Unnatural
flow variability of the Pigeon River caused by the Golden Lotus Inc. Dam.
Andrew J.
Nuhfer
David J.
Borgeson
and
Kurt Newman
Michigan
Department of Natural Resources
June 2009
Abstract
The operation of the Golden Lotus Inc. dam cause huge
unnatural increases and decreases in flow in the Pigeon River downstream of the
dam. In June 2008, one of these
abnormal manipulations of flow at the dam caused a massive fish kill in the
Pigeon River. Historically, most
hydroelectric dams in Michigan were operated as peaking projects, which
released large amounts of water during periods of peak electrical demand and
low amounts of water during non-peak periods, usually at night. The Golden Lotus dam is operated as a
peaking project and to maintain specific water levels in the impoundment. Routine operation of the Golden Lotus Dam
commonly produces flood and drought conditions on a daily and even an hourly
basis. Peaking operations of the Golden
Lotus Dam during the spring of the year exacerbate fluctuation of discharge in
the Pigeon River during a time when young trout fry are already at risk from
natural variability in discharge. Such
extreme fluctuations undoubtedly have a negative effect on the habitat quality
and aquatic community, particularly salmonid populations, in the Pigeon
River. The continued existence of the
dam poses a constant risk of future fish kills and other ecosystem damage.
Introduction
Biologists, anglers, and other users of the Pigeon
River have long known that operation of the Golden Lotus Inc. dam cause
unnatural changes in water depth and flow in the river downstream of the
dam. When the dam is operated to
generate electricity or to lower the water level in the impoundment, water depth
in the river downstream rises and the increases in flow are associated with
increased turbidity. When the dam is
operated to increase water level in the impoundment, water depth and flow in
the river downstream declines to unnatural levels. Flow changes of 100%-300% over short time intervals of just 6 to
12 hours are common. Even larger
increases in peaking flows have been documented over periods of 18 to 24
hours. Most aquatic organisms are not
adapted to these unnatural daily flow fluctuations and hence aquatic
productivity downstream of peaking facilities is reduced (Cushman 1985). Walker (2008) reported that the pattern of
siltation and turbidity observed in the Pigeon River down from the dam was most
likely attributable to the unnatural rising and falling flows caused by
operation of gates at the dam.
Objectives of this report are to present data that
illustrate how the Golden Lotus dam causes unnatural flow conditions in the
Pigeon River and to describe ways that this damages and diminishes the aquatic
ecosystem downstream of the dam.
Methods
Analysis of flow variation in the Pigeon River
Daily
and seasonal variation in streamflow discharge (Q) of the Pigeon River
downstream of the Golden Lotus Dam was compared to variation in the adjacent
Sturgeon River watershed. Data were
obtained from records of stage height and discharge collected at USGS gauging
stations located near Vanderbilt, MI on the Pigeon River and at Wolverine, MI
on the Sturgeon River from October 1989 through October 2007 (http://ida.water.usgs.gov/ida/)
(Figure 1). Stage height data were
recorded electronically at either 15 minute or 1 hour intervals. MDNR used the USGS data to compute daily
minimum, mean, and maximum discharge for each river. Since the rivers are not the same size at the gaged sites, MDNR
standardized daily flow variation for the respective rivers by computing daily
percent variation in discharge from the daily average using the equation shown
below.
Percent daily variation =
((maximum daily discharge –
minimum daily discharge) / (average daily discharge))*100
MDNR
also presents graphics depicting daily flow variation in both rivers on the
same days to illustrate how dramatically the regulated flow of the Pigeon River
differs from the natural unregulated flow of the Sturgeon River. MDNR characterized the frequency of certain
extreme events such as extreme low flows and extreme high flows to illustrate
the constant risk to the health of the Pigeon River posed by the continued
existence of the Golden Lotus Dam.
Finally,
MDNR evaluated probable effects of flow variation on fish populations and other
biota in the Pigeon River with reference to scientific literature relating
discharge instability to population parameters such as reproductive success and
survival.
Results
Flow variability
Operation
of the gates at Golden Lotus Dam frequently cause extreme flood and drought
conditions on a daily basis in the Pigeon River whereas wide fluctuations in
flow do not occur in the adjacent unregulated Sturgeon River. Median daily percent flow variation in the
Pigeon River was 62.9% as compared to 5.6% in the adjacent Sturgeon River
(Figure 2). MDNR’s analysis of flow
data collected from October 1989 through September 2007 showed that in the
Pigeon River daily flow varied by over 100% about 24% of the time, or 1,388 out
of 5,818 days. In the adjacent Sturgeon
River daily flow varied over 100% on only 9 days out of 5,812 days of flow
records (0.15% of days).
