COMPARATIVE HYDROLOGIC FLOW REGIMES OF RELICENSED
DRAFT REPORT
Email comments to mjwiley@umich.edu
A RETROSPECTIVE ANALYSIS OF PRE- AND POST-RELICENSING
FLOW REGIMES ON THE LOWER MUSKEGON RIVER by
B. Rudy, M. Wiley, and P. Richards
The Croton hydroelectric facility on the Muskegon River, Newaygo County
{This report is based on a thesis submitted by Bruce C. Rudy in partial fulfillment of the requirements for the degree of
Master of Science
(Natural Resources and Environment)
University of Michigan
August 2003} i
ABSTRACT
In 1994, three hydroelectric facilities on the Muskegon River (Rogers, Hardy, and
Croton Dams) were relicensed by the Federal Energy Regulatory Commission.
Relicensing terms reflected, in part concerns regarding the impacts dam operations were having on the downstream river ecosystem. These concerns included fisheries habitat degradation from increased water temperature, decreased dissolved oxygen content, and elevated rates of bank erosion associated with “peaking” operations. The 1994 FERC agreement mandated changes in operations of the dams with the goal of significantly changing hydrologic regime of the Muskegon River below.
The focus of this study was to compare the flow regimes associated with the pre- and post-relicensed hydropower facilities and discuss how the relicensing of these facilities has in fact altered the downstream hydrologic regime and hydraulic potential.
The three criteria used in the analysis of the altered flow regimes were event peak delay and attenuation impacts, water balance and flow frequency impacts, and alterations to the river’s hydraulic energy and sediment transport potential.
Results of the study suggest that relicensing the hydroelectric facilities has in fact altered the water balance and flow regime of the lower river albeit in ways not necessarily anticipated in the FERC relicensing plan. Furthermore, hydraulic energies in the Muskegon River appear to have been significantly reduced. On the other hand, storage delay was minimally altered by the change in operations and hydrograph attenuation was almost nonexistent. ii
ACKNOWLEDGEMENTS
We would like to thank everyone who helped to assure the success of this study.
Funding came from the Great Lakes Fisheries Trust as a part of the GFLT Muskegon
River Initiative. This study was based upon data collected, and generously provided by the USGS, NOAA, the Michigan DNR, and Research staff from the School of Natural
Resources and Environment, University of Michigan. iii
TABLE OF CONTENTS
Flow Duration Analysis and Total Water Balance ............................................. 14
January and February Flow Duration and Water Balance .................................. 16
March and April Flow Duration and Water Balance .......................................... 17
May through August Flow Duration and Water Balance ................................... 19
September through December Flow Duration and Water Balance .................... 21
iv
LIST OF FIGURES AND TABLES
Table 1. Physical characteristics of the Rogers, Hardy, and Croton impoundments. ...... 30
Table 2. Operating characteristics of the Rogers, Hardy, and Croton impoundments. ... 30
Table 3. Land use characteristics of the Rogers, Hardy, and Croton impoundments. ..... 31
Table 4. USGS gauging station information for selected sites on the Muskegon and Little
Table 5. Flow duration percentiles and percent difference for pre-relicensing (1990-
1993) input and output and post-relicensing (1996-2000) input and output for the
Table 6. Hydrograph flows for input, output, ET, and reservoir flux (δ) for 1991 and
Table 7. Flow duration percentiles and percent difference for pre-relicensing (1990-
1993) and post-relicensing (1996-2000) input and output for the Muskegon River in
Table 9. Flow duration percentiles and percent difference for pre-relicensing (1990-
1993) and post-relicensing (1996-2000) input and output for the Muskegon River in
Table 10. Flow duration percentiles and percent difference for pre-relicensing (1990-
Table 11. Flow duration percentiles and percent difference for pre-relicensing (1990-
1993) and post-relicensing (1996-2000) input and output for the Muskegon River in
Figure 2. Linear representation of the inflows and outflows of the Rogers, Hardy, and
v
Figure 3. The Rogers hydroelectric facility on the Muskegon River, Mecosta County. . 35
Figure 4. The Hardy hydroelectric facility on the Muskegon River, Newaygo County. . 35
Figure 5. The Croton hydroelectric facility on the Muskegon River, Newaygo County. 35
Figure 6. Scatter plot and linear regression for correlation of measured stream flow at
Figure 7. Scatter plot and linear regression for correlation of measured stream flow at
Figure 8. Scatter plot and linear regression for correlation of measured stream flow at
Figure 9. Water balance components for Muskegon River hydrologic equation. ........... 37
Figure 13. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing
Figure 14. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing
(1996-2000) input and output in January and February for the Muskegon River. ........... 39
vi
Figure 19. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing
(1996-2000) input and output in March and April for the Muskegon River. ................... 42
Figure 24. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing
(1996-2000) input and output in May through August for the Muskegon River.............. 44
Figure 29. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing
(1996-2000) input and output in September through December for the Muskegon River.
vii
Figure 35. Double mass plot for cumulative input versus cumulative output for 1970 –
1973, 1974 – 1977, 1978 – 1981, 1982 – 1985, 1986 – 1989, pre-relicensing (1990 –
viii
INTRODUCTION
The Muskegon River, which runs through central and western Michigan, is 220miles long, fed by 94 tributaries, and has a watershed of approximately 2,634 square miles. The river begins in a tiny stream in Roscommon County called Big Creek, which drains to Higgins then Houghton Lakes via a channel known locally as “the cut”
(Alexander, 1994c). Once the river exits Houghton Lake and Reedsburg Dam, it slowly grows and makes it way through relatively flat upper reaches. Just above the town of
Evart, the Muskegon’s gradient becomes steep and the river’s velocity increases. It is in this middle, higher gradient portion of the river where three large hydroelectric facilities
(Rogers, Hardy and Croton) intercept the Muskegon’s path to Lake Michigan. Below this section of the Muskegon, the river flattens out once again as it meanders through a freshwater estuary and ends its journey in Muskegon Lake.
While the Muskegon is one of the best known recreational rivers in the State of
Michigan, many are concerned that it functions more like a series of shorter rivers, rather than the one continuous 220-mile river it is (Seelbach, 1999). The history of the
Muskegon River reveals much about how it became a “fragmented” river. The first sawmill appeared on the river in 1837 in the town of Newaygo and the first dam was built in Big Rapids in 1866. From 1837 to 1906, about 30 billion board feet of wood was floated down the river. Between 1900 and 1908, three more dams were built in the middle portion of the Muskegon River: Newaygo Dam (1900), Rogers Dam (1906), and
Croton Dam (1907). The last sawmill closed in 1910 and in 1931, Hardy Dam, the largest earthen dam at the time, was built. The last dam to be built on the Muskegon
River was the Reedsburg Dam in 1940 (Alexander, 1999a). In 1966, the Big Rapids Dam was dismantled and in 1969, the Newaygo Dam was removed.
1
2
The Rogers, Hardy, and Croton dams, and their effects both positive and negative, have however remained, and continue to be a source of controversy.
The role of dams in river ecosystems has gained increasing attention from the scientific community in recent decades (Chin et al., 2002). While dams have provided numerous benefits such as flood control, water supply, recreational activities, and hydroelectric power, they have also altered flow regimes and ecologically fragmented rivers systems, as well as often causing geomorphic and ecological change (Graf, 1992;
Dynesius and Nilsson, 1994). The Muskegon River mainstem dams have offered increased recreational opportunities on the river and have offered flood control and electricity generation to the residents of Mecosta and Newaygo Counties. But, Rogers,
Hardy, and Croton Dams have also had real impacts on the Muskegon River ecosystem, including increased fish mortality due to entrainment in the power plants, blockage of fish passage, and alterations of channel habitat.
