High Water Period Research Articles

Water Transformation Relationship in Inner Mongolia Section of the Yellow River Basin Based on Stable Hydrogen and Oxygen Isotopes

By collecting the atmospheric precipitation, surface water, and groundwater in the Inner Mongolia section of the Yellow River Basin in July 2021 （wet season）, October （normal season）, and April 2022 （dry season）, stable isotope technology was used to analyze the temporal and spatial changes in hydrogen and oxygen stable isotopes in the "three rivers" of the basin, and the MixSIAR mixing model was used to reveal the water body transformation relationship. The results showed that the mean difference in the groundwater isotope was small in the abundance period, flat period, and dry period in the Mongolia section of the Yellow River Basin. The groundwater regeneration was slow, the retention time was long, the seasonal variation was not obvious, and the δD value of surface water was higher in the abundance period than in the normal period and dry period. According to the δ18O and δD diagrams, the slope and intercept of surface water lines in the three periods were smaller than those of local precipitation lines, and surface water was affected by evaporative fractionation after receiving precipitation recharge. The δD values of surface water on the north bank of the Yellow River showed a trend of first increasing and then decreasing from upstream to downstream, while the δD values of surface water on the south bank of the Yellow River showed a trend of gradually decreasing from upstream to downstream. The recharge contribution of groundwater in surface water in the high-water period accounted for 2.9%, precipitation accounted for 97.1%, surface water accounted for 5.0%, atmospheric precipitation accounted for 95.0%, surface water accounted for 56.6%, and precipitation accounted for 43.4%, and the recharge contributions of precipitation and surface water to groundwater in the high water period were 47.6% and 52.4%, respectively. Those in the normal period were 30.7% and 69.3%, and those in the dry period were 37.8% and 62.2%, respectively. Atmospheric precipitation was the main replenishment source of surface water, showing that the replenishment ratio in the wet season was larger than that in the normal season and dry season, which was closely related to the total precipitation and its distribution in each period. Surface water was the main replenishment source of groundwater, showing that dry season > normal season > wet season.

Comparative study between low and high-water quality and the zooplankton community of the Niger river, Niger

Seasonal variations in zooplankton abundance, diversity and the physicochemical properties of the Niger River were studied during 2018 and 2019.The aim of this study is to carry out a comparative study of water quality and the zooplankton community in the River Niger between the high-water period (February 2019) and the low-water period (April 2018). To do this, three water samples were taken at each period and at each station, in order to determine the physico-chemical parameters and then identify the zooplankton. Qualitative analysis of zooplankton revealed the presence of 48 taxa belonging to three main taxonomic groups: Rotifera, Cladocera and Copepoda. During low-water periods, the most frequent taxa were rotifers (74.89%), followed by copepods and copepodites (20.17%) and cladocera (4.93%). In contrast to high-water sampling, copepods and copepodites are the most important (53.2%), followed by rotifers (32.63%) and cladocerans (14.09%).Rotifers are the most abundant group and the most resistant to changes in environmental variables. The physicochemical parameters that significantly influence zooplankton populations are pH, dissolved oxygen, temperature, total phosphorus, silica and chlorophyll-a.

Climatic and hydrological variability in the Oued Lakhdar watershed (Central High Atlas, Morocco)

Abstract The results of this study highlighted significant changes in hydroclimatic conditions over the period studied. Annual rainfall shows significant variability, with years such as 1996 characterised by exceptional humidity, while others, such as 2017, stand out for their particularly marked drought. This variation can be quantified using the Rainfall Anomaly Index (RAI), providing crucial information for water resource management. Temperatures also show seasonal fluctuations, oscillating between hot summers and cold winters. In particular, 2017 was exceptionally warm, while 2011 was unusually cold. In terms of river flows, there has been considerable variability, with some years showing high flows (e.g. 2011) and others with very low flows (e.g. 1990). However, the general trend towards an increase in flow from the 2010 onwards is notable (Sgat station). The RCV index, which classifies years according to surplus or deficit, highlights the predominance of deficit years. In addition, the Monthly Flow Coefficient (MFC) allows us to subdivide the hydrological regime into periods of high and low water. These results highlight the importance of monitoring hydro-climatic conditions for effective management of water resources and the implementation of measures to adapt to climate change.

