Impacts of the Proposed Site C Dam on the Hydrologic Recharge of the Peace-Athabasca Delta Submission to the Site C Joint Review Panel Prepared for: Athabasca Chipewyan First Nation Industry Relations Corporation Fort McMurray, Alberta Mikisew Cree First Nation Government and Industry Relations Fort McMurray, Alberta Prepared by: Martin Carver, PhD, PEng/PGeo, PAg November 25, 2013 Project #501-06 Aqua Environmental Associates Table of Contents Disclaimer ........................................................................................................................................................................... 5 Executive Summary .................................................................................... 6 1.0 Introduction ...................................................................................... 9 1.1 Objectives ....................................................................................................................................................... 9 1.2 Approach and Limitations .............................................................................................................................. 9 2.0 Hydrologic Recharge of a Complex Deltaic System .......................... 11 2.1 Controls on Hydrologic Recharge of the PAD............................................................................................... 11 2.1.1 Recharge Mechanisms and Flood Zones .............................................................................................................. 13 2.1.2 Controls: Integrated Factors that Enable the Mechanisms .................................................................................. 15 2.2 Effects of Existing Stressors on PAD Recharge ............................................................................................. 15 2.2.1 Flow Regulation .................................................................................................................................................... 16 2.2.1.1 Regulated Hydrograph ..................................................................................................................................... 17 2.2.1.2 Flow Reversals .................................................................................................................................................. 19 2.2.1.3 Downstream Ice ............................................................................................................................................... 21 2.2.1.4 Geomorphology and Sediment Transport ........................................................................................................ 26 2.2.1.5 Integration ........................................................................................................................................................ 27 2.2.2 Climate Variability and Climate Change ............................................................................................................... 29 2.2.3 Oilsands Water Withdrawals ................................................................................................................................ 32 2.3 Discussion ..................................................................................................................................................... 33 3.0 Site C: Incremental Pressure on a Stressed Delta ........................... 36 3.1 Site C EIS ....................................................................................................................................................... 36 3.1.1 Hydrologic Recharge Mechanisms ....................................................................................................................... 37 3.1.2 Flow Regime ......................................................................................................................................................... 40 3.1.3 Downstream Ice Regime ...................................................................................................................................... 42 3.1.4 Fluvial Geomorphology and Sediment Transport ................................................................................................ 46 3.1.5 Cumulative Effects ................................................................................................................................................ 47 3.2 Deficiencies in the EIS Assessment .............................................................................................................. 48 3.2.1 BC Hydro’s Impact Narrative ................................................................................................................................ 49 3.2.2 Ice-Jam Recharge Mechanism .............................................................................................................................. 55 3.2.3 Open-Water Recharge Mechanisms .................................................................................................................... 62 3.2.4 Climate Change .................................................................................................................................................... 64 3.2.5 Subjectivity ........................................................................................................................................................... 67 3.2.6 Uncertainty ........................................................................................................................................................... 71 3.2.7 Precautionary Risk-Based Mitigation ................................................................................................................... 73 4.0 Integration and Conclusion ............................................................. 77 4.1 A Complex System Under Increasing Stress ................................................................................................. 77 4.2 Addressing EIS Gaps in Assessment and Interpretation .............................................................................. 78 4.3 Implications .................................................................................................................................................. 79 4.4 Conclusion .................................................................................................................................................... 81 5.0 References ...................................................................................... 82 Site C Downstream Impacts – Submission to JRP, Nov 25, 2013 2/89 Aqua Environmental Assoc. List of Figures Figure 1. a) The Peace-Athabasca Delta situated in northern Alberta at the confluence of the Peace and Athabasca Rivers. b) Makeup of the PAD showing its extent and illustrating its main constituent lakes and rivers. ........................................... 12 Figure 2. Monthly mean (both regulated and unregulated) flows during 1960-1966 (wild) and 1992-2010 (regulated) for a) Hudson’s Hope, BC and b) Peace Point, AB. .. 17 Figure 3. Mean regulated hydrograph at Hudson’s Hope, Taylor, Town of Peace River, and Peace Point (1992-2012) contrasted with the mean unregulated hydrograph (1960-1966) and highlighting the seasonal hydrograph changes. .................... 18 Figure 4. Effect of Peace River on the PAD’s flow-reversal recharge mechanism. Plot illustrates the annual volume of reversed flow, highlighting the sharp drop in flow reversals with regulation and the sharper decline during the reservoir-filling period. .................................................................................................... 19 Figure 5. Winter flow of Peace River at Peace Point, contrasting consistent pre-regulation flow (1966) against fluctuating regulated winter hydrographs (1969-1979). ..... 25 Figure 6. Winter-flow comparison of Peace River at Hudson’s Hope versus Peace Point illustrating downstream influence of variations in discharge from Dinosaur reservoir. ................................................................................................. 25 Figure 7. Volume of annual Peace River flow reversals (1959-2012) illustrating the relative importance of recharge controls. Flow reversals occur when the Peace River is hydraulically damming the PAD – they may be augmented in a given year by relative brief periods affected by ice-jams (the shrouded points in the figure). Flow reversals are shown in relation to the freshet recharge score which is a scoring of the strength of the freshet to promote open-water recharge mechanisms, and expressed in relation to three dominant freshet characteristics. The plot distinguishes those years that are also affected by significant ice jams highlighting the importance of ice jamming in promoting recharge. ................. 28 Figure 8. Maximum annual extent of upstream ice-front progression (km downstream of Bennett Dam) from 1973 through 2011 (extracted from data provided by BC Hydro). .................................................................................................... 31 Figure 9. Changes in lake levels illustrating general regional declines and the accelerated decline of Lake Athabasca, suggestive of regulation effects. ........................... 34 Figure 10. Monthly mean (unregulated) flows for Peace River locations from Hudson’s Hope to Peace Point during a) 1960-1966 and b) 1992-2010. (Note different y-axis magnitudes.) ...........................................................................................