Hydrographic Network Research Articles

Environmental monitoring of heavy metal content in the hydrographic network of a large city river

ABSTRACT Samples of edaphotopes were taken from a depth of 0–15 cm for analyses in this study. It was found that the water in the areas of the Hnidavske swamp and Teremnivski ponds was the most polluted. The level of Zn (0.01 mg/dm3) exceeded the maximum permissible concentration (MPC) at site 5 (Lypnyany village, outside the city of Lutsk, the content was 0.015 mg/dm3) and Hnidavske marsh (0.019 mg/dm3). At all study sites, Cr (0.001 mg/dm3) ranging from 0.002 to 0.005 mg/dm3, Co (0.005 mg/dm3) from 0.008 to 0.01 mg/dm3, and Ni (0.01 mg/dm3) from 0.02 to 0.036 mg/dm3 were also found to exceed the MPC. However, Cd levels (0.005 mg/dm3) did not exceed the MPC and was within the normal range at all study sites (0.0016–0.003 mg/dm3).

Influence of Longitudinal Fragmentation on Length–Weight Relationships of Fishes in the Someșul Cald River, Romania

Romania has a rich hydrographic network, which permitted the construction of over 80 large dams on its water courses, estimating a number between 545 and 674 hydropower plants that were either built or were in a different construction stage on the rivers of Romania in 2021. These hydropower plants were often built outside specific legislation regarding ecological impacts, especially before 1990. Longitudinal fragmentation of rivers causes severe ecological impacts on biodiversity, food chains, and nutrient cycles. Someșul Cald River is the main tributary of Someșul Mic River, the most important water source for the northwestern region of Transylvania. On its course, several dams and reservoirs were built from 1968 to 1980 for electricity production and population freshwater supply. The present study aimed to analyze the length–weight relationships (LWRs) and condition factors occurring in the longitudinally fragmented Someșul Cald River. The LWRs, relative condition factor Kn, and Fulton condition factor K were determined based on total length and wet body weight. Comparisons of LWRs, Kn, and K across river sections constrained by dams showed that some fish species exhibited similar growth patterns and physiological conditions, while others differed significantly. Freshwater fish physiology is altered by longitudinal fragmentation, both natural and artificial. Barriers such as dams influence the energy gradient, limiting feed availability and, consequently, the life history of fish species. Long-term management plans regarding conservation should take into consideration existing fish species population dynamics, along with their physiological and somatic status.

Effects of urbanization on river morphology in a Mediterranean coastal city (Genova, Italy)

From the geomorphological point of view, urbanization changes fluvial systems more drastically than any other single human activity. Its impact on rivers is of interest as it results in serious issues concerning geomorphic instability, ecosystem service reduction, and geo-hydrological risk increase. The present study provides a quantitative and qualitative assessment of landscape changes driven by urbanization, which occurred from the mid-19th century to the present day along the lower reaches of the Bisagno and Polcevera rivers and their tributaries in the Mediterranean coastal city of Genova (NW Italy). The bankfull channel morphological adjustments, the minor hydrographic network disappearance, the land use and land cover changes, and the current physical accessibility of river margins were investigated. This work is based on collection and review of historical data, photograph interpretation, GIS analysis, and field surveys. Urbanization essentially occurred between the mid-19th century and the late 1930s. The bankfull channel of the Bisagno and Polcevera rivers experienced large narrowing associated with widespread establishment of channelization structures. The minor hydrographic network essentially disappeared underground. After the 1930s, further minor anthropogenic interventions were implemented to accommodate urban expansion and consolidate channelization works; however, the overall geomorphological setting remained unchanged. The geomorphological evolution of the Bisagno and Polcevera rivers followed three different phases associated with the urban expansion process. Nowadays, the study area is completely urbanized, the fluvial stems flowing through the valley floor are totally disconnected from their adjacent areas, the main rivers show a relevant geomorphological stability induced by anthropogenic pressures, and the accessibility of river margins for people is rather limited. The outcomes from this study represent an essential knowledge base for technicians and policymakers to plan urban development and inform effective and sustainable management measures. Moreover, they provide insights into the medium- and short-term morphological evolution of urban rivers.

