Water Level Analysis of Lower St. Marys River September 15, 2010

Transcription

1 Water Level Analysis of Lower St. Marys River September 15, 21 Purpose and Scope This report presents the results of the data analysis of the St. Marys River levels and flows in support of several study tasks which are part of the current International Upper Great Lakes Study. The objective is to review the relationships between Lake Superior outflows and water levels and how peaking and ponding operations affect these levels. Past studies have shown that peaking and ponding operations have negligible impacts on the river levels upstream of Sault Ste. Marie, Michigan and Ontario. Hence, this study focused on the river from below the hydropower plants to Lake Huron. Physical Settings The St. Marys River is the outlet of Lake Superior connecting to Lake Huron. The upper reach of the river from Point Iroquois on eastern Lake Superior to the US navigation canals at Sault Ste. Marie, Michigan falls about 8 cm over a distance of 22 kilometres. Next, the river falls about 6 metres over a distance of 2 kilometres with most of the fall occurring at the rapids. The lower reach, from below the rapids to Lake Huron falls about.6 metre for a distance of 77 kilometres. A rock ledge at the St. Marys Rapids at Sault Ste. Marie, Ontario and Michigan acted as natural control regulating Lake Superior s outflows. Hydropower and navigation developments led to full artificial regulation of the outflows in Each month, the Lake Superior Board determines the Lake Superior outflow and the amount of water available for hydropower purposes after other priority needs are met namely domestic and sanitary, navigation, and needs for the fishery remedial works. The flows in the lower St. Marys River is sub-critical in that gravity is the main driving force acting on the river. Due to variations in channel geometry and bottom profile, the flow is non-uniform such that the rise and fall in water level is not uniform along the channel as the flow changes. The slope of the water surface profile is relatively steep at the upper reach just below Sault Ste Marie, and next becoming mild towards Lake Huron. This mild slope enables backwater effects from Lake Huron to reach upstream as far as the foot of the rapids. The three hydropower plants Cloverland, Brookfield and US Government plants divert water from the river above the rapids and compensating works and return the water to the river downstream of them. Peaking is the variation of the flow at the hydropower plant about the daily mean flow, and ponding is the variation of the daily mean flow about the weekly mean flow. When the allocated water is less the plant s capacity, the operator may choose to conduct peaking and ponding operations following guidelines approved by the International Joint Commission to fit with unit maintenance and market demand. Figure 1 is an example of peaking conducted by the Cloverland plant resulting in variation in the hourly flows of the lower St. Marys River. Tides are known to exist on the Great Lakes. Available literature shows that they are small ranging from 1 to as much as 4 centimetres on Lake Superior and Lake Erie. However, they are masked by meteorological phenomena such as wind and seiche on the lake. 1