THE SALINITY ORIGIN OF THE SURFACE WATER IN THE WATERSHED DAM ZARDEZAS, EASTERN ALGERIA

: The deterioration of the physico-chemical quality of surface waters in the Algerian Northeast is caused by several factors. Our study aims to fill the knowledge gap on the control of hydro-chemical evolution of surface waters in wetlands. The main focus is on major elements in surface waters of the Skikda region in northeastern Algeria. To address this issue, we received 45 samples during the 09 campaigns conducted during the period of low and high water of the year 2015-2016, distributed over five points, namely the tributary Oued Khemakhem, Oued Bouadjeb, Oued Safsaf, reservoir of the Zerdazas dam and the downstream of the Zerdazas dam. First, we studied the variation of physical elements such as pH and EC. Then, using PCA and FA, we characterized the physicochemical properties of the water to demonstrate the relationship between the elements and the factors controlling the distribution of the major elements and the heavy metals Pb2+, Fe2+ and Sr2+. The specific formula of the dominance of the different concentrations in the surface waters of the study area followed the sequence: Ca-Mg-Na-K and Cl-SO4-HCO3 from which a predominant specific facies emerges on 67% of the samples, is of the chloride and sulfate-calcoMagnesian facies.

Landscape Pattern Changes of Aquatic Vegetation Communities and Their Response to Hydrological Processes in Poyang Lake, China

Hydrology is an important environmental factor for the evolution of wetland landscape patterns. In the past 20 years, Poyang Lake, the largest freshwater lake in China, has experienced significant inundation shrinkage and water level decrease, posing a significant threat to the local vegetation community. To explore the potential relationship between aquatic vegetation and hydrological processes in the recent hydrological situation, in this study, the landscape patterns of aquatic vegetation communities in Poyang Lake were studied using time-series Landsat remote sensing images and a support vector machine classifier. The stepwise regression analysis method was adopted to analyze the relationship between the vegetation area and hydrological factors. The results indicated that the area of submerged and emergent vegetation in the entire lake decreased significantly from 2001 to 2017, whereas the area of moist vegetation showed a remarkably increasing trend. The average distribution elevation of the submerged vegetation increased by 0.06 m per year. The corresponding landscape patterns showed that the degree of fragmentation of aquatic vegetation communities in Poyang Lake increased. Several hydrological factors were selected to quantify the potential impact of water level fluctuations. The correlation analysis results indicated that hydrological conditions during the rising- and high-water periods may be the key factors affecting the area of aquatic vegetation. This study systematically investigated the evolution of vegetation communities in Poyang Lake wetlands over the past two decades, which contributes to the protection and management of this unique ecosystem.

Introduction dynamics: the advancement of peacock bass (Cichla sp.) in aquatic ecosystems of the pantanal (mato grosso)

The aim of this study was to survey the spatial distribution of the Cichla sp. species in aquatic bodies around the municipality of Cáceres-MT and the evolution of records for the Brazilian Pantanal. Collections took place in the marginal lakes and troughs of the Caramujo, Padre Ignácio and Paraguay rivers, with collections during high and low water periods in 2018 and 2019. Interviews were conducted with fishermen using a semi-structured questionnaire and obtaining locations where tucunaré occur. Secondary data was obtained by searching for articles on the occurrence of species in the Pantanal. Thirty-five specimens of Cichla kelberi were caught in 21 localities in the study area. Interviews revealed 44 localities, predominantly on the left banks of the Paraguay River. In the literature, there have been 9 studies on the occurrence of tucunaré in the Brazilian Pantanal, 7 of which in the southern Pantanal. The data points to a distribution of C. piquiti further south and C. kelberi further north in the biome, which may be due to the routes of introductions and the characteristics of the biome reducing the speed of diffusion.

