Toward a Great Lakes Watershed Ecological Sustainability Strategy (GLWESS): Modeling Workshop. Lansing, MI May 3, 2012

Transcription

1 Toward a Great Lakes Watershed Ecological Sustainability Strategy (GLWESS): Modeling Workshop Lansing, MI May 3, 2012

2 Presentation Outline Overview of ecological concerns General modeling overview How models can support transactions Specific modeling tools SWAT watershed models Western Lake Erie Ecosystem Model (WLEEM) Model uncertainties/limitations Interaction with related modeling efforts Summary 2

3 Overview of Ecological Concerns Impact of degraded stream habitat and water quality on fish and macroinvertebrate indicators Watershed export of sediment and nutrients: Phosphorus (P), especially soluble reactive P Nitrogen (N) Suspended solids Eutrophication & sedimentation impacts in Western Lake Erie Basin (WLEB): Harmful algal blooms (HABs) Nuisance benthic algae in WLEB High sedimentation rates in Federal navigation channel 3

4 Toledo Harbor Sedimentation USACE has mandate to maintain Toledo Harbor Federal navigation channel Annual dredging volume: ~640,000 yd 3 (70% to open lake) Annual cost of dredging & disposal: $5 million Tributary Suspended Solids Other 6% Detroit 16% Maumee 78% 4

5 Harmful Algal Blooms & Nuisance Benthic Algae in WLEB Total Phosphorus October 2011 Microcystis bloom in Maumee River plume in western/central Lake Erie Other 5% Maumee 52% Detroit 43% Lyngbya wollei blooms wash up on western basin shoreline 5

6 General Modeling Overview (Modeling 101) 6

7 General Watershed Schematic Upland Processes Point Sources Non-Cultivated Lands Channel/Flood Plain Processes Cultivated Fields

8 General Watershed Model Irrigation Tile Drainage

9 Maumee River Watershed (major basins, flow routing) St. Joseph Tiffin Tiffin Flow Sediment Nutrients Lower Maumee Western Lake Erie Basin Lower Auglaize Blanchard Upper Maumee St. Marys Upper Auglaize

10 Modeling Algal Biomass Nutrients Loss by Grazing Light Algal Growth Algal Biomass Loss by Respiration Temperature Loss by Settling V da dt R growth R loss 10

11 Sediment Bed Water Column Sediment Transport Modeling Upstream Load Watershed Load (via surface runoff) Sediment Classes: Cohesive - 3 classes Non-cohesive - 3 classes Downstream Export Deposition Shear Stress (via waves/currents) Resuspension

12 Scientific Basis for Modeling Watershed Model: Decades of research & field studies of surface runoff, erosion, evapotranspiration, groundwater flow, etc. Development of empirical relationships to describe surface runoff and erosion behavior as a function of 1) land use/cover, 2) soil drainage, and 3) land slope Studies of sediment/nutrient transport in stream networks Aquatic Ecosystem Model: Decades of research on nutrients, algal dynamics, sediment movement, etc. in river and lake environments Well-established relationships between nutrient (N/P) availability, water clarity, and algal growth Adequate data required to constrain model processes 12

13 How Models Can Support Transactions 13

14 Linked Models to Support Transactions Linked watershed-lake model provides physically-based tool for estimating ecological benefits resulting from candidate agricultural management actions Watershed model: Quantify current delivery of sediment/nutrients to Lake Erie Attribute sediment/nutrient loads to specific land areas Predict sediment/nutrient loading reductions in response to management actions Aquatic ecosystem model: Quantify relationship between algal production and nutrient loadings (+ water clarity) Quantify reductions in algal production in response to reduced nutrient loading (via watershed management actions) Quantify sediment-related ecological endpoints: sedimentation in Maumee Bay/navigation channel, turbidity at water intakes 14

