New Approaches to Watershed Modelling Using STELLA. WeSMART Conference, December 11, 2014 Heather Cray & Michael McTavish

Transcription

1 New Approaches to Watershed Modelling Using STELLA WeSMART Conference, December 11, 2014 Heather Cray & Michael McTavish

2 Ecosystem Modelling What are models and ecosystem models? Broadly, a model is a tool used to represent some feature of a larger, more complex system to help us better understand that system An ecosystem model generally studies the complex interactions between the biotic and abiotic features of ecological systems Generally interested in the movement of material and energy through the system (e.g. water, nutrients, organisms, etc.)

3 Modelling in Complex Systems in STELLA This model was constructed using STELLA (V ) from isee systems. Modeling and Simulation Software for Education and Research A tool for understanding systems dynamics (a methodology and modelling approach for exploring complex systems) Users construct models through a visual interface (equation layer generated automatically)

4 Modelling in Complex Systems in STELLA The visual layer of a STELLA model consists of 3 main elements: Stocks: state variables representing reservoirs of material, energy, populations, etc. Flows: movements between stocks Converters: auxiliary variables representing algebraic relationships, additional parameters, constants, etc., which typically modify how stocks/flows interact

5 Modelling in Complex Systems in STELLA An example of a simple population model constructed in STELLA using stocks, flows, and converters Information that we possess: Initial population size Estimated birth rate individual -1 Estimated survivorship/death rate

6 Modelling in Complex Systems in STELLA An example of a simple population model constructed in STELLA using stocks, flows, and converters Information that we possess: Initial population size Estimated birth rate individual -1 Estimated survivorship/death rate

7 Modelling in Complex Systems in STELLA An example of a simple population model constructed in STELLA using stocks, flows, and converters Information that we possess: Initial population size Estimated birth rate individual -1 Estimated survivorship/death rate Population(t) = Population(t - dt) + (Births - Deaths) * dt INIT Population = 50 INFLOWS: Births = Population*Birth_Rate OUTFLOWS: Deaths = Population*Death_Rate Birth_Rate = 0.3 Death_Rate = 0.2

8 Modelling in Complex Systems in STELLA An example of a simple population model constructed in STELLA using stocks, flows, and converters With sufficient data, future conditions can be (cautiously) extrapolated through time. (In this example we follow the growth of an initial population N 0 = 50 through 20 years)

9 The Pine River Watershed Located in Southern Ontario along the eastern shore of Lake Huron in Bruce County Sub-watershed of the Lake Huron Basin 160 km 2 of mixed land cover dominated by agriculture with smaller areas of forest, wetlands, and urban infrastructure

10 The Pine River Watershed Land Use Historically over 90% forest cover consisting of mixed upland stands Current forest cover is below 5% Soil is primarily till with a few bands of sandy deposits Due to its high agricultural productivity, much of the land has been cleared of wetlands and forests and remaining woodlots are fragmented

11 Overall Model Structure When asked to construct an ecosystem model for the Pine River Watershed, we went looking for existing environmental data

12 Overall Model Structure When asked to construct an ecosystem model for the Pine River Watershed, we went looking for existing environmental data Soils Invasive Species Etc. Urbanization Forest Cover Riparian Cover Wetlands Etc. Nutrient Loading Habitat Biodiversity Etc. Drainage decades of monitoring data exist for the Pine River Watershed, mostly in disconnected datasets.

13 Overall Model Structure We selected key parameters of interests and organized them into connected Modules (model components which can run independently or jointly with other modules): Background Modules provide user-controlled inputs which modify the behaviour of the Primary Modules.

14 Overall Model Structure The Calendar Module tracks the progression of months (the basic time step for the model) and is used to cue seasonally-specific events. Month Counter Month 1 January 2 February 3 March 4 April 5 May 6 June 7 July 8 August 9 September 10 October 11 November 12 December Modules Hydrology Turkey Deer Demographics Demographics Precipitation; Evapotranspiration; Stream Discharge - - Precipitation; Evapotranspiration; Stream Discharge - - Precipitation; Evapotranspiration; Stream Discharge - - Precipitation; Evapotranspiration; Stream Discharge Nest Initiation - Precipitation; Evapotranspiration; Stream Discharge Spring Hunting - Precipitation; Evapotranspiration; Stream Discharge - - Precipitation; Evapotranspiration; Stream Discharge - - Precipitation; Evapotranspiration; Stream Discharge - - Precipitation; Evapotranspiration; Stream Discharge - - Precipitation; Evapotranspiration; Stream Discharge Fall Hunting - Precipitation; Evapotranspiration; Breeding; Hunting - Stream Discharge Season A Precipitation; Evapotranspiration; Stream Discharge - Hunting Season B

15 Land Use Module Land use change and habitat loss have been identified as leading threats to biodiversity and sustainability within the Pine River Watershed Different land classes have various consequences for animal habitat, hydrology, etc. Wetlands Impervious surfaces Cropland vs pasture (erosion, fertilizer, pesticide ) 5 classes used: Wetland, Woodland, Urbanized, Cropland, and Pasture

16 Land Use Module The Land Use Module provides the breakdown of all land within the modelled area across 5 land use classes. Land class areas were calculated for current conditions but can be modified by: 1) setting new fixed values; or 2) setting fixed rates of land use change between classes (e.g. 2% cropland to urbanized per year).

