During the past decades, groundwater-dependent ecosystems in the Netherlands have been threatened by a decline in the water-table level. However, information on water-table depths and changes in water-table depths is insufficient and outdated. For policy evaluation, spatially explicit and detailed information on water-table depths is required, especially in areas with groundwater-dependent ecosystems including wetlands. Some 35,000 observations of seasonal fluctuation characteristics of water-table depths in nature conservation areas were made since 1980 during soil surveys. These observations were derived from characteristics of the soil profile or from measurements in boreholes. These observations were used in a space-time geostatistical analysis to map the seasonal fluctuation of water-table depths between 1980 and 2007. First, systematic differences between different estimation modes used through the years were corrected. Next, observations were correlated with area-wide available ancillary data using multiple linear regression. Simple kriging was used to interpolate the resulting space-time residuals. Maps of the predicted mean spring water-table depths and the accuracy of these predictions were used to identify areas where the water-table is deeper than favorable. Changes of water-table depths on the national scale over the past 25 years were assessed, and recommendations were made to increase the accuracy of future predictions.