Estimating Groundwater Gradients Through A Complex Kriging Approach

Water plays a key role in the functioning of several systems on earth. A correct understanding of the hydrological cycle is fundamental to define optimal water management strategies. The definition of the origin and flow of groundwater represents a challenge in many nations. This issue is compounded by the scarcity of available data. In this context, the estimation of groundwater hydraulic gradients is fundamental for hydrogeology and groundwater management. For instance, the evaluation of the direction and velocity of groundwater flow, which are determined by hydraulic gradients, are crucial for forecasting the path and dispersion of contaminants in an aquifer. However, there are few studies which apply geostatistical methods to estimate groundwater hydraulic gradients. The novelty of this work is focused on the use of complex kriging to evaluate groundwater gradients for the years 2002 and 2007 in the upper aquifer of the southern part of the Basin of Mexico aquifer system, which suffers from acute water scarcity. The complex kriging uses hydraulic head data directly to compute hydraulic gradients. These gradients are assigned to triangle centroids by means of the Delaunay triangulation method and then considered as vectorial data to perfom the complex analysis through complex ordinary kriging. The statistical measures, including Mean Absolute Error (MAE) and Root Mean Square Error (RMSE), show a satisfactory goodness-of-fit for the complex covariance model in assessing the spatial correlation of the vectorial components.