<< Click to Display Table of Contents >> Navigation:  Wadiso 6 User Guide > Tank Cost Optimization to be included in future Wadiso version > Additional Wadiso Tank Sizing Data Definition > Tank Parameters

For each tank to be sized in the optimization, certain parameters have to be specified. The tank parameters can be entered in the Tank Table, or the default parameters generated by the program may be accepted. The tank parameters required for each tank to be sized are:

•AVERAGE LEVEL: The user should give the average level (e.g. m or ft above ground elevation) of the balancing volume of the tank. For instance, if the tank has a full level of 7 m above ground, and a draw down to 4 m is allowable on a peak day, the average level of the balancing volume would be 5,5 m. (All the storage below 4 m may be emergency storage.) This average level need not be the same as the water level which was assigned to the tank in the steady state data, and which is used for the calculation of pressures in the system, when the system is balanced. Returning to the above example, the level to be used for pressure calculations may be 4 m, which is the critical (lowest) tank level for pressure calculations, while the average level for the balancing volume of the tank remains 5,5 m. Initially, the level entered for the tank in steady state data is accepted by the program as the default average level for the balancing volume.

•EMERGENCY VOLUME: This is the volume in the tank (e.g. ih m³ or USgal), which is required by the water authority and/or fire authority to be always available during emergency situations, such as pipe breaks, pump failures and fire flows. Initially the required emergency volume of the tank defaults to 0 (zero). Whatever is calculated by the program as the required balancing volume of the tank for a given combination of pipe diameters, will be added to the required emergency volume specified here to obtain the total volume required for the tank. In the context of optimization, the emergency volume is therefore important due to the effect of "economy of scale".

•EXISTING VOLUME: If the tank is an existing tank, the volume of the tank (m³ or gal) should be entered. Initially the existing volume defaults to 0 (zero). The existing volume is important when calculating tank cost. If, for instance, a given combination of pipes does not require more capacity (emergency plus balancing storage) in an existing tank than is already available, the cost associated with the tank would be zero. However, if the combination of pipes require more storage capacity than is available in the existing tank, it means that a supplementary tank has to be built on the same location, at a cost which is in accordance with the specified tank cost function (see COST FUNCTION below). In some cases it may not be possible to add such a supplementary tank, due to space limitations on the site. By specifying a cost function number 99 for an existing tank, the user could force the program to consider only those combinations of pipes, which would not require the capacity of the existing tank to be exceeded.

•COST FUNCTION: The user is allowed to enter up to six different tank cost functions. The user also has to specify which one of the six functions applies to the tank under consideration. By default, the program assumes that cost function number 1 (one) must be used. As described above under EXISTING VOLUME, a tank cost function number 99 may be entered for an existing tank if it is not possible to build a supplementary tank on the same location. In the enumeration, the program would then only consider those combinations of pipes, which do not require the capacity of the existing tank to be exceeded.