Tectonic Inversion of Intracontinental Basins and the Conundrum of Plate‐Scale Stress Propagation: The Case of the Jatobá Basin, NE Brazil

AbstractWe chose the Jatobá Basin (JB) in the Borborema Province in northeastern Brazil to address two outstanding problems, basin tectonic inversion and stress propagation, because (a) evidence of tectonic inversion is conspicuous in the JB, and (b) the basin sits on intracontinental northeastern Brazil, far from plate boundaries and the most obvious stress sources. We found robust evidence of oblique reverse faulting inside the basin, putting sediments of the JB's depocenter hundreds of meters above the hard granitic host basement. We also found sound evidence of hydrographic flow reversal, that is, earlier basement‐to‐basin runoff, followed by basin‐to‐basement runoff. This change means that formerly the basement stood higher than the basin, and later the basin was uplifted (inverted) to currently stand hundreds of meters higher than the basement, especially where the gravity anomaly map shows the deepest depocenter. Coarse conglomerates, sourced in the uplifted basin and blanketing the adjacent basement for kilometers, are only cut by the current hydrographic network. From these main lines of evidence, we infer recent basin tectonic inversion (Quaternary, i.e., <2.6 Ma?). The WSW‐ENE orientation of the maximum compressive stress needed to invert the basin likely results from Mid‐Atlantic and Andean pushes. We conclude that lithospheric plates can deform in their cores because of stresses propagating from plate boundaries to distant plate interiors, where the lithosphere has been locally weakened and strain has concentrated.

Environmental factors affecting the distribution of Spongillidae (Porifera) in an artificial channel (in north-western Italy)

The hydrographic network of the upper Po Valley (NW Italy) is characterized by the presence of numerous hydroelectric plants, often powered by artificial channels. These man-made water courses, which range from a few hundred meters to several kilometers in length, are used to convey water from the rivers to the electricity production plant. Power canals are usually characterized by concrete banks and bottoms, a geometric profile, and the absence of riparian vegetation so that they host peculiar invertebrate communities, often extremely well adapted to life in a completely artificial habitat. Sponges are an often little considered component of the freshwater macroinvertebrate fauna, whose functions and role within communities can be of considerable interest. These sessile, filter-feeding organisms can colonize artificial channels, but little is known about the local environmental characteristics that influence their distribution. In this study, we investigated the distribution of a freshwater sponge family Spongillidae, in a 4.5 km long artificial channel in Rocca Grimalda (Alessandria, NW Italy). A total of 863 specimens were localized and measured, and selected environmental characteristics were recorded. Results suggested that the distribution of sponges depends mainly on the lighting rather than the type of substrate or other local factors, so that this taxon is well-suited to colonizing artificial environments with good water quality conditions.

Inconsistent Regulatory Mapping Quietly Threatens Rivers and Streams.

Even the most stringent environmental law cannot protect a river if its tributaries remain exposed to pollution and other threats upstream. Excluding a subset of watercourses from legal protection therefore threatens to alter freshwater ecosystems across entire river networks and the services they provide, such as drinking water and flood regulation. Considerable attention has been devoted to defining the scope of environmental laws protecting watercourses. Yet how these definitions are implemented through regulatory mapping, the cartography of waterbodies that legally qualify as watercourses and are thus protected, has not been examined outside of the United States. Here, we demonstrate the consequences of regulatory mapping on the extent of river networks that are protected, using France as a case study. By assembling the first map of France's watercourses protected under the Water Law, we estimate that a quarter of previously mapped hydrographic segments were excluded from protection and found stark geographical variations in the extent of protected ecosystems. Headwater and nonperennial segments are disproportionately excluded by 28% compared to their prevalence (67%) in the overall hydrographic network, with potentially far-reaching implications for biodiversity and people. We expect regulatory frameworks in most countries to be equally susceptible to local interpretation of legal definitions.

