Soils as water reservoirs

Science Teams Activities

Soils as water reservoirs

Soil consists of many mineral particles, between which there are cavities called pores. The size of the pores varies depending on the grain size and the structure of the soil, which is essentially a consequence of the activity of the soil organisms. The pores are filled with either air or water. Depending on their size, they allow the rapid transport of water to deeper layers or store it as soil water. A soil consisting mainly of sand transports water quickly and therefore can store little soil water for plants. In contrast, a soil composed primarily of finer-grained silt has many medium-sized pores that can store water for a long time. Thus, the water storage capacity of a soil depends largely on the soil type. Because soils can store water, they release rainwater to streams and rivers with a delay, thus reducing the risk of flooding. However, this so-called retention of water is only possible on undeveloped soils. Undeveloped soils are also the prerequisite for groundwater and our supply of drinking water. Built-up and sealed soils can no longer fulfill these regulatory functions in the water balance.

Schematic representation of soil as a water reservoir

Soils as filters

Soil is capable of filtering, neutralizing, and binding chemical elements and compounds that are carried in with rainwater. This applies to both nutrients and toxic substances. In this way, soil prevents the transport of pollutants into the groundwater and thus, in the long term, into our drinking water. The filtering capacity of a soil depends on the grain size composition, the amount of humus and the level of pH. During filtration, pollutants and generally all elements and compounds dissolved in soil water are bound to humus and clay particles. This means that a soil with high proportions of the grain size clay can filter much better than a pure sandy soil.

Soils as temperature regulators

The heat stored in the soil and the evaporation of soil water controlled by plants affect the air temperature and humidity on site. The temperature difference between developed and undeveloped soil surfaces is immense. A vegetated soil provides significant cooling via evaporation. In addition, a vegetated soil heats up less than an asphalt surface. The effect is very noticeable on warm summer days in parks or in the forest.

Mapping

First, mapping and analysis of land use/siltation was conducted through aerial photo interpretation and tapping of area percentages in www.tim-online.nrw.de.

Total area of OHS with locations of sampling

Sealing by buildings

Sealing due to traffic/parking areas

unsealed areas

Analysis of the land use

The following ratios of sealed to unsealed areas and the degree and type of sealing on the Otto Hahn Schools site are obtained:

The traffic/parking areas (water-bound: pavement, gravel), sports field were calculated as remaining areas.

Sealed surfaces and unsealed surfaces on the Otto Hahn School site in percent.

Water-permeable surfaces and water-impermeable surfaces on the Otto Hahn School site in percent.

Sampling

Based on the mapping, three soil samples were collected and the soil type, infiltration capacity, and soil temperature were subsequently investigated.

Development Of The City Challenges

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