Mediterranean River Basin Research Articles

A Cost–Benefit Analysis for the Economic Evaluation of Ecosystem Services Lost Due to Erosion in a Mediterranean River Basin

Soil degradation in Europe is mostly represented by soil erosion that, as a sediment production mechanism, is the main environmental threat to many watersheds, including the Bovilla watershed (Tirana), useful for the supply of drinking water to the city, and therefore, the care of water quality is of particular interest. The soil erosion of the Bovilla watershed was monitored in a work set up in June 2017. Following this work, this research updates the previous data on soil loss at the Bovilla watershed in t/ha/year to September 2019 and focuses on the identification and monetary evaluation of the ecosystem services (ESs) linked to soil erosion (loss of carbon, loss of mineral elements, habitat quality, crop productivity, and sustainable tourism suitability). Then, we applied the replacement cost analysis to test the economic convenience and suggest the adoption of sustainable land management practices (e.g., reforestation) able to improve the quality water in this watershed. The study carried out demonstrates that the values of soil lost due to erosion vary depending on the type of land use (ranging from average values of 120.32 t/ha for bare land to values of 8.16 t/ha for wooded areas). Furthermore, from the application of monetary methods for the evaluation of some ecosystem services linked to erosion (loss of carbonaceous and mineral elements, habitat quality, productivity, suitability for sustainable tourism), it clearly emerges that the value of the productivity of agricultural crops varies from EUR 0 to 35,320.50/ha and that the service represents a more incisive service than the previous ones, so much so as to make the conversion of some agricultural land with high productivity values into wooded areas economically disadvantageous. The data from this study may help to develop Bovilla watershed management strategies for erosion and pollution control and sediment remediation mainly in agricultural lands. A program of measures can be effective for controlling soil erosion, but it must be implemented over long time frames, and it requires relevant investments from the public and private sectors, also with a view to increase the allocation of economic values of monetary compensation aimed at those who decide to start forestation projects on highly productive soils.

Drivers of Macroinvertebrate Communities in Mediterranean Rivers: A Mesohabitat Approach

We investigated the relationship between benthic macroinvertebrate community attributes (richness, abundance, biodiversity, and climate-specific and resistance forms) and the physical characteristics of distinct mesohabitats (hydromorphological unit types) discretized into fast (e.g., riffles or rapids) and slow (e.g., pools or glides) flow types in four Mediterranean rivers of Spain. Key attributes of hydromorphological units, including length, width, depth, shade, substrate composition, embeddedness, abundance of aquatic vegetation, and density of woody debris, were considered. Through a comprehensive suite of multivariate analyses, we unraveled taxonomic and habitat distinctions among rivers and hydromorphological unit types, with a notable influence of spatial proximity (greater similarity within the same river basin). In slow hydromorphological units, aquatic vegetation, depth, and abundance of coarse substrate emerged as pivotal factors shaping macroinvertebrate assemblages, whereas in fast-flowing units, vegetation, substrate embeddedness, and density of woody debris were the most important. Contrary to the remaining community attributes, the studied resistance forms (absent, eggs, cocoons, and cells against desiccation and diapause) exhibited uniformity across rivers despite observed variations in macroinvertebrate communities, underscoring regional functional analogies in biological and ecological mechanisms within the investigated Mediterranean river basins. This study contributes valuable insights for anticipating the repercussions of ongoing climate change, particularly in regions where fast-flowing hydromorphological units are more susceptible to depletion during drought periods.

