Nicolaos Theodossiou

Evaluation and optimisation of groundwater observation networks using the Kriging methodology

Abstract Groundwater simulation models have nowadays a decisive role in the development and application of rational water policies. Since the accuracy of the simulation depends strongly on the available data, the task of optimising the observation networks is of great importance. In this paper an application is presented aiming at the optimisation of groundwater level observation networks and the improvement of the quality rather than the quantity of the obtained data. This technique is based on the application of the Kriging methodology and the evaluation of its results in conjunction with the statistical analysis of the available groundwater level data. This procedure that involves different analysis methods of the available data, such as estimation of the interpolation error, data crossvalidation and time variation, is applied to a case study in order to demonstrate the potential of improvement of the quality of the observation network.

Application of Non-Linear Simulation and Optimisation Models in Groundwater Aquifer Management

The need for rational and overall water resources management has become, during the past decades, a problem ofmajor importance due to the rising water demands. In this paper atechnique is presented through which a management model that combines the useof two separate models, a flow simulation and an optimisation one, isused for groundwater management. The necessary stages for the formulationand the combined use of the two models, along with a number of problemsthat might arise during the development of the management model are alsopresented. This technique is applied to a large-scale case study problemthat forms an optimisation approach with a large number of non-linear decisionvariables. The results of the application of the management modeldemonstrate the importance of the use of such models both in managing rationallyavailable water resources and in reducing the operational cost of theirexploitation.

Combined use of BEM and genetic algorithms in groundwater flow and mass transport problems

The boundary element method (BEM) can be used very efficiently, in solving groundwater flow problems. Genetic algorithms (GAs) constitute a very efficient optimization tool. In this paper, BEM and GAs have been combined to find optimal solutions in three classes of commonly encountered groundwater flow and mass transport problems: (a) determination of transmissivities in zoned aquifers (inverse problem), based on a restricted number of field measurements; (b) minimization of pumping cost from any number of wells under various constraints; and (c) hydrodynamic control of a contaminant plume, by means of pumping and injection wells. Application examples show that the proposed combination is very efficient in optimizing development and protection of groundwater resources.

Multiobjective Pump Scheduling Optimization Using Harmony Search Algorithm (HSA) and Polyphonic HSA

Harmony Search Algorithm (HSA) is a metaheuristic method that has attracted the scientific interest since its first presentation in 2001. It is a music inspired method, imitating the music creation process in order to find optimal solutions in complicated problems. HSA’s successful application on single – objective optimization problems has resulted to an increasing interest in the implementation of HSA towards multiobjective optimization. The authors have adjusted HSA in order to deal successfully with multi-criteria water management problems. This adjustment has resulted to the creation of Multiobjective – HSA (MO-HSA). In addition, they have designed the multiobjective variant Polyphonic-HSA (Poly-HSA), which is inspired by the independent development of different voices in music and borrows elements from Swarm Intelligence and the single-objective variant Global-Best HSA. In the first part of this paper, both methods are presented in detail. Moreover, the performance of the proposed Algorithms is evaluated using standard multiobjective test – functions. ZDT and DTLZ multiobjective tests have been chosen and indicators such as Hypervolume, C – metric and diversity metric – Δ have been used to measure the convergence to the optimal front and the diversity of the solutions obtained by the proposed methods. In the second part, MO-HSA and Poly-HSA have been introduced towards the optimization of a pump scheduling problem. The objectives considered are water supply, pumping cost, electric power peak demand and pump maintenance cost. Both methods converged to non-dominated fronts and provided excellent results which are presented in 3d figures, indicating that these methods can be effectively used in multiobjective water management problems.

Assessing the Impacts of Climate Change on the Sustainability of Groundwater Aquifers. Application in Moudania Aquifer in N. Greece

In this paper, the impacts of climate changes over an aquifer system in northern Greece are investigated. Climate estimations over a number of parameters, such as temperature, rainfall, humidity, wind velocity, solar radiation etc., were extracted using one of the most recent Regional Climate Models, KNMI-RACMO2. They were then inputted to the groundwater model MODFLOW in a series of transient simulations, in an effort to investigate the impacts of anticipated changes on parameters, such as infiltration and evapotranspiration that affect the water balance over the watershed. Five different methods for the calculation of evapotranspiration were implemented in order to minimize any bias or uncertainty. The aim of the methodology presented in this paper is to lead to the clarification of whether a change to the current water resources management practices, in order to ensure the sustainability of the aquifer system, is necessary and to what extent. The results of this application indicate that if current practices continue to apply in the future, the water balance in the aquifer will be negatively affected. In order to reverse this situation, a number of measures need to be taken, with the most important to introduce a more rational use of water, especially in the agricultural sector. Since the case study aquifer can be characterized, according to the meteorological conditions and the water uses, as a typical Mediterranean one, the same conclusions are expected to be deducted in many other similar groundwater systems as well.

Delineating well-head protection areas under conditions of hydrogeological uncertainty. A case-study application in northern Greece

The delineation of well-head protection areas, especially for water supply wells, is of most importance in ensuring water quality. The areas delineated under this concept must be large enough to ensure that no pollutants will end-up and be pumped-off by abstraction wells but at the same time, small enough to minimize the social and economic cost of applying restriction measures to nearby land owners. The whole concept of applying well-head protection areas is based on the recognition of the hydrogeological parameters of the aquifer. The fact that these parameters are, by nature, characterized by uncertainty makes the whole application very difficult. In this paper, the delineation of well-head protection areas is simulated through a mathematical model and the methodology is applied on the aquifer of Moudania in Chalkidiki, taking into consideration a number of equally probable realizations of the geological structure of the aquifer. This aquifer is characterized by the spatial variability of its hydrogeological parameters, making the introduction of uncertainty in its simulation, an absolute necessity.

Renewable energy production management with a new harmony search optimization toolkit

The design goals of the developed software are described followed by its architecture, which is presented in detail. The GUI-based interface supports a variety of environmental management problems and can provide best practices in a timely manner. The toolkit is generic and applicable to any scientific field. It was applied on a renewable energy (RE) system’s management. The developed model simulates the hydraulic characteristics of a small-scale hydropower (SHP) station. Harmony search algorithm (HSA) toolkit optimized the SHP’s operation, without violating the ecological constraints related to environmental flow (EF) regimes. This was equal to maximizing the revenues from SHP’s energy production in terms of a hypothetical fluctuating market. Apart from securing the provision of EF regimes, HSA toolkit’s outcome provided management practices that increased the total economic gains. Supporting the economic viability of SHPs and their environmental friendliness is needed to strengthen their role in the RE mix.

Corrigendum to “Evaluation and optimisation of groundwater observation networks using the Kriging methodology” [Environ. Model. Softw. (2006) 991–1000]

Corrigendum to ‘‘Evaluation and optimisation of groundwater observation networks using the Kriging methodology’’ [Environ. Model. Softw. (2006) 991e1000] Nicolaos Theodossiou*, Pericles Latinopoulos Division of Hydraulics and Environmental Engineering, Faculty of Civil Engineering, School of Technology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece Available online 18 September 2006