PLOT OF THE MONTH
Environmental Homeland Security
Herndon, VA
Contributed by:
Sorab Panday, Ph.D. Director of Research & Development
Don DeMarco, Project Hydrogeologist
HydroGeoLogic, Inc.
Simulation and Animation Technology for Addressing Environmental Homeland Security Concerns.
ASSERT technology, Advanced simulation to assess the Status and Security of the Environment in Real-Time, was proposed to meet specific Environmental Protection Agency (EPA) water quality objectives, achieve specific U.S. Navy real-time forecasting objectives, and attain national goals to develop forecasting technology to support homeland security.
The plot of the month features results from a rigorous, mass conservative, fully-coupled simulation of surface water and groundwater with chemical transport on the Mobile and connected rivers, estuaries, bays and aquifers in Alabama.
Notable features of the simulation results include:
- A contaminant release in the surface water and groundwater systems upstream of Mobile Bay.
- Pollutants are carried downstream in the river and in the subsurface aquifers.
- A simulated storm causes overland runoff, drastic river fluctuations and flooding.
The pollutants are spread into Mobile Bay and onto the land surface where the river banks overflow.
Environmental problems that require quantification of the entire hydrologic cycle, such as those listed on the left, have received increased attention recently. This awareness has grown as water management practices have evolved in response to population growth and improved technologies.
Problems involving simulation of the complete hydrologic cycle have previously presented significant modeling challenges, primarily because of either model or computational limitations. Earlier models quantified individual hydrologic components using simplified procedures that dangerously compromised details of the flow physics (e.g., unit hydrograph, empirical formulas). Furthermore, models based on complex multidimensional governing equations had not received much attention because of their computational, distributed input and parameter estimation requirements.
Today with the availability of powerful personal computers, efficient computational methods and sophisticated Geographic Information Systems (GIS), remote sensing and advanced visualization tools such as Tecplot, the hydrologic community is realizing the tremendous potential and utility of physically based numerical simulators.
Intense simulated rainfall causes the Mobile river to flood its banks and spread polluted water across the floodplain. Surface-water and groundwater models such as this are used in support of environmental restoration, water resource assessment and management, human health and ecological risks evaluation, and contaminant hydrogeology.
Recognizing the increasing impetus for numerical simulation of complex groundwater-surface water interactions, HydroGeoLogic, Inc. was motivated by the challenge to develop a state-of-the-art, comprehensive, physically-based spatially-distributed model that overcomes both the functional and computational limitations of previous models.
The result of HydroGeoLogic's efforts was the development of MOD-HMS (MODFLOW-Hydrologic Modeling System). MOD-HMS integrates all components of the hydrologic cycle in a single model, that utilizes a rigorous, mass conservative modeling approach having fully coupled the surface water flow equations with the 3-D, variably saturated groundwater flow equations. This approach is significantly more robust than previous conjunctive approaches that rely on linkage of separate surface water and groundwater codes. The fully implicit coupling approach used by MOD-HMS provides for a mass conserved solution scheme essential for systems with strong interactions between regimes. MOD-HMS has additional capability for contaminant transport.
MOD-HMS system conceptualization.
The Mobile Bay project was contracted by the EPA to demonstrate the utility of MOD-HMS as a forecasting tool in support of Homeland Security. ASSERT is a collaborative effort between HydroGeoLogic, Inc., HydroQual and Los Alamos National Laboratories.
Current and future benefits of ASSERT include:
- Evaluation of human-health and ecological risks.
- Improved short- and long-term forecasting of coastal conditions.
- More accurate simulation of environmental quality using a comprehensive, physically based modeling approach.
- Ability to predict the impacts of a wide range of potential environmental security threats.
- Applicability in strategic planning, preparedness assessment, and development of emergency response measures.
Tecplot and advanced visualization capabilities are critical components of ASSERT technology. Images and animations help conceptualize the problem and results, and there is often the need to display several integrated sets of data simultaneously (for example, contaminant concentrations, surface elevations, rainfall, river fluxes, river depths, hydraulic head contours). Tecplot allows HydroGeoLogic to do this efficiently.
For more information on HydroGeoLogic, Inc. or the capabilities of MOD-HMS, please contact Sorab Panday or Don DeMarco.