| Abstract [eng] |
The aim of the work - assess the conditions of subsidence of the main aquifers of the northern Lithuanian karst district and water quality, which determine the peculiarities of the choice of individual water supply systems. The work reviewed the prevalence of Europe's karst regions and groundwater quality, and described systems for water supply and improvement. On the basis of the data of previous studies and cartographic information, the geological-hydrogeological conditions of the main aquifers used for water abstraction in the karst district of Northern Lithuania were assessed. Summarizing the experience of installing water wells in the karst area, using technical-economic calculations, the costs of individual water wells installed in different aquifers were assessed. The summarising of the data from the chemical analyses of water in water wells carried out over the last six years has assessed the quality of water extracted from different aquifers in the area. The need for water improvement and technologies have been assessed, and the economic calculations of their installation and operation have been based. It was established that the quality of aquifers in the karst district depends on the lithologic composition of the layers, the depth of the subsidence, the flow of water between the layers, and the intensity of the agricultural activity carried out. The main problematic indicators of water quality of the karsturing Istra-Tatula and dolomitic Kupiškis-Suosa are very high water hardness, sulfates, iron and ammonium. In order to be suitable for human and household use, water must be prepared by devaluation, softening and reversing osmosias systems. Since the values of the indicators are distributed very unevenly, an individual water treatment system should be selected in each case. The water quality of the deepest-moving terigenic šventosios-upninkai aquifer complex is good, only in individual areas the iron concentration exceeds 0.5 mg/l, therefore only the iron removal filters are used there. Economic calculations of the installation and operation of wells have shown that in the long term (20-50 years) it is more economically advantageous to install wells in the aquifer of Šventoji – Upninkai. In the short term (10 years) the drilling and operation of the upper layers of Istra-Tatula and Kupiškis-Suosa are more economically advantageous. The choice of aquifer is currently determined by short-term economic benefits. Individual wells are rapidly multiplying in the upper aquifers of Istra-Tatula and Kupiškis-Suosa. Solving the situation requires a complex approach and a system that includes and combines economic, social and environmental components in solving problems and regulating water use in the karst district. |