Annual fish entrainment in 1997 at the three dams was estimated to be 301,583 fish with a total annual mortality was 44,042 fish. The river fragmentation that resulted from these structures has had both positive and negative effects. The dams have acted as a barrier to pest species, such as the Sea Lamprey, keeping them from invading the upper reaches of the river. But, the dams have also acted as a barrier to the movement of desireable migratory fish. Changes to river water quality have in the past included elevated temperature and decreased dissolved oxygen content downstream of the dams, and in the view of some increased bank erosion due to regular cycles of saturation and drainage associated with peaking operations. Peaking hydroelectric operation is defined as operations where a dam holds water and only releases it at peak times when electricity
3 prices are the greatest (Geis, 1982). Impacts attributed to this operational strategy include losses in downstream fish habitat due to high water velocities during peak discharge (Q); increased sediment erosion and lowering habitat diversity; disruption of normal downstream movement of carbon materials important to aquatic life; and creation of lake environments within the river system which resulted in lower fish productivity and shifts in fish communities favoring lake species (O’Neal, 1997).
Many of these concerns were raised and addressed during the relicensing of the
Rogers, Hardy and Croton hydroelectric facilities in 1994. The Federal Energy
Regulatory Commission (FERC), working with the Michigan Department of Natural
Resources (MDNR) and Consumers Power Company, the owners of the dams, undertook a study on the environmental impacts of the dams on the river prior to the relicensing.
The study determined that altering the operations of the facilities from peaking to run-ofriver might mitigate many of the negative impacts of the dams. Run-of-river hydroelectric operation is defined as operations where the flow out of a reservoir is equal to the flow into a reservoir (Geis, 1982).
In this report, we compare the flow regimes associated with the pre- and postrelicensed hydropower facilities and discuss how the relicensing of these facilities has altered the downstream hydrologic regime and hydraulic potential. To accomplish this, we examined the effects the dams have had on pre- and post relicensing hydrographs in regards to peak delay and attenuation. Additionally, we compared the pre- and postrelicensing impacts to the river’s water balance and flow regime. Lastly, we examined the effects of the altered operations on the river’s hydraulic energy and erosion potential.
METHODS
The Study Site
This study focuses on the three impoundments within the Muskegon River watershed in Mecosta and Newaygo Counties, Michigan (Figures 1 and 2). The
Muskegon River, from Reedsburg Dam in Roscommon County, Michigan, travels approximately 134 miles and drops about 280 feet before reaching the Rogers hydroelectric facility (Figure 3). Once the Muskegon River passes through Rogers Dam, it enters Hardy Pond. Hardy Pond is 25 miles long and terminates at the Hardy hydroelectric facility (Figure 4). Water flowing over Hardy Dam enters Croton Pond.
Croton Pond is about 6 miles long and terminates at the Croton hydroelectric facility
(Figure 5).
Through the length of the impoundments, there are several small tributaries that enter the mainstem through the reservoirs. The total catchment area of these streams is approximately 131 square miles. The catchment area of the Muskegon River measured at the tailwaters of the Croton dam is approximately 2,313 square miles. The tributaries represent about 5.7% of the entire Muskegon River catchment at this point.
Rogers Facility
The Rogers facility is the uppermost impoundment of three impoundments within this study. It is located at river mile (RM) 83.7 on the Muskegon River. A full description of the impoundment’s physical characteristics has been provided by
Consumers Power (Table 1). Built in 1905-1906 by the Grand Rapids Muskegon Power
Company (GRMPC), the hydroelectric facility was historically and continues to be a runof-river facility (Consumers Power Company, 1994b). Detailed information on the post-
4
5 relicensing operating characteristics of Rogers Dam and the land use surrounding the
Rogers impoundment were provided by Consumers Power (Tables 2 and 3). The impoundment is maintained at 861.3 feet above sea level and is allowed to fluctuate plus/minus one foot (Consumers Power, 1994b).
Hardy Facility
The Hardy impoundment is between the Rogers and Croton facilities. It is located at river mile (RM) 58.7 on the Muskegon River. The largest of the impoundments, Hardy
Reservoir’s physical characteristics were provided by Consumers Power (Table 1). Built in 1929-1931 by Consumers Power (CP), the Hardy facility was and continues to be operated as a peaking facility (Consumers Power Company, 1994c). Detailed information on the post-relicensing operating characteristics of Hardy Dam and the land use surrounding the Hardy impoundment were provided by Consumers Power (Tables 2 and 3).
Hardy impoundment is lowered from nine to twelve feet in January and February of every year to prepare to store river flows anticipated in March and April from the annual snowmelt and thaw. This spring draw down allows the Hardy impoundment to absorb the snowmelt and runoff from the surrounding watershed upstream of the facility
(Sluka, 2002). During May through December, the impoundment is maintained at 822 feet above sea level and is allowed to fluctuate plus/minus one foot (Consumers Power,
1994c).
Croton Facility
Croton pond is the last of the impoundments within this study. The Croton hydroelectric facility is located at river mile (RM) 52.8 on the Muskegon River. A full
6 description of the impoundment’s physical characteristics has been provided by
Consumers Power (Table 1). Built in 1906-1907 by GRMPC, the Croton facility was historically a run-of-river facility. The relicensing of the Croton hydroelectric facility resulted in a change in the operation of the dam to “re-regulate” or “smooth out” the peaking operation at Hardy Dam (Consumers Power Company, 1994d). As a result of this change in operations, the three hydroelectric facilities on the Muskegon River now operate in a run-of-river manner. Detailed information on the post-relicensing operating characteristics of Croton Dam and the land use surrounding the Croton impoundment were provided by Consumers Power (Tables 2 and 3). The impoundment is maintained at 722 feet above sea level and is allowed to fluctuate plus/minus one foot (Consumers
Power, 1994d).
Regulatory History
The FERC issued the original operating licenses for the Rogers (FERC #: 2451-
004), Hardy (FERC #: 2452-007), and Croton (FERC #: 2468-003) hydroelectric facilities on May 24, 1968 (Consumers Power Company, 1994a). The licenses allowed the Muskegon River Dams to operate in a manner that promoted electricity production at the time of its highest price (i.e. peaking operations). The Michigan Department of
Natural Resources claimed that operating the facilities in this manner has been shown to put undue stress on the ecosystem downstream from the facilities. In general, streambed scouring, channel armoring, bank and island erosion, and stream channel degradation often result from peaking operations (Grant et al., 2003). On the Muskegon, bank erosion was and still is common. It was attributed in pre-relicensing debates to peaking operations.
7
New operating licenses were issued by the FERC for the Rogers, Hardy, and
Croton hydroelectric facilities on July 15, 1994 (Consumers Power Company, 1994a).
The new licenses required the Muskegon River hydroelectric facilities, as a total unit, to operate in a way that resembled the natural flow regime of the river (i.e. run-of-river).
Specifically, the Croton facility, which had historically operated as a run-of-river facility, would be forced to alter its operations to re-regulate the flow from the Hardy hydroelectric facility and allow the river to re-equilibrate to its natural flow regime
(Consumers Power Company, 1994a).
The goal of the new licenses was to operate the Croton hydroelectric facility so that the flows leaving the Croton facility were approximately equal to the inflows of the upstream Rogers’ facility plus the inflows from the Little Muskegon River (Figure 2).
The Rogers facility is operated in run-of-river mode, therefore, flows at the peaking
Hardy facility are re-regulated by the Croton impoundment to return the Muskegon River to its natural flows. To accomplish this, the sum of the projected mean daily discharge from the Hardy Reservoir plus the inflow from the Little Muskegon River are adjusted for time of passage and water accretion and are then measured at the downstream Croton gauge. This comparison is made on an hourly basis. Time of passage and water accretion from Hardy Dam to Croton Dam was estimated to be 0.5 hours and 2.6%, respectively. Time of passage and water accretion from the Little Muskegon to Croton
Dam was estimated to be 3 hours and 3.2%, respectively (Consumers Power, 1998).
