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Non‐perennial streams have a global prevalence, but quantitative knowledge of the temporal dynamics of their flowing length—namely the extent of the wet portion of the stream network—remains limited, as the monitoring of the spatiotemporal configuration of wet channels is challenging in most settings. This work combines the high spatial resolution of visual surveys and the high temporal resolution of camera‐based approaches to reconstruct the space‐time stream network dynamics in a 3.7 km2 Mediterranean catchment of central Italy. Information on the hydrological status of the stream network derived from 40 field surveys and sub‐hourly images collected with 21 stage‐cameras are combined exploiting the hierarchical principle. The latter postulates the existence of a Bayesian chain, defined from the local persistence of the nodes that dictates their wetting/drying order during expansion/retraction cycles of the flowing stream network. Our results highlight the complexity of network dynamics in the study area: while the number of wet nodes decreases during the dry season and increases during the wet season, the local persistency exhibits a highly heterogeneous non‐monotonic spatial pattern, originating a dynamically disconnected network. Despite this heterogeneity, the hierarchical model well approximates the temporal evolution of the state of the network nodes, with an accuracy that exceeds 99%. Crucially, the model allows the reconstruction of the wet portion even in cases in which part of the network was not observed. This work provides a novel conceptual approach for the reconstruction of the wet portion of the network in poorly accessible sites. Key Points: Field data on the hydrological status of the drainage network are collected via heterogeneous spatiotemporal resolution techniquesData are combined to reconstruct the long‐term active drainage network dynamics exploiting the hierarchical principleThe model reproduces the complexity of the non‐monotonic pattern of the wet portion of the network in the study site [ABSTRACT FROM AUTHOR]

We present here, and make freely available, two long‐term datasets on the hydrology and hydrochemistry of two small catchments totally or partially covered by holm oak (Quercus ilex) forests. Data have been collected over four decades of research on the ecology of Mediterranean evergreen forests. The datasets contain data on water fluxes in precipitation and runoff, and on the ion concentrations and fluxes in precipitation, throughfall and streamwater. Among other applications, these data have been used to obtain catchment budgets of water and elements, to document decadal changes in atmospheric deposition and streamwater chemistry, to assess the role of Saharo‐Sahelian dust on forest nutrient cycling, and to model habitat suitability for an endangered amphibian under future climates. To encourage their further use by the scientific community, in this paper we summarize the data context and methods, and give a nutshell of obtained results. We provide the links to these datasets on the Zenodo platform. [ABSTRACT FROM AUTHOR]

Study region: The Bas-Loukkos catchment, a Mediterranean catchment in northern Morocco exposed to growing water withdrawal caused mainly by agricultural development. Study focus: For adaptation to climate change, water managers have to consider the high and various uncertainties. To assess impacts of climate change on projected water resources, this study aimed to develop a smart analysis framework to provide scientific information by exploring the complexity of many projections combined with hydrological models. Uncertainties were quantified using 13 pair-wise combinations of 5 regional climate models forced by 4 global climate models under two emissions scenarios (RCP4.5 and RCP8.5), data with and without bias correction (using empirical quantile mapping), and two sets of GR2M hydrological model parameters corresponding to different precipitation conditions. The Budyko hypothesis was used to analyse combined effects of climate change on water resources according to water-withdrawal scenarios. Climate and hydrological projections have been analyzed over three periods: short-term [2020–2040], medium-term [2041–2060] and long-term [2081–2100]. New hydrological insights for the region: Results from all simulations indicate that, in the long term (2081–2100), precipitation and discharge will decrease by ca. 21–38% and ca. 50–71%, respectively, compared to the reference period (1981–2005). Consequently, this decline in water resources will require water management strategies to adapt to the future climatic conditions and water demand.

