Area types of nat. Water balance
Description
The average natural water balance in our region is characterised by the fact that about 75 % of the fallen precipitation evaporates, about 15 % leaks and thus contributes to the formation of groundwater and drains about 10 % superficially. Depending on geomorphological and hydrogeological site characteristics (e.g. terrain inclination, groundwater level, soil type), the percentages of the water balance components evaporation (V), groundwater new formation (GWN) and runoff (A) for specific areas differ. The types of areas describe which water balance components outweigh due to the natural nature of the areas compared to the average distribution. The thematic group includes the following types of areas of natural water balance: I – drain-dominated (A ~18 %, GWN ~ 7 %), II – drain- and evaporative-dominated (A ~ 13 %, V ~ 77 %), III – evaporation-dominated (V ~ 78 %, GWN ~ 15 %), IV – leakage-dominated (GWN ~ 35 %, A < 5 %, V ~ 65 %), V – evaporation-dominated (V ~ 86 % A < 7 %, GWN < 7 %). For area type V, a distinction is made between V a and Vb. V a includes clearly demarcatable areas with low groundwater level < 2 m (almost areas, old lbarm, secondary valleys of the Elbe with auelehm distribution, near-natural wet and wet sites) which are thus dominated by evaporation. The area type Vb makes it clear that local groundwater levels < 2 m can occur within area types I to IV (however, this has to be investigated for the specific case) and then dominates the evaporation.
Source:
The topic group was developed by the Environment Office of the state capital Dresden on the basis of the estimation of medium water balances based on Dörhöfer & Josopait (A method for the area-differentiated determination of groundwater new formation rate – Geological Yearbook C 27, pp. 45 to 65, Hannover 1980). The data for this were the environmental atlas maps 3.6 leaching possibilities of precipitation water and 4.4 groundwater level.
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