INTERNATIONAL RAINY LAKE BOARD OF CONTROL INTERNATIONAL RAINY RIVER WATER POLLUTION BOARD SPRING 2006 REPORT

Transcription

1 INTERNATIONAL RAINY LAKE BOARD OF CONTROL INTERNATIONAL RAINY RIVER WATER POLLUTION BOARD SPRING 26 REPORT Submitted to The International Joint Commission March 2, 26

2 TABLE OF CONTENTS 1 INTRODUCTION LAKE LEVEL REGULATION OVERVIEW ASSESSMENT OF PROPOSED ALTERNATE REGULATION OPERATIONS BASIN ISSUES AND OTHER BUSINESS HYDROPOWER PEAKING EMERGING ISSUES BOARD DIRECTIVES MEETINGS... 7 APPENDIX... 9 BOARD MEMBERS AND STAFF Canada USA IRLBC Members Syed Moin, PhD PEng Michael Pfenning PhD COL Peter Williams PEng Leland Grim IRRWPB Members John Merriman Jeffrey Stoner PG William Darby PhD Nolan Baratono IRLBC Engineering Advisors Rick Walden PEng Edward Eaton PE Joint Board Secretary Kenton Spading PE IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg i

3 1 INTRODUCTION The International Rainy Lake Board of Control (IRLBC) and the International Rainy Water Pollution Board (IRRWPB) report jointly to the International Joint Commission (IJC) in the spring and the fall of each year. Both reports address activities and basin issues of interest occurring since the previous report and may include sections on specific topics under review by the Boards. In addition, the spring reports address regulation of Rainy and Namakan lakes over the past calendar year, while the fall reports address environmental quality and related issues. Section 2 of this report summarizes the regulation of Rainy and Namakan lakes during 25 and includes the Boards response to a proposal for alternate regulation operations. Some of this material was included in the Fall 25 report to the IJC. Section 3 of the report addresses other activities of the Boards and items of interest in the basin. A map of the basin (Figure 1) can be found in the Appendix. 2 LAKE LEVEL REGULATION 2.1 Overview The year 25 proved to be another variable one for water levels in the Rainy-Namakan basin, especially for Rainy Lake. Although the lake did not reach the high levels of 21 and 22 or the low levels of 23, it nevertheless rose above its upper rule curve with its dam fully open in June and was quite low in its rule curve with outflow reduced to the specified minimum in September. The 25 quarter-monthly precipitation for the Lac la Croix and Rainy-Namakan subbasins is shown in Figure 2. Water levels, net inflows and outflows for 25 are shown on Figures 3 and 4, respectively, for Namakan and Rainy lakes. Figure 5 provides a legend for these figures. Namakan Lake started the year 4 cm (1.5 in) above its IJC operating band and rose to a high of 5 cm (2 in) above its upper rule curve on January 6. This was due to a water level gauge error that was discovered in early January; the malfunctioning gauge had shown the lake to still be within the IJC operating band. Rainy Lake was at 74% of its band at the start of the year. Inflow to both lakes stayed mostly in the normal to high normal range; only minor adjustments to outflow were needed to keep the lake levels declining through to the end of March. On March 31, Namakan and Rainy were at 51% and 48% of their respective operating bands. A slightly above normal snowpack water content over the basin and unseasonably mild temperatures right at the end of March hinted at a possible early snowmelt runoff and ice out. Both the Namakan and Rainy basins received strong freshet inflows in April, in excess of 9%ile. However, by late April to early May, inflows to both lakes had declined into the normal range and outflows were reduced in order to keep the lake levels rising. In fact, in the case of Rainy Lake, the level would have actually declined in early May without a significant outflow reduction. Since the snowmelt runoff peaked quickly and then strongly declined, the levels of both lakes were allowed to continue rising within the upper portion of their rule curve bands, where they had been pushed by the quick runoff, rather than returning them closer to the middle portion of their bands. This was consistent with the IJC Order and the results of the study that lead to the revised Year 2 rule curves. By doing so, there were potential benefits for the fishery and power generation. Very heavy rainfall was received in late May and significant amounts continued through June. For the May 25 through June 3 period, the Rainy-Namakan basin precipitation was 83%ile (rank in 1 IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 1

