Watershed Approach to Mitigating Hydrologic Impacts of Transportation Projects: Conduct of Research Report (2022)

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268 Appendix B. Watershed Model Summaries This appendix describes hydrological models that are potentially applicable for evaluating project impacts and out-of-kind mitigation techniques within a watershed context. An overview of HSPF, SWMM, SWAT, SUSTAIN, and WMOST is provided along with additional references for the interested reader. In addition, the WMS, is available to State DOTs by a license agreement with the FHWA. WMS serves as a pre- and post-processor for HSPF, GSSHA, SWMM, and other models but it does not represent a distinct watershed modeling tool itself. B.1. HSPF HSPF is a comprehensive package for simulating watershed hydrology and water quality for a wide range of conventional and toxic organic pollutants. With its predecessors dating back to the 1960s, HSPF is the culminating evolution of the Stanford Watershed Model (SWM), watershed- scale Agricultural Runoff Model, and Nonpoint Source Loading Model (NPS) into an integrated basin-scale model that combines watershed processes with in-stream fate and transport in one- dimensional stream channels. HSPF simulates watershed hydrology, land and soil contaminant runoff, soil profile nutrient processes and runoff, and sediment-chemical interactions. The model can generate time series results of any of the simulated processes. Overland sediment may be divided into three types of sediment (sand, silt, and clay) for in-stream fate and transport. Pollutants interact with suspended and bed sediment through soil-water partitioning. The most recent release is HSPF Version 12, which is distributed as part of the USEPA BASINS system (USEPA, 2007). (Summary modified and updated from Shoemaker et al. 2005) In HSPF, a subbasin is typically conceptualized as a group of various land covers all routed to a representative stream segment. Several small subbasins and representative streams may be networked together to represent a larger watershed drainage area. Various modules are available and may be readily activated to simulate various processes, both on land and in-stream. Land processes for pervious and impervious areas are simulated through water budget, sediment generation and transport, and water quality constituents’ generation and transport. Hydrology is modeled as water balance of soil (or storage) in different layers as described by the SWM methodology). Interception, infiltration, evapotranspiration, interflow, groundwater loss, and overland flow processes are considered and are generally represented by empirical equations. Sediment production is based on detachment and/or scour from a soil matrix and transport by overland flow in pervious areas, whereas solids buildup and washoff is simulated for impervious areas. It includes agricultural components for land-based nutrient and pesticide processes and a special actions block for simulating management activities. HSPF also simulates the in-stream fate and transport of a wide variety of pollutants, such as nutrients, sediments, tracers, dissolved oxygen/biochemical oxygen demand, temperature, bacteria, and user-defined constituents. For model documentation, underlying theory, and parameterization, the HSPF users’ manual is a recommended source (Bicknell et al. 2001). Assumptions: • Land simulation component is a distributed model by land cover but ignores the spatial variation within a land cover in a subbasin. • For overland flow, model assumes one-directional kinematic-wave flow.

269 • Model also assumes subbasins and streams as a network of reservoirs for routing flows. • The receiving waterbody assumes complete mixing along the width and depth. Model Strengths: • One the few watershed models capable of simulating land processes and receiving water processes simultaneously. • Capable of simulating both peak flow and low flows. • Simulates at a variety of time steps, including subhourly to 1 minute, hourly or daily. • Simulates the hydraulics of complex natural and man-made drainage networks. • Includes capabilities to address a variable water table. • Simulates results for many locations along a reservoir or tributary. • Includes user-defined model output options by defining the external targets block. • Can be setup as simple or complex, depending on application, requirements, and data availability. Model Limitations: • Relies on many empirical relationships to represent physical processes. • Lumps simulation processes for each land cover type at the subbasin level (i.e., does not consider the spatial location of one land parcel relative to another within the subbasin). The model approaches a distributed model when smaller subbasins are used; however, this may result in increased model complexity and simulation time. • Requires extensive calibration. • Requires a high level of expertise for application. • Is limited to well-mixed rivers and reservoirs and one-directional flow. Application History The modeling concept had its debut in the early 1960s as the SWM. During the 1970s, water quality processes were added. A FORTRAN version was developed in the late 1970s, incorporating several related models and software engineering design and development concepts funded by EPA’s research laboratory in Athens, GA. In the 1980s, pre- and post-processing software, algorithm enhancements, and use of the USGS binary Watershed Data Management system were developed jointly by the USGS and EPA. Since 1980, all model code changes have been maintained by Aqua Terra Consultants, under contract with EPA and USGS. During the mid to late 1990s, Tetra Tech, Inc., under contract with EPA developed the BASINS system and NPSM, resulting in the first Windows-based interface for the HSPF model. The current supported model release is Version 12, distributed with BASINS 3.0 as the WinHSPF model and interface. HSPF is a proven and tested continuous simulation watershed model. It is one of the models recommended by the EPA for complex TMDL studies, and by FEMA for floodplain assessment and delineation under the NFIP. The HSPF model has been widely used and its application has been documented throughout its development cycle.

