Climate Change & Urbanization Have Changed River Flows in Ontario

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1 Climate Change & Urbanization Have Changed River Flows in Ontario by Trevor Dickinson & Ramesh Rudra Water Resources Engineering University of Guelph

2 Acknowledgements Agencies NSERC, OMAF & Environment Canada Personnel Barry Smith - Retired Program Manager, Water Survey of Canada Golmar Golmohammadi Post Doctoral Research Fellow Graduate & Undergraduate Student Assistants

3 The Story Line The climate and landscape have changed across Southern Ontario. * Winter streamflows have increased and spring runoff/freshettes have decreased, primarily as a result of climate change. * Summer flows in urban areas have increased significantly, primarily as a result of urban development.

4 Rural River Flows Have Changed Flow Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Winter Spring Summer Fall For Rural Watersheds like the Moira River at Foxboro: winter flows have increased, spring flows have decreased, & summer flows have remained unchanged.

5 Urban River Flows Have Changed Flow Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Winter Spring Summer Fall For a highly Urbanized Watershed like the Don River at Todmorden: winter flows have increased, spring flows have decreased, & summer flows have greatly increased.

6 No Change in Precipitation Volumes 12 Average Annual Precipitation (mm) Nith at New Hamburg Grand at Brantford Cedar Creek at Woodstock Moira near Foxboro Linear (Nith at New Hamburg) Linear (Grand at Brantford) Linear (Cedar Creek at Woodstock) Linear (Cedar Creek at Woodstock) Linear (Moira near Foxboro)

7 Possible Causes of Changes - Other Changes in Climate, and/or - Changes in Land Use i.e. Urban Development

8 Changes in Winter Hydrology in Ontario Winter Temperature Frost-Free Days Winter Snowmelt Winter Rainfall Snowfall End of Winter Snowpack Winter Surface Runoff and/or Winter Infiltration Spring Runoff and/or Springmelt Infiltration Winter Tile Flow Springmelt Tile Flow Winter Streamflow Springmelt Streamflow Variable has increased Variable has decreased Data Available

9 The Effect of Winter Climate Change Flow Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Winter Spring Summer Fall

10 Water Quality Impacts? Are we now seeing more frequent and greater: - field & streambank erosion, - stream sediment loads, and - nutrient loads during the winter months? Have these loads become smaller and less frequent during spring snowmelt events? What are the implications for monitoring and managing water quality variables?

11 Urban Summer Flow Volumes Have Increased Flow Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Winter Spring Summer Fall Summer flows have increased significantly in volume

12 There Are More Urban Summer Flow Events Flow (cms) Dec Dec Dec Jan Jan Jan Feb Feb Feb Mar Mar Mar Apr Apr Apr May May Jun Jun Jun Jul Jul Jul Aug Aug Aug Sep Sep Sep Oct Oct Nov Nov Nov Flow (cms) 4 Winter Spring Summer Fall and in frequency on the Don River at Todmorden. What s going on?!

13 Seasonal Runoff Response Mean event runoff coefficient April May June July August September October In rural watersheds, during June through September, there are virtually no direct runoff events and runoff coefficients are essentially zero.

14 Growing Season (May 1 st to Sep 31 st ) Estimated Probability of Runoff Coefficient Rainfall Depth > 4 mm 2 to 4 mm < 2 mm Zero Runoff Coefficient

15 Urban Runoff Coefficients Have Increased Mean event runoff coefficient April May June July August September October Before Urbanization Initial Urbanization Significant Urbanization (5%)

16 Estimated Probability of Runoff Coefficient Non-Growing Season (Oct 1st to Apr 3th).8 Rainfall Depth.7 > 4 mm 2 to 4 mm < 2 mm Zero Runoff Coefficient

17 Streamflow Volumes So in Ontario urban watersheds, summer flow volumes have increased dramatically, in volume and frequency, as a result of development.

18 Urban Water Quality Impacts? Are we seeing more frequent flushes and greater volumes of: - streambank erosion, - suspended sediment loads, - Chlorides and other pollutants, and/or - sewage bypasses? What are the implications for monitoring and management?

19 Conclusions The climate and the landscape have changed across Southern Ontario. As a result: * river flows have changed in winter and spring - primarily due to climate change; and * flows have changed during summer months - primarily due to urban development.

20 5 Flood Events (1925 to 195) 5 Flood Events (195 to 1975) 4 4 % of Events 3 2 % of Events Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec Month Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec Month 5 Flood Events (1975 to 2) 5 Flood Events (2 to 216) % of Events % of Events Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec Month Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec Month

21 Questions???