The rapid underground dissolution of gypsum, and the evolution of the gypsum karst in Lithuania and England, results in subsidence problems which can make construction difficult. The natural dissolution yields sulphate-rich groundwater of poor quality and the karst is susceptible to the rapid transmission of pollutants.In the north of Lithuania gypsum karst is developed in Devonian gypsum. Here the towns of Biržai, Pasvalys and the surrounding countryside suffer subsidence and some buildings have been damaged. The majority of the potable water in these areas is derived from groundwater abstracted from sandstone sequences that underlie the gypsum. In Lithuania conservation measures have been introduced to control agriculture and prevent pollution of the gypsum karst. These measures include environmentally-friendly farming, restrictions on land use and exclusion zones around subsidence hollows.In England subsidence caused by the dissolution of Permian gypsum has caused severe problems in the vicinity of the town of Ripon. Numerous buildings have been damaged and new sites are difficult to develop. Here formal planning regulations have recently been introduced to help to mitigate against the worst effects of subsidence resulting from gypsum dissolution.

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Groundwater utilization and groundwater quality vary in the Baltic and Nordic countries mainly because of different geological settings. Based on the geology, the countries were treated in the following three groups: (1) Fennoscandian (Finland, Sweden, and Norway) countries, (2) Denmark and Baltic (Estonia, Latvia, and Lithuania) countries, and (3) Iceland. Most of the utilized groundwater resources are taken from Quaternary deposits, but Denmark and the Baltic countries have in addition, important resources in Phanerozoic rocks. The groundwater quality reflects the residence time of water in the subsurface and the chemical composition of the geological formations. Concentrations of ions in the Fennoscandian bedrock are elevated compared to Iceland, but lower than in Denmark and the Baltic countries. Compared to groundwater in the bedrock, groundwater in Quaternary deposits has usually lower concentrations of dissolved minerals. Unconfined Quaternary aquifers are vulnerable to contamination. Examples from Denmark and the Baltic countries illustrate challenges and successful effects of mitigation strategies for such aquifers related to agricultural application and management of nitrogen. Confined and deeper groundwater is better protected against anthropogenic contamination, but water quality may be affected by harmful compounds caused by geogenic processes (namely, sulfide, arsenic, fluoride, and radon).

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The qualitative status of groundwater is often underestimated. This is because distinguishing trends of hydrogeochemistry variation linked to anthropogenic pressure from natural trends in groundwater is challenging. The study aims to evaluate the effect of the natural processes on the limits of temporal variability of the natural background level (NBL) in springs draining aquifer units with different vulnerabilities. Shallow groundwater samples of eighteen natural springs were investigated. Statistical analysis and geochemical modelling were used. The results showed that the natural temporal variability limits of HCO3−, Na+, K+, Cl− and SO42− in high vulnerability aquifers were narrower than in moderate and low vulnerability aquifers. This pattern was determined by the stronger buffering effect of carbonate equilibrium, sulphate reduction, and dilution processes on the variation of these major ions in high vulnerability aquifers. Meanwhile, natural temporal variability limits of TDS, Ca2+ and Mg2+ in high vulnerability aquifers were wider than in moderate and low vulnerability aquifers. This pattern was related to the stronger buffering effect of ion exchange on the variability limits of Ca2+ and Mg2+ in springs of moderate and low vulnerability aquifer units than the buffering effect of weaker carbonate dissolution and higher dilution intensity on the variability limits of Ca2+ and Mg2+ in springs of high vulnerability aquifer. The results of this research could be helpful for the reasonable integrated management and effective protection of groundwater resources.