4 years). As a result, inflows to both lakes rose strongly and were above 95%ile for 3 days on Namakan Lake and for 7 days on Rainy Lake. For the whole spring period, April 1 through June 3, inflows to Namakan and Rainy were 82%ile and 95%ile respectively. The Companies responded quickly to open sluices in the dams but, with inflows exceeding outflow capacity, lake levels rose rapidly and exceeded the upper rule curves. In total, the level of Namakan Lake was above its upper rule curve for 9 days, from May 26 through June 3. The peak level reached was m ( ft) on May 3, which was 7 cm (3 in) above the upper rule curve on that date and 3 cm (1 in) above the maximum upper rule curve level (June 1). This peak level was rank 52 over the past 93 years of record and was 1.2 m (4 ft) below the peak level reached in 195. Namakan Lake did not reach its All-Gates-Open requirement level (3.1 m or ft) but Crane Lake did rise a little above this level. The water level situation was more severe on Rainy Lake, with the lake level being above its upper rule curve for days, from May 25 through July 4. The peak level reached was m (118.8 ft) on June 15, which was 28 cm (11 in) above the upper rule curve on that date and 2 cm (8 in) above the maximum upper rule curve level (July 1 to August 15). This peak level was rank 27 over the past 94 years of record and was 1.3 m (4 ft) below the peak level reached in 195. Rainy Lake was above its All-Gates-Open requirement level (337.9 m or ft) for 17 days (June 5-21); the gates were fully open for 24 days (May 31 through June 23). The inflows to both lakes, having peaked in late May, declined steadily through June and July. In fact, the wet conditions of May and June gave way to relatively dry conditions by early August, which continued through September. In response, lake outflows were reduced significantly as the Companies attempted to keep the lakes from declining too far below mid-band. Namakan outflow was reduced to near its IJC minimum of 3 m 3 /s in the latter part of September, while Rainy outflow was set at the IJC minimum of 1 m 3 /s for much of the period from late August through September. Nevertheless, by the end of September, Namakan Lake was at only 25% of its rule curve band and Rainy Lake was at 18% of its band. October saw a recovery in the water supply for the Rainy-Namakan basin. With significant rainfall through October and November, inflows steadily increased from lower quartile (Namakan) and lower decile (Rainy) to the upper quartile range by early December. Outflows from both lakes were increased in response. Namakan Lake ended the year with its level at 78% of band, its inflow at 8 percentile and its outflow at 7 percentile. Rainy Lake ended the year with its level at 59% of band, its inflow at 7 percentile and its outflow at 8 percentile. 2.2 Assessment of Proposed Alternate Regulation Operations Compared to recent past events, the Boards heard relatively little from the public in response to the 25 event, but there was some criticism regarding the regulation of Rainy Lake. In particular, the Border Lakes Association requested an operational review of Rainy Lake. Specifically, the Association expressed concern about recurring high water levels on Rainy Lake since the implementation of the year 2 rule curves, and proposed that: The level of Rainy Lake be maintained in the lower portion of the IJC operating band during April, May and early June in years of normal or above normal snowpack, and especially when the previous fall has been wet. The summer drawdown on Namakan Lake be delayed in years when Rainy Lake is experiencing high water. IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 2

