Large Floodplain Research Articles

Fifty years marshland changes in a large floodplain lake: Natural driving or human impact?

Study region: Poyang Lake, the largest freshwater floodplain lake in China. Study focus: Marshlands in a floodplain, as the typical natural wetland offering vital habitats for various organisms, are sensitive to environmental changes. The spatiotemporal changes of marshlands were investigated and their driving forces from both natural factors and human activities were discussed. The remote sensing image data from 1973 to 2022 was adopted to explore the long-term changes of marshlands exposed in dry season. New hydrological insights for the region: Over the past fifty years, the total area of marshlands in Poyang Lake is around 2540–2718 km2 and has undergone substantial changes. It follows the bell-shaped curve pattern with continuous rise since 1970s and reach the maximum at the end of 20 century and then fluctuating decline. Different evolutionary patterns were identified in different lake regions owing to the combination of human activities and natural processes. The expanding marshlands mainly concentrate in the central lake, while the significant losses of marshlands are observed in the northern lake（By sand mining and dyke constructions）. In the southern lake, sediment input from inflow rivers deposited naturally in the river mouth elevated the lake bed and lead to delta expansion（A 3.1 km expansion has been observed）. The complex geomorphological processes and fishery activities also create the dish-shaped internal sub-lakes in marshlands.

Population structure and vital rates of Shortnose Gar Lepisosteus platostomus in a large floodplain river

Population structure and vital rates of Shortnose Gar Lepisosteus platostomus in a large floodplain river

Detection of Brucella S19 Vaccine Strain DNA in Domestic and Wild Ungulates from Brazilian Pantanal.

The Pantanal region, the largest floodplain in the world, has a huge biodiversity and is an important livestock center. Bovine brucellosis has been reported in the region over the last three decades, posing implications for cattle industry as well as for the maintenance of biodiversity. We aimed to investigate the presence of B. abortus S19 vaccine strain DNA in unvaccinated domestic and wild ungulates from the Brazilian Pantanal. Fifty-two heifers, 63 ovine, 24 domestic pigs, 28 feral pigs, and three Pampas deer were sampled. Brucella spp. was detected through bcsp31 PCR of blood samples in 45.3% (77/170) of the sampled animals, of which 36.4% (28/77) showed positivity in ery PCR corresponding to B. abortus S19 strain. Feral pigs presented the highest occurrence of positive samples in bcsp31 PCR (75%), followed by ovine (47.6%), domestic pigs (41.7%), and unvaccinated heifers (30.8%). We did not observe positivity in Pampas deer. Our results strongly suggest that vaccination against bovine brucellosis may promote spill-over of B. abortus S19 strain in the Pantanal region. Moreover, our data indicate that wild strains of Brucella circulates in the Pantanal Biome.

Integrating Sentinel 2 Imagery with High-Resolution Elevation Data for Automated Inundation Monitoring in Vegetated Floodplain Wetlands

Monitoring inundation in flow-dependent floodplain wetlands is important for understanding the outcomes of environmental water deliveries that aim to inundate different floodplain wetland vegetation types. The most effective way to monitor inundation across large landscapes is with remote sensing. Spectral water indices are often used to detect water in the landscape, but there are challenges in using them to map inundation within the complex vegetated floodplain wetlands. The current method used for monitoring inundation in the large floodplain wetlands that are targets for environmental water delivery in the New South Wales portion of the Murray–Darling Basin (MDB) in eastern Australia considers the complex mixing of water with vegetation and soil, but it is a time-consuming process focused on individual wetlands. In this study, we developed the automated inundation monitoring (AIM) method to enable an efficient process to map inundation in floodplain wetlands with a focus on the lower Lachlan floodplain utilising 25 Sentinel-2 image dates spanning from 2019 to 2023. A local adaptive thresholding (ATH) approach of a suite of spectral indices combined with best available DEM and a cropping layer were integrated into the AIM method. The resulting AIM maps were validated against high-resolution drone images, and vertical and oblique aerial images. Although instances of omission and commission errors were identified in dense vegetation and narrow creek lines, the AIM method showcased high mapping accuracy with overall accuracy of 0.8 measured. The AIM method could be adapted to other MDB wetlands that would further support the inundation monitoring across the basin.