Human‐induced afforestation has been one of the main policies for environmental management of farmland abandonment in Mediterranean areas. Over the last decades, several studies have reviewed the impact of afforestation activities on geomorphological and hydrological responses and soil properties, although few studies have evaluated the effects on water table dynamics. In parallel to human‐induced afforestation activities, natural revegetation occurred in abandoned fields and in fields where the intensity of human activity declined, driving the expansion of shrubs. This research addresses the spatial and temporal variability of water table dynamics in a small afforested sub‐catchment located in the Central Spanish Pyrenees. Differences between afforestation (Pinus nigra and Pinus sylvestris) and natural plant colonization (shrubs, mainly Genista scorpius, Buxus sempervirens, and Juniperus communis) and early abandoned meadows (G. scorpius), are analysed in terms of runoff generation and seasonal water table depth dynamics. Precipitation, runoff and water table datasets recorded for the 2014–2019 period are used. Results show a high temporal and spatial variability with large fluctuations in discharge and water table. Groundwater dynamics varied markedly over the year, identifying a wet and dry period with different responses suggesting different runoff generation processes (Hortonian flow during dry and wet periods, and saturation excess runoff during wet conditions). Furthermore, important differences are noted among the various land cover types: (i) in the natural revegetation area (shrubland and meadows) a marked seasonal cycle was observed with short saturation periods during winter and spring; and (ii) in the afforestation areas, the water table dynamics showed a seasonal cycle with a high variability, with fast responses and rapid oscillations. Likewise, the relationship between the depth of water table and hydrological variables was not straightforward, suggesting complex hydrological behaviour. [ABSTRACT FROM AUTHOR]

Event-based models are often used for flood prediction because they require fewer data than more complex models and account for a small number of parameters. We present the performance of such a model in simulating Mediterranean floods, with a focus on the initialization and on the impact of the rainfall uncertainties on the calibration of the model. The distributed event-based parsimonious Soil Conservation Service Lag-and-Route (SCS-LR) model was applied in the Real Collobrier catchment, France, which has a very high density of raingauges. The initial condition of the model was highly correlated with predictors, such as baseflow or soil water content. A reduction in the raingauge density can markedly change the calibration of the model. As the density of raingauges is generally low in most catchments, the uncertainties associated with rainfall measurement are thus expected either to mask the actual accuracy of the model, or to alter the model parameters. [ABSTRACT FROM AUTHOR]

Mediterranean catchments experience already high seasonal variability alternating between dry and wet periods, and are more vulnerable to future climate and land use changes. Quantification of catchment response under future changes is particularly crucial for better water resources management. This study assessed the combined effects of future climate and land use changes on water yield, total nitrogen (TN) and total phosphorus (TP) loads of the Mediterranean Onkaparinga catchment in South Australia by means of the eco-hydrological model SWAT. Six different global climate models (GCMs) under two representative concentration pathways (RCPs) and a hypothetical land use change were used for future simulations. The climate models suggested a high degree of uncertainty, varying seasonally, in both flow and nutrient loads; however, a decreasing trend was observed. Average monthly TN and TP load decreased up to − 55% and − 56% respectively and were found to be dependent on flow magnitude. The annual and seasonal water yield and nutrient loads may only slightly be affected by envisaged land uses, but significantly altered by intermediate and high emission scenarios, predominantly during the spring season. The combined scenarios indicated the possibility of declining flow in future but nutrient enrichment in summer months, originating mainly from the land use scenario, that may elevate the risk of algal blooms in downstream drinking water reservoir. Hence, careful planning of future water resources in a Mediterranean catchment requires the assessment of combined effects of multiple climate models and land use scenarios on both water quantity and quality. [ABSTRACT FROM AUTHOR]

