Introduction

In general, sustainable use of groundwater resources requires a thorough understanding of the hydrodynamics of groundwater system and its interactions with other environmental and anthropogenic systems. The highly heterogeneous character of karst systems needed massive research on groundwater exploration techniques for more than three decades, beginning from the 1960s. Research on groundwater exploitation techniques in karst have been followed by management strategies.

Groundwater management is a term which concerns to the sustainability of the resource in terms of quantity and quality, thus requiring the knowledge of the

International Research Center for Karst Water Resources, Hacettepe University, Ankara, Turkey e-mail: [email protected]

distribution of the groundwater flow velocity vector in the flow domain [1]. The only way of defining such a vector field seems to be a distributed parameter modeling [2]. However, modeling efforts in karst have been concentrated in the identification of the processes inside the karst system by analyzing hydrologic, chemical and isotopic observations at the outflow point, mostly springs. The success of the distributed numerical models is very poor, and utilization of such models in water resources management is still not possible. In general, the available numeric groundwater flows are designed for laminar flow conditions. There are attempts to combine the ground-water flow models with conduit-based turbulent flow modules [3, 4, 5] to simulate the karst system. Formulations for the conduit turbulent flows within a network of cylindrical pipes and for high conductivity turbulent flow layers are incorporated into well-known groundwater USGS groundwater model, MODFLOW 2005 [6], to simulate the conduit and preferential flow paths. However, this type of models are yet not able to predict the well yields, flow directions and velocities, due to all uncertainties in hydraulic, geometry and boundary definitions of the karst system.

Studies have revealed that even short term climatic changes affect the hydrologi-cal and chemical response of aquifers, including karst springs. This fact suggests that future climatic changes will increase the uncertainty of the models when and if they are to be used for karst groundwater management. Discussion of the pros and cons of different approaches in modeling is beyond the aim of this paper. Instead, a simplified approach is suggested herein this paper to classify karst aquifers toward adaptation of management strategies under climate change.

Therefore, any attempt to establish an effective management needs to be based on a sound conceptualization of the hydrogeological system. Hobbs and Smart [7] proposed a very important model to conceptualize a karst aquifer. They use three fundamental parameters, namely recharge, storage and flow, to describe the response of a carbonate rock aquifer. Classification of karst aquifers according to their morpho-hydrological characteristics can be regarded as the first step of conceptualization. Extension and thickness of karst formation, karstification base, mode of natural discharge, recession characteristics, regulation power coefficient, residence time, basin constant, and Fourier number or time constant of karst aquifer are among the major parameters to be used in classifying karst aquifers.

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