Soil flooding filters evolutionary lineages of tree communities in Amazonian riparian forests.

Inundations in Amazonian black-water river floodplain result in the selection of different tree lineages, thus promoting coexistence between species. We investigated whether Amazonian tree communities are phylogenetically structured and distributed along a flooding gradient from irregularly flooded forests along streams embedded within upland (terra-firme) forest to seasonally flooded floodplains of large rivers (igapós). Floristic inventories and hydrological monitoring were performed along the Falsino River, a black-water river in the eastern Amazon within the Amapá National Forest. We constructed a presence-and-absence matrix and generated a phylogeny using the vascular plant database available in GenBank. We calculated the standardized values of the metrics of phylogenetic diversity (ses.PD), average phylogenetic distance (ses.MPD), and average nearest-neighbor distance (ses.MNTD) to test whether the history of relationships between species in the community is influenced by inundation. We used the phylogenetic endemism (PE) metric to verify the existence of taxa with restricted distribution. Linear regressions were used to test whether phylogenetic metrics have a significant relationship with the variables: maximum flood height, maximum water table depth, and maximum flood amplitude. The results show that forests subject to prolonged seasonal flooding have reduced taxon richness, low phylogenetic diversity, and random distribution of lineages within communities. On the other hand, terra-firme riparian forests showed higher rates of taxon richness, diversity, and phylogenetic dispersion, in addition to greater phylogenetic endemism. These results indicate that seasonal and predictable soil flooding filters tree lineages along the hydrographic gradient. Different adaptations to root waterlogging are likely requirements for colonization in these environments and may represent an important factor in the diversification of tree lineages in the Amazon biome.

Taxonomic and functional response of fish assemblages to flood-triggered water level fluctuations in a large floodplain lake along the Yangtze River

Taxonomic and functional response of fish assemblages to flood-triggered water level fluctuations in a large floodplain lake along the Yangtze River

Effects of different hydrological conditions on the taxonomic structure and functional traits of mollusk communities in a large floodplain wetland.

Floodplain wetlands are critical to the conservation of aquatic biodiversity and the ecological integrity of river networks. However, increasing drought severity and frequency caused by climate change can reduce floodplain wetlands' resistance and recovery capacities. Mollusks, which are common inhabitants of floodplain wetlands, are among the most vulnerable species to drought. However, the response of mollusk communities to drought has received little attention. Here, we investigated how the structure and functional traits of mollusk communities changed in response to varying hydrological conditions, including a flash drought (FD) in the Poyang Lake floodplain wetland. Our findings showed that FD strongly reduced mollusk abundance and biomass, decreased both α- and β-diversity, and resulted in the extinction of bivalve taxa. A sudden shift in community trait structure was discovered due to the extinction of many species. These traits, which include deposit feeding, crawling, scraping, aerial respiration, and dormancy, help mollusks survive in FD and tolerate completely dry out of their Changhuchi habitat. Finally, we discovered that dissolved oxygen was an important controlling variable for mollusk communities during drought. Our findings provide a scientific basis for the management and conservation of floodplain wetland biodiversity in the context of increasing drought frequency and intensity.

Fish assemblage structure and habitat relationships of a large floodplain river in western North America

AbstractUnderstanding complex river floodplains is critical to conserve species of fish and their ecological functions. In 2011 through 2013, longitudinal gradients in fish assemblage were investigated in the Willamette River in western United States. Of 36,586 individual fish collected, 93% were native and 7% non‐native. The best predictors of fishes collected with a boat electrofisher were percent embeddedness, macrophytes, longitudinal river distance, average depth, and velocity. Habitat type (mainstem or slough) was also a significant predictor. The best predictor of fishes collected in nearshore habitats with a backpack electrofisher were longitudinal river distance, velocity, and percent embeddedness. Fish communities differed significantly between mainstem and slough habitat. Overall, 25 of 40 species had high fidelities to mainstem or slough habitats. Native species showed a high fidelity to both mainstem and slough habitats while non‐native species were significantly related only to slough habitats. Environmental characteristics strongly influenced fish assemblage structure in this large floodplain river. Maintaining and restoring mainstem and off‐channel habitats are critical for maximizing native species resilience in the face of non‐native species encroachment and a changing environment. Restoring the natural flow regime to the degree possible is needed to increase connectivity between the floodplain and mainstem and provide thermal and flood refuges for native fishes. Understanding habitat relationships provides essential context for fish conservation and management by resource agencies and landowners.