In a catchmnent, nitrogen (N) export from terrestrial ecosystems to rivers is controlled by the hydrological processes and N balance. In the present paper, the soil system N budget and riverine export were quantified in a Mediterranean watershed, the Celone (South-East, Italy). The study area (72 km 2 ) consists of agricultural land (70%) and deciduous forests with three small residential areas. Major N inputs derived from fertilizers and animal manure, corresponding for the whole watershed area to 68 and 12 kg N ha −1 yr −1 , respectively. N input from point sources was 1% of total input and atmospheric depositions measured in a gauging station near the study area was quantified in ∼6 kg N ha −1 yr −1 . Crop N uptake was the main N output from agricultural land; it was estimated in ∼37 kg N ha −1 yr −1 by using data on crop yields provided by local farmers. Total flux of N in surface water was quantified for a year at the outlet of the study area by using continuous measures of flow and discrete measures of N concentrations carried out with a different frequency during the normal and low flow and when floods occurred. The hydrological regime of the stream, which is a temporary river, plays an important role in N transport. Water quality was found to vary considerably through the year in terms of both nutrient concentrations and loads. Riverine N export was quantified in 41% of total N input, and it was mainly transported during flood events, ∼60% of the annual load was delivered during floods occurred in 38 days. Organic nitrogen and nitrate were the main N forms in surface water, and the contribution per hectare was about 24 and 14 kg N, respectively. On a yearly basis, the difference between N inputs and outputs including riverine export was estimated in about 4 kg N ha −1 yr −1 for the whole watershed area. This amount partly accumulates in soils in different N forms and the remaining part, mainly in form of nitrate, percolates through unsaturated soil towards groundwater. This study reports an important analysis of N pollution in a Mediterranean watershed with a temporary river system and limited data availability. Data acquisition and handling have proved to be an important challenge to overcome in N balance quantification. The results and the methodology of the present work can be useful for understanding nitrogen loss dynamics and for functional water management and land use planning. [ABSTRACT FROM AUTHOR]

The Soil and Water Assessment Tool (SWAT) is a well-established eco-hydrological model that has been extensively applied to watersheds across the globe. This work reviews over two decades (2002–2022) of SWAT studies conducted on Mediterranean watersheds. A total of 260 articles have been identified since the earliest documented use of the model in a Mediterranean catchment back in 2002; of which 62% were carried out in Greece, Italy, or Spain. SWAT applications increased significantly in recent years since 86% of the reviewed papers were published in the past decade. A major objective for most of the reviewed works was to check the applicability of SWAT to specific watersheds. A great number of publications included procedures of calibration and validation and reported performance results. SWAT applications in the Mediterranean region mainly cover water resources quantity and quality assessment and hydrologic and environmental impacts evaluation of land use and climate changes. Nevertheless, a tendency towards a multi-purpose use of SWAT is revealed. The numerous examples of SWAT combined with other tools and techniques outline the model's flexibility. Several studies performed constructive comparisons between Mediterranean watersheds' responses or compared SWAT to other models or methods. The effects of inputs on SWAT outputs and innovative model modifications and improvements were also the focus of some of the surveyed articles. However, a significant number of studies reported difficulties regarding data availability, as these are either scarce, have poor resolution or are not freely available. Therefore, it is highly recommended to identify and develop accurate model inputs and testing data to optimize the SWAT performance. [Display omitted] • SWAT review on Mediterranean hydro-climatic studies. • Lack of SWAT assessment on Mediterranean catchments. • A comparison of data from different Mediterranean basins. • Enhancing data availability for SWAT applications. • Developing a comprehensive knowledge of Mediterranean watersheds. [ABSTRACT FROM AUTHOR]

This work examines 140 hydrological studies conducted in the Mediterranean region. It identifies key characteristics of the hydrological responses of Mediterranean catchments at various time scales and compares different methods and modelling approaches used for individual-catchment studies. The study area is divided into the northwestern (NWM), eastern (EM) and southern (SM) Mediterranean. The analysis indicates regional discrepancies in which the NWM shows the most extreme rainfall regime. A tendency for reduced water resources driven by both anthropogenic and climatic pressures and a more extreme rainfall regime are also noticeable. Catchments show very heterogeneous responses over time and space, resulting in limitations in hydrological modelling and large uncertainties in predictions. However, few models have been developed to address these issues. Additional studies are necessary to improve the knowledge of Mediterranean hydrological features and to account for regional specificities.Editor D. Koutsoyiannis Associate editor A. Efstratiadis [ABSTRACT FROM PUBLISHER]