During the draw down and refill of the Hardy facility in the spring, the Croton facility releases the projected mean daily discharge from the Hardy impoundment plus the inflow from the Little Muskegon River (Consumers Power, 1994a).
8
Data Collection
Discharge data used for this thesis came from the United States Geological
Survey (USGS) gauging stations above and below the three impoundments (Table 4).
Due to the changes in gauging stations as a result of the FERC relicensing, two sets of gauges were used, one set for the pre-relicensing data and one set for the post-relicensing data. Linear regression was used to predict what the flows at the pre-relicensing gauging stations might have amounted to at the post-relicensing gauging stations during the prerelicensing flow regime (Figures 6, 7, and 8). The slope of the regression equation was used to correlate the flows.
Pre-relicensing Streamflow Data
Stream discharge for 1970 – 1993, was collected at the Evart gauging station
(USGS #: 4121500), Little Muskegon at Morley gauging station (USGS #: 4121900), and
Newaygo gauging station (USGS #: 4122000). Detailed information about these gauging stations was provided by the USGS (Table 4). Average daily flows in cubic feet per second (cfs) were used for the years 1970 – 1993. The term pre-relicensing years is defined as the time period 1990 – 1993. Fifteen-minute flows in cfs were used for the year 1991 in the peak delay and attenuation analysis.
Post-relicensing Streamflow Data
Stream discharge for 1996 – 2000, was collected at the Big Rapids gauging station (USGS #: 4121650), Little Muskegon at Oak Grove gauging station (USGS #:
4121944), and Croton gauging station (USGS #: 4121970). Detailed information about these gauging stations was provided by the USGS (Table 4). Average daily flows in cfs were used for the years 1996 – 2000. The term post-relicensing years is defined as the
9 time period 1996 – 2000. Fifteen-minute flows in cfs were used for the year 2000 in the peak delay and attenuation analysis.
Precipitation and Evapotranspiration Data
Precipitation data for the area surrounding the three impoundments was collected at the Big Rapids Waterworks station (NOAA COOP ID: 200779). Daily precipitation in hundredths of inches was used for this site for both the pre- and post-relicensed years.
Calculation of evapotranspiration (ET) was determined using Penman’s equation.
An Excel-based version of Penman’s equation written by R.L. Snyder (2000) from the
University of California was used for this calculation. The calculation required monthly maximum and minimum temperatures, average wind speed, average dew point temperature, and net solar radiation. This data, with the exception of monthly net solar radiation, was collected at the Muskegon County Airport station (NOAA COOP ID:
205712) for both the pre- and post-relicensed years. Due to the lack of consistent monthly net solar radiation data, the maximum monthly net solar radiation was assumed for the pre- and post relicensed years.
Data Analysis
The data were analyzed using a variety of standard hydrologic techniques.
Components of the water balance were attenuation for both the pre-relicensing and postrelicensing years. Flow duration curves, hydrographs, and double mass plots were developed for pre- and post-relicensed time frames.
Water Balance
Data available to estimate water balance for the reservoir system (Rogers to
Croton) included gauged input along the mainstem of the Muskegon above Rogers Dam
10 and from the Little Muskegon River (Input
USGS
), gauged output along the mainstem below Croton Dam (Output
USGS
), and ET estimates (see above). Input from ungauged smaller tributaries draining into the reservoirs (Input tribs
), and change in reservoir storage
(dS/dt), and groundwater (GW) (Figure 9). A water balance equation for the combined reservoir system can be written as: dS/dt = Input
USGS
+ Input tribs
+Gw in
– (Output
USGS
+Gw out
+ ET) (1)
The Input
USGS
component used for water balance estimates was the sum of the
Evart and Little Muskegon at Morley gauging station for the pre-relicensing time period and was the sum of the Big Rapids and Little Muskegon at Oak Grove gauging stations for the post-relicensing time period. The Output
USGS
component of the water balance was the Newaygo gauging station for the pre-relicensing time period and the Croton gauging station for the post-relicensing time period. Linear regression was used to correlate the flow data from the pre-relicensing gauging stations to the post-relicensing gauging stations (Figures 6, 7, and 8).
Several of the water balance components could not be measured directly. The sum of dS/dt, GW, and Input tribs
were unmeasured and termed reservoir flux, designated gamma (
).
=
dS/dt
GW + Input tribs
(2)
Since from the water balance (equation 1),
Output
USGS
= Input
USGS
- ET
Then,
= Output
USGS
– Input
USGS
+ ET
(3)
(4)
11
Based on the run-of-river operating characteristics of the impoundments, dS/dt was assumed to be near zero for the months May through December. The 12-foot draw down of the Hardy impoundment during January and February equals a volume of 1.3 billion cubic feet, and dS/dt was assumed to be constant over the draw down period (e.g. volume of draw down/number of days of draw down) (Consumers Power Company,
1994a). The requisite fill-up of the Hardy impoundment during March and April was calculated in a similar manner. The value associated with dS/dt during the draw down and refill was determined to be approximately 14.7% of the output measured at the
Croton gauge. Based on the contributing drainage area, the input associated with the ungauged tributaries (Input tribs
) should be approximately 5.7% of the output measured at the Croton gauge. GW is presumably the remaining flux associated with
and represents the majority of the “reservoir flux” within the impoundments.
Because a time of passage was estimated by Consumers Power and in this study
(see Results), the input component of the water balance was shifted two days forward to account for the travel time of the river from the gauging stations above the impoundments to the gauging station below the impoundments (Consumers Power Company, 1998).
Flow Duration Curves
Flow duration curves used in the analysis of pre- and post-relicensed operations of the facilities offered a perspective on the change in the input and output flows that occurred through the three facilities from 1990-1993 to 1996-2000. Average daily flow data was sorted in descending order, ranked from one to n , and then given an exceedance probability by using the formula:
T = ( n + 1)/ m (5)
12
Where n is the flows of record and m is the rank magnitude of that flow (Allan, 1995).
Double Mass Analysis
Ambiguities due to both delayed and/or non-linear hydrologic response can be avoided by use of a double mass analysis (Linsley et al., 1982). Double mass plots were used in the analysis of pre- and post-relicensed operations of the facilities to offer a perspective on how the output of the pre- and post-relicensed systems responded to precipitation and to input. Discharge (output) and input were measured in cfs and converted to cfd. Precipitation was measured in hundredths of inches and converted to inches.
Power Estimations
The result of the hydrologic regime change at the three hydroelectric facilities on the Muskegon River was an altered hydrologic energy. The amount of energy available for geomorphic work is proportional to both the amount (mass) of water being moved in the channel (discharge (Q)), and the rate of fall (slope (S)) of the channel (Knighton,
1998). The equation that represents the power of a river is:
Ω = 10QS
(6)
Calculations of this equation were applied to both pre- and post-relicensing operations of the Muskegon facilities to determine the change in power of the system.
Discharge (Q) was determined from the fifteen-minute data in cfs and converted to cubic meters per second (cms). Slope (S) was determined from USGS gauge #: 4121970 at the tailwaters of Croton Dam to the mouth of Muskegon Lake (USGS gauge #: 4060102), which has fluctuated an average of 4.92 ft. since 1990 (Boutin, 2000). The distance between these two gauges was determined to be 47 river miles (Alexander, 1999b).
13
Based on the fluctuation, the slope was calculated to be 0.00042 to 0.00044; 0.00043 was used for the calculation. The results of the power equation were in kilowatts per foot
(kW ft
-1
) and were converted to MWh ft
-1
for the pre- and post-relicensing operations in
1991 and 2000, respectively.
RESULTS
Hydrograph Delay and Attenuation
Consumers Power Company (1998) estimated the time required for the passage of water from Big Rapids to Croton Dam to be approximately 48 hours. Inspection of graphs of input, from Big Rapids, and output, from Croton Dam, support the Consumers
Power estimate (Figures 10 and 11). In the pre-relicensing operations the peak delays were approximately 2 days (Figure 10) and in the post-relicensing operations, the peak delays were again approximately 2 days (Figure 11).