Disclosing the effects of climate, land use, and water demand as drivers of hydrological trends in a Mediterranean river basin

Mediterranean basins face significant water scarcity which demands examining long-term data to prospect their trends in water availability and quality. This study focuses on The Onyar River (Inner Catalan basins, NE Spain), to explore its historical streamflow changes, the influencing climatic and land-use factors, and the consequential impacts on water quality. We analyse key hydro-climatic variables—streamflow, precipitation, temperature, and evapotranspiration (both PET and AET)— across a 60-year span (1960 -2020) and their relationship with recent stream water chemistry data (2007-2020). We compare these patterns to the changes in land use, and to the variations in water demand according to urban use, livestock, and crop production estimates. Our findings highlight a consistent decline in streamflow, most pronounced over the last two decades, accompanied by an increase in PET, and a probable decrease in groundwater recharge. Notably, these changes co-occurred with higher concentrations of river water ammonium and nitrate. We attribute these patterns to changes in land use such as afforestation and intensive fertilization, as well as increased groundwater withdrawal, particularly during irrigation seasons. Additional factors include growing urban water demand and the discharges of treated wastewater back into the river system. This study offers a comprehensive overview of the declining water quantity and quality in the Onyar River, attributing these trends to an interplay of climatic and anthropogenic factors. The findings underscore the need for integrated water resource management strategies to mitigate the implications of these changes.

Landscape features shape people’s perception of ecosystem service supply areas

Landscapes have typically been produced by varied, diverse, and long-term interactions between people and nature. However, most landscape planning and ecosystem service mapping approaches focus on the biophysical aspects of landscapes rather the social. Spatial representations of people’s perceptions, mental models, and local knowledge of ecosystem services can be created using participatory mapping. This study uses participatory mapping to identify how peoples’ perceptions of provisioning, regulating and cultural ecosystem service supply areas coincide or mismatch with the landscapes features of two Mediterranean river basin areas in north-eastern Catalonia, Spain. We found that the random forest and geographically weighted regression techniques are able to strongly associate landscape features with stakeholders’ perceptions of ecosystem supply areas. These results demonstrate that the stakeholders associate various geographic elements with different types of ecosystem service supply areas. Visible geographical features, such as a reservoir, mountains, wetlands, showed great importance in the perception of supply areas of ecosystem services, compared to ecological or biophysical indicators, when mapping and spatially associating certain benefits to ecosystem services supply areas. These findings reveal that, often, the ecological processes and dynamics of functioning of ecosystems are invisible and not fully understood. We argue that integrating these aspects into participatory landscape planning, policies and practice can make the invisible visible and, consequently, increase the understanding for a more targeted and effective management. This could allow stakeholders to better understand the ecological processes behind the visible geographic features of the landscape, fostering a shared knowledge and better environmental management outcomes.

Stable isotopes reveal organic nitrogen pollution and cycling from point and non-point sources in a heavily cultivated (agricultural) Mediterranean river basin

The Pinios River Basin (PRB) is the most intensively cultivated area in Greece, which hosts numerous industries and other anthropogenic activities. The analysis of water samples collected monthly for ∼1 ½ years in eight monitoring sites in the PRB revealed nitrate pollution of organic origin extending from upstream to downstream and occurring throughout the year, masking the signal from the application of synthetic fertilizers. Nitrate concentrations reached up to 3.6 mg/l as NO3−-N, without exceeding the drinking water threshold of ∼11.0 mg/l (as NO3−-N). However, the water quality status was “poor” or “bad” in ∼50 % of the samples based on a local index, which considers the potential impact of nitrate on aquatic biological communities. The δ15Ν-ΝΟ3− and δ18O-NO3− values ranged from +4.4 ‰ to +20.3 ‰ and from −0.5 ‰ to +14.4 ‰, respectively. The application of a Bayesian model showed that the proportional contribution of organic pollution from industries, animal breeding facilities and manure fertilizers exceeded 70 % in most river sites with an overall uncertainty of ∼0.3 (UI90 index). The δ18O-NO3− and its relationship with δ18O-H2O revealed N-cycling and mixing processes, which were difficult to identify apart from the uptake of nutrients by phytoplankton during the growing season and metabolic activities. The strong correlation of δ15Ν-ΝΟ3− values with a Land Use Index (LUI) and a Point Source Index (PSI) highlighted not only the role of non-point nitrate sources but also of point sources of nitrate pollution on water quality degradation, which are usually overlooked. The nitrification of organic wastes is the dominant nitrate source in most rivers in Europe. The systematic monitoring of rivers for nitrate isotopes will help improve the understanding of N-cycling and the impact of these pollutants on ecosystems and better inform policies for protection measures so to achieve good ecological status.