In the semi-arid Mediterranean environment, the rainfall-runoff relationships are complex because of the markedly irregular patterns in rainfall, the seasonal mismatch between evaporation and rainfall, and the spatial heterogeneity in landscape properties. Watersheds often display considerable non-linear threshold behavior, which still make runoff generation an open research question. Our objectives in this context were: to identify the primary processes of runoff generation in a small natural catchment; to test whether a physically based model, which takes into consideration only the primary processes, is able to predict spatially distributed water-table and stream discharge dynamics; and to use the hydrological model to increase our understanding of runoff generation mechanisms. The observed seasonal dynamics of soil moisture, water-table depth, and stream discharge indicated that Hortonian overland-flow was negligible and the main mechanism of runoff generation was saturated subsurface-flow. This gives rise to base-flow, controls the formation of the saturated areas, and contributes to storm-flow together with saturation overland-flow. The distributed model, with a 1D scheme for the kinematic surface-flow, a 2D sub-horizontal scheme for the saturated subsurface-flow, and ignoring the unsaturated flow, performed efficiently in years when runoff volume was high and medium, although there was a smoothing effect on the observed water-table. In dry years, small errors greatly reduced the efficiency of the model. The hydrological model has allowed to relate the runoff generation mechanisms with the land-use. The forested hillslopes, where the calibrated soil conductivity was high, were never saturated, except at the foot of the slopes, where exfiltration of saturated subsurface-flow contributed to storm-flow. Saturation overland-flow was only found near the streams, except when there were storm-flow peaks, when it also occurred on hillslopes used for pasture, where soil conductivity was low. The bedrock-soil percolation, simulated by a threshold mechanism, further increased the non-linearity of the rainfall-runoff processes. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This article addresses the critical need for a better quantitative understanding of how water resources from the Hérault River catchment in France have been influenced by climate variability and the increasing pressure of human activity over the last 50 years. A method is proposed for assessing the relative impacts of climate and growing water demand on the decrease in discharge observed at various gauging stations in the periods 1961–1980 and 1981–2010. An annual water balance at the basin scale was calculated first, taking into account precipitation, actual evapotranspiration, water withdrawals and water discharge. Next, the evolution of the seasonal variability in hydroclimatic conditions and water withdrawals was studied. The catchment was then divided into zones according to the main geographical characteristics to investigate the heterogeneity of the climatic and human dynamics. This delimitation took into account the distribution of climate, topography, lithology, land cover and water uses, as well as the availability of discharge series. At the area scale, annual water balances were calculated to understand the internal changes that occurred in the catchment between both past periods. The decrease in runoff can be explained by the decrease in winter precipitation in the upstream areas and by the increase during summer in both water withdrawals and evapotranspiration in the downstream areas, mainly due to the increase in temperature. Thus, water stress increased in summer by 35%. This work is the first step of a larger research project to assess possible future changes in the capacity to satisfy water demand in the Hérault River catchment, using a model that combines hydrological processes and water demand.Editor Z.W. KundzewiczCitation Collet, L., Ruelland, D., Borrell-Estupina, V., and Servat, E., 2014. Assessing the long-term impact of climatic variability and human activities on the water resources of a meso-scale Mediterranean catchment. Hydrological Sciences Journal, 59 (8), 1457–1469. http://dx.doi.org/10.1080/02626667.2013.842073 [ABSTRACT FROM PUBLISHER]

