La teledetección proporciona información espacial y temporal con la que conocer la dinámica hidrológica de las lagunas. Este trabajo usa imágenes satelitales Sentinel-2 procesadas en la plataforma Google Earth Engine (GEE) como base para la generación de series temporales de altura de lámina de agua de la laguna de Tíscar (sur de la provincia de Córdoba). Se utilizan cuatro índices espectrales de detección de agua: NDWI, MNDWI, WIW y NDWI-WIW. El rendimiento de los índices en la identificación de lámina de agua puede verse afectado por la sensibilidad de estos a factores como la nubosidad o la vegetación. Sin embargo, la aplicación de filtros y umbrales de detección permite reducir la incertidumbre. Así, valores de R2 entre 0,73 y 0,92 y raíz del error cuadrático medio entre 0,07 y 0,12 cm han sido obtenidos al comparar las series de altura de lámina de agua generadas y los datos de referencia. La capacidad de procesamiento masiva de datos de GEE y el rendimiento de los índices ponen de manifiesto el potencial de la teledetección como herramienta para la monitorización hidrológica de humedales, lo que es fundamental para su adecuada conservación.

Remote sensing provides spatial and temporal information to predict the hydrological dynamics of wetlands. This study uses Sentinel-2 satellite images processed on the Google Earth Engine (GEE) platform for generating temporal data series on the water depth of the Tiscar wetland (southern C & oacute;rdoba province). Four spectral indices for water detection have been applied: NDWI, MNDWI, WIW, and NDWI-WIW. The performance of these indices in the identification of water height can be affected by its sensitivity to factors such as cloud cover or vegetation. However, the application of filters and detection thresholds reduces uncertainty. Thus, R2 values between 0.73 and 0.92 and root mean square error between 0.07 and 0.12 cm have been calculated comparing generated water height series and the reference field data. The massive data processing capacity of GEE and the performance of the indices highlight the potential of remote sensing as a tool for hydrological monitoring of wetlands. This is crucial to support decision-makers regarding wetlands conservation.

The Torreguadiaro lagoon is a permanent coastal wetland located in the province of Cadiz. Knowledge about its water functioning is very limited and in order to define the processes that control its dynamics, a monitoring network has been designed in which piezometric, hydrochemical and isotopic data have been collected between 2022 and 2025. The temporal evolution of the Cl-content versus the delta 18O value describes isotopic hysteresis patterns, with seasonal cycles of ionic reconcentration and dilution, which show a very good connection between the lagoon and the aquifer, although with notable outflows due to evaporation. During low water levels, coinciding with spring-tides, sporadic flows of groundwater from the east have been detected, with signs of mixing with seawater. The mixing and evapo-concentration models confirm that the integration of these processes explains the hydrodynamic and hydrochemical functioning of the wetland.

La laguna de Torreguadiaro es un humedal costero permanente situado en la provincia de Cádiz. El conocimiento sobre su funcionamiento hídrico es muy limitado y con el fin de definir los procesos que controlan su dinámica, se ha diseñado una red de control en la que se han recogido datos piezométricos, hidroquímicos e isotópicos entre 2022 y 2025. La evolución temporal del contenido en Cl⁻ frente al valor de δ¹⁸O describe patrones de histéresis isotópica, con ciclos estacionales de reconcentración iónica y dilución, que evidencian una muy buena conexión entre la laguna y el acuífero y notables salidas por evaporación. En épocas de estiaje, coincidiendo con situación de mareas vivas, se han detectado aportes puntuales de aguas subterráneas desde el este, con señales de mezcla con agua marina. Los modelos de mezcla y de evapoconcentración confirman que la integración de estos procesos explica el funcionamiento hidrodinámico e hidroquímico del humedal.