From Past to Present: Decoding Precipitation Patterns in a Complex Mediterranean River Basin

Enhancing spatial data attributes is crucial for effective basin-scale environmental modelling and improving our understanding and management of precipitation patterns. In this study, we focused on reconstructing homogeneous areal precipitation data in the complex terrain of the Calore River Basin (CRB) in Southern Italy. Until 1869, weather observations in the region were inconsistent, unstandardised, and lacked coordination, but the establishment of meteorological observatories brought a more unified approach to weather monitoring. We relied on the rainfall data obtained from two of these historical observatories: Benevento (1869–present) and Montevergine (1884–present). We utilised a statistical regression framework that considered rainfall measurements and temporal properties from specific locations to reconstruct and visually analyse the evolution patterns of annual mean areal precipitation (MAP) in the CRB from 1869 to 2020. The analysis revealed that mean MAP decreased from 1153 mm yr−1 (1869–1951) to 998 mm yr−1 (1952–2020). This decrease was accompanied by a reduction in interannual variability (from 168 mm yr−1 to 147 mm yr−1 standard deviation), and the difference between the means was significant (p < 0.0001), suggesting a sudden shift in the time-series. These findings provide a basis for CRB water resource management and insights for modelling other complex Mediterranean basins.

Impact of alternative water policies for drought adaptation in the Guadalquivir Mediterranean river basin, southern Spain

Study regionThe Guadalquivir Basin in Spain as a representative Mediterranean basin. Study focusThe aim of this study is to assess the adaptive capacity of Mediterranean basins to long periods of severe drought. To do so, a hydro-economic model has been developed that includes a spatial representation of the major economic uses of water and enables an analysis of the economic and environmental effects of alternative water management policies under a single event of water scarcity. New hydrological insights for the regionResults highlight the trade-offs among economic uses of water and environmental flow requirements since water resources in the Guadalquivir are fully allocated. Moreover, the increase of irrigated perennial crops area will aggravate vulnerability to drought by limiting the adaptive capacity of the basin. Survival irrigation is the first option for farmers to adapt to the simulated extreme drought. 148,000 ha are shifted from normal irrigation to survival irrigation in the Drought Management Protocol scenario. These findings call for policy interventions to ensure greater management flexibility toward optimising water use while meeting environmental goals. For instance, enabling water trading among farmers would reallocate 22 % more water to the upper basin, reducing drought losses by 22 M EUR. The hydro-economic model developed here can be adapted to basins elsewhere and the results show that it can be a useful tool to guide the design of efficient water management policies to address severe droughts in water-stressed basins.

Optimizing Reservoir Water Management in a Changing Climate

One of the UN agenda 2030 Sustainable Development goals is associated with water availability and its sustainable management. The present study intends to improve multipurpose reservoir management under climate change scenarios in water scarce regions such as the Mediterranean. Implemented methods include the sequential use of climate model results, hydrological modelling, and reservoir water balance simulation, which are used to estimate future water availability. This work focuses on developing an innovative reservoir management approach based on rule curves and a dynamic assessment of water needs, to improve the management of reservoirs that are dependent on a water transfer system. The proposed methods are implemented in two reservoirs located in a typical Mediterranean river basin and assessed under long-term climate change scenarios up to the year 2100. The results show that the proposed approach can ensure 100% of the urban water supply, improve the reliability of the irrigation supply from 75% to 86–91%, and provide 92–98% of the river ecological flow. It is also demonstrated that this management approach is beneficial, particularly in the case of multipurpose reservoirs in watersheds facing water scarcity risks, to optimize the balance between supply reliability, water transfer volumes, and costs.