Abstract: The aim of this study was to gain insights on the potential hydrological and biogeochemical mechanisms controlling the response of two nested Mediterranean catchments to long-term changes in atmospheric inorganic nitrogen and sulphate deposition. One catchment was steep and fully forested (TM9, 5.9ha) and the other one had gentler slopes and heathlands in the upper part while side slopes were steep and forested (TM0, 205ha). Both catchments were highly responsive to the 45% decline in sulphate concentration measured in atmospheric deposition during the 1980s and 1990s, with stream concentrations decreasing by 1.4 to 3.4μeqL−1 y−1. Long-term changes in inorganic nitrogen in both, atmospheric deposition and stream water were small compared to sulphate. The quick response to changes in atmospheric inputs could be explained by the small residence time of water (4–5months) in these catchments (inferred from chloride time series variance analysis), which was attributed to steep slopes and the role of macropore flow bypassing the soil matrix during wet periods. The estimated residence time for sulphate (1.5–3months) was substantially lower than for chloride suggesting unaccounted sources of sulphate (i.e., dry deposition, or depletion of soil adsorbed sulphate). In both catchments, inorganic nitrogen concentration in stream water was strongly damped compared to precipitation and its residence time was of the order of decades, indicating that this essential nutrient was strongly retained in these catchments. Inorganic nitrogen concentration tended to be higher at TM0 than at TM9 which was attributed to the presence of nitrogen fixing species in the heathlands. Our results indicate that these Mediterranean catchments react rapidly to environmental changes, which make them especially vulnerable to changes in atmospheric deposition. [Copyright &y& Elsevier]

Fluvial systems in Mediterranean areas are subject to strong precipitation seasonality, characterized by a low flow period, and, in severe conditions, the complete disruption of surface flow continuum. The Fuirosos is a Mediterranean intermittent stream that has been monitored since 1998. It is located near Barcelona (Spain) in a catchment almost untouched by anthropic activity. Thus it has become a target for many studies on biogeochemistry and fluvial ecology. Some of these studies especially emphasize the role of the dry-wet cycling and its influence on other aspects of fluvial processes. This text provides a wide overview of the research conducted in Fuirosos catchment and highlights the relevance of the alternation of hydrological periods in Mediterranean systems. [ABSTRACT FROM AUTHOR]

Scent marking is a common behaviour used to delineate territories by carnivores, yet it remains insufficiently understood as there are several alternative hypotheses, one being that sites are marked where resources are abundant, thus guaranteeing their exclusive use. Small Mediterranean rivers are highly variable environments throughout the year, representing an ideal scenario to test this theory, as prey availability changes as a function of the spatial and temporal variability of the flow regime. We studied seasonal variation in the habitat selection of latrine (i.e. scent-marked) sites, prey availability and prey selection of the Eurasian otter, Lutra lutra, between two contrasting fluvial systems, the regulated mainstem of River Bullaque and four unregulated tributaries (River Guadiana basin, central Spain). In 2010, we measured habitat variables, collected otter spraints and used electrofishing to compare the diet with prey abundance. Latrines were more frequent at shallow sites, and otters did not discriminate between fluvial systems across seasons. Also, latrines were associated with sites where the main prey, the calandino, Squalius alburnoides, was more abundant in the tributaries during spring and summer. However, this abundance was not translated into prey selection, with calandino being preyed below its availability in the mainstem. This observation suggests that otters mark places where fishing is especially easy (i.e. shallow sites with proportionally more fish). Calandino was substituted by red swamp crayfish, Procambarus clarkii, which was easier to catch but of lower energetic value, where higher water levels made fishing more difficult (i.e. the regulated mainstem). [Copyright &y& Elsevier]

Abstract: In the north rim of the Mediterranean region, where forest cover is increasing as a result of land abandonment and temperatures are rising as a result of climate change, there is increasing interest for the effects of such changes on the runoff of water courses. This is a paramount issue for the conservation of many freshwater habitats and species. In this work we studied the effects of both an increase in forest cover after depopulation and land abandonment and an increase in temperature on the runoff of a Mediterranean catchment and on the aquatic and semi-aquatic fauna species of the stream (Olzinelles valley, NE Spain). Although in our simulation no decreasing trend in runoff is detected, the monthly runoff-rainfall ratio is now 15% lower than 30 years ago, a fact that may be attributed to a drier period rather than to the small afforestation experienced by the catchment in the last decades. Other factors such as increasing temperatures, changing rainfall patterns and increasing canopy cover are discussed. The observed decrease in the water flow has caused the disappearance of white-clawed crayfish (Austropotamobius pallipes), Mediterranean barbel (Barbus meridionalis), chub (Squalius cephalus), European eel (Anguilla anguilla), and southern water vole (Arvicola sapidus). Our results suggest that in a progressively warmer climate, and especially after land abandonment processes, management of Mediterranean mountain areas should be oriented towards an appropriate distribution of agrarian and forest land-covers in terms of water availability. Down to the stream scale, the pools that keep water throughout the year should be conserved and extended to enhance its potential to maintain aquatic and semi-aquatic species populations. [ABSTRACT FROM AUTHOR]