BENTHIC MACROINVERTEBRATE COMMUNITY IN TWO AMAZONIAN UPLAND LAKES

Studies of biological communities in Amazonian lakes are limited to floodplains of large rivers. However, the high-altitude lakes of the Serra dos Carajás differ from other lakes in the region due to the high natural concentration of iron and manganese. An important component of this biological community are the macroinvertebrates, some of which are sensitive to environmental and chemical variables. However, little is known about the influence of heavy metal concentrations on this community component in Amazonian lakes. In our study, we observed the importance of variables such as water depth and concentration of chemical elements in sediments on the macroinvertebrate community. Through a redundancy analysis, we found that the depth of the lake affects the number of species and the composition of the benthic macroinvertebrate community. We also found a relative importance of the concentration of manganese in the sediment for the community studied. Our results indicate that the macroinvertebrate community is differentiated in the marginal and central regions of the lake, since the deposition of organic matter and heavy metals in the sediment is different in these two regions of the lake. The relationship found has implications for the management and restoration of upland lakes in the Amazon, helping to preserve this unique ecosystem.

Шакал (Canis aure¬us) на півночі Полісся України: виявлення у природі, статус та повільне розселення

The golden jackal continues to slowly inhabit the north of Central Polissia and to disperse. Mostly single individuals are found. The social structure of the jackal is flexible and groups of more than two individuals are found in places of food concentration. A similar situation occurred in the Ubort River valley near the Ukrainian–Belarusian border, when visual encounters of jackal family consisting of probably 3–4 animals were very frequent near the burial place of livestock corpses. In the north of Central Polissia of Ukraine, the jackal has been recorded since 2014. The species is rare here. According to the registration of tracks, this predator is found on a less forested forest ridge between the settlements of Ovruch–Velidnyky–Slovechno–Levkovychi and in the valley of the Ubort River, which is a natural corridor of the species’ northward dispersal. Given Ukraine’s course towards EU membership and the position of the Baltic countries on the jackal, our country will obviously have to take into account the special status of the jackal as a species that has expanded its range on its own. Accordingly, this predator should not be considered an invasive species. Obviously, the problem with the jackal in forested regions of north of Ukraine will be much less severe than in the south in the floodplains of large rivers. In the Polissia, in trophically rich broadleaf forests with mosaic forest cover, the jackal is likely to coexist successfully with the wolf. Interspecific relations between wolves and jackals do not take the form of direct pursuit, but rather by marking territory. It has been found that jackals respond to chemical and visual markings of wolves during dispersal and try to quickly leave areas with high wolf population density. Unlike solitary wolves in the wild, solitary jackals are able to forage for food much more efficiently and therefore have a higher chance of survival in the wild. The preconceived notion of the jackal as a problematic species may not allow for an unbiased assessment of its impact on ecosystems. In its relations with humans, the jackal in the Polissia is a less problematic species compared to wolves, foxes, or American minks. It is necessary to inform the Ukrainian public, authorities and politicians about existing international legal instruments and European experience in managing populations of carnivorous mammals, including the golden jackal.