270 Perhaps one of the most relevant applications to the current study is the WWHM (Clear Creek Solutions 2006) which is an interactive software package to predict stormwater runoff for sizing stormwater control facilities. Such facilities are evaluated based on comparison of and matching flow duration curves both under natural conditions and with the control facilities in place. The WWHM has been used in Western Washington (i.e., 19 Western Washington Counties) for more than a decade and has been adapted and extended for applications in the San Francisco Bay Area and San Diego. Model Evaluation HSPF has been widely reviewed and applied throughout its long recent history (Hicks, 1985; Ross et al., 1997; and Tsihrintzis et al., 1996). One of the largest applications of the model was to the Chesapeake Bay Watershed, as part of the EPA’s Chesapeake Bay Program’s management initiative (Donigian 1990, 1992). Tsihrintzis et al. (1994, 1995) applied HSPF in a GIS shell (using ARC/INFO) to evaluate the impact of agricultural activities, specifically transport of sediments, nutrients, and pesticides, on streams and groundwater in Southern Florida. An extensive HSPF bibliography has been compiled to document model development and application and is available at http://hspf.com/hspfbib.html. Sensitivity/Uncertainty/Calibration HSPFParm is a free HSPF parameter database distributed with EPA’s BASINS System. The software is installed independent of the BASINS system. It provides regionalized model parameters for published applications across the United States. It serves as a good starting point for parameter selection during model setup and calibration. The Expert System for calibration of HSPF (HSPEXP) is an interactive program that evaluates modeled versus observed time series using over 35 rules and some 80 conditions (Lumb et al. 1994). It uses Artificial Intelligence techniques, incorporating expert advice, based on statistics and evaluation results, to recommend which parameters should be adjusted. An enhanced expert system for HSPF Model Calibration (HSPEXP+) (Mishra et al. 2017) was recently developed and released to simplify the generation of HSPF Model Calibration statistics and constituent loading reports, along with various plots and analyses. HSPEXP+ is open source and the latest versions are available on the GitHub repository RESPEC 2019. Through the years, multiple new capabilities have been added to HSPEXP+ and it is now used by multiple researchers and modelers to assist in model calibration and assessment (Borah et al., 2019). HSPEXP+ provides several reports that included loading rates of nutrients from all the land operations, and budget of each nutrient in the river operations. These reports can be produced for each year of model simulation, averaged over the entire simulation period, for the overall watershed, or averaged over a specific area. The Parameter Estimation software package (PEST) is a model calibration aid that can be run in conjunction with HSPF (Doherty 2003). The objective function’s goal is to minimize the least squares of the difference between modeled and observed flow by varying model parameters over a range that the user defines. PEST then iterates through a series of HSPF model runs, changing selected parameters and rerunning the model, until the objective is satisfied. References Cited/Reviewed:

