Sediment erosion/runoff from both on-site and off-site land use can impair streams on military installations. On Fort Benning, military training, forested areas subjected to prescribed burning, unpaved roads, and construction are the primary sources of sediment loads. Urban encroachment or the expansion of urban centers upstream of the installation also can contribute to sediment loads measured in Fort Benning's streams. Military installations are concerned about sustaining their training lands, maintaining compliance (i.e., related to Clean Water Act, Energy Independence and Security  Act Section 438, and Endangered Species Act), and justifying budgets associated with best management practices (BMPs) designed to reduce sediment loads and their associated impacts.

The objective of this project was to provide a management tool for addressing watershed and water quality impacts of activities on military installations and initially for Fort Benning, while concurrently advancing the application of science to watershed modeling.

This project leveraged the U.S. Environmental Protection Agency (EPA) Better Assessment Science Integrating Point & Non-point Sources (BASINS) modeling system. The BASINS system contains a geographical information system (GIS) MapWindow, linkages to national databases, and data analysis and modeling codes. Collectively, the system is designed to support watershed-based analyses.

Two BASINS’ modeling codes were applied, the Hydrological Simulation Program– FORTRAN (HSPF) and AQUATOX, an aquatic ecosystem model. HSPF is a comprehensive model of watershed hydrology and water quality that allows the integrated simulation of land and soil runoff processes with in-stream hydraulics and sediment chemical interactions. HSPF provides a time history of the runoff flow rate, sediment load, and contaminant concentrations (i.e., nutrients and toxicants), along with a time history of water quantity and quality at any point in a watershed. AQUATOX extends the model endpoints of HSPF and simulates aquatic ecosystem processes to predict the environmental fate and ecological effects of environmental stressors on aquatic biota.

The research-focused component of this project investigated six areas of model enhancements. Based on the outcome and specific objective of each model enhancement investigation, most of these enhancements were incorporated in the Fort Benning Baseline Model, which then became the Fort Benning Enhanced Baseline Model (EBM).

1. – A hybrid modeling technique was developed that improves the ability to represent and evaluate combinations of sources and endpoints that have significantly different spatial scales. This technique incorporated the U.S. Forest Service Water Erosion Prediction Project (WEPP) Model and its interface WEPP:Road to generate sediment loads from unpaved roads at a finer scale than the HSPF watershed model. These finer-scale results were integrated into the watershed-scale HSPF model to more accurately depict the sediment contribution from unpaved roads.
2. – A methodology was developed to quantify the impact of military training activities on soil compaction and vegetation, so that its subsequent impacts on runoff and sediment washoff/erosion rates are modeled by adjusting infiltration rates and land cover based on the training intensity level.
3. – The combination of Environmental Fluid Dynamics Code (EFDC)/ Sediment transport algorithm for EFDC (SEDLZJ) and a bank erosion algorithm were investigated to determine the improvement to channel flows (particularly low and high flow events), sediment transport, and stream bank erosion.
4. – Linkages to ecological indicators using AQUATOX to simulate impacts of watershed management practices to indicators of aquatic health were investigated.
5. – Improved representation of hydrologic and water quality processes for aboveground vegetation and forest canopy compartments was developed.
6. – The value of incorporating additional flow data and rating curves at Fort Benning for calibration of component sub-watersheds, and implications for technology transfer to other military installations was investigated.

The hybrid modeling technique using WEPP and WEPP:Road, the military training intensity methodology, the improved forest canopy compartment, and data from additional rating curves became part of the Fort Benning EBM and its applications. Three sets of management alternative evaluations were conducted to demonstrate proof-of-principle of the Fort Benning EBM: (1) impacts of 2005 BRAC (Base Realignment and Closures) Implementations (i.e., increased area of heavy maneuver training exercises); (2) impacts of BMPs on a single maneuver training area (i.e., the Good Hope Mechanized Training Area, GHMTA); and (3) linkage to AQUATOX.

The simulation results from the proof-of-principle model applications indicate that the Fort Benning EBM performed within an acceptable/reasonable range; it is judged to be a reliable tool to account for cumulative impacts across the entire installation and to distinguish between off-site and on-site contributions. As expected, the model results from the 2005 BRAC Implementation management scenario identified unpaved roads and military training in heavy maneuver areas as the largest contributors to sediments loads. The proof-of-principle application for the GHMTA demonstrated that the model can be used to address specific management decisions regarding BMPs and has the scientific rigor to support budget analyses and requests for BMP implementation. The proof-of-principle application involving AQUATOX demonstrated a means for generating biotic endpoint information that can support regulatory compliance regarding aquatic species of concern.

The combined products of this project are encompassed in BASINS.MIL, the BASINS framework modified for military considerations and land uses. BASINS.MIL can be used by a military resource manager to identify the options for data, methodologies, and software to build an HSPF model for a military installation. The transferability of BASINS.MIL includes all of the national extent of BASINS supporting data bases, and the system’s development philosophy uses tools and models that can be applied to 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).

Watershed models can be valuable tools to manage Department of Defense (DoD) operations, activities, and lands to avoid or minimize impacts to wetlands, groundwater, and surface waters or adjacent to installations. However, a significant financial investment associated with data requirements and expertise is needed to develop and apply a watershed model on an installation. Under the current budget allocation process on DoD installations, funding must be strictly connected to a specific regulatory requirement and need. Thus, the tool used for a watershed modeling approach needs to be accepted by the regulatory community and designed to address the key regulatory concerns. The BASINS modeling system – developed by EPA to address Clean Water Act issues – fulfills this fundamental requirement. However, before BASINS.MIL is fully transferable, in-depth modeling applications that span the full capability of the military-enhanced modeling system and a more cost-efficient development of a baseline model on another military installation are needed to transition the technology toward full acceptance and utilization across DoD.