US EPA

EPA announced the release of VELMA 2.1 Model and accompanying supplemental user's guide (Apr 2022) on the EPA website. EPA's VELMA tool helps assessor's model effective decisions for a wide array of environmental issues. It is a spatially explicit ecohydrological watershed model that planners can use to visualize the effects of their decisions. VELMA can be used to help improve the water quality of streams, rivers, and estuaries by making better use of both natural and engineered green infrastructure (GI) to control loadings from point and nonpoint sources of pollution. It is designed to help users assess green infrastructure options for controlling the fate and transport of water, nutrients, and toxics across multiple spatial and temporal scales for different ecoregions and present and future climates. VELMA also addresses GI maintenance and longevity to predict how once-effective riparian buffers can fail, depending upon contaminant loads, soil properties, changes in climate and other factors. VELMA was designed for use by communities, land managers, policy makers, and scientists and engineers.

Updates

The VELMA ecohydrological model has been updated from version 2.0 to 2.1 for assessing the effectiveness of green and gray infrastructure options for reducing storm water contaminant loads to aquatic systems. Details of the hydrological and biogeochemical processes controlling spatial and temporal dynamics of the fate and transport of 6PPD-Quinone and other toxins from points of deposition to stream and estuary are poorly understood. This VELMA update includes high-resolution (10-m) spatiotemporal estimations and animations of urban contaminant fate and transport for various alternative green and gray infrastructure treatments.

Note: View VELMA disclaimer following download of the model.

Background

VELMA helps communities, land managers, policy makers and other decision makers assess the effectiveness of GI options for improving water quality of streams, rivers and estuaries. VELMA predicts how natural and engineered green infrastructure options control the fate and transport of water, nutrients and toxic chemicals across multiple spatial and temporal scales – from plots to basins, from days to centuries.

VELMA also quantifies how different GI strategies affect ecosystem service co-benefits and tradeoffs – that is, the ecosystem’s capacity to simultaneously provide clean water, flood control, food and fiber, climate (greenhouse gas) regulation, fish and wildlife habitat, etc.

VELMA is a spatially distributed, eco-hydrological model that links a land surface hydrology model with a terrestrial biogeochemistry model for simulating the integrated responses of vegetation, soil, and water resources to interacting stressors. For example, VELMA can simulate how changes in climate and land use interact to affect soil water storage, surface and subsurface runoff, vertical drainage, evapotranspiration, vegetation and soil carbon and nitrogen dynamics, and transport of nitrate, ammonium, dissolved organic carbon and nitrogen, and contaminants to water bodies. VELMA differs from other existing eco-hydrology models in its simplicity, flexibility, and theoretical foundation. The model has a user-friendly Graphical User Interface (GUI) for easy input of model parameter values. In addition, advanced visualization of simulation results can enhance understanding and communication of results and underlying concepts.

U.S. EPA. Visualizing Ecosystem Land Management Assessments (VELMA) 2.1 Modeling Tool. U.S. Environmental Protection Agency, Washington, DC, , 2022.