There was attenuation of storm peaks between the input measured at Big Rapids and the output measured at Croton Dam. On the contrary, the input versus output for both pre- and post relicensing years suggests that there was often significant accretion occurring between the input measured at Big Rapids and the output measured at Croton
Dam (Figures 10 and 11). This accretion implies that additional volumes of water entered the Muskegon River system between Big Rapids and Croton Dam.
Water Balance and Flow Regime
Flow Duration Analysis and Total Water Balance
The pre-relicensing years witnessed a greater amount of precipitation than did the post-relicensing years (Figure 12). The pre-relicensing flows exceeded the postrelicensing flows for all exceedance probabilities, likely due in part to greater precipitation in the pre-relicensing years (Table 5, Figure 13). The pre-relicensing output exceeded the pre-relicensing input for the majority of flows. The difference in median flow (Q
50
) for the pre-relicensing input and output was 27.56%. Post-relicensing input and output flows were more closely aligned and very close at high flows (Q
5
)
14
15
The difference in Q
50
post-relicensing input and output flows was 4.25%. The differences in shape of the pre- and post-relicensing input and output suggest that the post-relicensing flows were managed carefully at all flows. Alternatively, pre-relicensing input and output resembled a less consistent flow regime that managed the difference in output to input at approximately 10% or more.
The total water balance for the pre-relicensing year 1991 and post-relicensing year 2000 offered a more detailed perspective on the components that comprise the
Muskegon River within the impoundments (Table 6). Again, the difference in volume of water balance components between pre- and post-relicensing operations could partially be explained by the precipitation difference in pre- and post-relicensing years (Figure
12). During the pre-relicensing year, total output exceeded total input by approximately
21 billion cfd. The post relicensing total output, on the other hand, exceeded total input by approximately 3.6 billion cfd. Total ET was similar for both pre- and post relicensing operations. The significant difference in pre-relicensing output to input was accounted as
δ values and was about 17 billion cfd greater than the post-relicensing reservoir flux.
The difference in pre- and post-relicensing δ values implies that the management of the impoundments has altered the Muskegon River’s water balance. Of the postrelicensing δ value of 2.78 billion cfd, 2.94 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been
–0.17 billion cfd. In contrast, during the pre-relicensing operations, of the δ value of
20.06 billion cfd, 5.78 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been 14.28 billion cfd.
These results suggest that, in addition to the greater tributary inflows during the pre-
16 relicensing year, the GW component of the δ values during the pre-relicensing year 1991 was the primary difference in the total water balance.
January and February Flow Duration and Water Balance
The Hardy impoundment is drawn down (see Methods) during January and
February of each year. The pre- and post-relicensing input flows were similar at all probabilities, but the pre-relicensing output flows exceeded the post-relicensing output flows for all exceedance probabilities (Table 7, Figure 14). The difference in Q
50
flows for the pre-relicensing input and output was 34.20%. Post-relicensing input and output flows were very close at Q
5
flows and diverged at increasingly lower flows. The difference in Q
50
post-relicensing input and output flows was 16.92%. The differences in shape of the pre- and post-relicensing input and output suggests that the post-relicensing flows were managed carefully at high flows, but as the flows became lower, matching of output to input was more difficult. Alternatively, pre-relicensing input and output for
January and February were consistently different by 28% or greater.
The water balance for January and February during the pre-relicensing year 1991 and post-relicensing year 2000 offered a more detailed perspective on the components that comprise the Muskegon River within the impoundments (Table 6, Figures 15 and
16). During the pre-relicensing year, output exceeded input by 4.8 billion cfd. The post relicensing output, on the other hand, exceeded total input by approximately 1.3 billion cfd. January and February ET was similar for both pre- and post relicensing operations.
The significant difference in pre-relicensing output to input was accounted as δ values and was 3.5 billion cfd greater than the post-relicensing reservoir flux.
17
Both pre- and post-relicensing δ values included a dS/dt value of 1.3 billion cfd.
Of the pre-relicensing δ value of 4.76 billion cfd, 0.81 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been 5.25 billion cfd. In contrast, during the post-relicensing operations, of the δ value of 1.28 billion cfd, 0.50 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been
2.08 billion cfd. These results suggest that the GW component of the δ values during the pre-relicensing year 1991 and post-relicensing year 2000 was the primary difference in the January and February water balance.
Normalized to output, January and February water balance components reinforced the abovementioned findings (Table 8, Figures 17 and 18). In both the pre-relicensing year 1991 input was 67% of output and in the post-relicensing year 2000, input was 82% of output. ET was 0% of output for both pre- and post-relicensing years. δ values represented the difference in input and output for pre- and post-relicensing years and were 33% and 17% of output, respectively. Considering that the Hardy Impoundment was drawndown during this time period, the significant change in δ values were comprised primarily of the influx of GW into the impoundments suggesting that the reduced reservoir level, especially at pre-relicensing flows, at Hardy allowed greater GW to enter the system.
March and April Flow Duration and Water Balance
The Hardy impoundment is refilled (see Methods) during March and April of each year. The pre-relicensing flows exceeded the post-relicensing flows for all exceedance probabilities (Table 9, Figure 19). The difference in Q
50
flows for the pre-
18 relicensing input and output was 14.31%. Post-relicensing input was quite similar to post-relicensing output for all. The difference in Q
50
flows for the pre-relicensing input and output was –3.70%. The differences in shape of the pre- and post-relicensing input and output suggests that the post-relicensing flows were managed carefully.
Alternatively, pre-relicensing input and output for March and April appeared to be more difficult to manage at the extreme low flows and were different by as much as 35% or greater.
The water balance for March and April during the pre-relicensing year 1991 and post-relicensing year 2000 offered a more detailed perspective on the components that comprise the Muskegon River within the impoundments (Table 6, Figures 20 and 21).
During the pre-relicensing year, output exceeded input by 2.9 billion cfd. The post relicensing output, on the other hand, exceeded total input by approximately 0.2 billion cfd. March and April ET was similar for both pre- and post relicensing operations. The significant difference in pre-relicensing input to output was calculated to be δ values and was 2.7 billion cfd greater than the post-relicensing reservoir flux.
Both pre- and post-relicensing δ values included a dS/dt value of –1.3 billion cfd.
Of the pre-relicensing δ value of 2.76 billion cfd, 1.35 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been 0.10 billion cfd. In contrast, during the post-relicensing operations, of the δ value of 0.05 billion cfd, 0.60 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been
–1.85 billion cfd. These results suggest that the tributary and GW components of the δ
19 values during the pre-relicensing year 1991 and post-relicensing year 2000 were the primary difference in the March and April water balance.
Normalized to output, March and April water balance components were quite different (Table 8, Figures 22 and 23). In the pre-relicensing year 1991, input was 87% of output and during the post-relicensing year 2000, input was 100% of output. ET was –
1% of output for both pre- and post-relicensing years. δ values represented the difference in input and output for pre- and post-relicensing years and were 13% and –1% of output, respectively. Considering that the Hardy Impoundment was refilled during this time period, the significant change in δ values was comprised primarily of the tributaries and
GW entering the impoundments during the pre-relicensing year 1991. This implies that the reservoir flux at the Hardy impoundment allowed greater GW to enter the system.
May through August Flow Duration and Water Balance
The pre-relicensing flows exceeded the post-relicensing flows for all exceedance probabilities from May through August (Table 10, Figure 24). The pre-relicensing output exceeded the pre-relicensing input for all flows. The difference in Q
50
flows for the prerelicensing input and output was 27.1%. Post-relicensing output exceeded the postrelicensing input for all flows as well. The difference in Q
50
flows for the postrelicensing input and output was 4.7%. The shape of the pre- relicensing input and output suggests that flows were not managed closely as output exceeded input by 18.6% or greater. Alternatively, post-relicensing input and output for May through August were managed more closely at all flows as output exceeded input by no greater than 6.4%.
