Modeling Workgroup

Scope and Purpose

The Chesapeake Bay Program integrated models include simulations of the airshed, watershed, estuary, living resources, and climate change. These integrated models assess effects of current and proposed watershed management on changes in nutrient and sediment loads delivered to the Bay, and the effect those changing loads have on water quality and living resources. The CBP Models assist CBP decision-makers in estimating the collective actions needed to achieve State and Federal water quality standards necessary to restore the Bay.

Core Values

The Modeling Workgroup has a responsibility to the Chesapeake Bay Program Partnership to provide state-of-the-art decision-support modeling tools that are built through community and participatory principles. The responsible planning and management of resources to provide the best available decision-support modeling tools requires the Modeling Workgroup members and participants to adhere to the core values of:

• Integration - Integration of most recent science and knowledge in air, watershed, and coastal waters to support ecosystem modeling for restoration decision making.
• Innovation - Embracing creativity and encouraging improvement in the development and support of transparent and robust modeling tools.
• Independence – Making modeling decisions on the basis of best available evidence and using the most appropriate methods to produce, run, and interpret models, independent of policy considerations.
• Inclusiveness - Commitment to an open and transparent process and the engagement of relevant partners, that results in strengthening the Partnership’s decision making tools.

Overall CBP Model Framework

The CBP model framework is designed to address questions of how Chesapeake Bay water quality will respond to changes in watershed and airshed management actions. In the first step of model scenario development, scenario management actions are interpreted by several models, including the Land Use Change Model, the Airshed Model, and Scenario Builder to produce input to the Watershed Model, as shown in the figure below. The CBP Land Use Change Model, predicts changes in land use, sewerage, and septic systems given changes in land use policy. The Airshed Model, a national application of Community Multiscale Air Quality Model (CMAQ), predicts changes in deposition of inorganic nitrogen due to changes in emissions. The Scenario Builder software combines the output of these models with other data sources, such as the US Census of Agriculture, to generate inputs to the Watershed Model. The Phase 5.3 Watershed Model predicts the loads of nitrogen, phosphorus, and sediment that result from the given inputs.The estuarine Water Quality and Sediment Transport Model (WQSTM) (also known as the Chesapeake Bay Model) predicts changes in Bay water quality due to the changes in input loads provided by the Watershed Model. As a final step, a water quality standard analysis system examines model estimates of DO, chlorophyll, and water clarity to assess in time and space the attainment of the Bay living resource-based water quality standards.

Additional information can be found at:

• CAST
• Phase 6 Modeling Tools
• Model Fact Sheet