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This study investigates the impact of hydraulic conductivity uncertainty on the sustainable management of the aquifer of Lake Karla, Greece, using the stochastic optimization approach. The lack of surface water resources in combination with the sharp increase in irrigation needs in the basin over the last 30 years have led to an unprecedented degradation of the aquifer. In addition, the lack of data regarding hydraulic conductivity in a heterogeneous aquifer leads to hydrogeologic uncertainty. This uncertainty has to be taken into consideration when developing the optimization procedure in order to achieve the aquifer’s sustainable management. Multiple Monte Carlo realizations of this spatially-distributed parameter are generated and groundwater flow is simulated for each one of them. The main goal of the sustainable management of the ‘depleted’ aquifer of Lake Karla is two-fold: to determine the optimum volume of renewable groundwater that can be extracted, while, at the same time, restoring its water table to a historic high level. A stochastic optimization problem is therefore formulated, based on the application of the optimization method for each of the aquifer’s multiple stochastic realizations in a future period. In order to carry out this stochastic optimization procedure, a modelling system consisting of a series of interlinked models was developed. The results show that the proposed stochastic optimization framework can be a very useful tool for estimating the impact of hydraulic conductivity uncertainty on the management strategies of a depleted aquifer restoration. They also prove that the optimization process is affected more by hydraulic conductivity uncertainty than the simulation process.Editor Z.W. Kundzewicz; Guest editor S. Weijs [ABSTRACT FROM AUTHOR]

A modeling system for the stochastic simulation and management of the overexploited groundwater resources of Lake Karla Basin in Central Greece is presented. The uncertainty of the hydrogeological environment which arises from the lack of the hydraulic conductivity data and aquifer's heterogeneity necessitates the stochastic simulation of the underlying aquifer. For the conditional stochastic simulation of hydraulic conductivity, the geostatistical approach was used generating Monte-Carlo realizations. The impact of Lake Karla (or reservoir) restoration and the accompanying projects on the aquifer, is examined through various management scenarios taking into consideration this parameter uncertainty. The target of the restoration plan is to rehabilitate aquifer's water table. This will be achieved through shutting down a great number of irrigation wells, as the irrigation needs of cultivations will be covered by the reservoir. The project with the highest environmental impact on the aquifer is the construction of 50 water supply wells at the lakeside zone of Lake Karla. Nowadays, due to the intense agricultural cultivation, the study area faces a serious water deficit problem, which has led to the over-exploitation of non-renewable groundwater and to a dramatic drawdown of aquifer's water table. The results of the stochastic simulation and management indicates that the operation of the new water supply wells will lead, despite the operation of the new reservoir, to a further drawdown of aquifer's water table, and will increase the effect of parameter uncertainty on hydraulic heads estimation by groundwater model. [ABSTRACT FROM AUTHOR]

This paper presents a study for finding the optimal management plan of an overexploited aquifer under global climate change. The study area is the aquifer of the basin of Lake Karla, located in the eastern part of Thessaly in Greece. An optimization method has been used to evaluate the optimum volume of water that can be extracted from the aquifer and the optimum position of the wells with the objective of water table rise to a desirable sustainable level, taking into consideration the climate change forcing. The modelling system consists of a series of interlinked models: a hydrological, a lake-aquifer, a reservoir operation, a groundwater, and an optimization model. The climate change forcing on precipitation and temperature has been evaluated using the outputs of Canadian Centre for Climate Model Analysis General Circulation Model (CGCMa2) and a hybrid downscaling method which combines a multiple regression (MLR) model and a timeseries model for two socioeconomic emissions scenarios. The results of this study show that climate change plays an important role, as it affects the optimum volume of the extracted groundwater and the position of the irrigation wells. [ABSTRACT FROM AUTHOR]

Aquifer overexploitation is a common problem in drinking water management. This will become more and more important given the general reduction of water resources. To overcome overexploitation, one of the most adopted solutions is the relocation of extraction wells. To establish the positions of new wells, a precise knowledge of the hydrogeological setting is required. Specific surveys are therefore necessary to obtain information over wide investigation zones. Geophysical methods, particularly electromagnetic and electrical, can be useful with this aim. In the present paper a case history on the combined use of Electric Resistivity Tomography and Time Domain Electromagnetic soundings is reported. Surveys have been performed within the Maggiore and Traversola Valleys, to investigate the uppermost part of the Quaternary deposits, hosting the near surface aquifer. The electromagnetic data have been inverted with a spatially constrained approach by assuming a quasi 1D model of the subsurface. Geophysical surveys allowed for depicting the depth and lateral continuity of the supposed aquifer level in the surveyed area up to a depth of about 200 m and proposing potential positions for well relocation. [ABSTRACT FROM AUTHOR]