271 Bicknell, B.R., J.C. Imhoff, J.L. Kittle, Jr., T.H. Jobes, and A. S. Donigian, Jr. 2001. HYDROLOGICAL SIMULATION PROGRAM - FORTRAN, Version 12, User’s Manual. (Computer program manual). AQUA TERRA Consultants. Borah, D. K., Ahmadisharaf, E., Padmanabhan, G., Imen, S., and Mohamoud, Y. M. (2019). Watershed Models for Development and Implementation of Total Maximum Daily Loads. Journal of Hydrologic Engineering, 24(1). Retrieved from https://doi.org/10.1061/(ASCE)HE.1943-5584.0001724 Clear Creek Solutions, Inc. 2006. Western Washington Hydrology Model, Version 3. User Manual. Prepared for Washington State Department of Ecology, Seattle WA. Clear Creek Solutions, Inc. 2016. Western Washington Hydrology Model, Version 2012. User Manual. Prepared for Washington State Department of Ecology, Seattle WA. Doherty, John, and John M. Johnston. 2003. Methodologies for calibration and predictive analysis of a watershed model. J. American Water Resources Association. 39(2):251-265. Donigian, A.S. Jr., and A.S. Patwardhan. (1992). Modeling nutrient loadings from croplands in the Chesapeake Bay Watershed. In Proceedings of water resources sessions at Water Forum ‘92, Baltimore, Maryland, August 2-6, 1992, pp. 817-822. Donigian, A.S., Jr., B.R. Bicknell, L.C. Linker, J. Hannawald, C. Chang, and R. Reynolds. 1990. Chesapeake Bay Program Watershed Model application to calculate bay nutrient loadings: preliminary Phase I findings and recommendations. Prepared for the U. S. Chesapeake Bay Program, Annapolis, MD by AQUA TERRA consultants. Donigian, A.S., Patwardhan, A.S., and R.M. Jacobson. 1996. Watershed Modeling of Pollutant Contributions and Water Quality in the Le Sueur Basin of Southern Minnesota. In Proceedings of Watershed 96, Baltimore, MD, June 8-12, 1996. Hicks, C.N. 1985. Continuous Simulation of Surface and Subsurface Flows in Cypress Creek Basin, Florida, Using Hydrological Simulation Program - FORTRAN (HSPF). Water Resources Research Center, University of Florida, Gainesville, FL. Lumb, A.M., McCammon, R.B., and Kittle, J.L., Jr. 1994. User’s manual for an expert system (HSPEXP) for calibration of the Hydrologic Simulation Program—FORTRAN. U.S. Geological Survey Water-Resources Investigations Report 94-4168. U.S. Geological Survey. Mishra, A., Bicknell, B., Duda, P., Donigian, A., and Gray, M. 2017. HSPEXP+: An Enhanced Expert System for HSPF Model Calibration-A Case Study of the Snake River Watershed Model in Minnesota. Journal of Water Management Modeling. Retrieved from https://doi.org/10.14796/JWMM.C422 Moore, L.W., C. Y. Chew, R.H. Smith, and S. Sahoo. 1992. Modeling of Best Management Practices on North Reelfoot Creek, Tennessee. Water Environment Research. 64(3):241-247. RESPEC (2019, April 1). BASINS Development Releases. Retrieved from https://github.com/respec/BASINS/releases Ross, M.A., P.D. Tara, J.S. Geurink, and M.T. Stewart. 1997. FIPR Hydrologic Model: User’s Manual and Technical Documentation. Prepared for Florida Institute of Phosphate Research, Bartow, FL, and Southwest Florida Water Management District, Brooksville, FL by University of South Florida, Tampa, FL.