17 Land Use Module Where do we find data? Stats Canada agricultural census Spatial analysis of satellite imagery Local studies and reports How is this useful? 1. Set stocks to current state of land cover 2. Simulate change by increasing or decreasing proportions 3. Use the land use module to provide input into hydrology and population Other modules respond dynamically to changes in land use

18 Hydrology Module Models the hydrology of the Pine River Watershed, as well as the total phosphorus exported into Lake Huron at the Pine River outflow Calculates runoff, precipitation, evaporation, transpiration, subsurface flow, and river discharge into Lake Huron As each land use will have different effects on how precipitation moves through the watershed, Land Use proportions inform the runoff calculations The Hydrology module is subdivided into five subsystems: 1. Precipitation (Environment Canada data) 2. Evapotranspiration (nearby weather station) 3. Runoff 4. Subsurface Flow 5. River Flow

19 Hydrology Module - Runoff Runoff was calculated for each Land Use soil type based on surficial geology and vegetation cover Runoff curve value Runoff term used for Subsurface Flow and River Flow subsystems Runoff

20 Hydrology Module Flow and discharge For the purposes of this model, we have assumed that runoff associated with agricultural land use and fertilizer addition is the primary source of phosphorous loading into the watershed Flow and discharge

21 Hydrology Module Customization 1. Evaluating habitat suitability for benthic and fish communities By including a more spatially-correlated dataset to represent the waterways (i.e. tributary versus main channel, water depths and widths, substrate, water temperature, velocity) This could be within habitat brackets (high : low quality) or for particular target species, such as trout or bass 2. Total Suspended Solids (TSS) in the water column based on the velocity and volume of water at peak flood periods Would require estimates of surface runoff which are spatially correlated to particular crop types and periods of fallow versus exposed soil 3. Potential Erosion based on topographic and slope variables, water velocity and volume, presence/absence/quality of riparian vegetation, and livestock access to stream Estimate topsoil loss and facilitate modelling various management schemes, including ongoing and potential riparian restoration options 4. E. coli and waste treatment options Point sources and mitigation options for the management of E. coli could be incorporated into the model using bacteria life cycle data and current/future manure and fertilizer regimes

22 Demographics Modules Two of the Primary Modules are demographic models for two species of interest within the watershed: Eastern Wild Turkey (Meleagris gallopavo silvestris) White-Tailed Deer (Odocoileus virginiana) Both modules are designed to provide insight into how human activities (land use change & hunting) impact animal populations.

23 Demographics Modules Population model for Pine River Watershed White-Tailed Deer

24 Demographics Modules Eastern Wild Turkey 3 age classes (poult subadult adult) Primary flows: birth, maturation, death (hunting & natural) Details such as maturation rates, sex ratio, clutch size, habitat requirement, mortality rates, etc., can be set manually or modelled from existing datasets An age- and sex-structured demographic model for the eastern wild turkey

25 Demographics Modules Eastern Wild Turkey Approximate carrying capacity estimated based on habitat requirements and land use Spring and fall hunting seasons contribute differently according to age class and sex (based on available harvest records) Model users may manipulate numbers of hunters, licenses, etc. Easily adapted to different species of interest (e.g. fish and fishing regulations)

26 Applications of Ecosystem Modelling What can we do with an ecosystem model? Structure & Function Prediction & Sensitivity

27 Applications of Ecosystem Modelling

28 Applications of Ecosystem Modelling

29 Applications of Ecosystem Modelling

30 Applications of Ecosystem Modelling

31 Applications of Ecosystem Modelling

32 Applications of Ecosystem Modelling

33 Applications of Ecosystem Modelling What can we do with an ecosystem model? Structure & Function Prediction & Sensitivity

34 Applications of Ecosystem Modelling What can we do with an ecosystem model? Structure & Function Prediction & Sensitivity Identify Key Features

35 Applications of Ecosystem Modelling What can we do with an ecosystem model? Structure & Function Prediction & Sensitivity Identify Key Features Identify Missing Features

36 Applications of Ecosystem Modelling What can we do with an ecosystem model? Structure & Function Prediction & Sensitivity Identify Key Features Identify Missing Features Interactions & Connectivity

37 Conclusions Ecological Monitoring What does ecosystem modelling have to offer?

38 Conclusions Ecological Monitoring What does ecosystem modelling have to offer? Improve understanding of ecosystem structure & function

39 Conclusions Ecological Monitoring What does ecosystem modelling have to offer? Improve understanding of ecosystem structure & function Organize and categorize existing data

40 Conclusions Ecological Monitoring What does ecosystem modelling have to offer? Improve understanding of ecosystem structure & function Organize and categorize existing data Identify gaps in data

41 Conclusions Ecological Monitoring What does ecosystem modelling have to offer? Improve understanding of ecosystem structure & function Organize and categorize existing data Identify gaps in data Identify connectivity between elements

42 Conclusions Ecological Monitoring What does ecosystem modelling have to offer? Improve understanding of ecosystem structure & function Organize and categorize existing data Identify gaps in data Identify connectivity between elements Visual representation of a complex system