Resilient spatial design strategies research of urban inland rivers: The case of Xinghai Lake wetland in Ningxia, China

Improving the resilience of rivers is a crucial method for mitigating urban flooding, restoring the ecological role of rivers, and promoting sustainable ecological development. This study specifically examines the relationship between changes in river morphology and river elasticity space, using the Xinghai Lake wetland as a case study. The MIKE 21 numerical model is employed to simulate and analyze the morphology changes of Xinghai Lake under various conditions during both the low-water and high-water periods. The findings indicated that during the period of abundant water, the inundation area of Xinghai Lake increased by 1.64 times, the average water level rose by 0.96 m, and the average flow speed decreased by approximately 11.8 % compared to the flat water period under the circulating condition within the lake. By utilizing Xinghai Lake as a channel for overflowing Yellow River water, the stability of the lake's body is improved. When Xinghai Lake is utilized as the channel for water from the Yellow River, it contributes to the increased stability of the lake. Based on the morphological characteristics of various river sections, this study identifies the potential areas for scouring, eutrophication, and flooding in the future. It also suggests specific strategic solutions to improve the resilience and ecological robustness of the river. These proposals aim to provide scientific support for enhancing the ecological robustness of urban inland lakes.

Microbial communities modulate chemical weathering and carbon dioxide cycling in an active orogen in Taiwan

Chemical weathering modulates carbon transfer between the crust, hydrosphere, and atmosphere. The extent to which microbial processes are involved in mineral dissolution remains elusive. Here, we performed geochemical and molecular analyses of river water and other materials collected from a rapidly exhuming catchment in eastern Taiwan. In addition to solute generation driven primarily by pyrite-induced carbonate weathering, highly skewed microbial community compositions with abundant Sulfuricurvum and Thiobacillus members were detected during high-water periods. The yields of these taxa were also correlated with those of sulfate and sediments, suggesting that pyrite oxidation and carbonate dissolution were facilitated by sulfur-respiring microorganisms inhabiting erodible materials at a pace comparable to the supply of sulfur-bearing minerals through rapid exhumation. The net CO2 export regulated by such potentially supply-limited, microbially-mediated mineral weathering greatly surpasses the global average, highlighting active orogens in high-standing islands as important CO2 contributors rendered by tandem biotic and abiotic processes.

Water and sediment chemistry drivers of chlorophyll-a dynamics within a Ramsar declared floodplain pan wetland system.

Floodplain pans are hydrologically dynamic in nature and characterised by variables such as chlorophyll-a (chl-a), water, and sediment chemistry over their hydroperiods. The present study investigated the spatio-temporal variations in water and sediment physico-chemical, and chlorophyll-a concentration characteristics of six floodplain pans found in the Ramsar declared Makuleke wetlands, Kruger National Park, South Africa. The water and sediment physico-chemical variable values were generally elevated during the high-water period, whereas chlorophyll-a concentrations varied across pans and hydroperiod. Benthic chl-a concentration significantly varied across pans with concentrations ranging from 161 to 1036.2mg m2. The two-way ANOVA showed significant differences in benthic chl-a concentration among hydroperiods, and no significant differences were observed in pelagic chl-a across pans and hydroperiods. Generally, pelagic and benthic chl-a concentration increased as water and sediment chemistry variables increased. Furthermore, three sediment variables, i.e. pH, calcium, and magnesium, and water conductivity were found to be significant in structuring benthic chlorophyll-a dynamics in pans. However, none of the sediment and water variables had a significant effect on pelagic chl-a. Hydroperiod had a significant effect on influencing chl-a concentration, with high and low water level periods being characterised by low and high chl-a concentration, respectively. The n-MDS results showed strong overlaps in chl-a biomass among the Makuleke floodplain pans across hydroperiods. The increasing chl-a concentration in these floodplain pans due to potential bioturbation effects as a result of large mammals could potentially lead to eutrophication, which in turn could affect the system's primary productivity and aquatic biota. Therefore, it is important to establish a continuous monitoring programme on these pans to inform sound management decisions.

