Water Quality in InfoWorks ICM: Non-Conservative Pollutants

Non-Conservative pollutants can grow/decay and interact with each other.  There are a number of ways we can allow water quality pollutants to interact with each other in Infoworks ICM.  It is possible to define decay/growth functions, create user-defined processes or use the in-built processes such as the dissolved oxygen process.  This blog deals with the user-defined functionality to define non-conservative pollutants.

Figure 1_WQ Parameters

Decaying Pollutants Infoworks ICM has 5 decay types which can be specified for any determinant in the Water Quality


  • None
  • Linear
  • Exponential Concentration
  • Exponential Time
  • Exponential Both.

The user must specify a determinant and then the decay type that they would like to specify.  Each decay type then has a number of user-defined values to represent the decay function.

Figure 2_WQ Parameters

User-Defined Processes

It is also possible to set up User-Defined Processes.  There are 2 types, Growth and Equilibrium which use the following equations:-



Where, S1, S2 and S3 are determinants and P1, P2, P3 and P4 are coefficients.  Again these are specified in the Water Quality parameters and can be applied to any determinant.  One example of where there can be used is the equation from Kneiss et al. 2009 which represents the degradation of organic matter can be represented as:-

Which can be represented in the water quality parameters dialogue as thus:-

Figure 3_User Defined Processes

There are also built in water quality processes such as the Dissolved Oxygen Process and the nutrient cycling processes associated with algae and macrophytes which will be described in a future blog.

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    About Duncan Kitts

    Duncan Kitts is a Senior Support Engineer with Innovyze in the United Kingdom, specializing in River modelling and 2D modelling. He has over 9 years experience of modeling the key hydraulic processes involved in both fluvial systems and urban drainage environments. Duncan is responsible for providing support of both infoworks ICM and Infoworks RS.
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