Cambios temporales y espaciales en la química del agua superficial en un río mediterráneo de Chile central: el caso del río Mataquito (~35°S)

Spatial and temporal changes in water chemistry were evaluated using surface water extracted from a Mediterranean river basin, i.e., The Mataquito River, central Chile. The processes that control water chemistry dynamics in the basin were determined by assessing the relationship between hydrologic events (rainfall, river flow, runoff rates), physical-chemistry properties, and major ion concentrations/distributions along the river. During the rainy period, major ion levels were controlled predominantly by weathering (rainfall). During the dry period, seawater intrusion was the main factor controlling water chemistry. Unusually high chlorine and sulfate concentrations suggested anthropogenic sources of the ions entering the basin. Thus, pollution from industrial and agricultural activities in the basin might be quantitatively important and should be considered in future studies of this area.

Spatial and temporal patterns of flow intermittency in a Mediterranean basin using the SWAT+ model

ABSTRACT Non-perennial rivers and streams are ubiquitous. Nonetheless, our understanding of their hydrological patterns is minimal. Hydrological models are powerful tools to study and characterize hydrological patterns, but few can simulate extremes such as non-flow events. We aimed to capture and accurately simulate the flow intermittency spatial and temporal patterns in a Mediterranean river basin with the restructured Soil and Water Assessment Tool (SWAT+). We calibrated the model using a multi-objective optimization algorithm and using data from two gauging stations in the mainstream for the period 2000–2020. Furthermore, we validated the flow intermittency simulations against stage data series at 14 stations. The results indicated that the model accurately simulates flow intermittency and low flows in the study period. We observed a significant variation in flow intermittency in both space and time with a remarkable inter-annual variability. We also observed an increase in flow intermittency over the study period.

Use of different indices to assess the ecological status of lake systems in the eastern mediterranean river basin

The objective of this research was to assess the ecological status of lentic systems in the Eastern Mediterranean River basin (Türkiye) using some biotic (Q index, PT-BV, MedPTI, TDIL, and PTI) and abiotic (WQI, WQImin-nw, TSI, TLI, and Kna) indices. Phytoplankton species such as Peridinium cinctum, Ceratium hirundinella, and Gyrosigma balticum were the species that contributed the most to the algal biovolume of lake systems with different ecological statuses in the basin. According to the results, it was seen that CCA coordination, which analyzed the relationship structures between dominant phytoplankton taxa and environmental water quality parameters, explained the variation sufficiently. As pointed out in the CCA analysis, conductivity and ammonium were the main environmental parameters influencing algal assemblages at sampling sites in the basin (p < 0.01). Strong correlations were observed between TSI and TLI (correlation coefficient: 0.99), and TDIL showed significant correlation only with the Q index (p < 0.01). TSI, TLI and WQI, abiotic indices, indicated significant correlations with most environmental parameters (p < 0.01), while PTI, a biotic index, had weak correlations with most environmental parameters (p > 0.05). Among the indices used in this study, it seems that diatom-based TDIL and physicochemical-based WQI appear to be the most suitable indices for assessing the ecological status of lentic systems in the Mediterranean region. Accordingly, it can be deduced that coupling biotic and abiotic indices is more accurate in determining the water quality of lentic systems.

An integrated approach to support a river ecological network: A case study from the Mediterranean

