Sites on the X axis are arranged from upstream (left side) to downstream (right side).

Figure 5 – Mean July water temperatures in the Pigeon River at sites located downstream of the Golden Lotus Dam in 2005 (solid bars) and projected temperatures if removal of the dam reduced July temperatures by 3 ⁰F. Sites on the X axis are arranged from upstream (left side) to downstream (right side).