This study investigates the geomorphological dynamics of badland areas in the Araguás catchment (0.45 km²) in the Central Pyrenees. The genesis and development of badlands in the Central Pyrenees is favoured by the presence of Eocene marls and a markedly seasonal climate. The Aragu²s catchment has been monitored since 2004. Analysis of weathering processes and regolith dynamics showed that alternating freeze-thaw and wetting-drying cycles are the main causes of regolith development and weathering, and effectiveness and intensity of these processes is maximum in winter and summer. Evolution of the badland surfaces is related to regolith moisture level and temperature, closely associated with the season and slope exposure, which cause cyclical variations in regolith physical conditions. The most important effect associated with regolith dynamics is the temporal delay between maximum rainfall erosivity and variation in maximum surface runoff generation, reflected in seasonal differences in sediment transport. The dynamics of weathering and erosion processes affecting badland areas are the principal factors controlling geomorphological development, and the extreme hydrological and sedimentological responses of badlands are the main effects of such morphologies. From a hydrological point of view, badlands increase water production, and flood frequency relative to neighbouring areas; from a sedimentological point of view, suspended sediment transport from badland areas can reach amounts two or three orders of magnitude higher than other nearby environments. Given these results, possible responses of badland dynamics to altered hydroclimatic regime are briefly discussed. [ABSTRACT FROM AUTHOR]

Flood frequency analysis based on a set of systematic data and a set of historical floods is applied to several Mediterranean catchments. After identification and collection of data on historical floods, several hydraulic models were constructed to account for geomorphological changes. Recent and historical rating curves were constructed and applied to reconstruct flood discharge series, together with their uncertainty. This uncertainty stems from two types of error: (a) random errors related to the water-level readings; and (b) systematic errors related to over- or under-estimation of the rating curve. A Bayesian frequency analysis is performed to take both sources of uncertainty into account. It is shown that the uncertainty affecting discharges should be carefully evaluated and taken into account in the flood frequency analysis, as it can increase the quantiles confidence interval. The quantiles are found to be consistent with those obtained with empirical methods, for two out of four of the catchments. Citation Neppel, L., Renard, B., Lang, M., Ayral, P.-A., Coeur, D., Gaume, E., Jacob, N., Payrastre, O., Pobanz, K. & Vinet, F. (2010) Flood frequency analysis using historical data: accounting for random and systematic errors. Hydrol. Sci. J.55(2), 192-208. [ABSTRACT FROM AUTHOR]

The article presents a study on the patterns of seepage losses and related groundwater recharge patterns during a typical Mediterranean runoff event at the scale of a ditch located above a shallow water table. Its aim is to evaluate the influence of ditches network on groundwater recharge and contamination by surface waters in farmed areas where severe problems of water contamination occur. Results show that seepage losses during a runoff event in a ditch can rapidly lead to a significant recharge of a shallow water table. It also points that the patterns of water table recharge and contamination in Mediterranean catchments with dense network vary largely in space and time, and will require dense monitoring networks to estimate the evolution of the average contamination levels.

