The objective of this paper is to establish a definition of deep aquifers, develop a methodological proposal to help select them as strategic groundwater reserves and develop a first inventory of deep aquifers in peninsular Spain, organized by hydrographic districts. The basic premises followed to consider a permeable formation as a deep aquifer are: water table depth greater than 300 m in free aquifers or the top of the permeable formation in the case of confined aquifers. A deep aquifer is also considered to be the lower horizon of very thick aquifers (from 300 m), from which the most superficial horizon is used. The definition of the potentially favorable areas and the initial characterization is based on a compilation and synthesis of geological and hydrogeological information, structured in 5 large blocks: location and identification, geology, hydrogeology, current status and bibliography. For its evaluation, a flowchart has been proposed with the basic lines of the evaluation process. The relevant aspects for suitability would be: stratigraphy and structural geology, prior knowledge of the conceptual model and water renewal, quality, viability of exploitation, effects, final knowledge, and management and governance. The final result allows the aquifer to be classified into three categories: strategic groundwater reserve, punctual reserve or non-viable reserve. The inventory carried out encompasses a total of 64 deep aquifers located in 13 basin districts. Finally, as example, three deep aquifers are presented: Amblés Valley, Madrid detritic aquifer and El Maestrazgo.

extensión de la pluma de recarga. En concreto, se establece que la pluma de recarga caracterizada como agua dulce (400-600 µS/cm) se extiende 400 m en dirección O-E y 250 m en dirección N-S. Además, las imágenes de ERT definen que una zona de mezcla entre ambas aguas, con CE por debajo de 2500 µS/cm, alcanzó una distancia de 600 m en dirección este. Capítulo Introducción 3 1.1. Presentación La presente investigación desarrolla una idea propuesta en el informe Methodological basis for Water Neutrality Projects. Case study: Colebega Plant (Valencia, Spain) (Morell et al., 2010a) auspiciado por The Coca-Cola Foundation (TCCF), en el contexto de su política de Water Neutrality, que pretende establecer mecanismos de compensación (offset mechanisms) del consumo de agua asociado a las actividades de las instalaciones de la compañía. En el informe mencionado, además de proponer unas bases metodológicas de aplicación general, se propusieron ocho actuaciones, de muy diversa naturaleza, para compensar el consumo de agua de la planta embotelladora COLEBEGA S.A., perteneciente al grupo Coca-Cola European Partners, situada en el término municipal de Quart de Poblet (Valencia, España). De entre las ocho opciones presentadas, se eligió como más apropiada la técnica de recarga artificial para luchar contra la salinización en acuíferos costeros y, a tal fin, TCCF financió durante tres años (2012-2014) el proyecto Facing the seawater intrusion recharging coastal aquifers with regenerated water (Water Recovery Project), liderado por el

A significant process of marine intrusion affects the detritic aquifer of Plana de Castellón, located on the Spanish Mediterranean coast. In its southern sector, an artificial recharge scheme with low mineralization water (330 µS/cm) has been implemented. The experience has lasted 175 days, with an average injection flow of 21 L/s and total refilled volume of over 300000 m3. The hydrodynamic effect caused was immediate, with an appreciable rise in piezometry in the first 24 hours around the recharge wells (radius of 80 m). Maximum water-table levels were obtained 79 days after the start of operations, with increase of 3-3.50 m. The decreases are very rapid when the injection ceases and the initial piezometry recovers after 16-17 days. The behaviour of the injected water, as well as its effects on the underground flow, has been studied by applying five hydrochemical parameters: electrical conductivity (EC), chloride concentration (Cl-), nitrate concentration (NO3-), oxygen 18 (δ18O) and deuterium (δ2H). With each of these variables, the rate of expansion of the recharge water has been determined. The velocity of the groundwater flow in each direction, calculated from the five parameters discussed, ranges from 2.4 to 6.3 m/d. The EC parameter is the one that best fits the average speeds, so it is ideal to be applied in this type of studies due to its low cost, immediacy and simplicity in obtaining the data. Consequently, the EC was also selected to characterize the movement of the recharge water through the different permeable formations of the aquifer, from vertical EC profiles made at the control points. Once the lithological columns are known at these points, the velocities of the groundwater flow have been correlated with the lithologies of the differentiated permeable sections. The highest, 6.0 m/d, correspond to gravels and sands with low clay content, while the smallest, 1.0 m/d, are obtained in sands with gravel.