5 In early July, the IJC asked the IRLBC for its views and advice regarding the Association s request and proposal. The Board provided a written response in late August and, following discussion with IJC staff in late October at the time of the IJC s semi-annual meeting in Ottawa, provided a slightly expanded version of its earlier response before the end of October. The body of that response follows. The IRLBC noted that, in the six spring seasons since the new rule curves were adopted, the level of Rainy Lake remained within its operating band in two years (2 and 24), fell well below its operating band in one year (23), and rose above its operating band in three years (21, 22 and 25). The Board also noted that, to date in the new millennium, the basin had experienced greater variability and extremes in rainfall and inflows than was typically seen during the 198s and 9s, but not greater than had been experienced in the basin historically. Regarding the 21 and 22 high water events on Rainy Lake, the hydrologic and operational aspects of both years were previously reviewed in detail by the Board. Reports documenting the reviews were submitted to the IJC. In both cases the Board concluded that the high water events were due to extreme events, were unavoidable, and that no changes in rule curves or operational procedures were required. Regarding the 25 event, IRLBC staff conducted modeling to determine what the effect of the above proposals would have been. It was found that, if the level of Rainy Lake had been kept to the middle of its operating band instead of being allowed to rise along the upper rule curve, the peak level would have been 8 cm (3 in) lower. If the level of Rainy Lake had been kept at its lower rule curve, the peak level would have been 15 cm (6 in) lower. It was also found that, if Namakan Lake had not been drawn below the maximum level of its upper rule curve (thereby storing more water in Namakan), the peak level on Rainy could have been reduced by 2 cm (1 in). These results are shown by the red lines (with numbers 2, 8 and 15 beside them) on Figure 6. In contrast, the numbers beside the blue lines on the graph show the number of years, since 1911, in which certain lake levels were equaled or exceeded. The peak reached in 25 was rank 27 out of 94 years. The peak level was considerably higher in a number of higher ranked years. Of the 26 years with higher peaks (than that reached in 25), two of them occurred with the new rules and 24 occurred previously. In presenting these model results, the Board stressed that they must be interpreted with caution. First, the model knows a day in advance what the next day's actual inflow will be and is able to increase outflow instantaneously. Second, assumptions must be made in the model about how the dams would be operated in response to changing inflows. For simplicity, the model allowed the Rainy Lake dam to release its maximum outflow capacity (corresponding to the current lake level) as soon as the lake level rose the slightest amount above the target level. In normal operating practice, one would expect a staged response to increasing inflows at any given lake level, with a faster and larger increase to be expected if the lake is high in its operating band, but with slower and smaller outflow increases at progressively lower levels in the operating band. In fact, many would consider increasing outflows to the maximum possible as soon as the level rises only slightly above the lower operating limit, and especially before the full extent and impact of the rainfall event is known, to be irresponsible. Nevertheless, for analysis purposes, and to avoid debate about what the most realistic operating practice might be, the extreme modeling approach was used to show the maximum benefit that might possibly be achieved. In interpreting the results, it must be realized that, in actual operations, the benefit of a lower lake level at the start of the rainfall event would be less than shown. Further, the modeled results likely become more optimistic as the starting lake level is lowered. IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 3

6 The Board made the following observations regarding the 25 event: While the modeling results show that the peak level of Rainy Lake could have been a little lower in 25 with the proposals made, the graph clearly shows that the difference is not significant in comparison to what has happened in the past and what local residents should be prepared to have happen again in the future. High water levels are not just a function of the new rule curves, but are more a function of extreme hydrologic input (rainfall) to the Rainy-Namakan basin. Namakan Lake simply does not have enough storage available to provide much relief to Rainy. Attempting to do so disproportionately increases the risk of high water to Namakan, with little gain for Rainy. During periods of higher inflows to the upper end of the Namakan Chain of lakes, the level of Crane Lake can be a foot or more higher than the mean level of Namakan and Kabetogama lakes, which is the level used for regulation purposes. In 25, the Namakan-Kabetogama level peaked at 3 cm (1 in) above the maximum level of the upper rule curve for Namakan Lake, whereas Crane Lake peaked at 22 cm (9 in) higher (see Figure 3). In addition, while the Namakan-Kabetogama level was above the maximum upper rule curve level for 7 days, the Crane lake level was above this point for 27 days. Delaying the summer draw down of Namakan, or maintaining Namakan levels at the top of the 197 rule curve band to help Rainy, as suggested by the Border Lakes Association, would have extended the duration of relatively higher water levels on Crane Lake. Past studies have shown that there is virtually no correlation between snowpack and total spring and early summer runoff. Consequently, basing springtime operations on winter snowpack has little merit. In 25, the snowmelt runoff was gone and inflows had declined into the normal range by late April to early May. In fact, without significant outflow reductions, the level of Rainy Lake would have declined in the period when stable or rising levels are recommended for the fishery. The subsequent high lake levels were the result of the heavy rains that started in late May, not of the basin conditions before then. The rule curves are not designed to minimize flooding at all costs but instead are designed to limit the risk of flooding while addressing other uses of the resource. They are a compromise. The new upper rule curve is actually only the mid-point of the band recommended by the International Steering Committee for the benefit of fish and other environmental objectives. Occasionally, when the runoff is early as it was in 25, and given that the basin was moving toward drier conditions before above-normal rainfall in May caused higher inflows, it is reasonable to operate closer to the upper rule curve to achieve the benefits such levels offer. Given that the Rainy-Namakan basin subsequently experienced a rank rainfall event (out of 1 years) for the late May through June period, and yet the peak Rainy level was only 2 cm (8 in) above the normal summer maximum level, it does not appear to the Board that this year's operations were overly risky. The range of water levels experienced in the Rainy-Namakan basin in the new millennium was adequately considered in the IRLBC's 1999 Rule Curve Study leading to the adoption of the year 2 rule curves. Apart from potential environmental benefits of higher levels on Rainy, there was a potential benefit to hydropower generation of not spilling excess water, especially given the move to drier conditions that was developing in late April and early May. Property owners, while they might experience some inconvenience, would certainly not experience any damage from a peak level only 2 cm (8 in) above the annual summer maximum if proper development standards were observed. Public expectations must be realistic. As shown on Figure 6, compared to past history, the low levels in 23 were more extreme than were the high levels in 25. This would suggest that the existing rules (the same for both 23 and 25) should not be altered to hedge against wet conditions. IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 4