Abstract: This paper analyses the temporal patterns of suspended sediment yield in the Araguás catchment, Central Spanish Pyrenees, a small experimental catchment with extensive badlands. The catchment has been monitored since 2004 to study weathering, erosion, and hydrological and sediment responses to understand the superficial dynamics of a badland area in a relatively humid environment. The development of badlands in the Central Spanish Pyrenees is favoured by the presence of marls and a markedly seasonal climate. The continuous observation of selected physical parameters and environmental variables enables us to establish seasonal patterns of weathering processes and identify those factors that control regolith development. Freeze–thaw cycles in winter and wetting–drying in spring–summer are the main processes involved in regolith weathering, thereby controlling slope development in combination with rainfall-related erosion processes. The 64 floods recorded during the study period (December 2005 to January 2007) were used for a hydrosedimentological analysis. The main observed features indicate that the Araguás catchment reacts to all rainfall events, resulting in steep rising and recession limbs on the hydrograph and a very short time lag. Floods show high suspended sediment concentrations and a heterogeneous temporal distribution related to seasonal variations in surface runoff production. These differences increase the degree of complexity involved in studying sediment response. Suspended sediment concentration and transport mainly depend on rainfall volume, maximum rainfall intensity, peak flow, and runoff occurrence. Finally, the similarities among the obtained hydrographs, sedigraphs, and hyetographs, in combination with the rapid response of most of the floods, suggest a large contribution of overland flow, derived mainly from infiltration excess runoff upon badland areas. Accordingly, the significant correlations obtained between rainfall intensity and sediment concentration (mainly during the dry season), which suggest a single source area for both runoff and sediment, also support the hypothesis of Hortonian hydrological response within badland areas. [Copyright &y& Elsevier]

The article discusses a study about the spatial and temporal variability of the hydrological response in a small Mediterranean research catchment, Cal Rodó. The main purpose of the study is to examine the rainfall-runoff relationship in the catchment in an attempt to characterize the non-linearity of its hydrological response. The greater seasonality of the hydrological response of the catchment was manifested at the event scale. The spatial and temporal non-linearities of the rainfall-runoff relationship observed in the catchment and reported in other Mediterranean catchments have direct implications on hydrological modelling.

Summary: It is essential to be able to model the surface–subsurface flow processes that occur within and at the vicinity of channels and ditches because of their major role in groundwater recharge in arid regions. The main aim of this study was to evaluate a three-dimensional Richards’ equation-based modelling approach for simulating groundwater recharge. Another aim was to evaluate various strategies for estimating the hydraulic properties of the soil–aquifer system near the ditch. The case study consists of two infiltration experiments on a ditch in a catchment located in South-France. One experiment was used for calibrating the soil hydraulic properties by inverse modelling and the other for validation. The simulations were performed with the SWMS_3D simulation code, which computes three-dimensional saturated–unsaturated water flow and solute transport. For calibration and validation, two criteria were considered: piezometric heads at different distances from the ditch and hydraulic head profiles. Four scenarios of hydraulic parameter distribution were tested: an “a priori” scenario with observed values obtained by classical measurement techniques and three calibration scenarios. These are “homogeneous isotropic”, “heterogeneous isotropic” and “heterogeneous anisotropic” scenarios. The results obtained show that a three-dimensional Richards’ equation-based approach could satisfactorily simulate groundwater recharge by seepage losses from ditches in case of induced surface ponding experiment. Although a multi-criteria calibration was performed, three sets of soil hydraulic properties of various complexity that could reproduce satisfactorily the flow experiments were found. Finally, the results obtained also showed that representing the variability of soil properties in greater detail did not necessarily improve water flow simulation. The Akaike information criteria was used in order to discriminate between the well-calibrated scenarios. The “homogeneous isotropic” scenario represents the best compromise between goodness of fit and parsimony. The study also indicates that hydraulic heads are not necessarily sufficient for the thorough evaluation of groundwater flow models. [Copyright &y& Elsevier]

