The map service displays 2 layers:
1.Longterm mean base flow for the period 1991-2020 (mean dynamic groundwater resources) - the mean values of the long-term base flow (BF), i.e. dynamic groundwater resources (l/s/km2) for the entire Czech Republic. It was generated from the long-term mean annual precipitation for the last thirty-year normal (period 1991-2020) on the basis of a tight relationship between the precipitation totals and total flow and base flow indexes (BFI) specific for individual hydrogeological districts determined by hydrograph separation on 480 profiles of Czech hydrometeorological institute (CHMI). Spatial resolution is 1 km2. According to the verification on 480 profiles of CHMI, the actual value of the base flow falls within the variance of ± 40% of given BF value. This is acceptable since BF is changing more than 1 order of magnitude within Czech Republic.
2. Base flow in the dry period (dynamic groundwater resources in dry year) - the base flow in a dry season, which was generated from layer of long-term mean base flow and the index of flow in dry year (M) for individual districts. The M index values were determined as the ratio between the base flow in the driest year of the decade 2010-2019 to the mean base flow derived from the separation of hydrographs on 480 profiles on watercourses in the Czech Republic. The values of the base flow in the dry season are significantly lower than the mean base flow, especially in lowland areas of the Czech Republic.