2 Selected Days for Analysis Eighteen events in 28 and 29 during the navigation season from May to December were selected (see Table 1) for analysis and the gauges used are listed in Table 2 and their locations shown in Figure 2. The criteria used in selecting the events are availability of hourly data, hydraulic conditions reflecting present channels and preferably below average level and flow conditions, and periods having peaking and ponding operations. Steady state events were selected as they provide data suitable for developing level-flow relationships. Some unsteady state events including disturbance on Lake Huron were selected to assess their effects on river levels. The data from two Lake Huron gauges - and - were also examined. Weather records from Sault Ste. Marie, Michigan and other sites around Lake Michigan-Huron were also examined as part of the analysis. Results of Data Analysis, and Other Observations Of the three plants, the Cloverland plant tends to conduct peaking and ponding operations more frequent as it allocated water is often less than its installed capacity. As the Lake Superior outflow approaches 2,31 m 3 /s, peaking and ponding operations cease as there would be no advantage to do so given the allocated water is at the plant capacity. The hourly outflow and water level hydrographs for the 18 events in 28 and 29 are shown in Figures Also plotted on these graphs are the levels which track well to show the meteorological effects on northern Lake Huron. levels give an idea of the north-south tilt on Lake Huron due to meteorological factors. A review of the 28 and 29 data shows that high flow in the peaking cycle extends as late as 11: p.m. The offsetting overnight flows and reduced flows during weekends lower the river levels below Sault Ste. Marie. During and following flow reductions at the hydropower plants, the level observed at U.S. Slip declines asymptotically towards a lower level (Events 12, 15 and 18). Flow increase has the reverse effect with similar asymptotic feature towards a higher level. The effect on river levels due to flow change essentially dissipates by the end of the following day. These can be seen in some of the 18 event-diagrams when Lake Huron disturbance was not a factor. These diagrams also show the time lag and direction in the transmission of the impacts due to flow changes at Sault Ste. Marie, or due to disturbance on Lake Huron. The maximum effects were observed at the U.S. Slip gauge owing to its close proximity to the hydropower plants. In 22, the Lake Superior Board conducted a statistical analysis of hourly outflows and found the correlation between flow change and U.S. Slip levels to be about 16 cm/1, m 3 /s. The findings from the current study are comparable. Events 1, 2 and 7 show a correlation of 17 cm/1, m 3 /s. Event 14 shows a correlation of 2 cm/1, m 3 /s, and Event 18 shows a correlation of 18 cm/1, m 3 /s. In both the and periods, Lake Michigan-Huron was below the long-term average ( ) by 17 cm. Backwater effects due to water level variations on northern Lake Huron the result of meteorological processes - are almost always present. The effects can be observed as far upstream as U.S. Slip and for some cases they exceed the effects of flow change on levels. The drawdown effects due to declining level on northern Lake Huron coinciding with flow reduction at the hydropower plants exacerbate the falling levels in the river, and stable level could not be attained at U.S. Slip, as shown in Events 1 and 14. 2

3 From the 18 events, it was possible to identify some steady state level-flow conditions of sufficient duration and the results are presented in Table 3 and graphically in Figure 3. As shown in Figure 3, at the same Lake Huron level, higher head and/or steeper gradient at the upper end of the St. Marys River just below Sault Ste. Marie is needed to convey higher volume of water downstream (Event 17 and 18, and Events 4 and 5). Some of the events include periods with unsteady water level conditions and to illustrate the impacts of storms and Lake Huron disturbance, the total range of levels observed at the gauges are shown in Table 4. For example, the Lake Huron disturbance in Event 14 resulted in the total range of 41 cm experienced at U.S. Slip. Some backwater effects can more than offset the effects of flow change at the hydropower plants. Of the eighteen events examined, only Event 18 may be considered having conditions sufficiently calm and steady to identify water level impacts and at best, they show a change of 1 to 2 cm at Rock Cut for the 38 m 3 /s flow change recorded at Sault Ste. Marie. The guidelines approved by the IJC following the Lake Superior Board s 22 study state that the Board may suspend ponding operations for the month if it is expected that ponding operations would result in sustained weekend levels at U.S. Slip gauge declining below chart datum elevation. Since then, it is noted that such a decision can be re-visited at half-month intervals. Also, the completion of the removal of some high spots in the river has lowered the threshold U.S. Slip level from 8 m to m, and this has greatly reduced restriction events. Peter Yee September 15, 21 3

4 Table 1 Selected Events for Data Analysis Event Days Flow, m3/s Event Days Flow, m3/s 1 May 9-11, Nov 23-26, May 23-24, Dec 21-22, June 6-8, Dec 26-28, July 3-6, May 3-4, Aug 8-13, May 13-16, Sept 5-7, June 8-9, Oct 1-2, Aug 15-16, Oct 11-12, Aug 22-23, Nov 14-15, Sept 3-9, Table 2 Water Level Gauges Used in the Analysis Site LWD, IGLD 85 Distance* from Compensating Works C.W. *. km U.S. Slip 8 m 2.3 km Little Rapids 8 m 5.6 km Frechette 8 m 8.1 km Lookout #4 2 m 29.5 km m 32.2 km Detour 176. m 72.2 km 176. m On northern Lake Huron Harbour Beach 176. m On southern Lake Huron 4

