VICKSBURG, Miss. - The U.S. Army Engineer Research and Development Center’s (ERDC) Coastal and Hydraulics Laboratory (CHL) recently announced the release of version 8.0 of the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model.
GSSHA is a watershed analysis and management tool with the ability to simulate the movement of water, sediment and associated constituents across watershed-scale areas. Developed by ERDC to simulate the processes that produce streamflow in a wide range of climatic and hydrologic settings, GSSHA is a process-based hydrologic model that simulates overland, channel and groundwater flow in an integrated fashion.
The process models in GSSHA allow it to be flexible and tailored to the situation so that it can model flooding, water balance and ecological flows. The spatially distributed nature of GSSHA allows for assessment of where changes occur, as opposed to just what changes occur.
The integrated process modeling enables changes in one domain to propagate naturally to other domains, such as increasing groundwater recharge in near surface zones that influence wetlands areas. Because GSSHA is a physical process driven model, it can simulate fundamental changes in hydrologic processes such as adding or removing tile drains or storm drainage networks, adding natural and nature-based features and examining large-scale changes in land use.
Three years in the making, GSSHA 8.0 is designed to enable programmatic access to the core GSSHA simulation tools. This will allow GSSHA to become part of more complex simulations as well as open up GSSHA parameterizations to external processes.
The GSSHA programmatic interface has been encapsulated into a library and built on an implementation of the Basic Model Interface. The interface allows for programmatic fine-grained control of the simulation and exposes five channel hydraulic properties and 30 grid-based parameterizations or hydraulic properties. Future work will continue to expand the exposed variables and create examples of how they can be accessed and modified externally.
While version 7.15 introduced significant feature enhancements, including the incorporation of a new momentum formulation for the streamflow model that greatly improved the stability and precision of streamflow simulations, GSSHA 8.0 includes an update to the permafrost model as well as the recent critical bug fixes and feature enhancements in version 7.15 designed to improve the model’s accuracy and performance. Notable bug fixes address issues with lake mass balance calculations, evapotranspiration computations for cloud cover and radiation, an OpenMP 2-layer soil moisture bug and a Havercamp mapping table issue. These corrections ensure more reliable simulations across various hydrologic scenarios, enhancing the model’s utility for watershed management and engineering design.
“These advancements and updates make GSSHA a more powerful and robust tool for hydrologic analysis, capable of providing detailed and reliable predictions for flood risk management, environmental restoration projects, and various other applications,” said Dr. Aaron Byrd, a research civil engineer with the ERDC-CHL. “Our organization remains committed to continuous improvement of the GSSHA model to meet the evolving needs of hydrologic engineers and scientists worldwide.”
U.S. Army Corps of Engineers projects and programs that contributed to the update include the Hydrology, Hydraulics, and Coastal Science and Engineering Technology; Forecast-Informed Reservoir Operations; and Engineering With Nature programs. Members of the research team include Byrd as well as Dr. Charles W. Downer, lead GSSHA developer, and Dr. Nawa Raj Pradhan, both research civil engineers with CHL.
The updated version of GSSHA can be downloaded from the GSSHA Wiki: https://gsshawiki.com/GSSHA_Download.