Abstract [eng] |
SUMMARY VILNIUS UNIVERSITY FACULTY OF CHEMISTRY AND GEOSCIENCES Modestas Kartenis ASSESSMENT OF THE PROTECTION ZONE OF ROKIŠKIS CITY WELLFIELD USING MATHEMATICAL MODELLING METHODS In the master's thesis, utilizing archival materials from the Lithuanian Geological Survey's database, including reconnaissance, groundwater resource assessment, and mathematical modeling data of Rokiškis city and other major water intakes in the district, a mathematical model of the subsurface hydrosphere in the Rokiškis area was developed. This model was created by analyzing and supplementing the data with information from new boreholes drilled into the Šventoji-Upninkai complex over the past decade. It was used to solve the main tasks of the work: refining the filtration parameters of the Šventoji-Upninkai complex exploited at the water intake; determining the predictive catchment areas and protection zones of the Rokiškis water intake, considering the hydrodynamic interaction with adjacent water intakes; and identifying the natural resources of the Šventoji-Upninkai complex in the Rokiškis area and the sources of groundwater resource formation at the water intake. The modeling determined that the filtration coefficient of the upper part of the Šventoji-Upninkai complex near Rokiškis is 4.8 m/d (with a water permeability coefficient of 390 m²/d), and for the lower part, it is 2.3 m/d (with a water permeability coefficient of 150 m²/d). The modeling results show that the majority of the study area (about 60%) is in the recharge area of the Šventoji-Upninkai complex. The complex is characterized by significant natural resources, amounting to 96,200 m³/d (16.72 mm/year, with a resource module of 0.53 l/s per km²). The main source of their formation is the groundwater flow from D3kp-s and the weakly permeable formations covering the groundwater layers of the complex, reaching 85,750 m³/d and forming 89% of the natural resources. The remaining portion of the natural resources is formed by lateral inflow of groundwater from neighboring areas bordering the study area. According to the modeling results, when operating the water intake at a predictive rate of 4,000 m³/d, the primary source of resource formation is the groundwater flow entering the catchment area through the productive upper part of the complex – the increase in its inflow and the decrease in outflow form 85% of the extracted water quantity, with the contribution from other sources being minimal. The protection zone of the Rokiškis water intake, established through modeling methods, including interaction with adjacent water intakes, consists of only two zones - the first (strict regime) and the second (microbial contamination restriction) zones. It is proposed to equate the strict regime zone to the current territory of the water intake, and to draw the second protection zone at a distance of 110 m, which is the prevailing size of the 200-day catchment area, around the strict regime zone. |