Characteristics of DOM and bacterial community in rural black and odorous water bodies under different dimensions

Analysis of dissolved organic matter (DOM) composition and microbial characteristics is crucial for tracing the sources of rural black and odorous water bodies (BOWB). The aim of this study was to explore the DOM and microbial diversity and identify the primary environmental factors in BOWB from various pollution sources during different periods using EEMs-PARAFAC and Illumina sequencing. It was found that the physicochemical properties vary widely across different pollution types of BOWB, with higher overall content during the high-water period compared to the normal-water period. The types of dissolved organic matter in BOWB are Tyrosine proteins, Fulvic acid, Dissolved microbial metabolites, and Humic acid. During the normal-water period, DOM originates primarily from terrestrial sources in various water bodies. However, DOM affected by livestock and poultry waste and industrial effluents is influenced by both internal and external sources during periods of high water levels. In industrial waste-type BOWB, the biological sources of water are weak. Proteobacteria, Actinobacteria, Chloroflexi, Firmicutes were the dominant bacterial phyla. According to the redundancy analysis, pH (p = 0.047), Total nitrogen (TN) (p = 0.045), Organic carbon (OC) (p = 0.044), and Nickel (Ni) (p = 0.047) are the primary environmental factors influencing the composition of bacterial communities.

Links between seasonal suprapermafrost groundwater, the hydrothermal change of the active layer, and river runoff in alpine permafrost watersheds

Abstract. The seasonal dynamic of the suprapermafrost groundwater significantly affects the runoff generation and confluence in permafrost basins and is a leading issue that must urgently be addressed in hydrological research in cold and alpine regions. In this study, the seasonal dynamic process of the suprapermafrost groundwater level (SGL), vertical gradient changes of soil temperature (ST), moisture content in the active layer (AL), and river level changes were analyzed at four permafrost watersheds in the Qinghai–Tibet Plateau using comparative analysis and the nonlinear correlation evaluation method. The impact of freeze–thaw processes on seasonal SGL and the links between SGL and surface runoff were also investigated. The SGL process in a hydrological year can be divided into four periods: (A) a rapid falling period (October to mid-November), (B) a stable low-water period (late November to May), (C) a rapid rising period (approximately June), and (D) a stable high-water period (July to September), which synchronously respond to seasonal variations in soil moisture and temperature in the AL. The characteristics and causes of SGL changes significantly varied during these four periods. The freeze–thaw process of the AL regulated SGL and surface runoff in permafrost watersheds. During period A, with rapid AL freezing, the ST had a dominant impact on the SGL. In period B, the AL was entirely frozen due to the stably low ST, while the SGL dropped to the lowest level with small changes. During period C, ST in the deep soil layers of AL (below 50 cm depth) significantly impacted the SGL (nonlinear correlation coefficient R2 > 0.74, P < 0.05), whereas the SGL change in the shallow soil layer (0–50 cm depth) showed a closer association with soil moisture content. Rainfall was the major cause for the stable high SGL during period D. In addition, the SGLs in periods C and D were closely linked to the retreat and flood processes of river runoff. The SGL contributed approximately 57.0 %–65.8 % of the river runoff changes in the period D. These findings will help to facilitate future hydrological research in the permafrost basins and the development and utilization of water resources in cold and alpine regions.