7 The Board received an unsolicited letter from the Rainy Lake Sportfishing Club, representing about 75 members, supporting the current rule curves and stating their belief that the high water event this year was not controllable. Similar views were publicly and privately expressed by several Namakan Lake residents to Board members and staff at the joint annual IRLBC-IRRWPB public meetings held in the basin in July. Several Rainy Lake residents expressed views at the meeting supportive of the Border Lakes Association's concerns. In summary, based on its review of the 25 event and its previous reviews of the 21 and 22 events, the IRLBC concluded that no additional restrictions, as proposed by the Border Lakes Association, should be placed on operations within the new rule curves. The IRRWPB concurred with this conclusion. 3 BASIN ISSUES AND OTHER BUSINESS 3.1 Hydropower Peaking Concerns about the impacts of hydropower peaking operations (at Fort Frances International Falls) on the Rainy were raised at public meetings held by the IJC in 21. The IJC subsequently directed the Boards to jointly review and report on the issue. Due to resource constraints, the Boards review was based primarily on the work of the Committee on the Environmental Effects of Peaking on the Rainy. The Boards findings appeared as a major section of their Spring 25 Report to the IJC, which included background on the issue, general comments on the Committee s report, an assessment of the Committee s recommendations, and the Boards own conclusions and recommendations. The material was also presented to the Commission at its spring 25 semi-annual meeting. The IJC subsequently requested the Companies (Abitibi-Consolidated and Boise-Cascade) to voluntarily refrain from peaking during the spring fish spawning period. The Commission also asked the Boards to review a report prepared by Daniel O Shea (an employee of the Minnesota Department of Natural Resources, upon whose preliminary work the Committee s report had mostly been based, but whose own report was not finalized until August 8, 25). The Boards submitted their review of this report to the IJC in late August. Since that time, discussion between the Boards and staff of the IJC has continued. At the fall 25 semiannual meeting, the Boards re-iterated their primary recommendations, which were that: The IJC should confirm its authority and intent regarding peaking operations The IJC and the Boards should initiate collaborative dialogue with the Companies regarding peaking operations during the spring spawning period Further study, which would require significant additional resources (funds and personnel), would be required to establish the basis for any further action regarding peaking These recommendations were the focus of the Boards discussion with the Commissioners following their presentation. Since then, IJC staff have asked the Boards to prepare more detailed work plans and cost estimates for the studies envisioned. Discussion of these matters with IJC staff are continuing. IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 5