5 Table 3 -Level Relationships Event U.S. Slip L Rapids Lookout 4 De Tour No data * * * No data * * * * * No data 1 * * No data No data No data No data * * * No data No data * * Event U.S. Slip L Rapids Lookout De Tour No data * * No data No data * * * * No data * * No data * * No data * * No data * * No data No data

6 Table 4 Estimated Range during Lake Huron Disturbance Event Flow (m3/s) Little Rapids Lookout #4 De Tour cm No data 19 cm 25 cm 13 cm cm No data 7 cm 11 cm 5 cm cm 15 cm No data 54 cm 47 cm cm 4 cm No data 39 cm 16 cm cm 8 cm No data 1 cm 6 cm cm 4 cm No data 9 cm 5 cm 6

7 Flows, m3/s Figure 1 Example of Peaking and Ponding Operations Peaking and Ponding at Plants on Sept 3-9, 29 (18) 2 2 Hourly s Not plotted: navigaion 12 m3/s, domestic 11 m3/s, comp works 85 m3/s 1 Brookfield (Great Lakes Power) 1 Cloverland (Edison Sault) US Government Plant Hourly Intervals Starting Sept 3 Thursday 7

8 Whitefish Bay Figure 2 Gauges on the St. Marys River Lake Superior Sault Ste Marie Lock Above SW Pier Little Rapids Gage Sault Ste Marie Lock Below Frechette Suga r U.S. Slip Islan d La ke Ni co let La ke G eo rg e Cell Dock Lookout #4 Gage Slab Dock Gage Lake Munuscon g Lake Huron 3 6 Approximate Scale in Miles USACE NOS CHS De Tour Village De Tour 8

9 Levels, metres IGLD 1985 Figure Surface Profile Between and De Tour N o te: F o r so me events, gradients between and Little R apids are no t sho wn due to lack o f data A B-23 (black dash) Distance downstream from Compensating Works (km) 9

10 Levels, metres IGLD 1985 s, m3/s Levels and s on May 9-11, 28 (1) Levels drop at after peaking, effects dissipating next day. tracks w ith De Tour. Lake Huron draw dow n on May 11. Note threshold levels Lookout Station 4 De Tour Hourly Intervals Starting May 9 Friday

11 Levels, metres IGLD 1985 s, m3/s Levels and s on May 23-24, 28 (2) Peaking effects dissipating next day. tracks with De Tour. Note time-lag direction along river. Lake Huron backwater effects on May 24. Ponding permitted with new threshold level at U.S. Slip. 2 1 Lookout Station 4 on south Lake Huron De Tour on north Lake Huron Hourly Intervals Starting May 23 Friday

12 Levels, metres IGLD 1985 s, m3/s Levels and s on June 6-8, 28 (3) Lookout Station DeTour Time-lag along river, Lake Huron backwater effects extends to US Slip Hourly Intervals Starting June 6 Friday Harbour Beach

13 Levels, Metres IGLD 1985 s, m3/s Levels and s on July 3-6, 28 (4) on Lake Huron Lookout Station DeTour tracks with De Tour. Lake Huron effect extending to Hourly Intervals Starting July 3 Thursday 1

14 Levels, Metres IGLD 1985 s, m3/s Levels and s on August 8-13, 28 (5) Hourly Intervals Starting August 8 Friday Lookout Station 4 DeTour Peaking-ponding effects dissipating but level recovery delayed by backwater effects from Lake Huron. tracks with De Tour. 1 1

15 Levels, metres IGLD 1985 s, m3/s Levels and s on September 5-7, 28 (6) Lookout Station 4 DeTour Note time-lag direction and tracks with De Tour. Lake Huron drawdown effects extend to U.S. Slip. Sept 5 SSM winds NE then NNW max gust 4 km/hr Hourly Intervals Starting Starting September 5 Friday