Functional zeta diversity can better reveal fish metacommunity assembly process in a transitional floodplain

Comprehending the mechanisms governing metacommunity assembly holds pivotal importance for effective conservation strategies. Amidst diverse theories in explaining metacommunity assembly processes, ecologists are progressively delving into the interplay between ecological stochasticity and determinism in shaping species assemblages. Given the ease of measurement, three null model-based methodologies have been widely employed to measure the stochastic and deterministic process, i.e., dispersal-niche continuum index (DNCI), elements of metacommunity structure (EMS), and zeta diversity calculations. However, it is still in doubt which approach can better detect the dominant ecological process governing metacommunity assembly. In this study, we concurrently utilized these three approaches to reveal the fish metacommunity assembly processes in a transitional floodplain among different habitats between high- and low-water levels. In general, our results recognized functional zeta diversity as indicative measurement in this study case since it uniquely unveiled the significant assembly transitions from stochasticity to determinism in response to water receding. Specifically, fish metacommunity in high-water periods was governed by stochastic processes, which can be ascribed to connectivity and easier dispersal in the flooding period. In contrast, the deterministic process shaped fish metacommunity in low-water phase since the stringent environmental loading enhance environmental filtering. This phenomenon is more pronounced in lotic habitats due to the more intricate environments there. It is worth noting that EMS and DNCI approaches showed blind response to this shift. In consequence, our findings advocate for favoring zeta diversity in resolving stochastic and deterministic contributions in governing metacommunity assembly. In addition, our findings also highlight the superiority of functional diversity over traditional taxonomic diversity, since we recorded a more reasonable metacommunity assembly process revealed by the functional group approach, which emphasizes the significance of incorporating functional traits in community ecology.

The Variation in the Water Level of Lake Baikal and Its Relationship with the Inflow and Outflow

Lake Baikal is the largest freshwater lake in the world, accounting for about 20% of the world’s fresh surface water. The lake’s outflow to the ocean occurs only via the Angara River, which has several hydroelectric power plants (HPPs) along its watercourse. The first such HPP, Irkutsk HPP, was built in 1956 and is located 60 km from the Angara River’s source. After two years, the backwater from this HPP expanded to the lake shores and began raising the Baikal Lake level. Currently, there is a dynamic balance between the new lake level, the lake inflow from its tributaries, and the Angara River discharge through the Irkutsk HPP. However, both the Angara River discharge and the Baikal Lake level were distorted by the HPP construction. Thus, to understand the changes to the lake basin over the past century, we first needed to estimate naturalized lake levels that would be if no HPP was ever built. This was an important task that allowed (a) the actual impact of global changes on the regional hydrological processes to be estimated and (b) better management of the HPP itself to be provided through future changes. With these objectives in mind, we accumulated multi-year data on the observed levels of Lake Baikal, and components of its water budget (discharge of main tributaries and the Angara River, precipitation, and evaporation). Thereafter, we assessed the temporal patterns and degree of coupling of multi-year and intra-annual changes in the lake’s monthly, seasonal, and annual characteristics. The reconstruction of the average monthly levels of Lake Baikal and the Angara River water discharge after the construction of the Irkutsk HPP was based on the relationship of the fluctuations with the components of the Lake water budget before regulation. As a result, 123-year time series of “conditionally natural” levels of Lake Baikal and the Angara River discharge were reconstructed and statistically analyzed. Our results indicated high inertia in the fluctuations in the lake level. Additionally, we found a century-long tendency of increases in the lake level of about 15 cm per 100 years, and we quantified the low-frequency changes in Lake Baikal’s water levels, the discharge of the Angara River, and the main lake tributaries. An assessment of the impact of the Irkutsk HPP on the multi-year and intra-annual changes in the Lake Baikal water level and the Angara River discharge showed that the restrictions on the discharge through the HPP and the legislative limitations of the Lake Baikal level regime have considerably limited the fluctuations in the lake level. These fluctuations can lead to regulation violations and adverse regimes during low-water or high-water periods.