The water balance for May through August during the pre-relicensing year 1991 and post-relicensing year 2000 offered a more detailed perspective on the components
20 that comprise the Muskegon River within the impoundments (Table 6, Figures 25 and
26). During the pre-relicensing year, output exceeded input by 5.8 billion cfd. The post relicensing output, on the other hand, exceeded input by approximately 1.1 billion cfd.
May through August ET was similar for both pre- and post relicensing operations. The difference in pre-relicensing output to input was accounted as δ values and was 4.4 billion cfd greater than post-relicensing reservoir flux.
Of the pre-relicensing δ value of 5.26 billion cfd, 1.51 billion cfd was calculated to have entered the impoundments from tributaries and the GW component was calculated to have been 3.75 billion cfd. In contrast, during the post-relicensing operations, of the δ value of 0.65 billion cfd, 1.08 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been –0.43 billion cfd. These results suggest that the GW component of the δ values during the pre-relicensing year 1991 and post-relicensing year 2000 was the primary difference in the May through August water balance.
Normalized to output, May through August water balance components were quite dissimilar (Table 8, Figures 27 and 28). In the pre-relicensing year 1991, input was 77% of output. In the post-relicensing year 2000, input was 96% of output, respectively. ET was –2% and –3% of output for the pre- and post-relicensing years, respectively. δ values represented the difference in input and output for pre- and post-relicensing years and were 20% and 1% of output, respectively. Considering that the operations of the hydroelectric facilities were considerably different during pre –and post-relicensed years, the overall difference in water balance components seems reasonable. The substantial differences suggests that operations of the hydroelectric facilities, during times of normal
21 operations of the Hardy Impoundment, could have had significant impact on the
Muskegon River system.
September through December Flow Duration and Water Balance
The pre-relicensing flows exceeded the post-relicensing flows for all exceedance probabilities from September through December (Table 11, Figure 29). The prerelicensing output exceeded the pre-relicensing input for all flows. The difference in Q
50 flows for the pre-relicensing input and output was 19.9%. Post-relicensing output exceeded the post-relicensing input for all flows. The difference in Q
50
flows for the post-relicensing input and output was 3.4%. The shape of the pre- relicensing input and output suggests that flows were not managed closely during September through
December. Alternatively, post-relicensing input and output differences were consistently less than pre-relicensing differences. Post-relicensing flows were managed more carefully at all flows but differences did become greater at the lowest flows.
The water balance for September through December during the pre-relicensing year 1991 and post-relicensing year 2000 offered a more detailed perspective on the components that comprise the Muskegon River within the impoundments (Table 6,
Figures 30 and 31). During the pre-relicensing year, output exceeded input by 7.5 billion cfd. The post relicensing output, on the other hand, exceeded input by approximately 1.0 billion cfd. September through December ET was similar for both pre- and post relicensing operations. The difference in pre-relicensing output to input was calculated to be δ values and was 6.6 billion cfd greater than post-relicensing reservoir flux.
Of the pre-relicensing δ value of 7.28 billion cfd, 2.10 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was
22 calculated to have been 5.18 billion cfd. In contrast, during the post-relicensing operations, of the δ value of 0.80 billion cfd, 0.78 billion cfd was calculated to have entered the impoundments from tributaries and the total GW component was calculated to have been 0.03 billion cfd. These results suggest that the tributary input and GW components of the δ values during the pre-relicensing year 1991 and post-relicensing year 2000 were the primary difference in the September through December water balance.
Normalized to output, September through December water balance components were, again, relatively dissimilar (Table 8, Figures 32 and 33). In the pre-relicensing year
1991, input was 78% of output. In the post-relicensing year 2000, input was 93% of output, respectively. ET was -1% of output for pre-relicensing operations and –2% of output for post-relicensing operations. δ values represented the difference in input and output for pre- and post-relicensing years and were 21% and 6% of output, respectively.
Considering that the operations of the hydroelectric facilities were considerably different during pre –and post-relicensed years, it appears that the hydroelectric facilities were operated in a more consistent, run-of-river scheme during the post-relicensing year versus the pre-relicensing year. Overall, it appears that the operations of the facilities had significant impact on the Muskegon River system during September through December.
Double Mass Analysis
In the double mass plot comparing the responsiveness of discharge to precipitation, pre- and post-relicensing discharge appeared to have a similar response to precipitation up to a cumulative precipitation of approximately 90 inches (Figure 34).
Above a cumulative precipitation of 90 inches, the pre-relicensing discharge became
23 more responsive to cumulative precipitation. The linear regression lines drawn through the curves suggest that post-relicensing cumulative discharge is less responsive to precipitation than pre-relicensing cumulative discharge.
The double mass plot of cumulative input versus cumulative output for 1970 through 1973, 1974 through 1977, 1978 through 1981, 1982 through 1985, 1986 through
1989, pre- relicensing (1990 through 1993), and post-relicensing (1996 thorugh 1999, and
2000) hydroelectric operations at the Rogers, Hardy, and Croton facilities implied a trend towards a lower input to output ratio (Figure 35). Post-relicensing operations have resulted in an output to input ratio closer to one-to-one. The pre-relicensing operations
(1990 through 1993) resulted in more output for given input. The data for the additional pre-relicensing years, 1970 through 1989, suggested that the post-relicensing operations were not a result of climate induced operations.
A scatter plot of input versus output for the pre- and post relicensing years with trend lines offered a perspective of the tendencies of the two operational strategies
(Figure 36). Post-relicensing operations exhibited a one-to-one input to output ratio, while pre-relicensing operations yielded more output for given input.
Energy and Erosion Potential
Pre-relicensing stream power exceeded post-relicensing stream power implying that the peaking operations of the Muskegon River dams resulted in greater stream power than the run-of-river operations (Table 12). Consideration must be given to the precipitation difference in pre- and post-relicensed years however (Figure 12). The greatest difference in stream power occurred from September to December while the smallest difference occurred May through August.
24
DISCUSSION
Hydrologic Regime and Energy Impacts
One of the goals of relicensing the Muskegon River dams was to help reduce the impacts the facilities have had on the river’s hydrologic regime. To accomplish this goal, the FERC relicensed the facilities so that the output of the hydroelectric facilities (i.e.
Croton Gauge) would have to approximately equal the input to the facilities (i.e. Big
Rapids Gauge) plus the flow at the Little Muskegon Gauge (Consumers Power Company,
1998). The result of this operational change has in fact altered flow regimes for the
Muskegon River below the dams, but in unexpected as well as expected ways.
During both both the pre- and post-relicensing periods , routing through Rogers,
Hardy, and Croton dams resulted in a predictable hydrograph peak delay of two days and little to no hydrograph attenuation, but instead hydrograph accretion (Figures 10 and 11).
This surprising result implies very significant groundwater loading between in the reach between Big Rapids and Croton. During the Post-relicensing period, and following the agreement, the Dam outputs were managed to minimize this discrepancy. An inspection of the input and output flow duration curves indicate this management was effective at all exceedence frequencies (i.e., Q
5
through Q
95
) (Figure 13). But, and presumably unexpectedly, the absolute dishrage from the impounded reach appears to have significantly declined as well. The post-relicensing Q
50
input was only 4.25% higher than the output, while the pre-relicensing Q
50
input was 27.56% higher than the output
(Table 5).
Pre- and post-relicensing water balance analyses offered another view of the impacts the change in operations of the facilities had on the individual components of the system (Tables 6 and 8). Of particular interest was the impact the altered operations had
25 on the δ values of the water balance equation. The δ value for the entire pre-relicensing year was 20.06 billion cfd. The δ value for the post-relicensing year was 2.78 billion cfd.
The post-relicensing operations appear to have resulted in a more consistent flow downstream of Croton, but also, on average, in lower flows measured at the Croton gauge.
