Integrated Surface-Groundwater Modelling of Nitrate Concentration in Mediterranean Rivers, the Júcar River Basin District, Spain

High nutrient discharge from groundwater (GW) into surface water (SW) have multiple undesirable effects on river water quality. With the aim to estimate the impact of anthropic pressures and river–aquifer interactions on nitrate status in SW, this study integrates two hydrological simulation and water quality models. PATRICAL models SW–GW interactions and RREA models streamflow changes due to human activity. The models were applied to the Júcar River Basin District (RBD), where 33% of the aquifers have a concentration above 50 mg NO3−/L. As a result, there is a direct linear correlation between the nitrate concentration in rivers and aquifers (Júcar r2 = 0.9, and Turia r2 = 0.8), since in these Mediterranean basins, the main amount of river flows comes from groundwater discharge. The concentration of nitrates in rivers and GW tends to increase downstream of the district, where artificial surfaces and agriculture are concentrated. The total NO3− load to Júcar RBD rivers was estimated at 10,202 tN/year (239 kg/km2/year), from which 99% is generated by diffuse pollution, and 3378 tN/year (79 kg/km2/year) is discharged into the Mediterranean Sea. Changes in nitrate concentration in the RBD rivers are strongly related to the source of irrigation water, river–aquifer interactions, and flow regulation. The models used in this paper allow the identification of pollution sources, the forecasting of nitrate concentration in surface and groundwater, and the evaluation of the efficiency of measures to prevent water degradation, among other applications.

Lugares olvidados. Degradación ecológica y abandono institucional en la cuenca alta del río Mijares (Teruel) / / / \ \ \ Forgotten places. Ecological degradation and institutional abandonment in the upper basin of the Mijares river (Teruel)

Resumen: La degradación de la calidad del agua y de la vegetación de ribera en los ríos mediterráneos es hoy en día un importante problema ambiental. El río Mijares discurre por la provincia de Teruel desde su nacimiento en la Sierra de Gúdar -municipio de El Castellar-, a 1.500 metros de altura y forma impresionantes cañones y paisajes fluviales en este tramo alto de un gran valor ambiental. Sin embargo, en este trabajo se analiza de manera cualitativa la calidad de sus aguas y de la vegetación de ribera para mostrar que este gran recurso territorial para el desarrollo rural de la zona presenta unos niveles de contaminación preocupantes. Posteriormente se argumenta a la luz de los datos obtenidos, que las áreas en despoblación y con muy escasa presencia humana también presentan problemas ambientales que están relacionados con una presencia institucional muy débil en este tipo de territorios. Palabras clave: cursos fluviales, problemas ambientales, despoblación, Teruel. Abstract: The degradation of water quality and riparian vegetation in Mediterranean rivers is today a major environmental problem. The upper basin of the Mijares river flows through the province of Teruel from its source in the municipality of El Castellar at 1,500 meters high and forms some impressive canyons and river landscapes in this upper section of great environmental value. However, this research qualitatively analyzes the quality of its waters and the riverside vegetation to show that this great territorial resource for rural development in the area presents important levels of degradation. Subsequently, it is discussed in the light of the data obtained, that the areas in depopulation and with very little human presence also present environmental problems that are related to a very weak institutional presence in this type of territories. Key words: rivers, environmental problems, depopulation, Teruel

Species sensitivity analysis as a tool for interpreting diatom metabarcoding for WFD bioassessment

Recent metabarcoding work in European rivers, including our own studies of Mediterranean rivers in Catalonia (Pérez-Burillo et al. 2020), has shown promising agreement between morphology- (LM) and DNA-based (HTS) assessments of diatom periphyton for the Water Framework Directive. However, in 10 out of the 164 Catalan sites we analysed, the ecological status class was downgraded from “Good”/ “High” with LM to “Moderate”/ “Poor”/ “Bad”by HTS. We call these the “critical” sites and they are especially important because the WFD requires remedial action to be taken by water managers for any river stretch with Moderate or lower status. In order to discover the reasons for downgrading we investigated the contribution of each species to the Indice de Polluosensibilité Spécifique [Specific Pollution-sensitivity Index, IPS] using a “leave-one-out” sensitivity analysis, paying special attention to the critical sites. Discrepancies in IPS between LM and HTS were mainly due to the misidentification and overlooking in LM of a few species, which were better recovered by HTS. This bias was particularly important in the case of Fistulifera saprophila, whose clear underrepresentation in LM was important for explaining 8 out of the 10 critical sites and probably reflected destruction of its very weakly-silicified frustules during sample preparation for LM. Another important bias was brought about by differences between species in the rbcL copy number per cell, which for example affected the relative abundance obtained by HTS for Nitzschia inconspicua and Ulnaria ulna; these species were also identified by the sensitivity analysis as important for the WFD. However, blanket application of a correction factor based on cell volume did not lead to a clear improvement in the agreement between HTS and LM assessments. Only minor IPS discrepancies could be attributed to the incompleteness of the reference library, as most of the abundant and influential species (to the IPS) were well represented there. Finally, we propose that leave-one-out analysis is a valuable method for identifying priority species for isolation and barcoding that are currently not, or only poorly, represented in the DNA reference database.

Governance spaces for adaptation to global change in Mediterranean rivers: the REDAPTA project in the basins of the Tordera and Serpis rivers

El proyecto REDAPTA, “Espacios de Gobernanza para la Adaptación al Cambio Global en Ríos Mediterráneos”, desarrolló sus actividades de forma simultánea en las cuencas de los ríos Tordera (Cataluña) y Serpis (Comunidad Valenciana). El proyecto trabajó en colaboración con dos “espacios de gobernanza”: la “Taula del Delta i de la Baixa Tordera” y la “Plataforma Ciutadana per a la Defensa del Riu Serpis”. Se siguió una metodología para el proceso de co-diseño, con el objetivo de intercambiar conocimientos y fomentar la deliberación, y el resultado fue un documento estratégico de adaptación, para cada cuenca, que incluye diez medidas concretas de adaptación co-producidas con los actores. El segundo resultado del REDAPTA fue un manual que describe los conceptos y el enfoque aplicados, las principales etapas metodológicas del proceso de co-diseño y las lecciones aprendidas durante su aplicación. Con el objetivo de concienciar a la ciudadanía y visibilizar la importancia del seguimiento participativo de actuaciones de mejora fluvial, se realizó una actividad en campo en ambos ríos, con una primera parte de capacitación y una segunda de toma de información. Los participantes pudieron conocer un tramo del río y, utilizando las herramientas digitales desarrolladas por el proyecto, pudieron registrar diferentes observaciones e indicadores para su caracterización básica. Por último, con el fin de promover el enfoque innovador del proyecto, se llevó a cabo una jornada de intercambio de experiencias entre diferentes organizaciones, explorando su interés en crear una “Red Ibérica de Espacios de Gobernanza para la Gestión del Agua”.