Water retention capacity of Bavaria’s soil function map 1:25,000 (BFK25) for three project areas

Soils fulfil important functions in the natural environment. The Federal Soil Protection Act protects these valuable soil functions. Soil function maps evaluate the performance of soils in the natural environment. The assessment is based on soil maps (mostly overview soil maps i.M. 1:25,000) and other information on the environment and location. The area information is implemented by means of linking rules to assessments. The soil has the important balancing function in the water cycle to absorb precipitation water, to store and to provide water delaying the vegetation, rivers and streams or the groundwater reservoir. The assessment of the soil as a balancing body in the water cycle is carried out on the basis of the criterion ‘water retention capacity of the soil’. This refers to the ability of the soil to store precipitation water in the pore room or to pass it on to deeper layers by leaching, thus removing the superficial drainage. Based on the saturated water conductivity, the usable field capacity and — in a flat or drain carrier location — the air capacity is estimated how much precipitation water a soil can absorb before surface drainage occurs. Soil hydromorphy, slope inclination and hydrogeological conditions are used as differentiation criteria. The maps can be used to take into account the balancing and protective effect of the soil on the water balance in terms of decentralised flood protection and water purification during planning and to be able to identify important water retention rooms. The soil function map “Compensation body in the water cycle” represents a soil protection evaluation of the soil map. Since the basic data of the soil function map are partly based on different topographical foundations, overlapping inaccuracies occur when comparing with current usage maps, especially at usage limits. In some cases, the evaluated areas in the soil function map are very inhomogeneous, so that in addition to the evaluation stage shown, different evaluations are also subordinated. Areas of less than 5 000 m² were added to neighbouring areas.土壤在自然环境中发挥着关键功能。《联邦土壤保护法》（Federal Soil Protection Act）旨在保护这些极具价值的土壤功能。土壤功能图用于评估土壤在自然环境中的功能表现，其评估以土壤图（多为1:25000比例尺的概略土壤图）及其他环境与区位相关信息为依据，通过关联评估规则实现区域评估信息的落地应用。土壤在水循环中具备重要的调蓄功能：可吸纳降水、储存并供给水分，延缓其向植被、河溪乃至地下水储层的运移。针对土壤作为水循环调蓄体的评估，以“土壤持水能力”指标为核心依据。该指标指土壤在孔隙空间储存降水，或通过淋溶作用将水分输送至深层土层，从而减少地表径流的能力。基于饱和导水率、有效田间持水量，以及平坦或具备排水条件区域的通气孔隙容量，可估算某一土壤在发生地表径流前所能吸纳的降水量。评估过程中还将土壤水文形态、坡度与水文地质条件作为区分判定标准。该土壤功能图可在规划阶段用于考量土壤对水平衡的调蓄与保护效应，助力实现分散式防洪与水体净化目标，同时可识别出重要的储水区域。“水循环调蓄体”土壤功能图是基于土壤图开展的土壤保护评估成果。由于该土壤功能图的基础数据部分依托不同的地形基准，在与现行土地利用图比对时会产生叠加误差，尤其在用地边界区域表现更为显著。部分情况下，土壤功能图中的评估区域均质性较差，因此除已展示的评估等级外，还存在其他从属评估结果。面积小于5000平方米的地块已并入相邻区域。