Summary: This study, based on a chemical and isotopic approach (major, trace elements and strontium isotopes), focuses on the geochemical hydrograph separation during flood events in a Mediterranean watershed (Hérault, Southern France). Major element contents present a typical decreasing logarithmic curve when plotted against river discharge. The concentrations measured during floods are, however, always higher than the theoretical dilution curve and can be related to (1) rainfall input in this sea-side basin, especially for Cl, and (2) water–rock interactions, which release elements in solution especially from the carbonate compartment of the watershed. Ca and HCO3 are not correlated with the river discharge, their content in the dissolved phase being controlled by calcite and aragonite mineral phases. Sr is a proxy of Ca regarding its physico-chemical properties, but it has been demonstrated that Sr is not controlled by these mineral phases and it presents a logarithmic variation with discharge. It is also very well correlated with Cl, which is a conservative element par excellence. Sr and its isotopic ratio can thus be used to constrain the geochemical behaviour of the dissolved phase during flood events. The main tributaries, characterised under various hydrological conditions, defined very well constrained end-members as the result of the diversity of the lithologies drained. Monitoring at the outlet of the watershed during four flood events showed that (1) during low flow periods, the signature at the outlet results from a binary mixing between the two main water sources in the basin; (2) each flood event studied presents a different temporal geochemical evolution (counter- or clockwise evolution in a 87Sr/86Sr vs. reciprocal Sr-content diagram) reflecting the predominance of different water sources during the flood, i.e., the tributaries versus the karst aquifers depending on rainfall intensity, duration and location; (3) the sequence of water origins during the flood seems also be controlled by the initial state of the soil and epikarst–karst continuum, inducing a more or less rapid and pronounced response after rainfall events. [Copyright &y& Elsevier]

Summary: This paper analyzed the seasonal dynamics of runoff-contributing areas in a small Mediterranean catchment (Can Vila catchment, 0.56km2). The aim was to provide a more detailed spatially distributed picture of the behavior of the catchment, which would help explain the high spatio-temporal variability of its hydrological response. Contributing areas for runoff were mapped during eight field surveys performed under varied hydrological conditions. Low permeable bare areas were recognised as classic source areas for infiltration excess runoff, and two types of saturated areas prone to saturation excess runoff were identified: A-type areas, linked to groundwater rising to the surface, and B-type areas, associated with saturation restricted to the upper soil profile. The amplitude of the seasonal variation in these saturated areas was similar to the amplitude found in more humid catchments, even if their decrease was more marked under dry conditions. In the Can Vila catchment, terraced topography promoted, however, more scattered saturation patterns than those usually described. A linear relationship between the extent of saturated areas and baseflow discharge was found; the relationship with the position of the water table was also direct, when saturated areas linked to groundwater rising dominated the saturation pattern. Using very simple methodology, a tentative quantification of the contribution of precipitation on saturated areas to storm-flow was performed, improving the overall understanding of the Can Vila Mediterranean catchment. [Copyright &y& Elsevier]

Soil erosion due to water is a major environmental problem in many parts of the world. Most of Mediterranean countries are concerned because of their specific climate and soils sensitivity, but also because of the recent intensification of human activities and agricultural practices. Accurate estimation of soil water erosion for various land-use and climate scenarios is so an important key to define sustainable management policies. In the last decades, several studies have been carried out to build models suitable for quantifying soil erosion. Among these models, the Water Erosion Prediction Project (WEPP, Flanagan, D.C., Nearing, M.A., 1995. USDA-Water Erosion Prediction Project: Hillslope profile and watershed model documentation. NSERL Report 10, USDA-ARS National Soil Erosion Research Laboratory, West Lafayette, IN, USA.) is a physically based, distributed-parameter model that has been developed and mainly validated in USA. Only few studies have investigated its applicability to environmental conditions that differs from those where the model was developed. The aim of this work is to test the efficiency of WEPP model to predict soil erosion at catchment scale in a Mediterranean semi-arid area. Continuous simulations have been conducted between 1995 and 2002 on an cultivated experimental catchment located upstream from a hill reservoir (Kamech catchment, 2.45km2, Cap Bon, Tunisia) where runoff and soil erosion measurements are available at the outlet. Comparison between predictions and measurements shows significant differences. Processes related to seasonal effects (as cracking soils) are pointed out as a weakness of WEPP model for Mediterranean conditions. [Copyright &y& Elsevier]