Coupled hydrogeological modeling and nitrate transport modeling in an anthropized valley, a case study of the lower Soummam valley (Bejaïa Northeast of Algeria)

Anthropogenic activities, including wastewater discharges and fertilizer use, were identified as the primary factors influencing nitrate concentrations in the lower Soummam Valley in the North-East of Algeria. This study aimed to investigate nitrogen pollution and simulate nitrate mass transport coupled with a numerical flow model. Hydrogeochemical findings revealed significant seasonal variations between the high-water period (May 2019 and 2021) and the low-water period (September 2019 to November 2020 and 2021). During the low-water period, both temperature and electrical conductivity increased. However, pH, dissolved oxygen, and nitrate levels decreased in the high-water period. Nitrites and ammonium exhibited irregular fluctuations. The numerical flow model was developed using PMWIN and coupled with a solute transport model simulated with the Model Transport 3 Dimensions (MT3D). Calibration was conducted under steady-state conditions from 2011 to 2021 and was validated by comparing piezometric heads and nitrate concentrations measured in May 2021. Three scenarios were devised to simulate transient conditions from 2011 to 2050, considering variations in both groundwater levels and nitrate concentrations. The simulation revealed that river and dependent head boundaries are the primary sources of groundwater recharge. These boundaries contributed to approximately 87% of the total inflow. The model also depicted the water exchange between the aquifer and the river. However, the constant head boundary represented the main outflow, accounting for 85.7% of the total. The nitrate model illustrated an increase in nitrate concentrations, reaching 3.8 mg/L in 27 out of the 29 simulated wells. Both the river and groundwater head boundaries were identified as the key factors governing the hydrodynamic aquifer system and nitrate transport in the alluvial aquifer of the lower Soummam Valley.

Integration of social and cultural dimensions in the assessment of environmental flows: case of the Ouémé delta in West Africa

The use of environmental flows as a technique for the diagnosis and sustainable management of aquatic ecosystems in West Africa is relatively new and cautious, despite being broadly implemented for many years in Western countries and Southern Africa. The present study, the first to evaluate the environmental flows in Benin, concentrates on the deltaic region of the Ouémé River. The assessment utilises the Building Block Methodology approach, and incorporates ecological, socio-cultural, and religious dimensions. The assessment focuses on the alterations in river flows and the impact on local communities’ livelihoods, beliefs, and cultural and religious practices. The results indicate that the population of the Ouémé Delta are significantly impacted by changes in the river’s flow. Indeed, floods play a crucial role in people’s daily routines and livelihoods, while a significant decrease in river flow results in economic instability. Moreover, there is a strong link between specific religious customs in the area and the river’s flow. To maintain the current provisioning, regulating, and cultural ecosystem services in the Ouémé delta, The study recommended to allocate 100% of the River Ouémé’s natural flow during low-water periods (December to May) and 50% of the natural flow during high-water periods (June to November). This allocation ensures that the environment’s water needs are met and will contribute to preserve the Ouémé delta’s ecosystem, ensuring the sustainability of its ecological habitats and biodiversity. However, the implementation of these recommendations would require more debate and a real consensus on the priority between development and environment.

EDNA metabarcoding reveals the role of habitat specialization and spatial and environmental variability in shaping diversity patterns of fish metacommunities.

Information is scarce on how environmental and dispersal processes interact with biological features of the organisms, such as their habitat affinity, to influence patterns in biodiversity. We examined the role of habitat specialist vs. generalist species, and the spatial configuration, connectivity, and different environmental characteristics of river-floodplain habitats to get a more mechanistic understanding of alpha and beta diversity of fish metacommunities. We used environmental DNA metabarcoding to characterize species (taxa) richness and composition in two separate floodplains of the river Danube (Austria and Hungary) during two different hydrological conditions. Results showed that differences in the number of generalist and specialist species and their responses to connectivity and environmental gradients influenced patterns in alpha and beta diversity. Of the components of beta diversity, richness difference (nestedness) showed consistently higher values than replacement (turnover), mainly due to the decrease of specialist species along the connectivity gradient (i.e., from the mainstem to the most isolated oxbows). Variance in both alpha and beta diversity could be well predicted by a set of local and regional variables, despite high environmental variability, which characterizes river-floodplain ecosystems. Of these, the joint or shared variance fractions proved to be the most important, which indicates that the effects of local and regional processes cannot be unambiguously separated in these river-floodplain systems. Local scale environmental variables were more important determinants of both alpha and beta diversity in the low water period than in the high water period. These results indicate the differential role of local and regional processes in community organization during different hydrological conditions. Maintenance of both local and regional scale processes are thus important in the preservation of alpha and beta diversity of floodplain fish metacommunities, which should be considered by environmental management.

