P. Latinopoulos

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.

Analytical solutions for two-dimensional chemical transport in aquifers

Abstract A method of obtaining analytical solutions for chemical transport in two-dimensional aquifers is presented. Assuming a constant velocity field, linear adsorption, and first-order decay the solution is obtained by integrating the solution of a modified one-dimensional differential equation. The procedure is simple and straightforward and can be applied to various sets of initial and boundary conditions as long as the corresponding one-dimensional transport equation has an analytical solution.

Analytical solutions for strip basin recharge to aquifers with Cauchy boundary conditions

Abstract Analytical solutions for groundwater recharge from strip basins to finite aquifers are presented. The problem concerns the impact of either continuous or periodic (seasonal) recharge schemes on aquifers with a boundary condition of the third kind (Cauchy). The solutions can be useful for assessing aquifer response as well as for calibrating numerical computer models.

A sensitivity analysis and parametric study for the evaluation of the optimal management of a contaminated aquifer

A typical groundwater remedation problem is studied by using a combined simulation-optimization model. The management procedure employs groundwater flow and contaminant transport simulation models in conjunction with linear and quadratic programming techniques. The methodology is applied to the hydrodynamic control of a contaminant plume that has to be stabilized and removed by a system of pumping wells. The paper focuses mainly upon a sensitivity analysis to the aquifer transmissivity. The effect of changes in the transmissivities of a zoned aquifer upon the optimal solutions of the management problem is examined by considering the optimal pumping rates, the time to remediation and the pumped groundwater volume as the key output variables of the remediation strategies. In addition, the influence of the dispersivities and the imposed hydraulic gradient upon the same output variables is critically evaluated. The results of the study illustrate the need for uncertainty reduction in the knowledge of the hydrogeologic parameters.

Analytical solutions for periodic well recharge in rectangular aquifers with third-kind boundary conditions

Abstract Analytical solutions for groundwater flow in rectangular aquifers are presented in the case of single-well recharge. The problem concerns the impact of a seasonal (periodic) recharge scheme of variable duration on aquifers with various boundary conditions of which at least one is of the third kind. Results can be obtained for any combination of boundary conditions and can be used in a preliminary assessment of the groundwater response to artificial recharge schemes.

Risk-Based Decision Analysis in the Design of Water Supply Projects

The application of a decision analysis methodology to a small-scale water-supply/aquifer-contamination problem is presented. The main characteristic of the study is the development of a series of alternative strategies to ensure a continuous water supply to a village under variable risk conditions. It is assumed that the risks involved in the analysis reflect the uncertainty as to the hydraulic conductivity. Thus, a stochastic simulation model for groundwater flow and contaminant transport is employed in order to evaluate the implications of uncertainty in the systems behaviour upon the overall design decisions. Alternative decision strategies are formulated by considering both actual and probabilistic costs, and they are finally compared using a risk–cost–benefit objective function.

A BOUNDARY ELEMENT AND PARTICLE TRACKING MODEL FOR ADVECTIVE TRANSPORT IN ZONED AQUIFERS

Abstract One of the most crucial factors that affects both the accuracy and efficiency of a groundwater transport model is the flow simulation method which produces the velocity field. This paper presents a boundary element technique that incorporates the zoning approach to allow aquifer heterogeneity. First, the accuracy of the flow model is verified by comparing it with analytic solutions for well-pumping and injection problems. The boundary element flow model is then coupled with a particle tracking procedure for advection-based transport simulation. The combined model also calculates streamlines, travel times and breakthrough curves and is therefore a powerful tool for simulation and management of advection-dominated contamination problems.

Periodic recharge to finite aquifiers from rectangular areas

Abstract Analytical solutions for groundwater flow in unconfined rectangular aquifers are presented for the case of recharge from rectangular areas. The linearised differential equation of the flow is solved using Laplace and finite Fourier transforms. The problem concerns the response of finite aquifers to periodic (seasonal) recharge schemes of variable duration. Results can be obtained for various combinations of Dirichlet and Neumann boundary conditions and can be easily used in a preliminary study of water resources management.

Well recharge in idealized rectangular aquifers

Abstract Analytical solutions for groundwater flow in rectangular aquifers are presented in the case of a single-well recharge. The problem concerns the impact of a seasonal recharge scheme of variable duration on aquifers with various boundary conditions. The results obtained from these idealized aquifers can be used in a preliminary assessment of the groundwater response to artificial recharge schemes.

Numerical simulation of pulsatile flow in constricted axi-symmetric tubes

A finite element algorithm is presented to solve the Navier—Stokes equations in an axi-symmetric tube of variable cross-section. The stream function and the vorticity are used as the unknown variables and under this formulation the relevant set of equations is solved in an explicit form using linear interpolating functions and the Galerkin approach. The element integrals corresponding to this type of equations are computed through explicit multiplication and term-by-term integration. The algorithm presented consists of an iterative procedure which ensures periodic solutions in both time and space. The accuracy of the model was satisfactorily tested against analytical solutions for straight tubes. The laminar oscillating flow of a Newtonian fluid through a tube with periodically varying cross-section is adopted as an approximation to the pulsatile flow in blood vessels. The effect of varying the basic parameters in this complicated flow can be evaluated by the means of solutions obtained from the finite element model. Using a representative set of cases it is shown that important properties, such as velocities and shear stresses, are strongly influenced by changes in the flow characteristics.