An expert system based on VIMS (Virginia Institute of Marine Science) TPWQM (tidal prism water quality model) was developed for VPDES (Virginia Pollution Discharge Elimination System). The goal was to provide an easy-to-use tool for water quality management of small coastal basins and tidal creeks in Virginia. The expert system consists of two stand-alone but sequentially connected programs. ‘Preprocessor for Geometry’ takes user input of geometric and tidal information of a coastal basin and performs automatic model segmentation based on tidal prism. ‘Tidal Prism Water Quality Model’ calculates dissolved oxygen based on proposed point source discharge of organic carbon and nutrients. Input parameters, evaluated from the analysis of extensive data sets and previous model applications for small coastal basins in Virginia, were embedded into the water quality model. The present version of the expert system was written for personal computers with Windows 95/98 and Windows NT operating systems.
 
 

Model Features:

1. Geometry Preprocessor

 

 

The model can be configured for up to 15 branches. Each branch can have up to 10 secondary tributaries. The minimum information required for automatic segmentation include tidal range, the length of the main channel, and the number of branches connected to the main channel. For each branch and the main channel, the width and mean low tide water depth at the mouth are required. The user can provide more width-depth information along the channel. The secondary tributaries read in length-width-depth information.
 
 

2. TPWQM

The left figure shows the flowchart of the TPWQM component. The model have four options: (1) saline or freshwater system; (2) nutrient sensitive or insensitive cases; (3) for summer season or winter season; and (4) including fecal coliform bacteria (FCB) or not. The model can handle as many as 6 point sources. For the basin information, salinity at the mouth and fresh water discharge rate to all the branches are needed. For each point source, the required information includes location, discharge rate, 5 day carbonaceaous biochemical oxygen demand (CBOD₅), total Kjeldahl nitrogen (TKN), and dissolved oxygen (DO), and total phosphorous TP or FCB depending on options.

The model generates a report including a recommendation based on the calculated spatially minimum values of both daily mean DO and daily minimum DO. If the water quality standard is violated, the user will have options of specifying different discharge information.

References

Kuo, A.Y., S.-C. Kim, K. Park, and M.D. Phillips, 1999, Development of an expert system based on a tidal prism water quality model for small coastal basins in Virginia. Special Report No. 357 in Applied Marine Science and Ocean Engineering, School of Marine Science/Virginia Institute of Marine Science, 61 p.
 
 

WQMdemo

This is a simplified version of TPWQM-VPDES. It can handle only one point source in a tidal creek without a branch. It is also specified as a saline system during the summer season. A nutrient-insensitive case was assumed and also no FCB is included. This can be downloaded by clicking here.
 
 

Disclaimer

This is calibrated with extensive data sets collected from Virginia small coastal basins. For other systems, the values of embedded parameters should be validated and revised if necessary.
 
 

For more information, contact Albert Y. Kuo or Sung-Chan Kim
 
 

¹Inha University, Department of Oceanography, Inchon, South Korea

²Virginia Department of Environmental Quality, Richmond, Virginia