8 3.2 Emerging Issues United States Steel Minntac Tailings Basin Discharge At the fall 25 IJC semi-annual meeting, the Boards advised the Commission that a proposed mine development near the headwaters of the basin might discharge runoff from taconite ore tailings into the basin, which could be a water quality concern. As the project was in its early stages, it had not been determined whether the discharge would enter the Rainy basin or another adjacent basin. Since that report, Minnesota Pollution Control Agency (MPCA) and US Steel staff met in January 26 to begin discussions regarding development of a National Pollutant System Eliminations Discharge Permit for the Minntac tailings basin. Three discharge options are under active consideration at this time. These options include two that would flow into the Rainy basin (the Dark, a tributary of the Little Fork, and the Sandy, a tributary of the Vermilion ), and one that would flow into the Lake Superior Basin (the West Two Reservoir). The IRRWPB has requested updates from MPCA and US Steel staff at the joint IRLBC and IRRWPB meetings in the summer of 26. Pine Island Peat Mining Project On February 24, 26, IRRWPB co-chairs received a fax of a letter of the same date from the Manitoba Eco-Network requesting that the Board investigate the possibility of trans-boundary mercury pollution from de-watering operations at the Pine Island Peat Mining Project located in Koochiching County, Minnesota, USA. The fax also noted the need for improved trans-boundary communication regarding official actions for facilities that may affect the water quality of boundary waters. The IRRWPB has acknowledged receipt of the fax and letter from the Manitoba Eco-Network through a telephone conversation on March 3, 26 with the Water Caucus Coordinator, Glenn Koroluk, indicating that an interim response will be forthcoming after the semi-annual meeting in Seattle. The IRRWPB will examine and assess the potential effects from mercury loading in the Black Watershed to the Rainy and provide the assessment, with recommendations for actions, if any, to the IJC prior to the fall 26 semi-annual meeting and before providing a more detailed response to the Manitoba Eco-Network. The Boards (IRLBC and IRRWPB) will seek ways to improve trans-boundary communication regarding agency environmental review and permitting actions within the Rainy Basin. The Boards will examine the possibility of developing a border waters communication framework that will improve communication and coordination with the goal of providing accurate information to interested parties and preventing misunderstandings. Proposed Hydropower Developments on the Namakan below Lac la Croix The government of the Province of Ontario has identified three sites on the Namakan (Hay Rapids, High Falls and Myrtle Falls) for potential hydropower development. The sites are totally within Ontario, have potential output ranging from 2 to 4.5 MW each and have developable heads up to about 6 m (2 ft). All are expected to be run-of-river operations, with minimal headponds. IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 6

9 While no impact is anticipated on international boundary waters, the Boards are monitoring the proposed developments. The province issued a Request for Proposals (for preliminary plans) last year. As of February 26, the Applicant of Record is Ojibway Power and Energy Group (OPEG) Ltd. The Applicant will next seek to secure a power purchase agreement with the province and, if successful, must then issue a public notice of commencement by February 27. If proceeding, an environment screening report will be required, with a 3-day public review period. 3 rd International Lake of the Woods Water Quality Forum Members from both the IRLBC and the IRRWPB attended the Forum held at Rainy Community College/Rainy Basin Water Resources Center March 8 th and 9 th. Members indicated they appreciated the opportunity to hear presentations on emerging science related to water management in the Rainy Basin and to speak directly with those conducting the research. Members attending the Forum specifically noted the concerns of both the scientific community and the general public regarding nutrient over-enrichment and erosion of Lake of the Woods. At the Forum, it was noted that the Rainy is the main source of inflow to Lake of the Woods and that, as a consequence, there is a need to link water quality issues on the two water bodies. This is potentially of interest in light of the IJC s watershed approach. 3.3 Board Directives In addition to the IJC Order for the Regulation of Rainy and Namakan lakes, both Boards have Directives from the IJC which define their duties and responsibilities. Both are currently out-of-date. The Boards have discussed the need to revise them, while also considering the IJC s desire to eventually move to a single watershed board. As neither Board currently believes a single watershed board would be appropriate for a few years yet, the Members intend to work with IJC staff on the updating of the existing Directives. 3.4 Meetings IJC Fall Semi-Annual Meeting IRLBC and IRRWPB members and staff attended the fall semi-annual meeting of the IJC in Ottawa on October 2, 25. The Boards presentation addressed water quality on the Rainy (monitoring programs, fish consumption advisories and municipal/industrial point source discharges), basin issues (hydropower peaking operations, rule curve monitoring program funding concerns and the proposed Minntac development), the June-July 25 high water event on Rainy and Namakan lakes, and other Board activities (July basin tour and meetings, review of O Shea fishery report, response to concerns of the Border Lakes Association and the September tour of water treatment facilities). Discussion between Board Members and IJC Commissioners focussed on hydropower peaking operations. Board Conference Calls and Meetings The two Boards continued to maintain close contact during the reporting period. Three joint conference calls were held; on January 31, March 2 and March 17, 26. Some Board members and staff and one IJC staff member also met in International Falls on March 9, 26 while attending the 3 rd annual International Lake of the Woods Water Quality Forum. Items discussed included basin issues (hydropower peaking, Minntac development, proposed Pine Island Peat Mine, proposed hydropower IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 7

