Rainwater calculations in scientific terms
This method, developed by hydrogeologists from the University of Wrocław, makes it possible to provide city planners and developers with data on rainwater management options and assist them in making land-use decisions.
The method in question is called DIS (depth of water tables – D, impact of vadose zone – I, and soil media – S), which makes it possible to assess and classify urban areas in terms of their ability to manage rainwater through infiltration into the ground. Researchers from the UWr dr hab. Robert Tarka, dr hab. Sebastian Buczyński and dr Tomasz Olichwer from the Department of Basic Hydrogeology of the Institute of Geological Sciences described it in the Hydrogeology Journal (Tarka R., Buczyński S., Olichwer, T., 2025. A novel method for the classification of urban areas in terms of rainwater drainage potential. Hydrogeology Journal 33: 49-61.)
Precipitation is an important element in the water cycle in nature; in urban areas it is regarded as an undesirable factor, posing a threat to existing infrastructure. On the other hand, infiltration of precipitation water restores groundwater resources by reducing the occurrence of hydrological and hydrogeological droughts. In addition, managing rainwater as close as possible to where it occurs reduces surface runoff and the load on the combined sewer or stormwater system. This reduces the risk of flooding or urban flooding.
The developed DIS method was applied to two catchments within the city limits of Wrocław: Lugowina and Brochówka.
The proposed methodology is based on data on the permeability of soils, the lithological formation of formations in the aeration zone and the depth of the aquifer.
The method developed takes into account the aforementioned elements as they have the greatest impact on the infiltration capacity of rainwater into the soil profile. The permeability of the soil influences how quickly rainwater will infiltrate (soak) into the ground. Infiltration that is too fast does not allow for proper water purification (and in this respect the soil plays an important role), while infiltration that is too slow leads to water accumulating on the ground surface for a longer period of time, which can cause negative effects such as rotting of vegetation and the development of mosquitoes. The rocks that build up the aeration zone determine the possibility of water moving down this zone. It is known that sands are more permeable to water than clay formations.
The depth of groundwater is also a key element. During infiltration of precipitation, the groundwater table rises. Hence, if the groundwater table is too shallow, flooding could occur in the surrounding area. Therefore, the deeper the groundwater table is, the more favourable the conditions for draining rainwater into the ground are.
Based on the DIS value, five classes of land suitability for rainwater management were proposed. It was assumed that with a DIS value below 1 there is no possibility of draining water into the ground, while above 2.5 there are good and very good conditions for the construction of infiltration basins or troughs.
– It is not that we are trying to exclude any areas for construction. They are lacking everywhere – says dr hab. Robert Tarka from the Department of Basic Hydrogeology (Institute of Geological Sciences, Faculty of Earth Sciences and Environmental Management). – Our method is only intended to allow us to set directions in rainwater management. Discharging rainwater into the ground is the simplest, cheapest and most environmentally beneficial way of replenishing groundwater resources, which is particularly important in urban areas where sealing the land surface from roads, buildings and other infrastructure results in limited groundwater recharge. The results of our analysis should be useful to planners when making decisions on how to develop the land – he adds and explains – For example, when DIS values are low, the land can be developed into green areas or other ways of draining rainwater can be used.
Thus, the construction of infiltration basins or absorption troughs at such locations due to the lack of infiltration capacity will not be effective and will lead to the negative phenomena (effects) we mentioned earlier.
The methodology developed makes it possible to provide urban planners or developers with data on the possibilities of managing rainwater on site and assisting in land-use decisions.
Undoubtedly, the scientific community has an important role to play here. – We should at least partly get away from our desks, computers and laboratories to participate to a greater extent in the professional meetings of those involved in land and water management – our researchers believe.
Both waterworks and developers are struggling with problems of rainwater management. – The cooperation so far indicates that we do not need to encourage developers and planners to make use of the scientists‘ research, but we do need to take the initiative and show these people what solutions we have to their problems – believes dr hab. Robert Tarka.
In most cases, the benefits of cooperation between the scientific community and the general socio-economic environment are so tangible that both parties are happy to cooperate. – In our case, cooperation with the Centre for New Technologies of the Municipal Water Supply and Sewage Company in Wrocław and the Plenipotentiary of the Mayor of Wrocław for Management of Rainwater and Meltwater is very beneficial – emphasises dr hab. Robert Tarka. – The new method we have developed and proposed to classify areas in terms of their capacity to discharge rainwater into the ground is a response to the reported problems in rainwater management in Wrocław, but can be successfully applied in other cities. It is a universal, cheap and fast method and the only condition determining its use is a good hydrogeological diagnosis.
Tarka R., Buczyński S., Olichwer, T., 2025. A novel method for the classification of urban areas in terms of rainwater drainage potential. Hydrogeology Journal 33: 49-61.
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Date of publication: 21.03.2025
Added by: M.J