El Parque Natural Cabo de Gata-Níjar es una de las regiones más áridas de Europa, lo que unido a un medio geológico (rocas volcánicas) de baja permeabilidad, conlleva escasez de recursos hídricos. Asociado al vulcanismo hay mineralizaciones auríferas como las explotadas en Rodalquilar. Los residuos de la cianuración usada para extraer el oro fueron acumulados en una escombrera de 0,13 km2. Tras analizar la composición química del agua subterránea y de la escorrentía que fluye por la escombrera se detectaron concentraciones altas de As, Pb, Cu, Mn y Zn. Los resultados de campo fueron contrastados con un experimento batch: muestras de suelo del entorno minero, de la escombrera y de sedimentos del valle de Rodalquilar. Las concentraciones más elevadas de As y Pb fueron detectadas en la muestra de suelo de escombrera y en el acuífero detrítico, aguas abajo de esta. Una vez infiltrada, las concentraciones de metales en el agua aumentan por efecto de la evapoconcentración (alta mineralización del agua por la reconcentración del aerosol marino). Por el contrario, disminuyen debido a la dilución y a la precipitación de minerales carbonatados y/o sulfatados.

The Cabo de Gata-Nijar Natural Park is one of the driest regions in Europe. The last and the fact that the geological environment (volcanic rocks) generally has a low permeability, leads to a low availability of water resources in the region. Related to volcanism, gold-bearing mineralisation can be found such as those exploited at Rodalquilar. The leakage from the cyanidation used to extract the gold were accumulated in a 0.13 km2 tailing dump. Analysis of the chemical composition of the groundwater and runoff flowing through the dump revealed high concentrations of As, Pb, Cu, Mn, and Zn. Field results were compared with those form a batch experiment: soil samples from the mining environment, from the waste dump, and sediments from the Rodalquilar valley. The highest concentrations of As and Pb were detected in the dump soil sample and in the detrital aquifer downstream of the dump. Once infiltrated, the concentrations of metals in the groundwater increase because of evapoconcentration (high electrical conductivity due to the reconcentration of marine aerosol). On the other hand, they decrease due to dilution and precipitation of carbonate and/or sulphate minerals.

Using more groundwater for irrigated agriculture is a logical response to the stress imposed by climate change. However, the scope for this in many arid regions may be less than expected because of the high (and often unsustainable) level of current groundwater resource exploitation. The extent to which further expansion is possible and managing groundwater use to avoid negative impacts are major issues for world water policy. Where opportunities do exist, water resource regulatory agencies need to be aware of the potential associated risks of groundwater salinization and pollution, if waterwell use is not properly managed, and these risks are thus discussed in some detail.

Human pressures and global change are threatening water resources. Circumstances vary in each location; therefore, finding solutions that address local issues helps achieve comprehensive water management strategies. In the Andean basins, the pre-Inca cultures used nature-based water management techniques to deal with the dry seasons. This knowledge and these techniques have been recognized as a strategy to increase water security. Additionally, they have been unconsciously applied to improve hydrological conditions in areas affected by extreme land-use changes. Water sowing and harvesting techniques have been used to manage territories dedicated to livestock and agriculture. This research evaluates three traditional infiltration ditch systems on two types of land use (páramo and cultivated pastures) in the Andean region of Azuay (Ecuador). The objective was to establish the potential for better management of water resources in dry seasons. Eosin-traced water diverted through channels or ditches, infiltrated into the soil, was retained for an average of 31 days in the páramo soil and from 90 to 111 days in the cultivated pasture soil. Controlled water infiltration contributes to effective water management by retaining water in the soil for extended periods. We conclude that nature-based systems perform better on soils with higher water retention capacity. These techniques are suitable for managing water in areas where land changes have reduced water storage potential.

Evaluation of transient storage in karst aquifers provides critical insights into factors influencing its hydrogeological behavior. This study assesses the applicability of a new approach that combines two key metrics to characterize internal flow constraints within an aquifer located southern Spain: a quantitative index of the hydrodynamic state (TSV) and hydrogeochemical parameters indicative of groundwater transit time (Total Organic Carbon -TOC-, Mg2+, delta 13CTDIC). Transient storage volume -TSV- is here defined as the difference between the cumulative functions derived respectively from daily global aquifer recharge and discharge. A common breakpoint of 3.2 hm3 in the relationships between TSV and discharge from two springs (Algarrobal and Garciago) suggests the presence of a geometric constraint (threshold) affecting groundwater flows, which drastically impact on the hydrodynamic functioning of the aquifer. The existence of this threshold is also deduced from hydrogeochemical transit time indicators. Bellow the TSV breakpoint, only Cornicabra spring exhibits natural responses induced proportionally to the magnitude of the recharge. For TSV values above 3.2 hm3 fast flows are activated within the aquifer with the subsequent effects on the natural responses of all springs, due to the mix of recently infiltrated water with previously stored in the saturated zone. Sensitivity analysis of the equations for estimating potential evapotranspiration (one of the key parameters driving recharge) could further enhance the calculations representativeness. At any case, improvements in the conceptualization through such approaches can be integrated into numerical modeling algorithms, thereby enhancing the model plausibility and alignment with the hydrogeological processes.