Some portion of these lower flows could be explained by the lower rate of precipitation in the post-relicensing years (Figure 12), but, double mass and input output analyses suggest that lower precipitation cannot account for all of the observed decline
(Figures 34-36).. A significant component of the water balance that appears to have been largely ignored in the relicensing of the facilities was ground water accrual. The soils surrounding the impoundments are highly conductive, and discharge accretion rates clearly indicate substantial flux. However, the run-of-river scheme proposed did not appear to explicitly factor this into the flow regulation equation (Consumers Power,
1994a).
Lower flows measured during post-relicensing operations could be a result of a reduced groundwater component in the water balance. There is little data available for reservoir head during pre-relicensing operations, but it seems reasonable to assume that the Croton reservoir level was less stable during the pre-relicensing period because eof peaking operations of the dams. The goal of the post-relicensing operations of Croton dam has been to maintain the level of the Croton reservoir at 722 feet above sea level, plus or minus one foot. The result of this constant head could be a suppression of groundwater flux into and out of the reservoir through the exertion of a more consistent downward pressure within the reservoir (Dunne and Leopold, 1978). The difference in
26 pre- and post-relicensing operations on the head level of Croton reservoir should be further investigated as a potential cause of the observed reduction in flows through the impoundments.
That the relicensing of the three hydropower facilities on the lower river has impacted the flow regime by reducing short-term (daily) peaking oscillations is clear.
Whether or not reduced overall flow was an expected (or is now desirable) consequence of the licensing restrictions is less clear. Reduced flows downstream of the facilities necessarily affect the energy dissipation rate and capacity for the Muskegon River to do geomorphic work. The total power dissipation rate of the Muskegon River appears to have been substantially reduced in the post-relicensing phase of the facilities (Table 12).
Sediment accretion and channel aggradation appears to be a major feature of the lower river’s behavior in recent (Wiley, 2003; Richards, 2003).
What seems clearest at this point is that the lower Muskegon River, postrelicensing, has carried less water, on average, than during pre-relicensing operations
(Table 6). The river could be in the process of altering its slope to accommodate for the altered stream power. The potential impact of the suppressed groundwatere accrual in the vicinity of the reservoirs certainly needs to be component considered in future modeling of scenarios involving Dam management. The current FERC licenses for the three hydroelectric facilities on the Muskegon River will expire in 2034. Additional flow data gathered throughout this period could offer a more accurate depiction of the impacts that the current run-of-river release strategy is having on the Muskegon River.
27
Limitations and Caveats
Several important data limitations, which could affect our observations and conclusions, must be made clear. First, the lack of consistent gauging sites above and below the impounded segments meant that in this analysis we relyedheavily on gauge correlations using linear regression to construct hydrographic time-series (figures 6-8).
While every attempt was made at accuracy, there can be significant error in using such relationships to reconstruct flow histories. We believe, however, based on an inspection of the residuals that while significant estimation error is likely in some of the calculations, there is no directional bias in these calibrations so that absolute errors in estimated discharge should be randomly distributed with respect to over or under estimation. Another limitation of this study was the lack of water level information in
Rogers, Hardy, and Croton impoundments. This data, for both pre- and post-relicensing operations, if available, would offer a good perspective on how the operations of the facilities might be impacted groundwater flux into and out of the impoundments. Finally, and perhaps most importantly, a longer data record is required to ultimately determine if the trends observed here are inherent in the current operation strategy or a transient result of regional hydrology and climate variation.. Pre-relicensing streamflow information for
Evart, Little Muskegon at Morley, and Newaygo exists for 1970 through 1993. Postrelicensing streamflow information for Big Rapids, Little Muskegon at Oak Grove, and
Croton only exists from 1996 to present. As more data is gathered for post-relicensing operations, a more accurate observation of the impact on the Muskegon River of these operations will be possible
28
Potential Ecological Impacts
Any systematic alteration of the hydrologic regime and related changes in the geomorphic energies of the Muskegon River below Croton impoundment likely will have ecological implications. The primary goals of the run-of-river operational scheme originally were to lower water temperatures on the lower Muskegon and maintain a more stable, oxygenated water quality. Managing the river-flood plain interactions and reducing erosive scouring events was also a goal of the relicensing agreement
(Consumers Power Company, 1994a).
If the 1994 release strategy is changing rates of groundwater flux within the
Muskegon River impoundments, the relicensing could be having a rather complex impact on the river’s temperature. We have not to date examined the thermal regime in a way that would be analogous to our hydrographic analysis here. However, if the groundwater component of the water balance continues to be reduced, river temperature could increase despite the reduction in reservoir residence times, because of the loss of relatively colder groundwater sources. In addition, there are a variety of concerns relating to the reduction in floodplain interaction on the lower Muskegon River that revolve around the river’s reduced power downstream of the hydroelectric facilities. Significant power reduction will inevitably lead to the river’s reduced ability to transport sediment load. The resultant channel instability could lead to further erosion and additional channel aggradation in the estuary zone of the river.
The importance of the interaction between a river and its floodplain has only recently been acknowledged. Previously thought to be a different ecosystem entirely, the floodplain is now considered an important contributor to river productivity, allowing it to obtain and carry needed nutrients for the organisms it supports (Allan, 1995). As stated
29 in the Multiple Projects Environmental Assessment for the Muskegon River projects
(1994a), the operation scheme will “minimize the inundation of the downstream floodplain”. A concern for the future management of the Muskegon River could be the impact the altered hydrologic regime will have on the river’s interaction with the floodplain.
Table 1. Physical characteristics of the Rogers, Hardy, and Croton impoundments.
Impoundment Characteristics
Location (RM)
Drainage Area (mi2)
Max. Surface Area (acres)
Max. Surface Level (ft)
Gross Storage Capacity (acre-ft)
Target Surface Level (ft)
Mean Depth (ft)
Normal Usable Storage Capacity (acre-ft) /
Impoundment Fluctuation (ft)
Normal Impoundment Fluctuation (ft)
Rogers
83.7
~1,746
449
861.6
4,678
861.3
10.4
300/0.7
0.7
Hardy
58.7
~1,851
3,902
822.5
134,973
822.0
34.5
5,007/1.3
1.0
Drawdown (ft.) : dewatered acres (% surface area) N/A 0.5 : 51 (1.3%)
Average Annual Flow (cfs) 1
Impoundment Retention Time (days) @ Avg. Annual
Flow 1
Flow exceeded 90% of time (cfs) 1
Flow exceeded 10% of time (cfs)
1
1,344
1.8
650
2,850
1,460
46.6
650
2,850
Table 2. Operating characteristics of the Rogers, Hardy, and Croton impoundments.
Operating Characteristics
Operating Mode
Min. Turbine Hydraulic Range (cfs) /
Flow Duration Curve
Max. Turbine Hydraulic Range (cfs) /
Flow Duration Curve
Subject to Winter Drawdown & Spring
Refill
Max. Winter Drawdown (ft) /
Drawdown Timing
Drawdown Impacted Surface Area /
Volume (acre-ft)
Rogers
Run-of-River
300 / 99%
2,420 / 15%
No
N/A
N/A
Hardy
Ponding and Peaking from 8am-11pm
1,600 / 27%
4,860 / 2.5%
Yes
12 / January & February
18%-25% / ~30,000
Operations During Winter Drawdown Run-of-River Winter Drawdown
Croton
Re-regulated flow release
300 / 99%
3,700 / 10%
No
N/A
N/A
Releases mean daily discharge from Hardy +
Little Muskegon
R. inflow
Croton
52.8
~2,224
1,209
722.0
21,932
722.0
18.1
1,181/1.0
1.0
1.0 : 57
(4.7%)
1,871
5.9
1,000
3,600
1
As calculated by CP using a 20-year (1967 to 1986) period of record collected at USGS gage #04121500 (Rogers & Hardy) and USGS gage #04122000 (Croton)
30
31
Table 3. Land use characteristics of the Rogers, Hardy, and Croton impoundments.