Integrating hydrogen into a hybrid system to meet a laboratory's electricity demand

Providing quality electricity to improve the living conditions of rural and urban populations in Africa, particularly in Cameroon, represents a challenging but achievable task. Indeed, Cameroon has the second largest hydrographic network in Central Africa, and thanks to this network, over 90% of electricity comes from aging hydroelectric dams that cause permanent power outages. The desire to take advantage of other benefits that nature has given this country has directed this work towards renewable energies. Thanks to the HOMER Pro software, a renewable energy hybrid system with hydrogen gas serving as storage and energy vector was adopted. Photovoltaic panels and wind turbines are proposed as primary energy sources for the permanent, low-cost supply of the IRAD laboratory at the University of Maroua. The software proposes three systems, one with the wind turbine as the only primary source, and considered as the most optimal. It has an energy cost equal to $0.0633, an NPC of $20330, and an initial capital of $8500. The other two systems are hybrids with a renewable fraction equal to 100%, and a load distribution strategy that is the charge cycle (CC) like the first system. The first less expensive hybrid system has an energy cost and an NPC respectively of $0.0778 and $24986. As for the second hybrid system, it has an NPC and an energy cost respectively of $26195 and $0.0778. Hydrogen fully plays its role as an energy vector and storage in all three systems. A sensitivity analysis was conducted in this work to ensure that the system proposed for the laboratory can also be adapted in the 9 other regions of the country. It appears that the values of wind resources, solar radiation, and temperature have a significant impact on the energy cost. The cities of Yaoundé and Ebolowa, displaying respective wind speeds of 2.07 m/s and 1.76 m/s, are recognized for having the lowest wind speeds in the country, which hinders the overall energy production and profitability of the system. The hybrid system suggested for these cities proves to be expensive, with energy costs exceeding the standard electricity price set by the energy distribution and marketing organization in the country.

Sabarmati and its connection with the Harappan port Lothal and the Nal corridor: A study using multi-sensor data, cloud-computing and multi-platforms

Lothal is situated approximately 30 km inland from the Gulf of Khambhat on the western coast of India in Gujarat. It served as a bustling port during the Bronze Age Harappan period (2600 BCE to 1900 BCE) and was connected to a series of Harappan production and distribution centres dotted along the Gulf of Kachchh and the Rann of Kachchh. Artefacts of foreign nature found in Lothal attest to its intercultural trade relation. Further, Lothal is renowned for its well-preserved brick-walled dockyard and warehouse. However, different views for and against the dockyard are available in archaeological literature. This study revisits the dockyard theory from the landscape perspective and integrates information extracted from early maps, multi-spectral and multi-temporal satellite data of different spatial resolutions, and Digital Elevation Models to understand the larger context of the palaeolandscape around Lothal, including both fluvial and coastal areas. The findings offer fresh perspectives on the hydrographic dynamics of the region, highlighting an evident direct connection between Lothal and the former course of River Sabarmati, one of the major rivers in Gujarat that currently flows 20 km east of Lothal. The reconstruction of the palaeolandscape, both fluvial and coastal, complements and verifies certain interpretations related to the dockyard theory, partially bridging the ‘credibility gap’ in the broader discussion and strengthening the arguments in favour of the dockyard theory. Additionally, the study underscores the significance of integrating various types of geospatial data to understand past landscapes. Further investigation of the reconstructed palaeolandscape, particularly the complex hydrographic network including rivers and creeks, of this historically important region has the potential to contribute to new insights into existing archaeological and geomorphological interpretations and may guide us about the past human adaptation to the natural dynamics.

Soil erosion risk assessment of the Lakhmess watershed (northwestern Tunisia) via the SEAGIS model: Inferred prioritization of risky sub-watersheds