Improving our comprehension of infiltration processes in karst systems is crucial for a better adaptation to the global change regarding water resources availability and management. In this work, the effective recharge under different meteorological conditions and its transfer along the vertically distributed compartments of a geologically complex karst aquifer in southern Spain have been evaluated. Continuous records of soil moisture and temperature values (at 5 and 10 cm depth and the soil-rock transition -average depth of 28 cm-) have been combined with hourly hydrodynamic and hydrothermal responses recorded at two springs with a marked influence of the unsaturated zone (UZ) and the saturated zone (SZ), respectively. Most rainfalls generate soil moisture signal in the shallowest probes. However, a mean increase of soil water content of 10.5% in summer (from background values of 2.5%) and 6.1% in autumn-winter (from 9.6%) at the soil-rock interface were needed to produce hydrodynamic responses in the system: first in the spring related to the UZ, with a time delay of 4-9 hours after moisture peaks, and then (14-18 hours) in the spring draining the SZ, but only during autumn-winter recharge events. In addition, recharge caused decreases (up to 0.9°C) in the temperature of the water drained by the first spring, while lagged rises (up to 0.6°C) occurred in the second outlet. Transmission of the input signal would be favoured by stronger karstification, but the presence of inter-bedded detrital formations in the lithological sequence of the aquifer (partially confined in the SE border) filter and buffer groundwater flows before being drained by the spring related to the SZ. These findings will help to assess thresholds for effective infiltration and to predict groundwater recharge in karst aquifers under different climate change scenarios.

Nitrate (NO3-) concentrations in aquifers constitute a global problem affecting environmental integrity and public health. Unfortunately, deploying hardware sensors specifically for NO3- measurements can be expensive, thereby, limiting scalability. This research explores the integration of soft sensors with data streams through an use case to predict nitrate NO3- levels in real time. To achieve this objective, a methodology based on Kafka-ML is proposed, a framework designed to manage the pipeline of machine learning models using data streams. The study evaluates the effectiveness of this methodology by applying it to a real-world scenario, including the integration of low-cost sensor devices. Additionally, Kafka-ML is extended by integrating MQTT and other IoT data protocols. The methodology benefits include rapid development, enhanced control, and visualisation of soft sensors. By seamlessly integrating IoT and data analytics, the approach promotes the adoption of cost-effective solutions for managing NO3- pollution and improving sustainable water resource monitoring.

Flooding is a recurring natural phenomenon that can have both life-giving and destructive aspects. In natural environments, floods are often an important element of the seasonal hydrologic cycle that provides water and nutrients to soil, supporting unique, rich and diverse ecosystems. However, flood events can also represent a destructive force that can endanger lives and cause significant damage in urban areas. Karst areas, in particular, are unique because of their special hydraulic characteristics in terms of flood occurrence, the dependence of ecosystems on such events, and attempts to actively store and manage floods. In this article, the hydraulic response of karst aquifers to heavy precipitation events, flood generation, and engineering interventions for flood control are discussed using several examples from karst areas in the Mediterranean region. Flooding mechanisms and regulatory structures in karst poljes are considered using several typical examples from the Dinaric mountain range. In addition, different variants of groundwater abstraction for increasing storage capacity and flood control are presented using examples from France and Montenegro. Managed aquifer recharge in karst areas and adjacent aquifers is demonstrated with examples from Jordan and Algeria. Finally, failed attempts at flood storage in karst reservoirs are presented with examples from Spain and Montenegro. These examples of flood retention in karst areas show the wide range of planning and technical measures and remind us of possible risks and failures in implementation as well as some positive and negative impacts on the environment and especially on ecosystems.

The key factors determining the operational cost and carbon footprint of public water supplies derived from groundwater are identified. Both remain low compared to alternative sources while groundwater levels remain stable and water quality potable, but can increase markedly if derived from overexploited and/or polluted aquifers. Thus, ‘potable source protection zones’ are strongly advocated, and examples from England (UK) and Spain are illustrated. The concept of minimising the carbon footprint of groundwater use for potable water supply is novel, and deserves greater attention.

