Groundwater impact assessment of Lake Czorsztyn after 25 years of its operation

Abstract

Artificial water reservoirs pose impact on the natural environment. Impact of the artificial Czorsztyn Lake on groundwater and land management is assessed. The study is based on long-term observations of chemistry, groundwater levels and spring discharges during reservoir construction, filling, and 25-year-long exploitation. Land management changes caused by reservoir construction were recognized using remote sensing. Reservoir construction resulted in land management change in the study area. Built-up and forest areas gained prevalence over farmland areas. Two types of groundwater dominate: HCO3–Ca and HCO3–Ca–Mg, both before reservoir filling (68% analyses) and afterwards (95% analyses), and in control analyses from September 2020 (100% analyses). Gradual decrease in the occurrence of water types with the sulphate ion exceeding 20% mvals is documented, which points to water quality improvement trends. Moreover, changes of water saturation index values with regard to aquifer-forming mineral phases during reservoir construction and early exploitation phasei ndicate hydrochemical modifications. Decrease of groundwater level was related with transformation of the Dunajec river valley during reservoir construction and, accordingly, decrease of regional drainage base level. Groundwater level increased after reservoir filling, which points to coupled impact of the reservoir and increased precipitation recharge. Construction of the Czorsztyn Lake resulted in gradual land management transformation from farmlands into tourist-recreational areas. This change and river valley flooding by surface waters did not cause significant modifications in groundwater quantity and quality. Organization of water-sewage management related with reservoir construction resulted in noticeably improved quality trends.

Keywords

• water reservoir,
• groundwater,
• river,
• hydrogeology,
• sustainable water management,
• pieniny klippen belt