ScopePursuant to a new law that will become effective in 2015, DINO, the national Dutch subsurface database operated by the Geological Survey of the Netherlands, is to become an official government register (a 'key register' / basisregistratie). In facing the responsibilities associated with this new status, the Survey is reconsidering and redesigning its operation and in that process a new, or at least sharper picture is emerging of geological surveying in the future.These developments set the final stages of a process of modernisation that geological survey organisations all over the world are currently entangled in (Allen, 2003;Jackson, 2010). Most surveys are replacing paper archives that were built in the AbstractOver the last ten to twenty years, geological surveys all over the world have been entangled in a process of digitisation. Their paper archives, built over many decades, have largely been replaced by electronic databases. The systematic production of geological map sheets is being replaced by 3D subsurface modelling, the results of which are distributed electronically. In the Netherlands, this transition is both being accelerated and concluded by a new law that will govern management and utilisation of subsurface information. Under this law, the Geological Survey of the Netherlands has been commissioned to build a key register for the subsurface: a single national database for subsurface data and information, which Dutch government bodies are obliged to use when making policies or decisions that pertain to, or can be affected by the subsurface. This requires the Survey to rethink and redesign a substantial part of its operation: from data acquisition and interpretation to delivery. It has also helped shape our view on geological surveying in the future.The key register, which is expected to start becoming operational in 2015, will contain vast quantities of subsurface data, as well as their interpretation into 3D models. The obligatory consultation of the register will raise user expectations of the reliability of all information it contains, and requires a strong focus on confidence issues. Building the necessary systems and meeting quality requirements is our biggest challenge in the upcoming years. The next step change will be towards building 4D models, which represent not only geological conditions in space, but also processes in time such as subsidence, anthropogenic effects, and those associated with global change.Keywords: Netherlands, applied geoscience, hydrogeology, geological surveying, mapping, geomodelling, geodatabase Netherlands Journal of Geosciences -Geologie en Mijnbouw | 92 -4 | 217-241 | 2013 217 course of many decades by electronic databases; many surveys started producing electronically distributed 3D subsurface models in addition to or instead of 2D geological maps that were their primary output since their establishment. For a variety of reasons explained below, the Dutch survey is among the early adapters in both respects.In this overview paper we present the Geological S...

The province of Zeeland is situated in the coastal zone of the Netherlands. The ground surface level is around or below mean sea level. Therefore seepage of brackish to saline groundwater is very common. Sea level rise as a result of climate change will very likely increase the pressure on the coastal groundwater system, leading to an increased salinization of the groundwater and surface water system. Still, freshwater agriculture is being practiced in large parts of the province. The vegetation extracts its fresh water from the unsaturated zone and thin rainwater lenses that 'float' on top of brackish and saline groundwater. Geophysical and hydrogeological data have been combined on two spatial scales to obtain a better insight into this fresh-brackish-saline groundwater distribution. This information is being used to: assess groundwater abstractions, plan landuse and improve the input of variable-density groundwater flow and coupled solute transport models.For over 6000 locations various types of data have been used to estimate the depth of the brackish-saline groundwater interface of 1000 mg [Cl -]/L. These types of data are both of geophysical (vertical electrical soundings, EM34, geoelectrical well logs and electrical cone penetration tests) and of hydrological origin (water samples and abstraction wells). These data have been interpreted and combined with knowledge on the distribution of geological units to make an estimation of the depth of the brackish-saline water transition for the whole province (~66 km × 63 km).In addition to the regional brackish-saline interface map, continuous vertical electrical soundings (CVES) have been executed to map the fresh-brackish-saline distribution on a local scale. The CVES profiles were made at eight different plots where brackish-saline water is occurring at shallow depths (<5 m below the surface) according to the regional map and where freshwater agriculture is still being practised. Six of the eight sites have thin (0-3 m) brackish to slightly saline water lenses. At two sites up to 15 m thick brackish water lenses have been observed with CVES. The thickness of the brackish water lenses varies laterally over short distances. Sandy sediment and a higher topography are favourable factors for the development of such lenses. aggradation. A Holocene sediment wedge with a maximum thickness of 50 m was formed, containing both clastic (sand and clay) and organic sediments. Most of Zeeland was submerged several times by the sea during the geological history. Around 1000 AD man became a dominant element in the evolution of the coastal landscape. Salt marshes were successively being embanked, the resulting polders were drained and peat (with the salt water it contained) was beginning to become exploited as a source of salt. This resulted in the subsidence of the polder surface due to compaction and peat oxidation. Nowadays, only a very small part of the original salt-marsh

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