Water erosion in Tunisian semi-arid regions causes harmful effects by silting reservoirs and reducing agricultural lands and soil fertility. Several factors are involved in the erosion process: rain erosivity, soil fragility, and degraded land cover on steep slopes associated with the intensification of inappropriate human practices. Thus, identifying erosion vulnerable sub-watersheds based on the assessed soil loss rate is very important to apply suitable conservation measures. The current research aimed to prioritize risky areas in the Lakhmess watershed, north-west Tunisia via the Soil Erosion Assessment using Geographical Information System (SEAGIS) model. To prioritize sub-watersheds vulnerable to soil erosion and sediment yield, the Lakhmess watershed, covering an area of 162 km2, was divided into 16 sub-watersheds (L1–L16), according to the hydrographic network. Then, the mean annual soil erosion rate and the mean annual sediment yield in the watershed were estimated by integrating the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) in the SEAGIS model and their spatial distribution was determined. The obtained results indicate that the estimated average annual soil erosion rate is 4.2 t/ha/y and the annual sediment yield is 2.6 t/ha/y. Maner's SDR model was selected as the best model for estimating SY, with standard error, standard deviation, and coefficient of variation values of 0.75%, 0.01, and 0.45%, respectively. The prioritization of the Lakhmess sub-watersheds based on the estimated soil loss rate reveals that among the 16 sub-watersheds, three sub-watersheds (L10, L12, and L15) were identified as being in a very high priority soil erosion class. The high soil erosion rate and sediment yield in these sub-watersheds is explained by the steep slope and a high rainfall erosivity factor. Six sub-watersheds (L2, L4, L5, L6, L7, and L16) were found to belong to a very low priority soil erosion class, as they are characterized by a very gentle slope, which appears to be an extremely determining factor. These findings constitute a basis for decision makers to plan effective conservation measures to conserve agricultural lands, soil, and water resources in northwestern Tunisia.

Multitemporal characterization of a proglacial system: a multidisciplinary approach

Abstract. The recession of Alpine glaciers causes an increase in the extent of proglacial areas and leads to changes in the water discharge and sediment balance (morphodynamics and sediment transport). Although the processes occurring in proglacial areas are relevant not only from a scientific point of view but also for the purpose of climate change adaptation, there is a lack of work on the continuous monitoring and multitemporal characterization of these areas. This study offers a multidisciplinary approach that merges the contributions of different scientific disciplines, such as hydrology, geophysics, geomatics, and water engineering, to characterize the Rutor Glacier and its proglacial area. Since 2020, we have surveyed the glacier and its proglacial area using both uncrewed and crewed aerial surveys (https://doi.org/10.5281/zenodo.8089499, Corte et al., 2023c; https://doi.org/10.5281/zenodo.10100968, Corte et al., 2023f; https://doi.org/10.5281/zenodo.10074530, Corte et al., 2023g; https://doi.org/10.5281/zenodo.10101236, Corte et al., 2023h; https://doi.org/10.5281/zenodo.7713146, Corte et al., 2023b). We have determined the bathymetry of the most downstream proglacial lake and the thickness of the sediments deposited on its bottom (https://doi.org/10.5281/zenodo.7682072, Corte et al., 2023a). The water depth at four different locations within the hydrographic network of the proglacial area (https://doi.org/10.5281/zenodo.7697100, Corte et al., 2023d) and the bedload at the glacier snout (https://doi.org/10.5281/zenodo.7708800, Corte et al., 2023e) have also been continuously monitored. The synergy of our approach enables the characterization, monitoring, and understanding of a set of complex and interconnected processes occurring in a proglacial area.

Integrating remote sensing classification techniques for land use mapping in semi-arid regions: a case study of the Tamlouka basin, Algeria.

Worldwide, the majority of countries are actively devising strategies to address the challenges associated with unregulated and unmanageable development, the decline in environmental quality and the depletion of valuable agricultural land. This has led to a growing emphasis on understanding land use and land cover. In order to determine a better land use policy, legislators and planners need to know the current distribution of agricultural and urban lands, as well as information about changes in their proportions. Our approach combines data centred on main four themes-geology, slope gradient, hydrographic network and land use-in order to exploit classifier complementarities in our targeted agricultural study area of Tamlouka Basin, Algeria. Landsat 8 OLI-TIRs multispectral imagery and Shuttle Radar Topography Mission (SRTM-1arc v3) were used experimentally for classification and Digital Elevation Model (DEM) analysis. The classification's accuracy is confirmed by comparing the results of the decision tree classification with the validation samples. Results of the combination of several maps of classifications from the different methods show that the Tamlouka alluvial plain, having an area of 19,300 ha and an average slope gradient of less than 2°, drains the elevated reliefs that surround it via hydrographic network. The plain occupies 37% of the total basin area, with over of 60% being used for crop cultivation, regardless of fallow land areas in agricultural rotation at that time. The slope has been identified as a crucial factor determining land use patterns in the study area. This result can be used in prospective watershed management.

