WaterWare Release Notes
    Release Level 5.0
    Release Date 2005 06
    Revision Level 1.0

SPILL/BLTM Surface Water Quality Model

SPILL/BLTM, a near-field surface water model for open channels is the second water quality model in WaterWare. It is designed to represent highly transient situations like the effects of storm water runoff, treatment plant failures, or accidental spills over short periods of time and immediately downstream of a source.

The entry point is a selector of scenarios, which can be sorted and filtered by several properties such as name, author, modification date, or location. Another option here is the possibility to create a new scenario with an empty template, or by copying an existing one. The first step there is to select the WRM scenario to be used as the basis for a new STREAM model scenario.

Once selected, information about a scenario includes its name and a short description, the author/owner, location (defined by a WRM node and the reach downstream of it), and the overall duration of the episode (simulation time(, together with the time step. A 48 hour duration, and an hourly time step are the defaults. In addition to the basic control parameters, the scenario is defined by:

  • detailed reach geometry;
  • flow pattern (hourly);
  • pollutant load, amount and pattern.

The load pattern for the pollutant (the spill) is defined in a separate editor: this includes setting
  • the total mass of pollutant involved,
  • the duration of the spill
  • the start of the decay of the spill rate
  • the decay pattern (linear or exponential).
Alternatively, the user can specify the maximum initial pollutant flow, from which the total mass involved will be calculated.

The detailed geometry of the reach affected is specified in terms of a set of trapezoidal cross sectional shapes.

The user specifies the total length of the reach, and for each of the cross sections its distance along the reach, its depth, and the bottom and surface width, using the simple trapezoidal approximation.
The model results are summarised in tabular form, indicating maximum concentration values and the exceedance of water quality standards.

The main output format is an animated display of the river reach with a color coded representation of the pollutant concentration. A tape-deck like control tool supports continuous animation/play, or single stepping through the simulation results, and jump to the first and last time-step, respectively.

In parallel, breakthrough curves (pollutant concentration over time) are shown for selected location along the reach. They are relevant, for example, to control water intakes including bank filtrate during a pollution episode.

The increasing distance of the control points is reflected in the time delay in the arrival and passing of the pollutant plume along the river.

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