Simulating Biota in EFDC+
In our earlier water quality blogs, we provided a preview of new features in the upcoming version of EEMS which will include unlimited phytoplankton and zooplankton classes. In this blog, we will discuss the biota modeling capabilities of EFDC+ along with other contemporary models. We will also show some preliminary results from the enhanced EFDC+ modeling capabilities.
Biota in waterbodies include aquatic autotrophs that use nutrients and energy to make their own food, and higher trophic-level organisms that consume these autotrophs. The organisms in the biota may be unicellular or multi-cellular and span the biological domains and kingdoms of life. Each of these can then further be classified into many categories that include thousands of species.
Water quality modeling in waterbodies involves simulating the biochemical transformation of nutrients and their movement through several water layers, sediment bed layers, and the aquatic biota. Each available modeling package simulates the biological and chemical processes occurring in waterbodies in different ways, depending upon the level of complexity of the model, and the modeling domain. The usefulness of these models mostly depends upon the final objective of the modeling exercise and the availability of data.
Some notable models are listed below.
HSPF – HSPF is a hydrologic and water quality simulation program, typically used at the watershed scale. It simulates the waterbody as a unidirectional mixed reach, and biochemical processes are simulated in three different routines.
- Phytoplankton – free-floating photosynthetic material
- Benthic algae – photosynthetic materials attached to the waterbody bed
- Zooplankton – zooplankton that feed on the phytoplankton
This formulation is simplistic and does not include any further species breakdown beyond these general categories.
EFDC+ – EFDC+ is a 1-, 2-, and 3-dimensional fully coupled hydrodynamic model that includes a water quality component derived from CE-QUAL-ICM. Until version 10.2, EFDC+ was limited to simulating up to three phytoplankton types (cyanobacteria, diatoms and green algae) and one macroalgae group. In addition, it has a sub-model for aquatic rooted plants and epiphytic algae growing on plant shoots. EFDC+ also includes a full sediment diagenesis model to simulate nutrient cycling among the biota and sediment bed.
In the natural world, however, multiple dominant species of algae, plants, and animals (e.g., zooplankton) may be present in a waterbody and require detailed modeling. The original limits of EFDC on the number of algal species and animals that could be modeled was not practical in some situations. To eliminate these issues, EFDC+ version 10.3 will now include a generic formulation for “macrophytes and algae” groups and zooplankton groups. This will give users the flexibility to model unlimited algal species and consider the role of zooplankton both as grazers that control algal population and as a food source for higher trophic-level organisms in a waterbody.
In EFDC+ 10.3, these “macrophytes and algae” interact with each other in their competition for nutrients and light. The model considers the preferences of zooplankton species with respect to other macrophyte and algae species. To verify these enhancements to EFDC+, a model of Pearl Lake, Minnesota, was built using EFDC+ and compared to a 2014 study carried out by USGS which used CE-QUAL-W2 (Smith et al, 2017). This earlier study assessed the algal community dynamics, water quality, and fish habitat suitability in Pearl Lake, which is an agricultural land-use dominated lake. The CE-QUAL-W2 study had successfully predicted water temperature, dissolved oxygen, as well as captured algal dynamics with four general groups: (1) diatoms, (2) green algae, (3) cyanobacteria, (4) haptophyta. These results were also replicated in the model simulated using EFDC+10.3.
Animations illustrating the change in temperature and concentrations of different algal classes modeled using EFDC+10.3 (testing version) in Pearl Lake, Minnesota, using EFDC+ (Left: plan view. Right: profile view).
WASP – WASP is a dynamic compartment-modeling program for aquatic systems, including both the water column and the underlying benthos. It can be used to model upto five classes of phytoplankton and three classes of macroalgae in one-, two-, or three-dimensional systems. In addition to the biochemical processes, WASP also includes a detailed sediment diagenesis model.
WASP needs to be linked with an external hydrodynamic and sediment transport model for flow, velocity, temperature, salinity, sediment, etc.
CE-QUAL-W2 – CE-QUAL-W2 or W2 is a two-dimensional, laterally averaged, hydrodynamic and water quality model. W2 has the flexibility to simulate any number of phytoplankton or epiphyton groups. W2 can also simulate multiple zooplankton species and it includes a full sediment diagenesis model.
QUAL-2K – QUAL–2K is a one-dimensional river and stream water quality model. It simulates a single species of phytoplankton and benthic algae.
We will keep on sharing our progress and new results as the testing process continues. Feel free to reach out to our experts, if you have questions.
Talk to the experts!
Paul Craig, PE
President and Senior Consultant
Tran Duc Kien, Ph.D
Water Resources Engineer
Smith, Erik A., Richard L. Kiesling, and Jeffrey R. Ziegeweid. Water-Quality Models to Assess Algal Community Dynamics, Water Quality, and Fish Habitat Suitability for Two Agricultural Land-Use Dominated Lakes in Minnesota, 2014. Report. Scientific Investigations Report. Reston, VA, 2017. USGS Publications Warehouse.