Riverine ecosystems are among the most impacted ecosystems worldwide since they are exposed to multiple stressors. Land Use/Land Cover (LULC) changes is the main human imprint on those ecosystems whose spatiotemporal habitat destructions pose a threat to biodiversity, ecosystem integrity and ecological processes. The most important statutory instruments for riverine ecosystem protection, conservation and restoration in the European Union are the Water Framework Directive (WFD) and the Habitats and Birds Directive (HBDs). In this study, we develop a methodological framework to spatially link the ecological integrity of river sub-basins with the protected areas therein, taking into account the influence of land use as expressed in the WFD. We combined a multi-criteria evaluation approach using six of the most frequently applied criteria for conservation evaluation to assess river basin integrity (RBI) index at the sub-basin level, and used as a proxy for functional connectivity categories. In addition, we used the distance of every sub-basin from the surrounding Natura 2000 sites as a measure of structural connectivity. Using ecological network design principles (i.e. Core areas; Corridors; Stepping Stones; Buffer areas; and Restoration areas), we incorporated the two aspects of connectivity into a framework, which links river management at the basin level with the site level assessment as dictated by the HBDs. We implemented this framework in a Mediterranean river basin located in Southern Tuscany, which is part of the Natura 2000 network. Six of the sub-basins (20%) have high functional connectivity, 14 sub-basins (47%) medium and 10 sub-basins (33%) low functional connectivity. Structural connectivity of the study area followed the same tendency as that of functional connectivity, with the majority of the sub-basins having medium connectivity (57%; 17 sub-basins), and 23% (7 sub-basins) and 20% (6 sub-basins) high and low structural connectivity respectively. As a result, six of the sub-basins were characterised as corridor areas while the majority of the sub-basins were identified as buffer areas (57%). Two sub-basins were characterised restoration areas and one as stepping stone (SS). Our approach is one of many plausible ecological networks, which although analytically simple, can be enriched with data on species and stakeholders’ involvement.

Deconstructing Ecosystem Service Conflicts through the Prisms of Political Ecology and Game Theory in a North-Western Mediterranean River Basin

Power relationships, access and control, (in)equity, and (in)justice are key modulators of conflicts arising from ecosystem services between multiple stakeholders. A greater knowledge of stakeholder value systems and behaviors is crucial for understanding socioecological dynamics. We propose an analytical framework that combines political ecology and game theory to analyze water ecosystem services. This integrated framework was used to reinterpret concepts such as common goods, (a)symmetric flows, and (un)fair trade-offs in the context of ecosystem services. The purpose was to gain a better understanding of behaviors and (a)symmetries in power relationships between multiple stakeholders. We studied the case of a north-western Mediterranean river basin using data obtained from stakeholder interviews and newspaper articles. Our findings uncovered different types of stakeholder relationships, ranging from mutual support and cooperation to conflict. The proposed analytical framework shows how social mechanisms can affect ecosystem services flows, potentially facilitating or hindering the development of more equitable management models for natural resources.

Contrary effects of flow intermittence and land uses on organic matter decomposition in a Mediterranean river basin

Flow interruption in intermittent rivers (IRs) generates a mosaic of terrestrial and aquatic habitats across the river network affecting ecosystem processes, as organic matter (OM) decomposition. Water use for farming in arid and semi-arid climates intensifies the dry conditions and affects local river characteristics. In that way, flow intermittence and the distribution of land uses may affect the OM processing along the river. To understand the role of IRs in global OM dynamics and how global change affecting water flow regimes determines these dynamics, it is important to estimate OM-processing rates at a basin scale. The aim of this study was to evaluate the effect of the intensity of flow intermittence on OM processing, and how this effect was modulated by local environmental factors related to land uses across a Mediterranean river basin. To do this, wood decomposition (mass loss and fungal biomass) was selected as a functional indicator. Drying duration and frequency were measured to characterize flow intermittence in different reaches along the river, as well as local environmental factors. Linear models stablished the role of factors on decomposition. The results showed that differences in decomposition rates across the river network were negatively related to the duration of flow interruption. Dissolved inorganic nitrogen associated with agriculture counteracted the negative effect of intermittence on mass loss (increasing by up to three times); but with a higher duration of dry conditions, its effect was insignificant. An increase of 20% of canopy (higher in natural areas) resulted in increases of up to 5% of mass loss. Overall, our study is relevant to understanding the interaction between flow intermittence and land uses on OM processing, especially considering the intensification of flow intermittence and its increased distribution to other regions, which is expected to be a consequence of climate warming and human activities.

Driving Factors of Geosmin Appearance in a Mediterranean River Basin: The Ter River Case.