272 Scheckenberger, R.B., and A.S. Kennedy. 1994. The use of HSPF in subwatershed planning. In Current practices in modelling the management of stormwater impacts, ed. W. James. Lewis Publishers, Boca Raton, FL. pp. 175-187. Shoemaker, L., T. Dai, and J. Koenig. 2005. TMDL Model Evaluation and Research Needs. Prepared for USEPA Cincinnati, OH, under Contract 68-C-04-007, November 2005. Tsihrintzis, V.A., H.R. Fuentes, and R. Gadipudi. 1996. Modeling Prevention Alternatives for Nonpoint Source Pollution at a Wellfield in Florida. Water Resources Bulletin, Journal of the American Water Resources Association. 32(2):317-331. Tsihrintzis, V., H. Fuentes, and R. Gadipudi. 1995. Modeling prevention alternatives for nonpoint source pollution at a wellfield in Florida. Water Resources Bulletin. 32(2):317-331. Tsihrintzis, V., H. Fuentes, and R. Gadipudi. 1994. Interfacing GIS and water quality models for agricultural areas. Hydraulic Engineering ’94, ed. G. Cotroneo and R. Rumer, ASCE, 1, pp 252- 256. USEPA, 2007. Better Assessment Science Integrating point and Nonpoint Sources -- BASINS Version 4.0. EPA-823-C-07-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC. Available at: http://www.epa.gov/waterscience/basins/. B.2. SWMM The EPA SWMM is a dynamic rainfall-runoff simulation model used for single event or long- term (continuous) simulation of runoff quantity and quality from primarily urban areas. The runoff component of SWMM operates on a network of subbasin areas that receive precipitation and generate runoff and pollutant loads. The routing portion of SWMM transports this runoff through a system of pipes, channels, storage/treatment devices, pumps, and regulators. SWMM tracks the quantity and quality of runoff generated within each subbasin, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period comprised of multiple time steps. Relevant characteristics include: • SWMM was developed to help support local, state, and national stormwater management objectives to reduce runoff through infiltration and retention. • Windows-based desktop program, open-source public software and is free for use worldwide. • Can be used to simulate runoff reduction via GI practices. • Typical uses include sizing detention facilities and their appurtenances for flood control and controlling site runoff using GI practices such as LID controls. • SWMM allows engineers and planners to represent combinations of GI practices as LID controls to determine their effectiveness in managing runoff. SWMM can explicitly model eight different generic GI practices: o Rain gardens. o Bioretention cells (or bioswales). o Vegetative swales.

273 o Infiltration trenches. o Green roofs. o Rooftop disconnection. o Rain barrels or cisterns. o Continuous permeable pavement. • Hydromodification studies require continuous simulation using hourly time step and model calibration. • For calculating infiltration, hydraulic conductivity and suction head are entered by subbasin. SWMM was first developed in 1971 and has undergone several major upgrades since then. It continues to be widely used throughout the world for planning, analysis and design related to stormwater runoff, combined sewers, sanitary sewers, and other drainage systems in urban areas, with many applications in non-urban areas as well. The current edition, Version 5, is a complete re-write of the previous release. EPA’s National Stormwater Calculator (SWC) uses SWMM as its computational engine. The SWC allows users to analyze site hydrology for small- to medium-sized (less than 12 acres) locations within the United States, including Puerto Rico, using LID controls. It estimates the amount of stormwater runoff generated from a site under different development and control scenarios over a long-term period of historical rainfall. SWMM is set up and run in the background without requiring any involvement of the user. The SWC accesses several national databases that provide soil, topography, rainfall, and evaporation information for a chosen site. SWMM’s widespread use and acceptance make it well suited for use in this type of study. It is open source and in the public domain, and it contains explicit representation of GI practices. However, it does require significant input data, parameterization, and calibration. EPA’s National SWC provides a simplified interface for SWMM, setting up and running SWMM using national databases of soils, topography, rainfall, and evaporation. References Cited/Reviewed: Gregory, M. 2015. "Flow Duration Hydrograph Analyses for Assessing LID Performance." Journal of Water Management Modeling C382. Lee, J., C. Nietch, and S. Panguluri 2018. SWMM Modeling Methods for Simulating Green Infrastructure at a Suburban Headwatershed: User’s Guide. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-17/414. Lee, J. G., Nietch, C. T., and Panguluri, S. 2017. Subcatchment characterization for evaluating green infrastructure using the Storm Water Management Model, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-166, in review. url: https://www.hydrol-earth-syst- scidiscuss.net/hess-2017-166/ Rossman, L., J. Berner, M. Tryby, M. Simon, S. Struck, D. Pankani, and M. Deerhake 2017. National Stormwater Calculator User's Guide - Version 1.2. USEPA Office of Research and Development, Washington, DC, EPA/600/R-13/085d.