Land Use Rogers Hardy Croton
Project Acreage / Impoundment Acreage
Shoreline (mi)
CP Owned
Agricultural
Forested
Residential
Open Gravel Pits
2,200 / 449
~19.4
18%
1%-4%
76%
17%
2.7%
5,000 / 3,902
~50
99.6%
1%-4%
81%
-
-
2,200 / 1,209
~22.9
11.3%
1%-4%
79%
17%
-
Table 4. USGS gauging station information for selected sites on the Muskegon and Little Muskegon
Rivers.
Station Name
Muskegon River at Evart
Muskegon River at Big Rapids
Little Muskegon at Morley
Little Muskegon at Oak Grove
Muskegon River near Croton
Muskegon River at Newaygo
Site Number Period of
Record
4121500 1930-present
4121650 1999-present
4121900
4121944
4121970
4122000
1966-1996
1995-present
1995-present
1930-1993
Latitude Longitude Catchment
(sq. mi)
43.8992 85.2553 1,433
43.6936 85.4675 1,751
43.5025
43.4308
43.4347
43.4222
85.3425
85.5956
85.6653
85.8011
121
345
2,313
2,350
Table 5. Flow duration percentiles and percent difference for pre-relicensing (1990-1993) input and output and post-relicensing (1996-2000) input and output for the Muskegon River.
Pre-relicensing Input (cfs)
Pre-relicensing Output (cfs)
% Difference
Post-relicensing Input (cfs)
Post-relicensing Output (cfs)
% Difference
5th
Percentile
4,458
5,023
11.25%
3,404
3,400
-0.11%
25th
Percentile
2,818
3,568
21.02%
2,085
2,200
5.23%
50th
Percentile
1,965
2,713
27.56%
1,513
1,580
4.25%
75th
Percentile
1,532
2,162
29.13%
1,163
1,230
5.43%
95th
Percentile
1,186
1,624
26.94%
834
885
5.76%
32
Table 6. Hydrograph flows for input, output, ET, and reservoir flux (δ) for 1991 and 2000 for the
Muskegon River impoundments.
Date
1991 Total
2000 Total
Jan & Feb 1991
Jan & Feb 2000
Mar & Apr 1991
Mar & Apr 2000
May – Aug 1991
May – Aug 2000
Sept – Dec 1991
Sept – Dec 2000
Total Input
(billion cfd)
80.39
48.03
9.49
7.52
20.84
10.18
20.71
17.72
29.34
12.61
Total Output
(billion cfd)
101.40
51.67
14.29
8.83
23.74
10.37
26.53
18.86
36.84
13.61
Total ET
(billion cfd)
-0.95
-0.85
-0.04
-0.04
-0.14
-0.13
-0.56
-0.49
-0.22
-0.19
Total Res. Flux
(billion cfd)
20.06
2.78
4.76
1.28
2.76
0.05
5.26
0.65
7.28
0.80
Table 7. Flow duration percentiles and percent difference for pre-relicensing (1990-1993) and postrelicensing (1996-2000) input and output for the Muskegon River in January and February.
Pre-relicensing Input (cfs)
Pre-relicensing Output (cfs)
% Difference
Post-relicensing Input (cfs)
Post-relicensing Output (cfs)
% Difference
5th
Percentile
2,614
3,668
28.75%
3,389
3,480
2.61%
25th
Percentile
2,035
3,025
32.74%
2,281
2,620
12.92%
50th
Percentile
1,837
2,791
34.20%
1,820
2,190
16.92%
75th
Percentile
1,578
2,519
37.35%
1,420
1,710
16.93%
95th
Percentile
1,246
2,126
41.37%
1,120
1,380
18.84%
Table 8. Average hydrograph flows for input, output, ET, and reservoir flux (δ) normalized to output for 1991 (pre-relicensing) and 2000 (post-relicensing) for the Muskegon River impoundments.
Date
Jan & Feb 1991
Jan & Feb 2000
Mar & Apr 1991
Mar & Apr 2000
May – Aug 1991
May – Aug 2000
Sept – Dec 1991
Sept – Dec 2000
Average Input
67%
82%
87%
100%
77%
96%
78%
93%
Average Output
100%
100%
100%
100%
100%
100%
100%
100%
Average ET
0%
0%
-1%
-1%
-2%
-3%
-1%
-2%
Average Res. Flux
33%
17%
13%
-1%
20%
1%
21%
6%
33
Table 9. Flow duration percentiles and percent difference for pre-relicensing (1990-1993) and postrelicensing (1996-2000) input and output for the Muskegon River in March and April.
Pre-relicensing Input (cfs)
Pre-relicensing Output (cfs)
% Difference
Post-relicensing Input (cfs)
Post-relicensing Output (cfs)
% Difference
5th
Percentile
5,759
5,628
-2.34%
4,662
4,720
1.23%
25th
Percentile
4,300
4,800
10.42%
3,157
3,160
0.10%
50th
Percentile
3,228
3,768
14.31%
2,468
2,380
-3.70%
75th
Percentile
2,411
2,861
15.74%
1,913
1,820
-5.11%
95th
Percentile
1,601
2,466
35.09%
1,515
1,540
1.65%
Table 10. Flow duration percentiles and percent difference for pre-relicensing (1990-1993) and postrelicensing (1996-2000) input and output for the Muskegon River in May through August.
Pre-relicensing Input (cfs)
Pre-relicensing Output (cfs)
% Difference
Post-relicensing Input (cfs)
Post-relicensing Output (cfs)
% Difference
5th
Percentile
3,293
4,046
18.62%
3,168
3,370
6.00%
25th
Percentile
2,177
2,791
22.00%
1,933
1,980
2.37%
50th
Percentile
1,623
2,225
27.07%
1,344
1,410
4.66%
75th
Percentile
1,340
1,890
29.12%
1,040
1,110
6.31%
95th
Percentile
1,151
1,540
25.27%
785
838
6.38%
Table 11. Flow duration percentiles and percent difference for pre-relicensing (1990-1993) and postrelicensing (1996-2000) input and output for the Muskegon River in September through December.
Pre-relicensing Input (cfs)
Pre-relicensing Output (cfs)
% Difference
Post-relicensing Input (cfs)
Post-relicensing Output (cfs)
% Difference
5th
Percentile
4,048
4,923
17.78%
2,076
2,170
4.35%
25th
Percentile
2,847
3,660
22.22%
1,547
1,590
2.69%
50th
Percentile
2,018
2,519
19.89%
1,285
1,330
3.38%
75th
Percentile
1,770
2,323
23.82%
1,090
1,120
2.68%
95th
Percentile
1,204
1,670
27.87%
809
872
7.28%
Table 12. Pre-relicensing (1991) and post-relicensing (2000) stream power and percent difference for the Muskegon River from the tailwaters of Croton Dam to Muskegon Lake.
Date
Jan. & Feb.
Mar. & Apr.
May. – Aug.
Sept. – Dec.
Pre-relicensing
Stream Power (MWh ft -1 )
2,735
4,643
10,804
14,481
Post-relicensing
Stream Power (MWh ft -1 )
1,641
2,130
7,565
5,060
% Difference
Stream Power (MWh ft -1 )
39.99%
54.12%
29.98%
65.05%
City of Fremont
Croton Dam
City of Big Rapids
34
Rogers Dam
Hardy Dam
Source: Muskegon River Watershed Assembly
City of Newaygo
Figure 1. The Muskegon River watershed surrounding the Rogers, Hardy, and Croton dams.
Muskegon River
Input
Rogers
Impoundment
Hardy
Impoundment
Croton
Impoundment
Muskegon River
Output
Figure 2. Linear representation of the inflows and outflows of the Rogers, Hardy, and Croton impoundments on the Muskegon River.
