How We Got Here: A Past and Future Look at Stormwater Quality Modeling


DURATION 4 minute read

Everyday human activities generate a wide range of pollutants including fertilizers, pesticides, oil and grease, toxic chemicals, bacteria and nutrients, and sediments. During rain events, pollutants are transported along stormwater runoff, potentially producing detrimental impacts on the eco-system and human health.  Most polluted runoff will eventually discharge to streams and lakes and/or replenish the Earth’s groundwater and water bodies – presenting a challenge to the environment and human health.  The natural resources impacted by pollution may be utilized either for recreation purposes or as a source of drinking water, potentially exposing humans to these pollutants.

As communities develop and the impacts of pollution were better understood, the need to monitor and control the levels of pollutants in stormwater runoff increased. Pushed by regulatory changes and technological advances, water quality modeling has come a long way since its inception. But how did the profession get to where it is now? And how will it look in the future?

What Has Driven the Evolution of Stormwater Quality Modeling?

Regulations have been the main driver behind the evolution of water quality modeling. Today, local and federal regulations dictate many facets of our industry. But it wasn’t until the early 19th century that Congress enacted the Rivers and Harbors Act of 1886 – one of the first federal regulations challenging unpermitted pollutant discharges into navigable waters.

It wasn’t until about a century later in 1948 that the Federal Water Pollution Control Act was enacted. This act was the first major federal regulation that addressed pollution in surface water and set the stage for future water regulations like the Water Quality Act in 1965 and the Clean Water Act in 1972.

Drinking water regulations have also been enacted in tandem with water pollution regulations. Since 1908, Congress has enacted a range of drinking water regulations that emphasize the protection of human health – providing motivation for further evolution of stormwater quality modeling. Most notably, the Safe Drinking Water Act in 1974, established minimum standards to protect the quality of tap water across the United States.

As water professionals, it is our job to analyze and understand these regulations and find solutions to help bring clean water to our communities. Since they’ve been released, such regulations have been the driving force behind the technological advances that have transformed the discipline into the art it is today.

Early Stormwater Quality Models

There is a strong relationship between water pollutant regulations and the evolution of water quality modeling technology. Though the earliest model was developed in the 1920s, the practice of water quality modeling didn’t fully expand until the creation of mainframe computers and use of Geographic Information System (1960), further expanding with the release in the 1980s of ARC/INFO (first commercially available GIS tool), and the graphical user interface (GUI) operating systems.

A variety of water quality models were developed during this early period, including the Water Quality Analysis Simulation Program (WASP), Dynamic Estuary Model (DEM), the Stormwater Management Model (SWMM) and more.

Sequential development was then driven by the availability of desktop computers, improved Windows operating systems and the internet (1990s). These developments helped redefine and generalize older models, such as the environmental fluid dynamics code, which has been instrumental in improving the predictions and capabilities of water quality models like WASP.

The goal of the development of more sophisticated models was to understand the water pollution problems and develop solutions to manage those challenges. As these tools evolved, so did our ability to analyze and understand complex problems that involved multiple sources of pollution, diverse pollutants and receiving waters, varying goals, as well as our capability to address spatial and temporal variations. The use of more robust tools allowed stormwater professionals to find effective solutions for such complex problems.


The Future of Stormwater Modeling 

Driven by regulatory changes, technological advances and complex pollution problems, water quality modeling will continue to improve.  Tools like faster computers, improved user interface and GIS software, greater access to environmental data and more robust modeling frameworks are just a few of the computer technologies that continue to drive the advancement of water quality modeling.

The evolution of stormwater modeling will be driven by current and predicted modeling and functioning needs, including ecological response, BMP integration and model integration. Engineers are constantly working to develop better tools and collect more data which will allow continued improvements to stormwater modeling and the engineering solutions that result from it.

Scientific advances are also expected to improve components of some of the lesser-known modeling processes like erosion, sediment transport and deposition, water quality changes and the integration of ecosystem services.



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