274 Rossman, L.A 2015. Storm Water Management Model User’s Manual, Version 5.1. EPA/600/R- 14/413b, Revised September 2015. U.S. Environmental Protection Agency, Office of Research and Development, Water Supply and Water Resources Division, Cincinnati, OH. Rossman, L.A. and Huber, W.C. 2016. Storm Water Management Model Reference Manual, Volume I – Hydrology (Revised). EPA/600/R-15/162A, Revised January 2016. U.S. Environmental Protection Agency, Office of Research and Development, Water Supply and Water Resources Division, Cincinnati, OH. Storm Water Management Model (SWMM), https://www.epa.gov/water-research/storm-water- management-model-swmm B.3. SWAT The Soil and Water Assessment Tool is a small watershed to river basin-scale model used to simulate the quality and quantity of surface and groundwater and predict the environmental impact of land cover, land management practices, and climate change. SWAT is widely used in assessing soil erosion prevention and control, nonpoint source pollution control and regional management in watersheds. Relevant characteristics include: • Non-proprietary software available from USDA/TAMU. • There is a suite of free and publicly available desktop software developed for SWAT model setup, simulation, and post-simulation analysis. • SWAT model is distributed through Texas A&M public portal website with parameter database and soil database. The model setup process in Arc-GIS will download necessary elevation and soil data GIS layers automatically and use them for model setup. It also provides weather input database of major NOAA monitoring stations. • The recent effort as published enabled SWAT to simulate at 15-minute time step and to represent detention basin, wet pond, sedimentation-filtration pond, retention irrigation system explicitly with distinct set of equations to represent the physical processes within each BMP structure. • The BMP modeling capability is relatively new. Its development and application mainly focused on example model watersheds provided by the City of Austin, Texas. The BMP simulation module is physically based, the algorithms are universally applicable (i.e., not site-specific). The physically based BMP model representation theoretically allows evaluation of stormwater BMPs typically associated with urban development. There were limited case studies involving the BMP model application and there is no internal BMP optimization capability. This model represents a promising/feasible strategy for state DOTS. References Cited/Reviewed: There are many published model applications using SWAT. Main effort to explicitly represent stormwater BMPs started since early 2010 by the joint effort of Blackland Research and Extension Center and Texas AgriLife Research, Texas A&M System. Since then, there are several publications that describe the progress and milestone developments as listed below:

275 Jeong, J., Kannan, N., Srinivasan R. 2011. Development of SWAT Algorithms for Modeling Urban Best Management Practices. Submitted to Watershed Protection Department, City of Austin. Jeong, J., Kannan, N., Arnold, J., Glick R., Gosselink, L., Srinivasan R., and Barrett M.E. 2013. Modeling Sedimentation-Filtration Basins for Urban Watersheds Using Soil and Water Assessment Tool. J. Environ. Eng., 139:838-848 Kannan, N., Jeong, J., Arnold, J. Gosselink, L., Glick R., and Srinivasan R. 2014. Hydrologic Modeling of a Retention Irrigation System. J. Hydrol. Eng., 19:1036-1041. SWAT 2007. Soil and Water Assessment Tool: SWAT model. College Station, Texas: Tex. A&M University. Available at:www.brc.tamus.edu/swat/soft_model.html. Accessed 21February 2007. B.4. SUSTAIN SUSTAIN is a decision support system that assists stormwater management professionals with developing and implementing plans for flow and pollution control measures to protect source waters and meet water quality goals. SUSTAIN allows watershed and stormwater practitioners to develop, evaluate, and select optimal BMP combinations at various watershed scales based on cost and effectiveness. EPA’s primary web page for SUSTAIN provides a summary of SUSTAIN’s capabilities and links to the executable, documentation, and source code. So, while it is non-proprietary, the main web page indicates that EPA is no longer developing or supporting SUSTAIN. The last release of SUSTAIN was in June of 2014 and included Arc-GIS plugins for BMP siting an analysis, though the