Sinkholes related to discontinuous pumping: susceptibility mapping based on geophysical studies. The case of Crestatx (Majorca, Spain)

Abstract

The Crestatx aquifer is the main source of water supply to the Bay of Alcudia, one of the largest resorts on the island of Majorca (Spain). This water has been used since the 1970s using several pumping wells, which draw an annual volume of 1.5 hm 3 . The seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level (up to 120 m) and dynamic water levels of down to 87 m below sea level. At the end of the 1990s, several sinkholes and subsidence depressions started being detected in a highly karstified area. Twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70,000 m 2 , with diameters up to 23 m and depth more than 15 m. The intense and continuous rainfall during recent years (2008)(2009)(2010) has considerably accelerated the process, increasing the dimensions of existing sinkholes and the appearance of new morphologies. By means of electrical tomography techniques, a ground study was carried out. Numerous cavities have been identified in the upper 30 m. Using a map of the surface morphologies and the geophysical profiles, we can determine that the propagation and orientation of the sinkholes lie along three main directions: N30°E, N130°E and N60°E. The first is the most relevant, which is parallel to the main tectonic structures in the area. The interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas, which is an effective tool to assess risk in the area, as there are roads and a housing development nearby. The high, but discontinuous, exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions, as it causes large variations of pressure and accelerates the dissolution process in the underlying rock.

A review on natural and human-induced geohazards and impacts in karst

“…(2) Water abstraction (Kemmerly, 1980;Newton, 1984;LaMoreaux and Newton, 1986;Chen, 1988;Waltham and Smart, 1988;Shaquor, 1994;Tihansky, 1999;Kaufmann and Quinif, 2002;He et al, 2003;Keqiang et al, 2004;Waltham, 2008;Dogan and Yilmaz, 2011;García-Moreno and Mateos, 2011), de-watering for mining and excavation operations (Foose, 1953;LaMoreaux and Newton, 1986;Chen, 1988;Xu and Zhao, 1988;Zhou, 1997;Li and Zhou, 1999;De Bruyn and Bell, 2001;Klimchouk and Andrejchuk, 2005;Sprynskyy et al, 2009;Pando et al, 2013), decline of water level in lakes (Yechieli et al, 2006;Frumkin et al, 2011), excavations acting as drainages (Fidelibus et al, 2011).…”

Hydrologic Modeling for Sustainable Water Resources Management in Urbanized Karst Areas

“…The expansion of hydraulically depressed areas caused by continued and excessive pumping can expand the zone of influence of these geo hazards. There are numerous studies relating overexploitation with water table declines and development of sinkholes [79,80,81,82,83]. According to these authors, excessive abstractions generate steep cones of depression that accelerate groundwater flow towards them, while slow phreatic recharge is replaced by more rapid downward percolation favoring suffosion, especially when the water table is lowered below the rock head.…”

Structural pattern of subsidence in an urban area of the southeastern Mexico Basin inferred from electrical resistivity tomography

“…The applicability of ERT to fractures and cracks mapping has been successfully tested (e.g., Hao et al, 2002;Tejero et al, 2002;Kim et al, 2007;Cardarelli et al, 2010;Ha et al, 2010;García-Moreno and Mateos, 2010). As we have mentioned, imaging electrical resistivity distribution of the subsurface could be helpful to determine changes in the intrinsic properties of the rocks and sediments like, permeability and porosity that are modified by the presence of a discontinuity like a fault, a fracture or a crack.…”