Determination of karst spring characteristics in complex geological setting using MODKARST model: Azmak Spring, SW Turkey

The MODKARST mathematical code is used to simulate both brackish and non-brackish karst springs and provides useful information on the hydrological and hydrogeological characteristics of their aquifers. Next to this, MODKARST can also explain the often peculiar behavior of these springs, inherited from the complexity of the structures that most of the times form fractures, cavities, and conduits in carbonate formations in tectonically complex areas. The simulation focuses on explaining the complex behavior of the Azmak spring. Azmak is a large brackish karst spring in SW Turkey, which displays peculiarities both in terms of its hydrograph and seawater intrusion mechanism. In particular, during the recession period, contrary to the chloride concentrations of its water which appears more or less stable, its hydrograph shows fluctuations. The MODKARST simulation showed that the discharge fluctuation during the recession period is due to the operation of a siphon, while the abnormal variation of its chloride content is due to its predominant seawater intrusion mechanism which is the Venturi effect.