Arc-GIS versions of the plugins are now outdated. The documentation includes system-level technical details as well as an early case study application of SUSTAIN. SUSTAIN simulates point BMPs (bioretention, cisterns, rain barrels, infiltration basins, surface sand filters, constructed wetlands, and dry and wet ponds), linear BMPs (infiltration trenches, grassed swales, vegetated filter strips, and non-surface sand filters), and area BMPs (porous pavement and green roofs). SUSTAIN’s input sequence contains numerous tables of parameters to define each BMP’s impact on hydrologic and water quality responses. Simulation of BMPs is primarily performed through a combination of SWMM and HSPF algorithms. SUSTAIN applies the above BMPs with imported land surface loading time series data imported from either the SWMM or HSPF model. Hydromodifications through land cover change would be handled within the SWMM or HSPF model. Optimization of BMP sizing or number of units can be performed to provide cost-effectiveness analysis of potential management scenarios. SUSTAIN is a powerful tool for performing BMP simulation and optimization. A calibrated SWMM or HSPF model is required for applying it. Additionally, developing parameters for the BMPs modeled in SUSTAIN requires research of regional BMP performance and costing or access to a limited number of SUSTAIN applications. One example application using SUSTAIN is SARA’s Water Quality Modeling Tools (https://www.sara-tx.org/flood-management/water-quality-modeling-tools/). SARA led the development of several innovative water quality modeling tools to allow quantitative water quality master planning and BMP/LID prioritization for three major watersheds in the San

276 Antonio River Basin. Multiple tools developed for SARA incorporated the core (non-GIS) SUSTAIN simulation and optimization code. The SARA Enhanced BMP Tool determines the optimal combinations that would minimize the BMP/LID costs while achieving the needed load reduction. The SARA Enhanced BMP Tool includes a comprehensive BMP Tool Database, compiling available BMP/LID data and the application of engineering economic analyses to convert the collected data to annual costs for equal-footing comparison and optimization. The SARA BMP Processor compiles individual BMP/LID unit-cost and effectiveness information to assess potential incentives for implementing BMPs/LIDs. The SARA WQ Tools represent application of SUSTAIN at two levels. The BMP Tool implements full simulation and optimization within HSPF modeled subbasins to achieve target reductions in hydrologic and water quality responses. The BMP Processor uses SUSTAIN to compile unit BMP reductions for all land covers within modeled subbasins, allowing for discrete hydromodification scenarios to be analyzed. SUSTAIN provides a rigorous representation of a significant number of BMPs. However, considerable effort is typically needed for applying SUSTAIN. Hydromodification through change in land cover would be performed through changes to the model (SWMM or HSPF) connected to SUSTAIN. The most promising use of SUSTAIN for this research would be through leveraging of existing SUSTAIN applications. SUSTAIN’s optimization features are likely beyond the scope of this effort, but precompiled BMP effectiveness and cost, as implemented in the SARA BMP Processor, could potentially be a resource for this effort. References Cited/Reviewed: System for Urban Stormwater Treatment and Analysis IntegratioN (SUSTAIN), https://www.epa.gov/water-research/system-urban-stormwater-treatment-and-analysis- integration-sustain Atkins, Inc. 2014. San Antonio River Basin Regional Modeling Standards for Water Quality Modeling, https://www.sara.tx.org/wpcontent/uploads/2017/08/SARA_WQModelingStandards_Final.pdf Lee, J. G., A. Selvakumar, K. Alvi, J. Riverson, J. X. Zhen, L. Shoemaker, and F. Lai 2012. A Watershed-scale Design Optimization Model for Stormwater Best Management Practices. ENVIRONMENTAL MODELLING & SOFTWARE. Elsevier Science, New York, NY, 37:6- 18. B.5. WMOST EPA’s WMOST is a decision support tool that facilitates integrated water management at the local or small watershed scale. It models the environmental effects and costs of management decisions in a watershed context that accounts for the direct and indirect effects of decisions. The model considers water flows and water quality. It is spatially lumped with options for a daily or monthly modeling time step. The optimization of management options is solved using nonlinear programming. WMOST is intended to be a screening tool used as part of an integrated watershed management process such as that described in EPA’s watershed planning handbook (EPA 2008). The target user group for WMOST consists of local water resources managers, including municipal water works superintendents and their consultants. Relevant characteristics include:

