Westhoff developed a customized water balance modeling tool, Westhoff Water Balance Model (WWBM), using a system dynamics simulation software GoldSim. The tool is composed of various elements to portray the physical properties of natural and man-made systems involved in water management as well as various datasets to represent climate and environmental information. The model completes simulations on an hourly basis and the result is produced in the form of daily timeseries. The time series of state variables (flows at various strategic locations of the system and water levels at various water bodies) are exported to excel files. Simulation results using past observed climate data are used for project planning, as well as water management and operation analysis.
WWBM helps to resolve urban stormwater management issues, featuring the following aspects, which may not be incorporated in conventional urban drainage modeling software:
• re-direction of flows from impervious surfaces into permeable landscaping, absorbent landscaping or bioretention /bioswale media;
• representation of rainwater harvesting and stormwater re-use;
• replenishment of soil moisture due to irrigation, either from harvested rainwater or stormwater;
• representation of the reduced infiltration during the winter months;
• reduction of the infiltration capability as a function of clogging over time; and,
• statistical and graphical representation of the performance of all stormwater management facilities.
WWBM is capable of modeling sub-catchments that drain to one or two storm ponds optionally. WWBM has provision for five sub-catchments, which may contain multiple land-use areas as schematically shown below.
WWBM is readily usable by the consulting industry in support of Master Drainage Plan (MDP), Staged Master Drainage Plan (SMDP), Pond Report and Stormwater Management Report submissions.
WWBM consists of user friendly interface panels along with the underlying computational equations. The user may enter appropriate data, select computational options, and invoke simulations through various user-interface panels.