The program RS138-LZ is used for the verification of seepage location and depression - infiltration ditch - systems with continuous long time simulation (DWA - A 138, 04/2005). The long time simulation to the full continuum of precipitation includes all dry periods. Thus the natural series of rain events and the possible superposition of filling and emptying processes in infiltration plants. Additionally, with the fixed/not fixed methods, the areas in the event-dependent discharge behaviour can be simulated.
RS138-LZ is an auxiliary module for the program RS138 (Dimensioning of infiltration plants) and draws on the same project database.
Analysis
The calculation of surface runoff takes place within a surface drainage model. In this, for the calculation of initial losses (wetting and hollow losses), different methods are used. Wetting losses are taken as the threshold value and deducted from the precipitation in the beginning. The hollow losses are computed according to the limit value method.
In RS138-LZ, for dry periods, the re-establishment of the wetting losses and the hollow drying are integrated. Thus the program makes a continuous simulation.
Unlike the storm-network computation with the single rain events, the evaporation plays a very important role with the long-term simulation having dry periods. The actual evaporation data for a long time are by far rare in comparison with the rainfall data. In RS138-LZ an yearly mean daily evaporation depth is used which can be modified by a variable hour factor. The evaporation calculation takes place only in dry periods. During a rainfall event, the evaporation is relatively low, and is therefore not be considered.
For the infiltration of the permeable layers, the approach of Horton is used. This describes the changing infiltration capacity, on the basis of an initial infiltration rate up to reaching the final infiltration, as a function of the time. It is assumed that during this time, the rain intensity is always same or larger than the infiltration capacity. For dry or poor-rain sections, where the rain intensity is smaller than the infiltration capacity, an extension of the Horton-approach by Paulsen is used. The surface-runoff can be traced through the above described realistic approach. An additional retention effect can be obtained through a linear cascade storage.