EFDC+ Hydrodynamic Model
Water Quality Modeling
Alberta Environment and Parks, Canada
Environment and Sustainable Resource Development, AEP
Dates of Performance:
The Little Bow River watershed is located in the headwaters of the Oldman River Basin in the southern region of the Province of Alberta. As a major tributary of the Oldman River, the Little Bow River receives diverted flow from Highwood River, direct precipitation, local runoff, municipal/industrial discharges. The Upper Little Bow River Basin occupies an area of approximately 3,491 km2. The watershed supports a wide variety of natural resources, including forests, minerals, wildlife, and agricultural lands.
To support flood mitigation work related to Highwood-Little Bow diversion system and Little Bow River, a model was developed as an assessment tool to evaluate the existing flow and water quality condition in the upper Little Bow River and potential impact of various flood related management plans. The Environmental Fluid Dynamics Code (EFDC) platform was selected for the Little Bow River system.
The main objectives of the modeling effort was to gather data to construct a computer simulation model of the upper Little Bow River main stem from the town of High River to upstream of Travers Reservoir, including an in-stream reservoir Twin Valley Reservoir and its tributary Mosquito Creek Bow River; ensure that the model accurately represents the system hydrodynamics and water quality (flow, temperature, dissolved oxygen and nutrient dynamics); conduct a sensitivity analysis; and assess performance of prediction of water quality loading by the running calibrated model under various scenarios conditions.
The model simulates: 2D-3D hydrodynamics, water temperature, dissolved oxygen, organic carbon, organic and inorganic phosphorous nutrients, organic and inorganic nitrogen nutrients, planktonic algae, macrophyte, and ice thickness. The water quality model computes the time and space dependent interactions of these constituents due to pollutant and nutrient loadings from a SWAT model. The model calibration period was from 2004 to 2012 and validation from 1997 to 2003. EFDC+ with Sigma Zed vertical layers was used for the calibration model in 2-D in the reach sections and in 3-D for the reservoir. The model was successfully calibrated for: flow on reaches, stratification in the Twin Valley Reservoir, temperature and DO; water quality state variables, algae, nutrients, phosphorous and carbon.
The calibrated model was used to simulate the scenarios for water management in the Little Bow River. Scenarios simulated included supporting Highwood Diversion Plan flow management, reservoir operation management, and WWTP effluent water quality improvement. The model can be used as a tool for analysis of future development of the water body.