Rockfall susceptibility analysis of the “San Michele Arcangelo” historic trail (Central Italy) based on virtual outcrops and multiple propagation models

The “San Michele Arcangelo” historic trail (Aurunci Regional Park, central Italy), located along the southern slope of Mt. Altino, which is highly prone to rockfalls, is hiked every year by thousands of faithful on pilgrimage who are exposed to such kinds of instabilities. To contribute to a better understanding of the condition and evolution of such phenomena, providing a susceptibility scenario able to support the adoption of mitigation measures, a specific analysis was completed based on field and literature data. Three-dimensional virtual outcrop models were obtained through both photogrammetric and iPad Pro LiDAR surveys to derive geomechanical features of outcropping rocks and estimate potential detaching block volume. Possible mechanisms of detachment were then analyzed using the Markland test method. Susceptibility to rockfall propagation and block deposition was analyzed using GIS processing and rockfall propagation simulations based on deterministic/stochastic models. Such models consist of a combination of a deterministic algorithm able to simulate the physics of rockfall movement during propagation and a stochastic treatment of input parameters based on random sampling within defined interval. Two different rockfall simulations were compared in this study using the Rockyfor3D™ (ecorisQ Association) software and the newly developed RocFall3© (RocScience) code. The use of iPad Pro LiDAR survey provides accurate and high-resolution point clouds, with high speed of acquisition and real-time processing of data. Discontinuity sets identified from 3D models have represented the input for kinematic analyses of slopes, allowing to identify potential failure mechanisms among wedge and planar sliding or toppling. Rockfall simulations indicate the potential for rock blocks propagation and deposition over the whole study area. Comparing the results of rockfall simulations with the geomorphological map of the area it is evident the control exerted by the hydrographic network on rockfall propagation as demonstrated by the presence of screes and slope deposits along the main channels. Understanding the potential susceptibility to both propagation and deposition of rock blocks along the trail provides useful indication for the assessment of appropriate mitigation measures to realize for the safer touristic fruition of the site.

Impact of Hydraulic Developments on the Quality of Surface Water in the Mafragh Watershed, El Tarf, Algeria

The wadis are environments of great ecological and economic importance. They are the seat of several hydraulic developments. The latter disrupts the functioning of the wadi in different ways. They modify their hydrological regime, disrupt the ecological conditions upstream and downstream of the reservoir, reduce the self-purification capacities, and modify the processes of erosion and solid transport. It is in this perspective that we have carried out a study of the impact of hydraulic installations on the quality of the waters of the Mafragh watershed. The hydrographic network of the watershed receives the wastewater discharged by the localities and by the industries located along these rivers. This wastewater contributes to the degradation of the water quality of the wadis. The spatio-temporal variation of the water quality index showed a good quality at the level of the dams, while at the level of the sites, which are located downstream, the quality generally varies between bad and very bad during the study period.

MANAGEMENT PLAN FOR RECREATIONAL FISHING IN THE HYDROGRAPHIC ÂNCORA RIVER BASIN

This work is the result of the most recent studies carried out by the ICNF in the drainage basin of the future recreational fishing area (ZPL) of the Âncora river. These supported the design of a plan for the sustainable management and exploitation of recreational fishing in this river basin, which is part of the Minho and Lima Hydrographic Region (RH1). Seven sampling stations were set up for this purpose. Six in the main watercourse and one in the Regueiro dos Enxurros, in the middle of an area of successive waterfalls, just before its confluence with the Regueiro da Lapa Ladrão, which is considered to be the source of the Âncora River. At these stations, hydromorphological quality assessments were carried out on 500 m stretches using the River Habitat Survey (RHS) methodology and fish community monitoring (three per station, for a total of twenty-one inventories) using the electrofishing technique. The results made it possible to consider implementing more sustainable management and exploitation measures for fishing in these continental bodies of water. In this context, the management options took marked account of conservation objectives associated with the presence of European eels (Anguilla anguilla) and red eels (Achondrostoma spp.), the wide distribution of trout (Salmo trutta) and the reduced presence of boga (Pseudochondrostoma duriense) whose distribution in the upper third of this drainage basin is conditioned by a very peculiar geomorphology, filled with numerous slopes, which give rise to beautiful waterfalls. With the information collected, data on the age, growth and physical condition of the ichthyofauna assessed was studied, and their relationship with the different types of habitat in which they occurred was established. The results show that these are watercourses with "Excellent" quality habitats, but with levels of artificialization ranging from "severely modified" to "predominantly unmodified", the result of anthropogenic actions over time. Trout (Salmo trutta) are the most widely distributed species along the main watercourse. The absence of exotic aquaculture species in the samples and the lack of medium to large water impoundment structures in the hydrographic network evaluated should be emphasized. The existing river compartmentalization is materialized by the numerous micro-weirs (many of which allow aquatic organisms to migrate for a good part of the year) and a few waterfalls (natural cascades) that prevent fish from passing through. The trout show isometric growth for all the sampling stations, a balanced physical robustness and a maximum lifespan of 6 years. As a practical result of this study, a Recreational Fishing Management and Exploration Plan for the Âncora River will be created, which will support the design of measures to promote the sustainable management of recreational fishing in the area of the future LPZ, reconciling this activity with nature conservation objectives.

