Evaporation measurements on enhanced water-permeable paving in urban areas

Pavements consisting of water-permeable paving stone have a certain retention and storage capability for rainwater in the event of intense rain. Applied on a large surface, this results in a mitigation of flood events. Compared to an impermeable surface area, the surface flow rate decreases while groundwater regeneration increases. To date, the actual change in the third water balance parameter, evaporation, is unknown. The man-made urban water cycle can more closely resemble the natural water cycle by increasing evaporation. The aim of the project described on the following pages is to vary and optimize the characteristics of water-permeable pavements (structure and constitution of the road base, underlay, structure and constitution of the paving stones used, width and filling of the seams, etc.) taking into consideration the applicable regulations, in such as way as to achieve evaporation rates that are as high and as constant as possible. The extensive future use of optimized products and pavings could improve the city climate and counteract the increased incidence of flood events. Measurement of the effective and active evaporation rate was carried out using a newlydeveloped tunnel evaporation gauge (WEIß et al. 2002). This measurement technique detects the actual evapotranspiration over plane, overgrown and non-overgrown surfaces. In the course of running-in the tunnel evaporation gauge, it was possible to gather first results.