Antonio Pulido Bosch

Pumping seawater from coastal aquifers for supplying desalination plants

The lack of water in the coastal areas demands an onerous search for an appropriate solution. One solution is that of water transfer from areas of surplus, but this is itself problematical. Technological developments have introduced the possibility of utilizing desalinated seawater as a drinking water source at a competitive price. Abstraction from coastal aquifers that are connected to the sea appears to be the cheapest means of supply. However, pumping poses some problems due to the corrosiveness of seawater. These problems include the difficulties of choosing suitable sites for the abstractions, drilling method, casing, filter pack, as well as the design of a monitoring system to assess aquifer behaviour as a result of the generally high exploitation rate. The 31 boreholes that have been drilled in the Andarax Delta near the city of Almeria are cited as an example of a real application.

A parsimonious distributed model for simulating transient water flow in a high-relief karst aquifer

A mathematical model of a highly heterogeneous functioning karst aquifer is described. The aquifer is in a high-relief karst massif and, as is common for such locations, data are scarce and there are no borehole, piezometer or pumping-test data. The scarcity of data in this case required a parsimonious approach to ensure that the level of complexity of the model was commensurate with the amount, type and quality of the available data. Parsimony also requires the model to include the minimum essential components that account adequately for the data, which in this and similar cases are the functional dualities of the karst system: duality in recharge, flow and discharge. The model is three-dimensional (3D) in the sense that the aquifer is discretized into 3D voxels, although the flow is one-dimensional (1D) and vertical in the vadose zone, and horizontal and two-dimensional (2D) in the saturated zone. The parsimonious model was designed by coupling a 1D unsaturated gravity-driven flow along the vertical (along each column of voxels that discretize the aquifer) and a 2D unconfined Darcy flow in the saturated zone. In the context of this type of aquifer, preferential recharge through the network of karst conduits implies a rapid rise in the water table, the location and extension of which are model parameters. The karst springs are simulated by drains. The methodology, which is completely general, is illustrated by application to the karst aquifer in the Sierra de las Nieves mountains in southern Spain.RésuméUn modèle mathématique d’un aquifère karstique fonctionnel très hétérogène est. décrit. L’aquifère est. situé dans un massif karstique de montagne; les données hydrogéologiques sont limitées au vu de l’absence de forages, piézomètres ou pompages d’essai, situation courante dans de tels contextes. Le peu de données dans ce cas exigeait la mise en œuvre d’une approche parcimonieuse afin de s’assurer de l’adéquation entre le niveau de complexité du modèle et la quantité, la nature et la qualité des données disponibles. Une modélisation parcimonieuse doit inclure le minimum des composantes essentielles permettant de rendre compte des données de manière adéquate, qui dans ce cas d’étude et d’autres cas similaires sont les dualités de fonctionnement du système karstique qui contrôlent la recharge, l’écoulement et le débit. Le modèle peut être considéré tridimensionnel (3D) car l’aquifère est. discrétisé en voxels 3D, bien que l’écoulement soit unidimensionnel (1D) et vertical dans la zone vadose, et horizontal et bidimensionnel (2D) dans la zone saturée. Le modèle parcimonieux a été construit en couplant un écoulement gravitaire vadose 1D vertical (le long de chaque colonne de voxels qui discrétisent l’aquifère) avec un écoulement 2D libre suivant la loi de Darcy pour la zone saturée. Dans le contexte de ce type d’aquifère, la recharge préférentielle au sein du réseau de conduits implique une montée rapide de la nappe phréatique, sa localisation et son extension sont fixées par les paramètres du modèle. Les sources karstiques sont simulées par des drains. La méthodologie, qui se veut générale, est. appliquée à l’aquifère karstique des montagnes de la Sierra de las Nieves dans le sud de l’Espagne.ResumenEn este trabajo se describe un modelo matemático del funcionamiento de un acuífero kárstico muy heterogéneo. El acuífero está en un macizo kárstico de relieve alto y, como es común en dichas zonas, los datos son escasos. No hay sondeos, ni piezómetros, ni datos de ensayos de bombeo. Esta escasez de datos requiere un enfoque parsimonioso del modelado del acuífero, ya que el nivel de complejidad del modelo se debe conmensurar con la cantidad, tipo y calidad de la información disponible. Esta parsimonia también implica que se incluyan los componentes mínimos esenciales para tener en cuenta los datos disponibles, que en este caso y en casos similares, son las dualidades funcionales del sistema kárstico: dualidad en la recarga, flujo y descarga. El modelo es tridimensional en el sentido de que el acuífero está discretizado en cubos tridimensionales, aunque el flujo es unidimensional y vertical en la zona vadosa, y horizontal y bidimensional en la zona saturada. Este modelo parsimonioso se ha diseñado para acoplar el flujo vertical inducido por la gravedad en la zona no saturada (a lo largo de las columnas de cubos) y un flujo darciano no confinado en la zona saturada. En el contexto de este tipo de acuíferos, la recarga preferencial se produce a través de una red de conductos kársticos e implica un incremento rápido del nivel piezométrico. La extensión y localización de dichas áreas son parámetros del modelo. Los manantiales kársticos se simulan mediante drenes. La metodología, que es completamente general, se ilustra mediante su aplicación al acuífero kárstico de la Sierra de las Nieves en el sur de España.摘要本文介绍了高度异质功能岩溶含水层的数学模型。该含水层位于高峻地形地块上,处于这样的位置上很普遍,数据非常匮乏,没有钻孔、测压或抽水试验数据。在这种情况下,数据匮乏需要简约方法确保模型复杂性的程度与现有数据的数量、类型和质量相称。简约还需要模型要包括能恰当解释数据的最低基本成分,这些重要成分在这个和类似的情况下是岩溶系统的功能二元性:补给、水流和排泄中的二元性。模型为三维模型,离散化为三维像素,尽管水流在包气带为一维和垂直的,在饱和带为横向和二维的。通过耦合沿垂直的一维非饱和重力驱动水流和饱和带二维非承压达西水流设计了简约模型。在这种含水层背景下,通过岩溶通道网络的优先补给意味着水位快速上升,通道的位置和扩展为模型参数。通过排水模拟了岩溶泉。该方法非常普通,通过应用到西班牙南部Sierra de las Nieves山区岩溶含水层对该方法进行了描述。ResumoUm modelo matemático de um aquífero cárstico em funcionamento altamente heterogêneo é descrito. O aquífero está em um maciço cárstico de alto relevo e, como é comum nesses locais, os dados são escassos e não há dados de furos, piezômetros ou testes de bombeamento. A escassez de dados neste caso exigiu uma abordagem parcimoniosa para garantir que o nível de complexidade do modelo fosse proporcional à quantidade, tipo e qualidade dos dados disponíveis. A parcimônia também exige que o modelo inclua os componentes essenciais mínimos que adequadamente dão conta dos dados, que neste e em casos similares são as dualidades funcionais do sistema cárstico: dualidade na recarga, fluxo e descarga. O modelo é tridimensional (3D) no sentido em que o aquífero é discretizado em voxels 3D, embora o fluxo seja unidimensional (1D) e vertical na zona vadosa, e horizontal e bidimensional (2D) na zona saturada. O modelo parcimonioso foi projetado acoplando um fluxo 1D não saturado por gravidade ao longo da vertical (ao longo de cada coluna de voxels que discretiza o aquífero) e um fluxo Darcy 2D não confinado na zona saturada. No contexto deste tipo de aquífero, a recarga preferencial através da rede de condutos cársticos implica num aumento rápido do nível freático, cuja localização e extensão são parâmetros do modelo. As nascentes cársticas são simuladas por drenos. A metodologia, que é completamente geral, é ilustrada pela aplicação ao aquífero cárstico nas montanhas de Sierra de las Nieves, no sul da Espanha.

