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- Title
A ground based gravity network for monitoring water mass movements in the Classical Karst region.
- Authors
Pivetta, Tommaso; Braitenberg, Carla; Gabrovšek, Franci; Meurers, Bruno; Gabriel, Gerald
- Abstract
The Classical Karst is a limestone plateau stretching between Italy and Slovenia over an areaof about 600km2. The aquifer of Classical Karst contains a complex network of conduits,shafts and large voids that are fed by the autogenic recharge and allogenic input of the RekaRiver. The Reka River sinks underground in the Škocjan Caves and continues its undergroundflow for almost 40km until it reaches the Adriatic Sea at the Timavo Springs. The river showshigh discharge variations; with minimal discharge below 0.3 m3/s and maximal dischargereaching over 350 m3/s. As the conduit system cannot efficiently drain large discharge, hugewater masses are stored in the epiphreatic voids of the aquifer during flood events.Škocjan Caves present such storage, where a vast amount of water is temporarystored during intense rain. Further evidences of the impressive water movementsin this system could be found in the geodetic time-series recorded by the GrottaGigante horizontal pendulums, which show deformation transients during Reka floodevents. Gravimetry could be a useful tool to obtain local mass balances of such complex system,contributing together with the other classical hydrologic prospections in depicting the waterdynamics in this karstic environment. In addition to this gravimetry represents the idealcompletion to the already set up geodetic instrumentation in the Classical Karstregion. In the last year, we installed two continuous recording gravity stations, near the Škocjancaves and inside the Grotta Gigante cave. The Škocjan caves serve as a test site because thecave geometry and the hydraulic system here are well known. The Grotta Gigante site offers aquiet place and long term geodetic time-series but on the other hand, the hydrodynamics hereare less clear. In this contribution, we present the simulations in support to the placement of theinstruments and the first analysis conducted on the observed gravity time-series. For theŠkocjan caves our simulations estimate that this mass accumulation could generate gravitysignals up to 30 microGal for extreme events with peak discharge over 250m3/s lasting for1-1.5 days, accumulating over 35 106 m3of water. The recorded data in Škocjan supports oursimulations: a prominent peak up to 5 microGal of amplitude was recorded during a 14 106m3 flood event on October 2018. We believe that the Classical Karst represents an interesting study case for both thegeodetic and hydrologic communities; the Škocjan cave offers a natural laboratory tooptimally assess the contribution of gravimetry as a tool for monitoring underground fluidmass movements.
- Subjects
SLOVENIA; ITALY; KARST; WATER masses; GRAVITY; GRAVIMETRY; WATER storage; CAVES; STALACTITES &; stalagmites; MASS-wasting (Geology)
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article