15 Flow, sediment, nutrient loading Transactions Ecological Endpoints Transactions Candidate Transactions Reverse auction Certification Improved Management Practices Type of practice(s) Affected land area Changes to crops, tillage, drainage, etc. Ecological Endpoints Improved Indices of Biological Integrity (IBIs) (various locations in stream network) Final Evaluation of Transactions Type Location(s) Funding *Relative ecological benefits *Bid ranking ($/lb algal reduction) Watershed Models (SWAT) Model Linkage Flow, sediment, nutrient Waterville Western Lake Erie Ecosystem Model (WLEEM) Reduced Nutrient & Sediment Delivery (@ tributary mouths) Reduced Algal Production and Sediment Problems in Western Lake Erie Microsystis blooms Sedimentation/turbidity 15

16 Modeling Tools: SWAT Watershed Model 16

17 Soil & Water Assessment Tool (SWAT) Developed in the late 1980s by NRCS-ARS Designed to simulate hydrology in large agricultural watersheds Simulates on a daily timescale: Hydrology (runoff, baseflow, channel routing) Sediment erosion & delivery to/from streams Nutrient delivery to/from streams Pesticide delivery Accounts for varying land use/cover, soils, management practices (e.g., tillage operations) 17

18 Irrigation SWAT Conceptual Diagram Precipitation Rainfall Snow Infiltration Snowmelt Surface Runoff Runoff (+ sediment & nutrient runoff) Streamflow Soil Storage Lateral Flow (+ dissolved nutrient load) Irrigation diversion Evaporation Evaporation Plant transpiration Tile Drainage (+ dissolved nutrient load) Soil transmission Percolation Routing downstream Shallow Aquifer Irrigation loss Evapotranspiration Seepage Groundwater Outflow (+ dissolved nutrient load) Irrigation Diversion Sediment deposition / erosion

19 Soil & Water Assessment Tool (SWAT) SWAT can represent: Water movement through all major pathways Sediment and nutrient yield (primarily via runoff) Relative improvements in hydrology & pollutant loading reductions resulting from watershed management actions SWAT can t represent: Every individual parcel / farm in the Maumee basin (due to data limitations, runtime constraints) Regional groundwater flow or deep groundwater storage 19

20 Soil & Water Assessment Tool (SWAT) Key Model Inputs: Climate (rainfall, air temperature, etc.) Physical (land use/cover, soil type, land slope) Fertilizer/pesticide application rates (& timing) Land management practices (e.g., tillage, tile drainage) Point source loads (location, magnitude) Key Model Outputs (available for any reach): Daily flow rate (m 3 /s) Total sediment loading (kg/day) Nitrogen & phosphorus loading (kg/day) Pesticide loading (kg/day) 20

21 Maumee SWAT Model - Subbasins Subbasin Scale: Based on USGS HUC-12 St. Joseph Tiffin Tiffin Average surface area: ~17,000 acres (70 km 2 ) Lower Maumee Lower Auglaize Blanchard Upper Maumee St. Marys Upper Auglaize 21

22 Tiffin River SWAT Model - Subbasins Subbasin Scale: Based on NHDPlus (medium resolution) Average surface area: 600 acres (2.4 km 2 ) 22

23 SWAT Hydrologic Response Units (HRUs) HRU #3 Outline of Subbasin Area HRU #2 Tiffin River HRU #4 HRU #1 HRU #3 HRUs represent multiple (non-contiguous) areas within subbasin with common characteristics: 1) Land use/cover 2) Soil drainage conditions 3) Land slope

24 Modeling Tools: Western Lake Erie Ecosystem Model (WLEEM) 24

25 Western Lake Erie Ecosystem Model (WLEEM) Developed by LimnoTech based on public domain modeling tools: EFDC (hydrodynamics, sediment transport water temperature) A2EM (water quality, eutrophication processes) Original funding provided by USACE-Buffalo District Continuing development funded by NSF Water Sustainability and Climate Project 25

26 EFDC-A2EM Modeling Framework Forcing Functions Wind, Temperature, Solar Radiation, Inflows, Bathymetry Forcing Functions Nutrients, Solids, Carbon, Biological ( phyto and zoo), Solar Radiation EFDC-SWAN Hydrodynamics A2EM Water Column Nutrient - Carbon Lower Food Web Temperature Dreissenids Cladophora Sediment Transport Initial Conditions For All Variables Sediment Nutrient - Carbon Material Flux