Hydrological modeling of a semi-arid Andarax river basin in Southern Spain

The 2,265 km2 Andarax river basin is located in Southern Spain. The basin is strongly affected by tectonic activity and coincides with one of the existing depressions in the Betic Cordilleras. The lithology is mostly Triassic schists and limestone in upland areas and Neogene-Quaternary sandstones, conglomerates and loams of marine origin in medium and lower-lying areas. The terrain changes from sea level at the coast to more than 2,500 m in the Sierra Nevada Mountains. It is one of the most arid regions in Europe with a precipitation of 200-350 mm/year, which mainly falls (70%) in autumn and winter. In the mountainous areas, where the unit Triassic schists dominates nearly all precipitation is converted into overland flow which runs directly to the river. When the river reaches the medium and lower-lying areas most of the water infiltrates into the highly permeable Detritic aquifer. Only at rare occasions and for high rainfall events the river discharges into the Mediterranean Sea and consequently nearly all excess rainfall generated from the upstream catchments areas is discharged as groundwater flow which thus determines the water availability in the delta region. The rather unique hydrological behavior of the Andarax river basin is simulated by the MIKE SHE code, which is a physically based, distributed and integrated hydrological model. Particular emphasis is given to the simulation of the seasonal and spatial distribution of recharge within the river catchment. As the availability of traditional hydrological data for the Andarax river basin data is rather sparse remote sensing data will be used to improve the estimation of the spatial and temporal distribution of the evapotranspiration. For this purpose an energy based model included as an option in the MIKE SHE code will be used based on remote sensing data for leaf area index (LAI), global radiation, albedo and air temperature.