In recent decades, human activity coupled with climate change has led to a deterioration in the quality of surface freshwater. This has been related to an increase in the appearance of algal blooms, which can produce organic compounds that can be toxic or can affect the organoleptic characteristics of the water, such as its taste and odor. Among these latter compounds is geosmin, a metabolite produced by certain cyanobacteria that confers an earthy taste to water and which can be detected by humans at very low concentrations (nanogram per liter). The difficulty and cost of both monitoring the presence of this compound and its treatment is a problem for drinking water treatment companies, as the appearance of geosmin affects consumer confidence in the quality of the drinking water they supply. In this field study, the evaluation of four sampling sites with different physicochemical conditions located in the upper part of the Ter River basin, a Mediterranean river located in Catalonia (NE Spain), has been carried out, with the aim of identifying the main triggers of geosmin episodes. The results, obtained from 1 year of sampling, have made it possible to find out that: (i) land uses with a higher percentage of agricultural and industrial activity are related to high nutrient conditions in river water, (ii) these higher nutrient concentrations favor the development of benthic cyanobacteria, (iii) in late winter–early spring, when these cyanobacteria are subjected to both an imbalance of the dissolved inorganic nitrogen and soluble reactive phosphorus ratio, guided by a phosphorus concentration increase, and to cold–mild temperatures close to 10°C, they produce and release geosmin, and (iv) 1–2 weeks after cyanobacteria reach a high relative presence in the whole biofilm, an increase in geosmin concentration in water is observed, probably associated with the cyanobacteria detachment from cobbles and consequent cell lysis. These results could serve as a guide for drinking water treatment companies, indicating under what conditions they can expect the appearance of geosmin episodes and implement the appropriate treatment before it reaches consumers’ tap.

Participatory Evaluation of Water Management Options for Climate Change Adaptation in River Basins

Climate and other human-induced changes will increase water scarcity in world areas such as in the Mediterranean. Adaptation principles need to be urgently incorporated into water management and stakeholder engagement needs to be strengthened at all steps of the management cycle. This study aimed to analyse and compare stakeholder-preferred water management options (WMOs) to face climate change related challenges and to foster adaptation in four Mediterranean river basins. The challenges and WMOs of the four river basins identified by stakeholders were analysed examining to what extent the WMOs tackled the identified challenges. The impact of the WMOs resulting from a participatory modelling method was included in a comparative analysis of the stakeholders’ WMOs preferences. The results indicate the participatory approach that was applied allowed local priorities and real-world challenges to be defined with adequate detail as well as the definition of tailored responses. The participatory impact analysis provided an integrated view of the river basin as an interrelated system. The participatory evaluation of the WMOs was able to consider a wide range of elements and was able reflect the combined preferences of the stakeholders. Moreover, it allowed groups of basin actors with highly diverse profiles and concerns to further promote sets of these WMOs as input into decision making processes.

A Proposal to Classify and Assess Ecological Status in Mediterranean Temporary Rivers: Research Insights to Solve Management Needs

The biomonitoring methods implemented by water authorities are mostly developed for perennial rivers, and do not apply to temporary rivers (TRs). We propose a new classification for TRs to better assess their ecological status. It arises from the LIFE+ TRivers project, which was conducted in the Catalan and the Júcar Mediterranean river basin districts (RBD). The European Water Framework Directive (WFD) provided two systems to set river types (systems A or B from Annex II), which have been officially used by water authorities across Europe to set “national river types” (NRTs). However, essential hydrological variables for TRs are largely omitted. NRTs established according to the WFD were compared with TR categories obtained by using a rainfall-runoff model, “natural flows prescribed regimes” (NFPRs), and with “aquatic phases regimes” (APRs) calculated by using TREHS software. The biological quality indices currently used in Spain, based on macroinvertebrates and diatoms (IBMWP, IMMI-T, and IPS), were compared with a “general degradation” gradient in order to analyze the two TR river classification procedures (NFPR and APR). The results showed that NRTs did not properly classify TRs, and that the APR classification identified ecologically meaningful categories, especially those related to stagnant phases. Four “management temporary river categories” based on APRs are proposed to be used for water managers to properly assess the ecological status of TRs.

