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Development of a Watershed Modeling System for Fort Benning Using the U.S. EPA Basins Framework

Client: Strategic Environmental Research Development Program (SERDP), Arlington, VA

Description

Watershed modeling systems are increasingly becoming critical to support military readiness and to ensure sustainability on military installations. Sustainability involves balancing the land use and resource protection within the carrying capacity of the watershed. The SERDP's Ecosystem Management Project (SEMP) has identified the need to provide Fort Benning, Georgia (and eventually other military installations) with "immediately usable and effective models" that can be implemented for compliance and long-term watershed planning for sustainability of the installation using adaptive management protocols. The most versatile tool available for evaluating the relationships between land and water uses and management practices to endpoint responses is a watershed modeling system that includes a suite of models and support tools, and an expandable repository of environmental data. The variety of management issues facing Fort Benning and other installations requires that the watershed model(s) be dynamic and comprehensive in nature.


Figure 1: Tank Trail in Ft. Benning

Objective

The objective of AQUA TERRA's 4-year effort is to identify, adapt, and develop watershed management model(s) for Fort Benning that address impacts on watershed hydrology and water quality and related ecosystem processes and outcomes resulting from military activities and natural resources management. The use and enhancement of the U.S. EPA BASINS modeling system will be the cornerstone of a dual-pathway approach. Project objectives are being met by concurrently pursuing two interrelated 'paths', an application path and a research path. The application path features integration of existing SERDP products into BASINS; development of an initial calibrated model of Fort Benning; and identification of apparent model/system limitations. The research path will design and implement model enhancements that improve on recognized watershed model weaknesses; more fully develop capabilities relevant to representing and evaluating military land uses and activities; and develop and apply modeling strategies that demonstrate the military-enhanced BASINS capabilities. A calibrated model of Fort Benning will be developed, and the model will have a high degree of transferability to other installations for use in adaptive management. Numerous products from previous SERDP projects will be integrated into an open-source modeling system (i.e. BASINS) that has extensive national scope data useful to installation managers, widespread use, strong institutional support, and highly developed user support features.

Our Project Team includes AQUA TERRA Consultants, US Army Corps of Engineers Engineer Research and Development Center (ERDC) and Eco Modeling. AQUA TERRA is the lead organization with responsibility for overall project management and technical direction, as well as specific technical tasks related to the watershed model enhancement, software development, and model application. ERDC has primary responsibilities for evaluating military-specific concerns related to science, land use and management needs from an environmental engineering perspective, along with being the focal point for merging data tools and methods/models into BASINS from SEMP and a broader range of completed and ongoing SERDP projects. Eco Modeling is the lead in aquatic ecosystem model development and application, specifically with the AQUATOX model, along with providing technical direction for all project efforts related to deterministic aquatic ecosystem simulation.



Figure 2: Project Objectives

Modifications and Plans

After investigating eight research topics to determine which topics would most benefit the Fort Benning model, it was recommended that significant model changes be made to accommodate modeling at multiple spatial scales, improve representation of channel phenomena, and develop and integrate a forest canopy compartment into the Fort Benning Model. AQUA TERRA is developing a generalized capability within HSPF that enables integrated use of small-scale high resolution models within a larger scale watershed model framework. The first demonstration of this capability will utilize USDA's WEPP:Road model to represent runoff and sediment erosion from Fort Benning's unpaved roads. Enhancements to three general categories of channel phenomena will be implemented: flow, sediment transport, and bank erosion. In order to improve flow modeling the 3D hydrodynamic model Environmental Fluids Dynamics Code will be added to HSPF, and to improve sediment transport, the SEDZLJ sediment transport model developed by Jones and Lick will be added to HSPF. Improved capabilities for modeling bank erosion modeling will be achieved by adding an empirical-based bank erosion model to HSPF such that the estimated sediment mass from the eroding bank is added to the sediment bed in the grid cell where the eroding bank is located. AQUA TERRA will implement improvements in modeling canopy processes, fire impacts, and other forest management practices, as follows: 1) refining the canopy processes in HSPF to accommodate multi-level forest conditions consistent and compatible with the current representation, and based on relatively simple model inputs comparable to the current HSPF formulations, i.e., adding another canopy (or multiple) layer for understory vegetation, and 2) refining the ability to accommodate fire impacts, either through improved model capabilities or development of a separate 'fire' module to oversee and impose adjustments to reflect fire occurrence, intensity, and areal distribution within the watershed.

In the final two years of the project refined strategies and model scenarios will be developed that take advantage of the enhancements to the data base, tools and watershed models that have been achieved throughout the first two years of the project. To better represent and evaluate activities and management issues at Fort Benning, the endpoints, indicators, and thresholds that were used for the preliminary model applications will be revisited. Assessment of additional endpoints at alternative scales will be considered. Approaches for comparing original model capabilities directly to enhanced model capabilities will be formulated.

The enhanced modeling strategies will provide a road map for the Project Team to develop and re-calibrate (if necessary) an enhanced comprehensive watershed management model for Fort Benning using the enhanced BASINS/HSPF watershed model. The preliminary Fort Benning Watershed Model will be refined to test/demonstrate the operation and significance of enhancements. Simulations performed using the pre-project BASINS capabilities will be repeated using the enhanced capabilities to demonstrate the impact of the code improvements and extensions. The resulting watershed modeling results will be suitable for input to the aquatic ecosystem models AQUATOX and will enable installation managers to evaluate ecological endpoints.

Technology Transfer

Among the strong features of the BASINS modeling system are the national extent of its supporting data base, and the system's development philosophy that produces/uses tools and models that can be applied to very different locations via selection of local time series and model parameter values that allow customizing each model application to fit its specific setting (climate, topography, soils, vegetation, ecohabitats). The BASINS' national scale databases and most of the model enhancements will likely support model applications at any location, recognizing that some local data and customization may be appropriate for specific sites. The degree of transferability of the Fort Benning application will be greatest in the local area and will decrease as the similarity of the Fort Benning setting to other military installation watersheds decreases.


Figure 3: Technology Transfer Opportunity

The Fall Line location of Fort Benning, in both the Piedmont and Coastal Plain provinces, makes it ideally suited as a starting point for transitioning to other installations. Since the Columbus Water Works has used BASINS in its watershed, water quality, and TMDL assessment efforts, including Upatoi Creek in its model configuration, the Fort Benning BASINS model will support a framework for regional efforts within the metropolitan Columbus area. In addition, the Fort Benning BASINS application will include parameters and conditions (climate, soils, vegetation, topography, etc.) reflecting characteristics of both physiographic provinces, with appropriate starting model values for applications to other Fall Line installations, like Fort Gordon, Fort Jackson, and Fort Bragg, and other installations throughout the state of Georgia including Coastal Plain installations at Fort Stewart and Camp Lejeune. With hundreds of past and ongoing applications in all regions of the US, the military-enhanced BASINS system will be well suited for potential use at all military installations across the country. The Transition Plan that will be developed for this project will address the increasing list of issues and enhancements required to transition the Fort Benning project products to installations across the country.


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