Karst water resources, traditionally used worldwide for drinking purposes, are highly vulnerable to contamination. Scientific-technical efforts must therefore be done to ensure sufficient water quality for human consumption. Early-Warning-Systems emerge as an effective spring scale protection strategy for real-time identification of contamination episodes at drinking water capture points. With this ambition, the proposed stepwise procedure for the implementation of site-specific Early-Warning-Systems (EWS), focuses on three critical features: identification of groundwater contamination proxy parameters, warning dissemination and system validation. It was tested at three karst springs affected by temporary faecal contamination and intended for supplying drinking water to populations in Spain (Ubrique) and France (Montpellier). The applied statistical techniques, coupled to the analysis of individual flood events at karst springs, allowed to identify the optimal combination of groundwater and contamination proxy parameters at each study site according to the main contaminants and recharge mechanisms. The decision tree-like workflow, used to evaluate groundwater quality at hourly time step and set up the EWS, was then constructed considering a specific combination of hydroclimatic, hydrodynamic and physical variables together with national regulations for drinking water. Hence, warning thresholds were adapted to the behaviour of each karst system, and used to trigger the alarm when specific parameters and proxies exceeded the defined limits. The performance of the EWS was assessed by implementing 4 specific Key Performance Indicators (KPIs) dedicated to appreciate the effectiveness of the workflows in identifying contamination events and verifying estimated warning thresholds. The performed analysis demonstrated an overall successful functioning of the EWS for the three case studies, with mean anticipation times ranging between 12 and 45 h and <3 % of failure rate.

AbstractKarst groundwater-dependent ecosystems (KGDEs) in the Mediterranean region are important in terms of ecosystem services and biodiversity but are increasingly under anthropogenic pressures and climate-change constraints. For this study, the ecohydrological characteristics, threats, and protection status of 112 selected KGDEs around the Mediterranean Sea, including caves, springs, rivers and wetlands, were evaluated, based on local expert knowledge and scientific literature. Results demonstrate that KGDEs contribute considerably to regional biodiversity. The diversity of karst landscapes, combined with the groundwater emergence at springs, leads to exceptional habitat diversity, particularly in arid climates, where KGDEs serve as a refuge for species that could not thrive in the surrounding environment. The most common threats identified among the selected sites are direct human disturbances, such as mass tourism or overfishing, water-quality deterioration and water shortage from aquifer overdraft and/or climate change. Although most of the selected sites are under protection, conservation measures are frequently insufficient. Such shortcomings are often caused by poor data availability, little knowledge on conservation needs of invertebrate species, and conflicts of interest with the local population. For this purpose, it is necessary to raise environmental awareness and promote interdisciplinary research, in order to monitor water quality and quantity in addition to the status of the biocenoses.

•Soil natural tracers were monitored throughout the vertical compartments of a karst aquifer.•The variations of the soil tracer signal diminish vertically along the flowpath.•The different vertically distributed compartments act as filter attenuating natural intrinsic fluorescence and TOC.•Joint analysis of TOC and δ13C helps to qualitatively date groundwater fluxes.•TOC, δ13C, and fluorescence are good unsaturated zone tracers, contrary to NO3−.

Fluorescence spectroscopy approaches like tryptophan-like-fluorescence (TLF) have been presented as a powerful tool to easily detect bacteriological contamination in groundwater used for drinking water supply in rural areas, since bacteria are able to synthetize L-Tryptophan. As commonly happens in karst springs, during flooding conditions high turbidity levels (and associated bacteria transport) are observed and thus, the exploitation of groundwater for human consumption is hindered. Hence, TLF has been considered as a potential early warning parameter to prevent polluted groundwater to reach drinking water capture points at Sierra de Ubrique carbonate karst aquifer (S Spain). The obtained results in the studied spring showed low correlation with faecal indicators (p = 0.26–0.75) and suggests the complexity in obtaining reliable continuous measurements mainly due to the multiple potential origins of tryptophan (cheese whey, bacterial activity in soil or karst conduits...) and the biochemical reactions in the soil, epikarst and karst conduits. The suitability test realized in Ubrique test site relegates TLF to a function as a biological risk indicator rather than an early warning parameter.