35
3500
3000
2500
2000
1500
1000
Figure 3. The Rogers hydroelectric facility on the Muskegon River, Mecosta County.
Figure 4. The Hardy hydroelectric facility on the Muskegon River, Newaygo County.
Figure 5. The Croton hydroelectric facility on the Muskegon River, Newaygo County.
5000 y = -5E-05x
2
+ 1.2835x + 209.69
R
2
= 0.9871
4500
4000
500
0
0 500 1000 1500 2000
Evart (cfs)
2500 3000 3500 4000
Figure 6. Scatter plot and linear regression for correlation of measured stream flow at Evart gauging station to Big Rapids gauging station.
4500
36
3000
2500
2000
1500
1000
500
1000
900
800
700
600
500
400
300
200
100 y = 0.0001x
2
+ 2.2203x + 44.158
R
2
= 0.834
0
0 50 100 150 200 250
Little Muskegon at Morley (cfs)
300 350
Figure 7. Scatter plot and linear regression for correlation of measured stream flow at Little
Muskegon at Morley gauging station to Little Muskegon at Oak Grove gauging station.
4500 y = -2E-05x
2
+ 0.9741x + 437.32
R
2
= 0.972
4000
400
3500
0
0 500 1000 1500 2000 2500
Newaygo (cfs)
3000 3500 4000 4500
Figure 8. Scatter plot and linear regression for correlation of measured stream flow at Newaygo gauging station to Croton gauging station.
37
Input
USGS dS/dt
Penmans
Output
USGS
Unknown
Figure 9. Water balance components for Muskegon River hydrologic equation.
Input
Output
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
1/1/91 2/20/91 4/11/91 5/31/91 7/20/91 9/8/91 10/28/91
Date
Figure 10. Fifteen-minute hydrograph for the year 1991. Input flows determined using the Evart to
Big Rapids correlation and output flows determined using the Newaygo to Croton correlation.
38
Figure 11. Fifteen-minute hydrograph for 2000. Input flows measured at the Big Rapids gauging station and output flows measured at the Croton gauging station.
Figure 12. Precipitation exceedance probabilities for pre-relicensing (1990-1993) and postrelicensing (1996-2000) years.
10,000
39
Pre-Relicensing Input
Post-Relicensing Input
Pre-Relicensing Output
Post-Relicensing Output
1,000
100
0.0% 10.0% 20.0% 30.0% 40.0% 50.0%
Exceedence Probability
60.0% 70.0% 80.0% 90.0% 100.0%
Figure 13. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing (1996-2000) input and output for the Muskegon River.
Pre-Relicensing Input
Post-Relicensing Input
Pre-Relicensing Output
Post-Relicensing Output
10,000
1,000
0.0% 10.0% 20.0% 30.0% 40.0% 50.0%
Exceedence Probability
60.0% 70.0% 80.0% 90.0% 100.0%
Figure 14. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing (1996-2000) input and output in January and February for the Muskegon River.
40
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
350,000,000
300,000,000
250,000,000
200,000,000
150,000,000
100,000,000
50,000,000
0
-50,000,000
Date
Figure 15. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for January and February 1991.
Figure 16. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for January and February 2000.
41
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
60%
40%
20%
0%
-20%
-40%
-60%
140%
120%
100%
80%
Date
Figure 17. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for January and February 1991.
Figure 18. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for January and February 2000.
10,000
42
Pre-Relicensing Input
Post-Relicensing Input
Pre-Relicensing Output
Post-Relicensing Output
1,000
0.0% 10.0% 20.0% 30.0% 40.0% 50.0%
Exceedence Probability
60.0% 70.0% 80.0% 90.0% 100.0%
Figure 19. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing (1996-2000) input and output in March and April for the Muskegon River.
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
600,000,000
500,000,000
400,000,000
300,000,000
200,000,000
100,000,000
0
-100,000,000
-200,000,000
Date
Figure 20. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for March and April 1991.
43
Figure 21. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for March and April 2000.
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
140%
40%
20%
0%
-20%
-40%
-60%
-80%
120%
100%
80%
60%
Date
Figure 22. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for March and April 1991.
44
Figure 23. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for March and April 2000.
Pre-Relicensing Input
Post-Relicensing Input
Pre-Relicensing Output
Post-Relicensing Output
10,000
1,000
100
0.0% 10.0% 20.0% 30.0% 40.0% 50.0%
Exceedence Probability
60.0% 70.0% 80.0% 90.0% 100.0%
Figure 24. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing (1996-2000) input and output in May through August for the Muskegon River.
45
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
500,000,000
450,000,000
400,000,000
350,000,000
300,000,000
250,000,000
200,000,000
150,000,000
100,000,000
50,000,000
0
-50,000,000
-100,000,000
Date
Figure 25. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for May through August 1991.
Figure 26. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for May through August 2000.
46
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
120%
100%
80%
60%
40%
20%
0%
-20%
-40%
Date
Figure 27. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for May through August 1991.
Figure 28. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for May through August 2000.
10,000
47
Pre-Relicensing Input
Post-Relicensing Input
Pre-Relicensing Output
Post-Relicensing Output
1,000
100
0.0% 10.0% 20.0% 30.0% 40.0% 50.0%
Exceedence Probability
60.0% 70.0% 80.0% 90.0% 100.0%
Figure 29. Flow duration curve for pre-relicensing (1990-1993) and post-relicensing (1996-2000) input and output in September through December for the Muskegon River.
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
700,000,000
600,000,000
500,000,000
400,000,000
300,000,000
200,000,000
100,000,000
0
-100,000,000
Date
Figure 30. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for September through December 1991.
48
Figure 31. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, for September through December 2000.
Input
Max ET
GW
Tribs.
Output dS/dt
Res. Flux
120%
100%
80%
60%
40%
20%
0%
-20%
Date
Figure 32. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for September through December 1991.
49
Figure 33. Hydrograph for the Muskegon River input, output, ET, and reservoir flux (δ), including dS/dt, small tributary inputs, and GW, normalized to output for September through December 2000.
Pre-Relicensing
Linear (Pre-Relicensing)
Post-Relicensing
Linear (Post-Relicensing)
4,500,000
4,000,000 R
2
= 0.9898
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
500,000
R
2
= 0.9623
0
0 20 40 60 80 100
Cumulative Precipitation (in.)
120 140
Figure 34. Double mass plot for cumulative precipitation versus cumulative output for prerelicensed (1990-1993) and post-relicensed (1996-2000) data.
160
50
4,500,000
4,000,000
3,500,000
3,000,000
2,500,000
2,000,000
‘86-‘89
Pre-Relicensing (1990-1993)
1970-1973
1978-1981
1986-1989
‘82-‘85
Post-Relicensing (1996-1999)
1974-1977
1982-1985
Post-Relicensing (2000)
‘90-‘93
‘74-‘77
‘78-‘81
‘96-‘99
‘70-‘73
1,500,000
1,000,000
500,000 ‘00
0
0 500,000 1,000,000 1,500,000 2,000,000 2,500,000
Cumulative Input (cu. ft. s
-1
)
3,000,000 3,500,000 4,000,000
Figure 35. Double mass plot for cumulative input versus cumulative output for 1970 – 1973, 1974 –
1977, 1978 – 1981, 1982 – 1985, 1986 – 1989, pre-relicensing (1990 – 1993) and post-relicensed data
(1996-2000).
Pre-Relicensing
Linear (Pre-Relicensing)
Post-Relicensing
Linear (Post-Relicensing)
8,000
R
2
= 0.8838
7,000
6,000
R
2
= 0.8875
5,000
4,000
3,000
2,000
1,000
0
0 1,000 2,000 3,000 4,000
Input (cu. ft. s
-1
)
5,000 6,000 7,000 8,000
Figure 36. Scatter plot of input versus output for pre-relicensing (1990-1993) and post-relicensing
(1996-2000) operations.
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