Unveiling Milan’s Navigli and Underground Water Heritage through Integrated Urban (Water) Design

Unveiling Milan’s Navigli and Underground Water Heritage through Integrated Urban (Water) Design

Hydrotechnical and ecological principles of water resources management for a mined-out mine field

The article considers the issue of predicting and managing water resources of flooded mines based on hydrotechnical and ecological criteria. Reproduction of a natural-technogenic situation within mine fields with many unknowns regarding the condition of a rock massif and influence factors became possible through a step-by-step construction and identification of a numerical geofiltration model. Balance components of formation for a technogenic underground water mode, capacity parameters and zonal water permeability of a rock massif are estimated as a result of methodical adaptation and creation of a hydrodynamic model of two adjacent mines with a complex hydrogeological structure. A duration and speed for groundwater level restoration at different time periods, an area of underflooding and flooding on the surface is established according to predictive calculations. The inefficiency of submersible pumps use is proven when capital workings lose their drainage functions and a massif has rheological dynamics. Variants for long-term pumping of mine waters with subsequent discharge into a hydrographic network do not bring the territory into a self-draining mode. Therefore, the mode of closing mines with full restoration of underground water level in a monitoring mode with a combination of drainage reconstruction of the surface is the most acceptable.

Estimating risk to prevent damage: predicting and preventing coypu (Myocastor coypus) damage to transport infrastructure.

A major impact of invasive Myocastor coypus in their introduction range is the collapse of riverbanks and nearby infrastructure, such as railway lines, due to the species' burrowing activities. Because widespread implementation of preventive measures along watercourses is unfeasible, identifying susceptible areas is key to guide targeted management actions. This study used species-habitat models to: (i) identify local environmental features of the railway line/watercourse intersections (RLWIs) that make them particularly susceptible to coypu damage, and (ii) predict species occurrence probability over a wide lowland-hilly area of northern Italy (Lombardy) to identify priority areas for monitoring. Local-scale models identified that the RLWIs most susceptible to burrowing were those surrounded by arable land with interspersed hedgerows locally characterized by high herbaceous vegetation and clay soil. In urbanized areas and areas of intensive agriculture, coypu dens were generally located significantly closer to the railway, increasing the risk of collapse. A landscape-scale species distribution model showed that lowland areas along major rivers and lake shores, and also agricultural areas with a dense minor hydrographic network, particularly in the southeast of the study area, are more likely to be occupied by coypu. Local-scale models showed that specific environmental characteristics increase the risk of burrowing near RLWIs. The landscape-scale model allowed us to predict which areas require thorough monitoring of RLWIs to search for such local characteristics to implement preventive management measures. The proposed model-based framework can be applied to any geographical context to predict and prevent coypu damage. © 2024 Society of Chemical Industry.