Variability in Population Traits of a Sentinel Iberian Fish in a Highly Modified Mediterranean-Type River

Human pressures on water resources have been suggested as a driver of biological traits that induce changes in native fish populations. This study highlighted the interplay between environmental stress factors, mostly related to flow regulation, and the longitudinal river gradient in biological traits such as the growth, size structure and somatic condition of a sentinel fish, Luciobarbus sclateri. We found an increase in size-related metrics and somatic condition at population levels associated with downstream reaches, although fragmentation and habitat alteration, flow regime alteration and the abundance of non-native fish were also significantly involved in their variability. Age-related parameters and growth were only explained by flow regime alterations and the abundance of non-native fish species. The high plasticity observed in L. sclateri population traits suggests that this is a key factor in the species adaptability to resist in a strongly altered Mediterranean river basin. However, the interplay of multiple stressors plays an important role in fish population dynamics and could induce complex responses that may be essential for long-term monitoring in sentinel species.

Impact of Climate Change on Worlds Economy and Hydrological System

The Mediterranean region appears to be particularly responsive to global and climate change. The global mean temperature has increased by 0.8°C compared with preindustrial levels while Europe has warmed more than the global average, especially in the Mediterranean, the north-east region, and mountain areas. Increasingly drier conditions are observed in the Mediterranean region both in the wet and in the dry season (~20%) with an increasingly irregular precipitation in both seasons (~ 40% in the dry season). The annual river flows have also decreased in the Mediterranean region, a difference projected to exacerbate due to climate and global change, which made the Mediterranean region most prone to an increase in drought hazard and water stress. Iberian Peninsula has been already affected by several major droughts, e.g. the recent one in 2005. These driving forces of global change impacts on water availability, water quality, and ecosystem services in Mediterranean river basins of the Iberian Peninsula, as well as their impacts on the human society and economy, makes it an important issue on the EU agenda. This thesis is an approach to quantify and analyze the water quantity, hydrological ecosystem services, and water supply in temperate regions under environmental changes. A hydrological model is developed for a low flow Mediterranean river (Francolí River) to assess the water allocation situation in the river basin using MIKE BASIN. Since the Mediterranean regions are hard hit by the changes in the global climatic patterns, the hydrological model focuses on the water distribution system & flow in the region.

Assessing the Effects of Wastewater Treatment Plant Effluents on the Ecological Quality Status in a Mediterranean River Basin

Many Mediterranean rivers are characterized by an inter-annual climatic variability, additionally intensified by climate change. Moreover, these rivers have limited extensions and a reduced dilution capacity which make them vulnerable to human pressures, especially to water pollution. During the 1970s, the Besos river basin had historically suffered the continuous discharge of untreated residual water, leading to be considered as the most polluted river in Europe. During the 1990s and 2000s, environmental laws such as the Catalan Treatment Plan and the Water Framework Directive (2000/60/EC) were implemented to resolve the problem. Consequently, the number of wastewater treatment plants (WWTPs) and long-term monitoring programs to assess the ecological status increased in the territory. In order to evaluate these changes, this study assesses the biological quality status (IBMWP, QBR and IPS) in the Besos river water at three spatial scales (headwater, middle and lower sections). Our results clearly show that water quality across the basin has been improved. This improvement has become more significant after the implementation of new treatment systems. The trends in ammonia concentrations (NH4+, in mg/L) and conductivity (EC, in μS/cm) discharged from 13 selected WWTPs during the period 2000–2018 displays a clear decreasing tendency. Finally, we have applied a thorough statistical analysis to the IBMWP dataset to demonstrate the positive influence of the treatment systems on the ecological quality status across the river basin. We conclude that the implementation and enforcement of environmental laws are valid and effective tools to improve water quality in Mediterranean rivers. • Wastewater treatment plant upgrading has positive effects on biological quality status. • High NH4+ and conductivity levels provoke alterations on biological quality status. • Correct quality status (IBMWP) is reached when NH4+ < 1 mg/L and EC is within 500–2000 μS/cm.