The
contrast in daily flow variation between the two rivers was even more striking
when MDNR examined how much higher daily maximum flows were than daily minimum
flows. From October 1989 through
September 2007 daily maximum flows in the Pigeon River averaged 2.2 times
higher than daily minimum flows and in one instance daily maximum flow was 17.8
times higher than minimum flow. By
contrast, in the Sturgeon River a daily maximum flow averaged only 1.1 times
higher than daily minimum flows and the most extreme difference was only 4.0
times higher than daily minimum flow during the same 18-year period from 1989
to 2007. On June 23, 2008 the daily
maximum discharge of 170.7 cfs in the Pigeon River was 23.4 times higher than
the daily minimum flow of 7.3 cfs. In
the Sturgeon River, the maximum discharge of 225.4 cfs on June 23, 2008 was
only 1.16 times higher than the minimum discharge of 195.1 cfs.
The
most extreme daily variation in stream flow in the Pigeon River generally
occurs during April and May when newly emerged brook trout and brown trout fry
emerge from their redds and are most vulnerable to mortality due to high
flows. Both species are less than an
inch long when they emerge from their redd and are unable to withstand fast
water velocities because they are very weak swimmers at that stage of development. Figure 3 graphically illustrates the
contrast between the extreme daily variations in flow in the Pigeon River
during spring 2006 as compared to the low daily variability in flow of the
Sturgeon River. On some dates, high
flows in the regulated Pigeon River were as high as or even higher than high
flows in the Sturgeon River. This would
not occur under natural conditions because the drainage area of the Pigeon
River upstream of the USGS gage is only 57.7 square miles as compared to a
drainage area of 192 square miles at the Sturgeon River gage.
Operation
of the gates of the Golden Lotus Dam during and after regional rain events
frequently result in extreme fluctuations in flow over very short time
intervals in the Pigeon River whereas similar fluctuations are not observed in
the Sturgeon River. The contrast in
flow patterns of the two rivers during the first day of the June 2008 fish kill
in the Pigeon River is shown in Figure 4.
The rainfall event that occurred caused a very modest and smooth rise in
discharge in the Sturgeon River. By
contrast, operation of the gates at the dam in response to the rain event
resulted in a steep and rapid rise in discharge in the Pigeon River and
resulted in a large release of sediment.
Subsequent operation of the gates resulted in extreme low flows that
exacerbated the severity of the fish kill.
Extreme
low flows such as those observed in June 2008 in the Pigeon River have also
occurred in the past due to improper operation of gates at Golden Lotus
Dam. Figure 5 shows that flow of the
Pigeon River fell to less than 10 cfs for more than 12 hours during
mid-September 2003 and was not restored to “normal” until about 24 hours after
the initial closing of the gates. During
this same time, flow of the Sturgeon River was stable (Figure 5). It is not known if the low flows in
September 2003 caused a fish kill because the dewatering was most severe at
night when a fish kill would not likely be observed. Other low flow events (< 20 cfs) have been observed during winter
months at times when brown trout and brook trout eggs and alevins in redds
would have been vulnerable to freezing due to the unnatural decline in
flows.
Discussion
The
peaking operation of the Golden Lotus Dam causes extreme flood and drought conditions
on a daily basis, which is stressful to aquatic organisms. Alteration in daily flow regimes creates
unnatural changes in the hydrological function of the river with accompanying
changes in erosion, sedimentation, shape of the channel, and ultimately
instream habitat. High flow conditions
during the time of incubation and fry emergence have been negatively correlated
with year-class strength, and accordingly the density of older age classes, for
salmonids such as brown trout in Michigan (Nuhfer et al. 1994, Zorn and Nuhfer
2007a, Zorn and Nuhfer 2007b) and elsewhere (Strange et al. 1992; Jensen and
Johnsen 1999; Spina 2001; Cattanéo et al. 2002; Lobón-Cerviá 2004). Golden Lotus Inc.’s operation of the gates
at Golden Lotus Dam (since October 1989) has frequently caused unnatural flow
extremes that have been shown to cause mortality of trout and other aquatic
organisms in other rivers. However,
MDNR can only detect large scale fish kills caused by operation of the dam
(e.g. the kills documented in 1984 and 2008) because direct observations of
mortality of smaller trout such as fry are next to impossible.