Hydrochemistry and Contamination in Sedimentary and Fractured-Rock Aquifers of The Upper Rio Negro Basin – Amazonas/Brazil

The Amazon region has the largest hydrographic network on the planet. However, cities and communities along rivers obtain water from tube wells without studying the chemical quality and, consequently, the potability of their water. In specific geological contexts, there is a significant probability of natural contamination by arsenic in groundwater in the region, already attested in previous works in the Solimões, Madeira and Amazonas rivers basins, but not yet found in the Negro river basin. As the Negro is the second largest river in the Amazon Basin, it has become necessary to study the chemical quality of its groundwater, relating it to the geology of the region. In this work, water samples were collected from 21 wells and 4 water springs used for human consumption, following the protocols proposed by the US – EPA. In the field, the physicochemical parameters of the in-situ water were measured, and alkalinity tests were carried out on the samples. The cations were analyzed at INPA and the anions at the Geological Survey of Brazil (SGB). From the 25 samples, 16 had analises results within acceptable ionic balance values, and 12 of the 16 had at least one of the following elements in concentration above World Health Organization and Brazilian Guideline Values: Al, As, Fe, Mn and Pb. The presence of values below the GV, but above what is considered natural, of NO3- in 66% of the contaminated points, associated with the shallow depth of most of the wells, installed in areas of recent sedimentary deposits and that do not show any or few signs of care demonstrate that the contamination in these localities is of anthropic origin. Two samples (16% of the contaminated samples) are from deep wells installed in fractured aquifers, which in this case indicate contamination of geogenic origin. Arsenic was found in association with iron and aluminum in a well installed in alluvial sediments, which indicates that more studies are needed for this specific geologic formation to know the quality of this water. For other locations and cities, short, medium and long-term measures are needed to prevent anthropogenic contamination of aquifers.

Technical note: Comparing three different methods for allocating river points to coarse-resolution hydrological modelling grid cells

Abstract. The allocation of points in a river network to pixels of a coarse-resolution hydrological modelling grid is a well-known issue, especially for hydrologists who use measurements at gauging stations to calibrate and validate distributed hydrological models. To address this issue, the traditional approach involves examining grid cells surrounding the considered river point and selecting the best candidate, based on distance and upstream drainage area as decision criteria. However, recent studies have suggested that focusing on basin boundaries rather than basin areas could prevent many allocation errors, even though the performance gain is rarely assessed. This paper compares different allocation methods and examines their relative performances. Three methods representing various families of methods have been designed: area-based, topology-based and contour-based methods. These methods are implemented to allocate 2580 river points to a 1 km hydrological modelling grid. These points are distributed along the entire hydrographic network of the French southeastern Mediterranean region, covering upstream drainage areas ranging from 5 to 3000 km2. The results indicate that the differences between the methods can be significant, especially for small upstream catchment areas.

Conservation Priorities for Threatened Fish to Withstand Climate Crisis: Sustainable Capture and Protection of Inland Hydrographic Ecosystems

Globally, suitable freshwater habitats are undergoing alterations and fish population declines, primarily attributed to the swift changes in climate and land use. Developing an effective conservation policy for freshwater fish necessitates careful consideration of the impacts of climatic and spatial factors. This study focuses on the analysis of 64 threatened freshwater fish in Bangladesh to anticipate their current and future climatically suitable habitats, utilizing the bioclim() species distribution model. Additionally, this study examines existing inland hydrographic networks and their corresponding harvest rates. The findings indicate that approximately 75% of the area of occupancy for the studied species is currently climatically suitable, but this is expected to decrease to 13% under future climate scenarios. Notably, 27 threatened species are at risk of lacking climatically suitable habitats in the future within their current area of occupancy. The three components of hydrographic networks—floodplains, rivers, and natural lakes—play varying roles in providing a climatically suitable habitat for the studied species. For instance, only 34% of threatened fish species are projected to find a suitable habitat over flood areas, 23% over rivers, and 16% over lakes. Existing protected areas presently offer limited protection (21% suitable area), expected to decline to 6% in the future, with no dedicated protected areas for freshwater fish. Floodplains are highlighted for providing habitat connectivity and facilitating brood fish dispersal. However, the unregulated and unmonitored annual harvest of freshwater fish from floodwater and rivers poses a potential silent cause for rapid population decline. Prioritizing the management of hydrographic components to maintain habitat connectivity, legal protection for threatened fish species, and establishing permanent protected areas for fish are crucial aspects in developing a conservation policy to mitigate the impact of future climate scenarios on threatened freshwater species.