November 7, 2018

Statistical Analysis of Streamflow Time Series

Posted by Jason Lillywhite

Using GoldSim's built-in probabilistic simulation capabilities, it is straightforward to perform statistical analysis of time series data. An example model was built and added to our library, which demonstrates how Monte Carlo simulation is used to analyze daily time series data of streamflow to produce daily, monthly, and annual statistics. In addition to this, the model finds a best fit probability distribution for these statistics.  

October 8, 2018

Reservoir Inflow Forecasting

Posted by Jason Lillywhite
Last month, at the annual symposium hosted by the Arizona Hydrologic Society, I presented on probabilistic reservoir forecasting using GoldSim. This model combines many existing components available in our library to forecast snowmelt driven runoff inflows to a reservoir and estimates risk of spills and/or shortages.

September 21, 2018

2018 GoldSim User Conference

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The 2018 GoldSim User Conference was held on September 10-12, 2018, and was a great success. The conference was held at the Washington Athletic Club in the heart of downtown Seattle. With nearly 60 attendees from North America, South America, Asia and Australia, the conference provided great opportunities for our users to discuss and present their GoldSim applications, and discuss simulation techniques with other users and GoldSim staff.

July 25, 2018

Graphical User Interface Examples in GoldSim

Posted by Jason Lillywhite

I've updated many of our dashboard examples to include the new embedded chart feature available in GoldSim 12.1. Many of these have been updated since my last blog post showing example dashboards. Below are screen captures showing some of these along with links to read more about them and even download the models so you can try them out yourself.

July 17, 2018

PID Controller in GoldSim

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The proportional-integral-derivative (PID) controller is a useful feedback control mechanism commonly used in industrial applications such as furnace temperature control, pH neutralization, and flow control. These systems commonly require that their state be monitored continuously and controls adjusted based on error from a setpoint or target. As seen in the schematic below, the controller makes a change to a process then a sensor is used to provide feedback to the input of the controller.

This type of control can also be used for controlling inflows and/or outflows from a storage facility like a lake or water tank. This blog post describes the application of the PID controller in 2 different GoldSim models: a detailed process flow model with a cylindrical tank and an environmental system with a large water supply reservoir. This logic is found to work well in both cases even though they .

July 11, 2018

GoldSim 12.1 is Released!

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We are excited to announce that GoldSim 12.1 is now available.

In addition to a number of other changes, GoldSim 12.1 includes the following new features:

  •  Embedded dashboard charts and tables: You can embed a result window (as either a chart or a table) directly into a Dashboard. 
  • Real-Time updating of result displays: Time History results are updated continuously (each timestep or each realization) during the simulation. 
  • Exporting time history probability statistics to a spreadsheet: Export multiple statistics from Probability History results.
  • Model inventory: Generate a simple XML file that can be viewed in a text editor, browser or XML editor that echoes out all of the elements in a GoldSim model. 
All of the new features in GoldSim 12.1 are described in detail in the GoldSim 12.1 Summary Document.

In addition to an updated Help system to describe all the new features, updated user manuals are installed with the software (in PDF format). Bound manuals can also be ordered directly from (and this is likely to be less expensive than printing and binding them yourself).

You can download GoldSim 12.1 directly from the GoldSim website. In order to use GoldSim 12.1, you must enter a new Activation ID. All users with current Maintenance should have received a new ID.

April 24, 2018

Building Blocks in GoldSim

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One of the many strengths of GoldSim is its graphically enhanced user interface, which allows you to quickly build your model from reusable components. During a recent webinar, I built a reservoir operations model that receives water from a snowmelt driven watershed using 6 existing models found in our Model Library. Once I understood what my modeling requirements were, I was able to quickly compile a probabilistic system model that is powerful in demonstrating how to operate a dam that services changing water demands and climate scenarios, which protects against downstream flooding.

April 13, 2018

GSPy: GoldSim/Python Interface for Scripting Support

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We want to alert you to an exciting new addition to our model library, a ready-to-use GoldSim/Python interface that enables you to define external functions in pure Python which are called by GoldSim during a simulation. Both 32- and 64-bit binaries are available, so you can choose the appropriate one for your installation of Python. Source code is also included for reference (or further development), if you are interested to see how the interface is implemented.

The GSPy interface provides support for passing scalars, vectors and matrices as input and output arguments, which we anticipate will meet the majority of interested users' needs. For more extensive support of data types (such as Lookup Tables and Time Series Elements), refer to this related model library example: Python DLL. One key difference between the two examples is that Python DLL uses Cython, a code generation tool, and must be compiled before you can use it. In contrast, GSPy does not require Cython-generated compilation and it is distributed with binaries requiring minimal setup. It also supports error relay from the Python module to GoldSim.

The following steps are recommended to get started:

1) Install the 32- or 64-bit Python 3.6 Anaconda distribution here: A significant advantage of installing the Anaconda distribution is that it comes already with several widely-used Python libraries such as NumPy, Pandas and SciPy. One of the examples that comes with GSPy uses NumPy to do matrix arithmetic.

2) Download and unzip and follow the setup and testing instructions in the README.txt file. Binaries include GSPy.pyd and TestGSPy.exe (32- and 64-bit versions). The README provides simple instructions for setting an environment variable (GSPY) with the path to your Python installation and running TestGSPy.exe from a command line console to confirm that everything is set up correctly.

3) After you have confirmed that the GSPy environment is set up correctly, be sure to go through the three GoldSim model examples included in the zip file: GSPyScalarAddition.gsm, GSPyMatrixAddition.gsm and GSPySnowmelt.gsm. It is strongly recommended that you read through the detailed comments in the corresponding Python module files:, and (note, as described in the README, you must change the name of the Python file to before running the example).

Have fun and please send us questions and feedback at Or better yet, come to our forum and post about it there where everyone can see it. We see great potential in combining the Monte Carlo simulation capabilities of GoldSim with the extensive well-supported and powerful scientific computing Python libraries that are freely available. The more chatter about this the better. So far, the topic has popped up in a couple places (here and here) in our forum. We hope to hear from you.

The following results were generated by GSPySnowmelt.gsm, which calls a Python implementation of the snow-17 snow accumulation and ablation model (Anderson, E. A. (1973), National Weather Service River Forecast System Snow Accumulation and Ablation Model, NOAA Tech. Memo. NWS HYDro-17, 217 pp., U.S. Dep. of Commer., Silver Spring, Md.).

February 22, 2018

GoldSim User Conference and Training: September 10-12, 2018

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We are excited to announce that the next GoldSim User Conference will be held in Seattle on September 10-12, 2018. GoldSim user conferences provide great learning and networking opportunities for both expert and novice users.

The conference will be preceded (on September 10) by an optional one-day Basic Training workshop focusing on novice users (and could also serve as a refresher course for more experienced users who have not used GoldSim recently). This training opportunity is particularly valuable since after attending the training you will then be able to meet expert users from around the world during the conference.

The conference itself will be held September 11 and 12. On the first day of the conference, Two parallel advanced training sessions will be held. Each session will consist of a series of 1 hour training workshops on advanced GoldSim applications and modeling techniques. Attendees will be able to move between the two sessions in order to select the workshops that best align with their interests. Topics will be based on attendee requests specified on Registration Form. The second day of the conference will consist of a number of invited papers by GoldSim experts, panel discussions, and a poster session. 

To facilitate effective networking opportunities, the Conference will host two fun social outings in Seattle during the evenings of September 10 and September 11. These events not only provide a great opportunity to meet and socialize with other GoldSim users and GoldSim staff, but also allow you to enjoy the sights of Seattle. Spouses/partners can attend these two events (for a modest fee).

Learn more.