Using GoldSim to Model System Dynamics and Uncertainty

Background

There are many modeling tools used in water resources and water quality solutions. So many that it is easy to confuse the abbreviations and names if you are not familiar with them: XPSWMM; Prioritize, Target, and Measure Application (PTMApp); HSPF; HEC-HMS; HEC-RAS; and many more. In some situations, a more flexible and customized approach to modeling is beneficial. This is especially true when what is being modeled is a complex system containing inherent uncertainty and the system or process is not adequately represented by commonly used software. HEI has a wealth of experience with commonly used water resource simulation tools, but for integrated systems, we utilize a flexible and powerful system dynamics model called GoldSim (https://www.goldsim.com/).

What is GoldSim?

GoldSim is a general purpose simulation software capable of dynamically simulating complex systems in engineering, science, and business. GoldSim is graphics-oriented, modular, and powerful. Why is GoldSim superior to spreadsheets and commonly used models?

• It is very visual, which enhances its use and understanding by both model builders and end users (clients).
• It includes a powerful, built-in methodology to evaluate how systems behave over time using probabilistic simulation. This key feature of GoldSim allows the user to quantify the variability and uncertainty of a system, which provides extremely valuable information for end users that want to optimize design or management of a resource or system.
• A fully customizable “dashboard” can be developed and delivered to the end user, which allows them to change model variables and assumptions, run scenarios, and visualize results. Scenarios can be run and viewed using the dashboard without purchasing a software license.

How has HEI Applied GoldSim to Water-Related Systems?

HEI has developed GoldSim models for shallow natural lakes, impoundments/reservoirs, and oxbow lakes. Modeling goals and purposes have been diverse and include detailed water balance simulations, quantifying sediment and nutrient balance, and the simulation of lake restoration design and management alternatives. HEI has utilized the GoldSim model to simulate the dynamics of a sediment containment basin, including how it fills with water and sediment based on a variety of hydraulic dredging pump rates and run times. HEI has also used GoldSim to predict lake drawdown times to determine the feasibility of an accelerated construction schedule under varying weather conditions. In most of HEI’s lake applications, data uncertainty and natural variability have been incorporated into the models to better understand the range and likelihood of system behavior over time. The information produced by this approach is much more meaningful to resource managers than annual average conditions, which, by definition, miss important seasonal variations and extremes.

Most recently, HEI has embarked on an effort to apply the GoldSim model to optimize operations and maximize benefits of a large irrigational canal and storage system in western Nebraska – the Perkins Canal project. This effort will provide the Nebraska Department of Natural Resources and its water partners the ability to fully understand how the system functions and quantify the impacts of potential climate change and operational decisions as well as explain the benefits to water users within and downstream of the system.

How and Where Else Can GoldSim be Utilized?

One of GoldSim’s major benefits is its versatility. Simply stated, GoldSim can be utilized to simulate any movement, storage, and change of a material. This material can be water, chemicals (such as nutrients), industrial/commercial products (machine and parts), vehicles/traffic, population dynamics, energy/power, or money.

When Should I Consider Using a System Dynamics Tool Such as GoldSim?

GoldSim offers advantages over spreadsheets and single-purpose modeling software programs whenever you want to:
• Simulate a complex system with a variety of integrated components (materials, pathways, storages, etc.).
• Optimize the design of system components in a way that considers potential variability and uncertainty.
• Simulate and visualize future conditions or scenarios via a user-friendly interface (GoldSim dashboard).