Zorn and Nuhfer (2007b) estimated the 50% swim-up
dates for brown trout fry in several northern Michigan streams during a
ten-year period (1995-2006) and found that the average date varied from
mid-April to mid-May, depending upon winter severity. The time period of elevated streamflows due to increased runoff
from spring snowmelt and seasonally high precipitation levels overlaps these
emergence dates in Northern Michigan.
Thus, peaking operations of the Golden Lotus dam on the Pigeon River
further exacerbate the problem of fluctuating stream flows during a time when
young fry are already at risk from natural variability in discharge. For example, daily stream flows in the
Pigeon River below the dam fluctuated wildly over 24-hr time periods during
April and May of 2006 (Figure 3). Daily
flow fluctuations in the neighboring Sturgeon River, which is unaffected by
dams, were much more gradual (Figure 3).
Such extreme fluctuations undoubtedly have a negative effect on the
habitat quality and aquatic community, particularly salmonid populations, in
the Pigeon River. Peaking operations at
dams are also known to diminish or change the diversity, density, and type of
macroinvertebrate communities downstream (Cushman 1985). Gislason (1985) reported that abundance of
benthic insects was 1.8-59 times higher under a stable flow pattern compared to
abundance in the same river when hydroelectric power-peaking induced large
daily flow fluctuations.
It is very likely that drought flows associated with
peaking operations at the dam reduce survival of salmonid embryos developing in
redds. Embryos buried in the gravel
require movement of water through the gravel to supply them with oxygen and to
remove waste products. Salmonids select
sites to lay their eggs based on habitat features such as water depth, velocity
and substrate composition. Trout that
spawn while water levels are high or normal in the Pigeon River sometimes
select redd sites that become unsuitable when flows through the dam are later
reduced to unnaturally low levels. Redd
dewatering due to fluctuating flows below dams has been documented in the
fisheries literature (e.g. Anderson and Nehring 1985; Pender and Kwak
2002). Disruption of brown trout
spawning by fluctuating flows has also been documented in the fisheries
literature (e.g. Nelson 1986). Brown
trout have also been observed to react to rising flows below hydropower dams by
abandoning redd construction (Pender and Kwak 2002). In April 2005 some steelhead redds downstream of the Golden Lotus
Inc. dam were dewatered at flow rates of 45 cfs (N. Godby, DNR Fisheries
Biologist, unpublished data). Minimum
flows that are this low, and far lower, are often observed in the Pigeon River
due to operation of the gates of the dam.
Salmonid sac fry and pre-emergent alevins are more likely to die from
effects of dewatering than recently deposited eggs and the highest mortalities
usually occur at lower levels of dissolved oxygen and at lower water velocities
(Shumway et al. 1964, Becker et al. 1982).
Reduced oxygen and flow also retard growth and development (Becker et
al. 1982). Dewatering of redds during
cold winter months increases the risk of mortality due to freezing of
developing embryos.
Thus, there is scientific evidence that the routine
operation of the Golden Lotus Dam causes chronic mortality of trout in the
river in at least three ways. Spawning
activity is disrupted, hatching success of trout eggs is reduced, and mortality
of recently emerged trout fry is higher than normal. In addition, it is very likely that turbidity from routine
peaking operations at the dams reduces foraging efficiency and that the
abnormal high flows that occur on virtually a daily basis increase energetic
costs for fish. Although these effects
may not be lethal, they certainly detract from the health and productivity of
the aquatic ecosystem in the Pigeon River.
When even greater deviations in flow occur, such as
the event in June 2008, catastrophic mortalities and disruption of the river
ecosystem occur. History demonstrates
that huge deviations from normal flow are quite common downstream from the
Golden Lotus dam and thus the river and its biota will continue to be in a
constant state of jeopardy unless the dam is removed.
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Figure
1─Round dots depict the locations of USGS water stage recorders on the
Pigeon River at Sturgeon Valley Road and the Sturgeon River in Wolverine.
Figure 2. – Frequency histograms of percent daily flow
variation of the Pigeon River at Sturgeon Valley Road compared to the Sturgeon
River near Wolverine from October 1989 through September 2007. Each graphic is based on discharge data
collected on over 5,800 days. Data are
from the United States Geological Survey.
