Sources can temporarily dry up in summer and autumn. The best season to map the state of sources will, thus, be winter and spring. In the mountains this time could change according to altitude and exposition. The source areas are easy to find at that time of the year, since the surrounding vegetation often consisting of not very open high herbaceous meadows is pressed onto the ground. Particularly striking are sources in lower altitudes in winter, when due to the "warm" temperature of the source water the source outflow stands out as a green spot free of snow in the landscape. The time of thaw should be avoided for mapping, because then many periodical and temporary sources appear.
A floristic record should be effected depending on the altitude, but mostly in early summer. In order to capture the whole fauna, the investigation should be performed twice a year, once in spring and once in autumn.

Due to their often very little spatial expansion sources are very difficult to find in the field. As a consequence, good maps are essential. For mapping works topographical maps with scale 1:25.000 are recommended or cadastre maps with scale 1:5.000 for investigations of a limited area. The responsible forestry office should be contacted before realising mappings in the forest, as usually there are also available forestry maps like ground plots or service maps, which might be very helpful.

Apart from the forestry office also the Water Conservation Bureau could give helpful information regarding existing sources for drinking water. In Bavaria, there is a department for legislation relating to water in the Lower Natural Conservation Board of the district administration, where information about old, unused source catchments could be found.

For a systematic mapping, the water course should always be followed downstream to upstream, i. e. in direction of the source. Only this way it can be avoided to overlook possible ramifications of the source creek not recorded in the map. If a source is approached in the field from above, an orientation will be very difficult. If no GPS is used, it will be very complicated to exactly indicate the location due to lacking orientation points. In many cases, the morphology of the area can give the decisive hint for a source outflow, as there may be notches or hollows in the source area due to regressive erosion. Should there be an obvious notch in the slope, for example, above a pipe outlet, then it is likely that the nowadays piped and dried out source outflow was at that point in former times.

The time required for the mapping of a source is mainly depending on the situation respective habitat and on the exactitude of the used maps. It is useful to get a first impression of the area by means of maps and literature. The topicality of the maps should then be confirmed during a general inspection of the area. Particularly, in forests the agreement of water course and pathes with the maps is not guaranteed, what naturally makes the orientation in the field more difficult and increases the time for processing.

Often the question arises how the investigated area could be limited. Mostly the limitation is realised by the political administration structure with the help of the district and municipality borders, e. g. with plan for the development of certain waters. However, waters do not stop at borders. Ecologically more sense makes a limitation related to the water catchment areas.