10 developments on the Namakan below Lac la Croix), development of study plans and cost estimates, Board resources (funding and personnel), preparations for Rainy modeling (collection of river cross-sectional data with funds allocated to the US Army Corps of Engineers by the US Section of the IJC), planning for a spring tour of water treatment facilities, Board reports and newsletters, Board Directives and their future working relationship, and preparation for meeting with the IJC at its April 26 semi-annual meeting. IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 8

11 APPENDIX Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Rainy Drainage Basin Map Rainy Basin Precipitation Namakan Lake Elevation, Net Inflow and Outflow Rainy Lake Elevation, Net Inflow and Outflow Legend for Lakes and Graphs Rainy Lake Elevation for 23-5, with Modeling Results NOTE All precipitation, water level and flow data used in the text and figures of this report were taken from the database of the Secretariat of the Lake of the Woods Control Board. At the time of preparation of this report, this data was still provisional and subject to revision. IRLBC/IRRWPB Spring 26 Report 26Mar2 Pg 9

12 of Lake N Warroad Woods Baudette Rapid Bemidji the Rainy Rainy Manitou Rapids FORT FRANCES INTERNATIONAL FALLS Big Fork Little Fork Big Falls Kabetogama Lake 3 Rainy Little Fork Hibbing Mine Centre Namakan Lake Orr T e u l r t Lake Virginia R e v i r 2 Kettle Falls Dam Seine Sturgeon Falls Vermilion Lake Lac la Croix Ely Maligne Atikokan 1 Marmion Lake Basswood Lake Kawishiwi Lac des Milles Lacs Upsala MINNESOTA Grand Marais e k a L Pigeon THUNDER BAY ONTARIO e p u S o i r r LEGEND International Boundary Drainage Basin Sub-Basins 1 Namakan Lake 2 3 Rainy Lake Rainy Control Dams Data Gauges (Near Real Time) Stream Flow Water Level Precipitation International Rainy Lake Board of Control IRLBC Rainy Drainage Basin km mi

13 LWCB Lake of the Woods Control Board 1 LAC LA CROIX PRECIPITATION 25 PRECIPITATION (mm) PRECIPITATION (in) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 1 RAINY-NAMAKAN PRECIPITATION 25 PRECIPITATION (mm) PRECIPITATION (in) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

14 LWCB Lake of the Woods Control Board NAMAKAN LAKE IJC 2 Rule Curves IJC 2 Drought Line IJC All Gates Open Crane Nam & Kab 25 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ELEVATION (m) ELEVATION (ft) NET INFLOW (m³/s) NET INFLOW (ft³/s) OUTFLOW (m³/s) OUTFLOW (ft³/s) 1 5 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

15 LWCB Lake of the Woods Control Board RAINY LAKE IJC 2 Drought Line IJC 2 Rule Curves IJC All Gates Open Rainy 25 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ELEVATION (m) ELEVATION (ft) NET INFLOW (m³/s) NET INFLOW (ft³/s) OUTFLOW (m³/s) OUTFLOW (ft³/s) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

16 LWCB Lake of the Woods Control Board LEGEND - LAKE AND RIVER GRAPHS PRECIPITATION Actual data for year shown, plotted as quarter-month totals (last quarter-month is usually incomplete) Average - over the years WATER LEVELS & FLOWS Actual Data Actual data for the dates shown - levels are 1-day means plotted daily - inflows are 7-day means plotted daily - outflows are daily values Rule Curves (Namakan & Rainy Lakes) Statistical Data IJC 2 Upper & Lower Rule Curves IJC 2 Drought Line IJC Upper Emergency Level IJC "All Gates Open" Level 5 Maximum level/flow recorded and its year of occurrence Level/flow has been above this line 1% of time. Normal level/flow range - level/flow has been above this range 25% of time - level/flow has been within this range 5% of time - level/flow has been below this range 25% of time Level/flow has been below this line 1% of time 77 Minimum level/flow recorded and its year of occurrence All statistical levels are based on 3-day means at month quarter points. All statistical flows are based on quarter-monthly means. Percent data is based on the period Datums for water levels are: - Namakan Lake - USC&GS (1912) datum - Rainy Lake - USC&GS (1912) datum

17 LWCB Lake of the Woods Control Board RAINY LAKE IJC 2 RuleCurves IJC 2 Drought Line IJC Emergency Line IJC All Gates Open J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D ELEVATION (m) ELEVATION (ft)