Challenges with Light Analysis and Submerged Aquatic Vegetation
Submerged aquatic vegetation (SAV) are marine, estuarine, and riverine angiosperms, and macrophytes. These are plants that grow to the surface of shallow water and only emerge from the surface at low tide. They serve vital ecosystem services in the shallow waters by providing refuge for small fish and shellfish from larger predators. They also provide food for birds, fish, and mammals, absorb wave energy and nutrients, produce oxygen, and improve water clarity. Moreover, they help to settle suspended sediment in the water and stabilize bottom sediments. A critical factor in the health of SAV is light penetration for their photosynthesis. Man-made and naturally occurring processes can negatively impact turbidity and the health of SAVs.
Solutions Provided by EEMS
For cases involving macrophytes or aquatic vegetation, EEMS provides a number of features to assist in analysis of light penetration, such as displaying percentage of bottom irradiance. Users can determine which parts of the domain fit the habitat criteria and calculate statistics for those cells.
EFDC+ also provides the necessary tools to allow the modeling of SAV with its rooted plant and epiphyte sub-model (RPEM). This model allows a variety of combinations for RPEM, including enabling simulation of rooted plants or epiphytes; enabling epiphytes growing on rooted plants; enabling the RPEM – Water Column Nutrient Interaction; and enabling RPEM – Sediment Diagenesis Interaction. EE contains a host of tools for post-processing data and helpful visualization of results.
Examples of Studies Done with EEMS
Little Bow River Water Quality Model Development
EEMS was used to model the Little Bow River Alberta, Canada. The modeling domain included the upper Little Bow River main stem from the town of High River to upstream of Travers Reservoir, an in-stream Twin Valley Reservoir, and its tributary Mosquito Creek. The model was calibrated to accurately represent the system hydrodynamics and water quality (flow, temperature, dissolved oxygen and nutrient dynamics). Rooted aquatic plants and epiphytes were simulated in the model. A sensitivity analysis was conducted and water quality loading under various scenarios was calculated.
Instream Hydrodynamic and Water Quality Model for the Oldman River
DSI supported AESRI, Canada, to develop an instream hydrodynamic and water quality model of Oldman River. EFDC was selected for the Oldman River system by client as the use of this model application allows the evaluation of contaminant loadings, and their effect on river water quality, under various management and engineering options in sub-basin. Additionally, the dynamic water quality model is the basis for a toxic integrated model and scenarios of the Oldman River to support watershed and regional planning. Constituents modeled included 2D depth averaged hydrodynamics, water temperature, dissolved oxygen, organic carbon, organic and inorganic phosphorous nutrients, organic and inorganic nitrogen nutrients, and planktonic algae. A sensitivity study of the rooted aquatic plant and epiphyte module (RPEM) was also conducted.
Download Example EE Models
Download an example model and run with the free EEMS Demo Version.
This model is provided as a useful exercise in how to build a hydrodynamic and a water quality model, using available data, which is provided in the “Data” folder. The steps to do this are provided in the How-to-guides in the EE Knowledge Base. The final models are also provided for comparison.