Atributos da comunidade refletindo a produção secundária do zooplâncton: usando abordagens de campo e experimentais

Abstract Aim We investigated the relationship between ecological attributes of the zooplankton community and its secondary production. Methods Samples were taken from lakes in the floodplain of the Upper Paraná River (Brazil), in low and high-water periods, and in a manipulative experiment realized in mesocosms. Results The highest amount of production was related to the dominance of few species. Secondary production of larger and long-lived organisms, such as copepods, had been most associated with the biomass, whereas smaller ones, such as rotifers, with the abundance. Conclusions These attributes of the zooplankton community (biomass and abundance) can be used as proxies to estimate the zooplankton secondary production in the floodplain, supporting the studies on monitoring and conservation of these ecosystems.

The impact of climatic variability on water resources in the Ouaoumana River basin in the Middle Atlas of Morocco (November 2021-May 2022)

This study is based on the evaluation and quantification of water resources in the Ouaoumana River basin, which is part of the Oum ER-Rabia basin and located in the Middle Atlas. The water resources of this watershed, which serve several purposes (such as filling the Ahmed El Hansali dam and irrigation), are facing numerous disturbances caused by climatic variability, high demand, and the overexploitation of groundwater. To conduct our study, we will rely on two methodologies. The first is a quantitative hydrological methodology based on flow measurements taken at several points along the river, from upstream to downstream, during the period from November 2021 to May 2022. This will generate hydrometric data, allowing us to extract the spatio-temporal variation in flows. The second methodology is statistical and will involve analyzing climatic data (rainfall, temperature) from the Taghzoute station, which is located downstream of the river basin, to better understand the climatic dynamics. The results indicate that the water resources of the Oued Ouaoumana watershed exhibit significant variation from upstream to downstream. The highest flow values are recorded in April, at 323 l/s, during the high-water period. However, in other months, including January, February, and March, the flow ranges between 20 l/s and 85 l/s, primarily due to heavy abstraction by local residents for farmland irrigation along the riverbanks, which creates several problems, especially for biodiversity.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin.

The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Assessment of physicochemical and microbiological quality using the SEQ-Eau approach for groundwater in the Saïss basin (Fez-Meknes region, Morocco)

The Saïss water table is one of Morocco's major agricultural regions. Its water resources satisfy domestic, agricultural, industrial, and tourist needs. The present work focuses on the technique used to detect spatiotemporal variations in the overall physicochemical, microbiological, and heavy metal quality of groundwater in the Saïss basin, as assessed by the SEQ-Eau water quality system. A total of 28 samples were collected during high and low water periods, respectively. The results show that 25% of the stations present average quality during the dry season, and are located mainly in the southern part of the Meknes plateau in the El Hajeb, Boufekrane, and Agouray regions, while this pollution is reduced during the wet season with a percentage of 7.14%. However, the poor quality of groundwater indicates that 75% and 92.85% occupy almost the entire rest of the basin during the dry and wet seasons. Mapping of nitrate pollution of groundwater indicates that the lowest nitrate concentrations were recorded in the southwest part of the aquifer. The highest values were recorded in the center of the study area, with a maximum value of 118 mg/l, which exceeds the Moroccan standard due to the anthropogenic impact of agriculture and water use.