Flysch-type aquifers in the Eastern Carpathians usually feed periodic and low-discharge springs. However, in some areas, such as in the upper part of the Połonina Wetlińska Massif, perennial springs with a relatively high discharge were identified. Therefore, the aim of this study was to identify recharge and groundwater flow patterns of three high-discharge springs based on the response of spring discharge to rainfall and on the relationship between specific electrical conductivity of water and spring discharge. The relation between spring discharge and rainfall was investigated by cross-correlation analyses. Generally, cumulative rainfall over a period from 10 days to 3 months is most strongly correlated with discharge; however, the response time of spring discharge varies throughout the year. Faster response to rainfall occurs in the spring after snowmelt, while in the summer and autumn months the response time increases. Two flow systems were identified: 1) a relatively deep, fissure-pore flow system with a long response time to precipitation and 2) a shallow, fissure-dominated system with a short response time, which is superimposed on the longer response. A small range of specific electrical conductivity combined with the varying discharge of two springs suggests that dilution of groundwater by rainwater does not play a significant role. The differences in the studied springs’ response to rainfall can be attributed to the recharge area, regolith features and local bedrock structures, i.e. occurrence of joints and faults, monoclinal dip of rock layers and gravitational slope deformations including ridge-top trenches, which, thus far, have been underestimated in determining groundwater storage capacity in the flysch part of the Carpathians.

The aim of the study is to assess the capacity of the flysch aquifer feeding springs in the Outer Eastern Carpathians using spring recession curves. The four selected springs are located in an area generally believed to be poor in groundwater. However, the selected springs were characterized by remarkably high average discharge of 3.2–9.6 L s⁻¹. Recession coefficients were estimated which enabled an aquifer capacity and groundwater residence time assessment. Despite similarities in elevation, precipitation, and lithology in the study area, a substantial variation in the recession coefficients and aquifer parameters was found. The average aquifer capacity of groundwater subsystems strongly varied in the small study area (4.9–49 m³ × 10³). The mean groundwater residence time varied from 11 days to 50 days depending on the volume of groundwater drained by the springs. Differences in discharge, recession coefficients, groundwater capacity, and residence time were related to recharge areas of different size. Simple relationships between the topographic catchment areas of springs and their hydrologic parameters can become altered by local structural features: faults and fissures. The study demonstrates that tectonically produced structures may facilitate a larger supply of groundwater and the occurrence of high-discharge springs in a given area.

Zmiany warunków hydrologicznych wynikające z tworzenia nasypów – przegląd przypadków