16 Levels, Metres IGLD 1985 s, m3/s Levels and s on October 1-2, 28 (7) Hourly Intervals Starting October 1 Wednesday Lookout Station 4 De Tour tracks with De Tour. Lake Huron effects along river, Harbor Beach consistently higher than Lookout Station

17 Levels, Metres IGLD 1985 s, m3/s Levels and s on October 11-12, 28 (8) faily steady. Lake Huron relatively calm. tracks De Tour. Oct 11 SSM winds E max gust 32 km/hr. 2 2 Lookout Station De Tour Hourly Intervals Starting October 11 saturday

18 Levels, Metres IGLD 1985 s, m3/s Levels and s on Nov 14-15, 28 (9) tracks w ith De Tour, time-lag along river, LKe Huron draw dow n effects extending to Lookout Station 4 De Tour Hourly Intervals Starting November 14 Friday 1 1

19 Levels, Metres IGLD 1985 s, m3/s Levels and s on Nov 23-26, 28 (1) 2 2 Lookout Station De Tour Note time-lag direction along river. Tilt on Lake Huron increased river gradient moderating peaking effects at and also kept river profile unsteady Hourly Intervals Starting Nov 23 Sunday 1

20 Levels in Metres, IGLD 1985 Hourly s and Levels on Dec 21-22, 28 (11) Disturbance on L Huron and outflow both factors affecting river levels. Note gradual increase in outflow on Monday as do river levels. s 2 1 Little Rapids De Tour Village Hourly Intervals Starting Dec 21 Sunday

21 Levels, Metres IGLD 1985 Levels and s on Dec 26-28, 28 (12) Little Rapids Disturbance on Lake Huron, time-lag along river, tracks with De Tour, effects extending to. Dec 28 SSM winds W briefly N then W again max gust 71 pressure rose sharply De Tour Hourly Intervals Starting Dec 26 Friday 1

22 Levels, metres IGLD 1985 s, m3/s Levels and s on May 1-4, 29 (13) Little Rapids 2 1 De Tour Stable flow since early May 1. Time-lag direction and level variations indicate large impacts due to Lake Huron disturbance Hourly Intervals Starting May 1 Friday

23 Levels, metres IGLD 1985 Levels and s on May 13-16, 29 (14) U.S. Slip Little Rapds 2 De Tour stable until May 14 evening. Lake Huron disturbance and wind effects both a factor. SSM May 13 ESE max gust 6 pressure falling; May 16 E then sharply W max gust 72 pressure falling then rising. May 16 drawdown effects dominating Hourly Intervals Starting May 13 Wednesday

24 Levels, metres IGLD 1985 s, m3/s Levels and s on June 5-9, 29 (15) U.S. Slip Little Rapids 1 1 De Tour 176. June 6 ponding effects dissipating next day. Lake Huron disturbance and wind effects followed Hourly Intervals Starting June 5 Friday

25 Levels, metres IGLD 1985 Levels and s on Aug 15-16, 29 (16) U.S. Slip Little Rapids 1 De Tour Lake Huron disturbance. tracks w ith De tour Time-lag along river. Aug 16 SSM E then SE max gust Hourly Intervals Starting Aug 15 Saturday

26 Levels, metres, IGLD 1985 s, m3/s Levels and s on Aug 22-23, 29 (17) U.S. slip Little Rapids / De Tour Effects of flow s mixed w ith dow nstream disturbance. N-S differential on Lake Huron. Aug 23 SSM NE then NW max gust 24 then S Hourly Intervals Starting Aug 22 Saturday 1

27 Levels, metres, IGLD 1985 outflows, m3/s Levels and s on Sept 3-9, 29 (18) Little Rapids 1 De Tour Fairly calm period. - De Tour gradient steady. Peaking effects dissipating next day. Note change in river storage during flow transition and time-lag direction. tracks well with De Tour. Internal oscillations in Lake Huron. Note old and new threshold level for U.S. Slip Hourly Intervals Starting Sept 3 Thursday