27 Western Lake Erie Ecosystem Model (WLEEM) Key Model Inputs: Bathymetry Tributary inflows Meteorological data (wind, air temperature) Sediment & nutrient loadings via watershed model (or data-based estimates) Parameters controlling key processes e.g., rate of algal growth Key Model Outputs: Nutrient concentrations (temporal and spatial profile) Biomass of different algal groups (temporal and spatial profile) Cyanobacteria (Blue-green algae) (Microcystis) Other good phytoplankton (e.g., Diatoms) Benthic algae (Lyngbya) Sedimentation rates and suspended solids profiles 27

28 Huron LMRM Grid Detroit Development Raisin Ottawa Stony Grid Characteristics 3D Curvilinear Grid 4,613 Grid Cells (max 10 layers) 26,387 Total Cells Maumee Cedar Portage

29 Navigation Channel Navigation Channel Maumee

30 WLEEM Chlorophyll-a Animation 31

31 Key Model Limitations & Uncertainties General sufficiency of watershed and lake datasets to support robust calibration of models Yield of sediment/nutrients from land vs. instream sources (e.g., bank or bed erosion) Attribution of sediment or nutrient loadings to different watershed land areas: Land use/cover conditions can change over time Ag practices can change over time (implementation & effectiveness) Other environmental conditions that affect algal growth (e.g., light, temperature, Dreissenids) 32

32 Interaction with Other Watershed Modeling Efforts 1. Tiffin River watershed modeling Funded via USACE s tributary modeling program - 516(e) LimnoTech currently developing model, preliminary calibration to occur in fall Will be used to inform reverse auction transactions in Tiffin watershed 2. WLEB Biological Endpoints Project (TNC/NRCS) Funded by Conservation Effects Assessment Project (CEAP) Involves development of a fine-scale SWAT model of entire Maumee basin ( NHDPlus scale) Expected to serve as the long-term model to inform GLWESS transactions across the full watershed 33

33 Summary How Models Interact with the Transaction Process 34

34 Using Model Results to Inform Transactions Provide guidance on areas to target for transactions Based on subbasin/hru nutrient yields in baseline model Evaluate candidate transactions & associated management actions: 1. Represent proposed changes to crop rotation, tillage practices, etc. as scenarios in SWAT model 2. Link changes in flow, sediment, nutrient loading to WLEEM 3. Calculate ecological benefit as predicted reduction in algal biomass production (i.e., lbs of algae biomass removed ) 4. Reverse auction bids (or other transactions) ranked based on cost-effectiveness with respect to algal biomass reduction 35

35 Using Model Results to Inform Transactions Example of ranking for reverse auction bids: Auction Bid Total Cost Estimated Algal Biomass Reduction (lbs) Cost- Effectiveness ($/lb) Final Bid Ranking Bid #1 $20,000 1,000 $20 2 Bid #2 $30,000 2,000 $15 1 Bid #3 $25,000 1,000 $

36 Flow, sediment, nutrient loading Transactions Ecological Endpoints Transactions Candidate Transactions Reverse auction Certification Improved Management Practices Type of practice(s) Affected land area Changes to crops, tillage, drainage, etc. Ecological Endpoints Improved Indices of Biological Integrity (IBIs) (various locations in stream network) Final Evaluation of Transactions Type Location(s) Funding *Relative ecological benefits *Bid ranking ($/lb algal reduction) Watershed Models (SWAT) Model Linkage Flow, sediment, nutrient Waterville Western Lake Erie Ecosystem Model (WLEEM) Reduced Nutrient & Sediment Delivery (@ tributary mouths) Reduced Algal Production and Sediment Problems in Western Lake Erie Microsystis blooms Sedimentation/turbidity 37

37 Questions/Discussion

38 Illustrative Example: Baseline Condition Problem: high runoff yield and sediment/ nutrient loading from cropland Conventional Fall Tillage Impacts: Mean summer baseflow: 100 cfs Mean phosphorus concentration: 300 ug/l Numbers are illustrative

39 Illustrative Example: Management Actions: 1. Conservation tillage reduces runoff and delivery of solids/nutrients Post- Management Activities 2. Buffer strips added to filter sediment & nutrients Improvements: Increased summer baseflow to 110 cfs Decreased phosphorus concentration to 100 ug/l Numbers are illustrative