277 • Non-proprietary software available from EPA. • Excel-based interface. • Operates at small watershed scale with spatially lumped calculations modeling one basin and one reach, but with flexibility in the number of hydrologic response units. • Operates at either daily or monthly time step. • Availability of over 20 potential management practices and goals related to: o Stormwater management practices: Up to 15 BMPs, including traditional gray infrastructure and GI and other LID practices. o Water supply: Demand management practices, surface and groundwater pumping, surface water storage, water treatment plant, and drinking water distribution system leak repair. o Wastewater: Septic systems, wastewater treatment plant, and infiltration repair in wastewater collection systems. o Nonpotable water reuse: Wastewater reuse facility and nonpotable distribution systems. o Others: Aquifer storage and recharge, transfer of water and wastewater between drainage basins, land conservation, minimum human demand, and minimum and maximum in-stream flow targets. • Specific BMP/LID cited include: o Bioretention Basin. o Extended Dry Detention Basin. o Sand Filter w/UD. o Biofiltration w/UD. o Infiltration Basin. o Porous Pavement w/UD. o Wet Pond. • Automated import of runoff and groundwater recharge rate time series from existing hydrology models and estimated performance of proposed BMPs. Runoff/Recharge Rates (RRR) can be consumed from models such as HSPF, SWMM, SWAT, SWC, and Generalized Watershed Loading Function (GWLF). • Some management practices, primarily BMP/LID, are simulated and optimized using EPA’s SUSTAIN tool. • It appears other simulation and optimization is performed through Excel macros. • Focus of analysis is on baseflow and peak flows. WMOST has been under development for the past 5 years and is now on Version 3.01. While not relevant to this research, recent enhancement includes the ability to assess water quality as well

278 as quantity. Case studies have been performed in several locations in the northeast and Chesapeake Bay Watershed. Assessment of a variety of hydromodification options are available and are integrated into WMOST’s workflow. While some of these options are intended for water supply analysis, a substantial number are well suited for mitigation of potential increases in runoff and streamflow. WMOST’s scale (single subbasin/reach with multiple HRUs) and level of analysis (i.e., screening) are well suited for this study. It contains a robust suite of hydromodification options that have been adapted by EPA for inclusion in the tool’s workflow. Further investigation and understanding of how the hydromodification options are implemented is warranted. Use of EPA’s SUSTAIN tool for simulation and optimization of BMP/LID is referenced, but it is unclear for which options this is used and which ones are simulated in a simpler manner. On a parallel track, further investigation of cost-effectiveness optimization methods used in WMOST is warranted. Overall, WMOST appears to be a strong resource in developing strategies for state DOTS. References Cited/Reviewed: WMOST has many cited resources for multiple release versions, from fact sheets to webinar and video presentations to user’s manuals. Several key resources listed here were used for most of this review. A greater understanding of WMOST’s technical details would be gained from a thorough review of its user’s manual and technical documentation. Detenbeck, N. Managing Watersheds with WMOST (Watershed Management Optimization Support Tool). Presented at Safe and Sustainable Water Resources (SSWR) Webinar Series (#1), Narragansett, RI, January 22, 2014. WMOST v2 Fact Sheet: https://www.epa.gov/sites/production/files/2016- 09/documents/wmostv2_fact_sheet_508.pdf Detenbeck, N.E. and C. Weaver 2018. Watershed Management Optimization Support Tool. Version 3.01. U.S. Environmental Protection Agency, Washington, D.C. EPA/600/R-19/039.