Environmental Flows and Habitat Suitability Index Assessments

Transcription

1 Environmental Flows and Habitat Suitability Index Assessments Latornell Symposium November 17, 2015 T2F Sam Bellamy

2 The Problem Hydrologists, hydrogeologists and engineers often inform on the hydrologic impact of a change E.g. A proposed water taking will reduce summer low flows by % Does not inform what the ecological impact may be What is the corresponding reduction in aquatic habitat?

3 Habitat Suitability Index Assessment Ability to quantify the change in suitable habitat for a specific species as a result of a change in flow. Habitat Suitability Index Hypothesis is specific aquatic species have preferences for certain hydraulic conditions (e.g. velocity and depth) and substrate. Uses high resolution hydraulic models to predict distributed values of velocity and depth. By combining species preferences with velocity and depth values, the suitability of a reach can be quantified. By evaluating multiple flow regimes, the change in habitat suitability can be assessed.

4

5 The Project: Innisfil Creek Drought Plan Watershed with large number of surface water takings. Regular low water conditions Predominantly warm water fishery, with some migratory rainbow trout and remnant brook trout populations MIKE SHE model was developed and used to assess the hydrologic impact of various water withdrawal scenarios Further evaulation required to assess the ecologic impact of the scenarios.

6 Habitat Suitability Index Process Step 1: Identify study reaches Reconnaissance to identify key habitat Step 2: Identify Target species: Coldwater: rainbow trout, sculpin; Warmwater:, white sucker, johnny darter, pumpkinseed Step 3: Complete detailed topographic survey of reaches Focus on in channel geometries Step 4: Develop River 2D model Hydraulic model produces distributed values of depth and velocity Step 5: Obtain/Develop Preference Functions Based on target species and others that may have some similar traits Focused on summer conditions, as this is the period of change. Substrate was uniform across reaches, therefore neglected. Step 6: Evaluate differences in HSI

7 Channel Survey This isn t your normal channel survey!

8 Hydraulic Model Development and Application Import Bathymetry Develop Model Mesh & Assign Manning s Coeff and Boundary Conditions (streamflow) Run and Export Velocity and Depth Values

9 Aquatic Habitat Classification Focus on velocity and depth USGS Study (Ozarks) linked habitat to Froude # Allows habitats to be identified and quantified

10 Aquatic Habitat Classification Habitat Froude # Range Add l Depth Criteria (cm) Add l Velocity Criteria (cm/s) Rapids 0.4+ >40 >20 (min) Riffle <40 >20 (min) Run >40 (min) >20 (min) Race < 40 >20 (min) Flat >75 Glide < 75 (min) Pool < 0.1 >75 (min) Shallow Pool < Edgewater < 0.1 < 25 (max) <15 (max)

11 Habitat Characterization I2 Reach 0.46 m 3 /s

12 Habitat Characterization I2 Reach 0.10 m 3 /s

13 Response in Habitat Classification Scenario Baseline Water Shift to GW Increased Increased No pumping Taking Takings Scenario #1 Scenario #2 Flow Rate (m3/s) Rapids Riffle 4% 4% 4% 3% 2% Run Race 22% 24% 24% 15% 9% Flat Glide 55% 55% 55% 48% 25% Pool Shallow Pool 2% 1% 1% 10% 14% Edgewater 16% 16% 16% 21% 48% Total change in Wet Area 0% 2% 2% 4% 12% Habitat shifts provides context into sensitivity of habitat to water withdrawals

14 Habitat Preference Functions Describe a species preference to depth, velocity and substrate conditions. Preferences vary with life cycle Limited information, but it is available If not available, don t discount knowledge from experienced biologists! Brook Trout Preference Curves U.S. Department of Interior, 1982

15 Adult Depth Suitability I2 Reach Flow 0.46 m 3 /s

16 Adult Velocity Suitability I2 Reach Flow 0.46 m 3 /s

17 Overall Adult Suitability Ranking I2 I2 Reach Flow m 3 /s 3 /s

18 Habitat Suitability Index Results Ranking Baseline Water Increased Scenario Increased Scenario No pumping Shift to GW Takings Taking #1 #2 Flow Rate (m3/s) Depth Velocity Overall Adult

19 Summary and Other Considerations Habitat Suitability Assessments allow one to investigate the habitat response to a change Modified streamflow Modified channel morphology Only one aspect of an environmental flow regime Suitability of physical habitat Other aspects Thermal refuge Food production Channel maintenance flows (pool scour, bed mobilizing, channel forming flows)

20 Acknowledgements Ministry of Natural Resources and Forestry Scott Bates Water Budget Program Analyst, Surface Water Monitoring Centre Andy Beaton Surface Water Analyst, Surface Water Monitoring Centre Nottawasaga Valley Conservation Authority Ryan Post Hydrogeologist Source Protection Coordinator