Evaluation of pond/aquifer flow exchanges using local discretization and contrasting different boundary condition in MODFLOW. Case of Santa Olalla pond (SW Spain)

<p>Almonte-Marismas is a coastal aquifer situated in Doñana Natural Park (Southwestern of Spain, Huelva). It supports one of the most important wetland areas in Europe due to its biodiversity, size and strategic location. Nowadays, the aquifer suffers serious threats due to the large amount of water extraction that takes place in the area due to the high demand for water that exists for the supply of tourism and irrigation.</p><p>There is a flow model of the regional aquifer which is used to support the water management Administration. However, this model does not take into account groundwater interactions with local ponds. Santa Olalla pond is a hypogenic wetland that, on a regional scale, it receives the discharge of the Almonte-Marismas aquifer. This fact allows it to maintain a permanent water regime without suffering a reduction in its volume of water. Despite of that, the intense pumping in the zone could affect it and be a risk in the future.</p><p>The objective of this study is the identification of an appropriate model structure to characterize and implement the Santa Olalla Pond in the current steady-state model of the regional aquifer of Doñana employing ModelMuse interface. For this purpose, different boundary conditions (LAKE and DRAIN packages) were contrasted to represent the pond, combined with different local grid refinement (LGR2 package). The contrast criteria to assess the goodness of the numerical representation have been the piezometric heads in the wells situated in the surroundings of the pond and the stage levels and water balance of the pond.</p>

Piezometric Assessment for Salinity in Multi Aquifer System in Dharoi Command Area, Gujarat

Our earlier study carried out in Dharoi command area in Sabarmati River Basin, in India, defined the sensitive parameters to address the problem of water logging and salinity in the shallow aquifer, contribution of multi-aquifer system in making the scenario complex, was thus evident. Therefore, extension of the study by analyzing the piezometric data of complex lithological setup is attempted in this paper. The present paper establishes and discusses the relationships of various depth wise aquifer zones with the help of the seasonal piezometric heads and TDS values, analyzed as tracers.

Study of Effect of Altered Piezometric Heads in Experimental Investigation of Bernoulli’s Equation

Bernoulli’s equation is found to be one of the most popular topics of the elementary physics. The paper presents the experimental behavior of the famous Bernoulli’s equation when the piezometric heads are altered and varied with respect to the heads 10cm and 15cm. The value of h in centimeters have been recorded in altered time periods and heads and in all the nine tubes. The calculation of the total energy (E) by changing the heads is obtained and the results achieved while equating the graphs between the total energy and distance from the reference point by changing the heads has been computed.

Hydrogeological Study of the Glacial—Fluvioglacial Territory of Grandate (Como, Italy) and Stochastical Modeling of Groundwater Rising

On November 2014, the Municipality of Grandate, near Lake Como, had to deal with a great emergency that was caused by the flooding of factory undergrounds. The authors realized a hydrogeological study to understand the causes of groundwater flooding and to prepare a pre-feasibility study concerning possible actions for groundwater control. The hydrogeological structure is rather complex and required time-consuming reconstruction of the conceptual site model. A transient numerical model was developed to analyse the system behaviour in different scenarios. The flow model was calibrated in a steady and unsteady-state using the automatic calibration code Model-Independent Parameter Estimation (PEST). The study demonstrated that the reason for floods was mainly due to the concurrence of three causes: (1) the hydrogeological structure of the area was recognized as a stagnation zone, (2) groundwater rising, and (3) extremely heavy rainfall in 2014. Through the PEST RandPar function, 100 random rainfall scenarios were generated starting from rainfall data for the last 20 years. The model was used to run 100 1-year long simulations considering the probability distribution of recharge related to the 100 randomly generated rainfall scenarios. Through collecting the piezometric heads that resulted from the simulations, monthly probability curves of groundwater exceeding a threshold level were obtained. The results provided an occurrence probability of groundwater level exceeding the underground structures level between 12% and 15%.

OPTIMIZED AQUIFER MANAGEMENT, USING LINEAR PROGRAMMING.AN APPLICATION TO THE AGIA VARVARA AQUIFER, DRAMA, GREECE

The present research analyzes the behavior of Agia Varvara aquifer in Drama, Greece. A comprehensive and complete simulation-management combination model is applied, capable of calculating the water mass balance of the aquifer and defining the optimal management solution. In order to simulate the aquifer, a finite difference model is used. By applying this model and the Response Matrix Method, the management of the aquifer is achieved. Once the simulation of the aquifer is finished, the Linear Programming analysis is performed to obtain the optimal values of piezometric heads and flow rates, imposed to the system on monthly basis, in order to meet the demand of water at the lowest cost. The resulting piezometric heads are compared with the initial ones, enabling scenarios about the maximum and minimum drawdown, and providing the critical months of irrigation. The Linear Programming is used to facilitate the operation of systems, maximizing the total amount of pumped water, under a given set of constraints.

Complexity versus simplicity: an example of groundwater model ranking with the Akaike Information Criterion

A groundwater model characterized by a lack of field data to estimate hydraulic model parameters and boundary conditions combined with many piezometric head observations was investigated concerning model uncertainty. Different conceptual models with a stepwise increase from 0 to 30 adjustable parameters were calibrated using PEST. Residuals, sensitivities, the Akaike Information Criterion (AIC), and the likelihood of each model were computed. As expected, residuals and standard errors decreased with an increasing amount of adjustable model parameters. However, the model with only 15 adjusted parameters was evaluated by AIC as the best option with a likelihood of 98%, while the uncalibrated model obtained the worst AIC value. Computing of the AIC yielded the most important information to assess the model likelihood. Comparing only residuals of different conceptual models was less valuable and would result in an overparameterization of the conceptual model approach. Sensitivities of piezometric heads were highest for the model with five adjustable parameters reflecting also changes of extracted groundwater volumes. With increasing amount of adjustable parameters piezometric heads became less sensitive for the model calibration and changes of pumping rates were no longer displayed by the sensitivity coefficients. Therefore, when too many model parameters were adjusted, these parameters lost their impact on the model results. Additionally, using only sedimentological data to derive hydraulic parameters resulted in a large bias between measured and simulated groundwater level.