Escaping the dry: Native and non‐native fish outmigration from a receding floodplain following managed inundation

Abstract Many fish rely on being able to move between rivers and floodplains to fulfil key life history events, but river regulation has reduced floodplain inundation compromising these connections and causing the loss of ecosystem function more generally. Managed inundations are being trialled in some systems as a solution, whereby engineered floods using built infrastructure, such as floodplain regulators, are used to deliver water to inundate floodplains. However, the use of managed inundations is still in early stages and their outcomes for native fish have been rarely assessed. We present the results from a series of investigations assessing the effectiveness of two managed inundations on the native fish community in a large floodplain in south‐eastern Australia. We firstly described changes in fish assemblages in wetlands before and after managed inundation (Aim 1). We then examined which potential exits are used by golden perch, a highly mobile species that regularly moves between rivers and floodplains (Aim 2), and then assessed outmigration patterns of native and non‐native species during receding phase from one of the major golden perch exits via a fishlock (Aim 3). Finally, we conducted two experiments to test if it was possible to modify operation of the fishlock to maximise fish movement by varying the length of the operating cycle, or whether operation occurs during the day or night (Aim 4). We found that native fish dominated the catch in wetlands before drawdown of the managed inundation, but that non‐native species, especially young‐of‐year carp, dominated after the drawdown (Aim 1). Outmigrating golden perch left the floodplain wetlands in a variety of locations but predominantly through a fishlock, which is a type of fishway (Aim 2). At this fishlock, native fish outmigrated before and during the early phase of the floodplain recession, moving to permanent riverine habitats, whereas non‐native fish (mostly carp) tended to migrate later in the recession especially as water levels dropped (Aim 3). There were no substantive differences in the numbers and size of fish moving through the fishlock at different operating cycle times (Aim 4). While there were no differences in numbers of non‐native carp migrating during the day or night, native species (carp gudgeon and Australian smelt) were more common during the day. Our study has provided knowledge of the eco‐hydraulic mechanisms of fish movement, in relation to managed inundaitons. This knowledge can be applied to help water managers plan floodplain watering regimes in the Murray‐Darling Basin to benefit native fish, while potentially restricting movement of undesirable non‐native species such as carp. More broadly, our results improve current understanding of fish movement in relation to managed floodplain recession, which is critical given the increased use of such managed inundations, and the need for information to help design and evaluate them.

Incorporating the riverscape into models of river–floodplain function

Rivers and their flooded alluvial plains integrate physical, biological, and human processes at the scale of continents. Despite their ecological and economic values, these complex ecosystems are poorly understood and highly modified by humans. A primary problem is that most research in fluvial ecosystems has been conducted in small streams and then scaled up to rivers. Furthermore, the point where a stream transitions into a river is not well understood. Although many conceptual models exist, the role that large river–floodplain complexes play within these frameworks is lacking. These models focus on flooding as a temporary reset to river ecosystems, but floodplains and rivers may continue to interact long after floodwaters recede. We revisit the concept of the riverscape, a unique mosaic of perennially interacting wetland and channel habitats that have unique ecological properties during both non-flood and flooding periods relative to the small tributary streams within the riverscape network. This strong bidirectional interaction within low-lying alluvial plains may define large rivers. To determine whether a riverscape is indeed a useful unit of study for river ecology, conservation, and restoration, baseline conditions with measurable, comparable metrics, such as primary and secondary production need to be established. Responses of these metrics to multiple stressors and restoration such as levee setbacks, wetland mitigation, and dam removals will inform both basic models of riverscape function and future management actions. Because humans currently affect nearly all aspects of the environmental structure and function of riverscapes, human perceptions of riverscape value and threat need to be considered as a fundamental component of riverscape ecology.

Using remote sensing to assess how intensive agriculture impacts the turbidity of a fluvial lake floodplain

Lake St-Pierre is set in the largest floodplain in the province of Quebec, Canada, and is a rich ecosystem of great ecological importance. However, Lake St-Pierre has seen its ecological integrity deteriorate in recent decades, largely due to the development of agriculture in and around its floodplain. This study uses a simple turbidity retrieval model (NIR and RED reflectances from Sentinel-2) to quantify the impact of land use on water turbidity within the lake floodplain during the 2019 and 2020 spring flood. Using a linear mixed effect model, we assessed how land use (wet meadows, cultivated grasslands, soybean, corn fields) impacts turbidity retrieved from Sentinel-2. Water turbidity was found to increase with the level of agricultural perturbations. During the severe and long 2019 flood, the turbidity was 5% higher over cultivated grassland fields, 35% higher over soybean fields and 70% higher over corn fields, compared to wet meadows. For 2020, a comparatively drier year, the corresponding impacts were 9% for cultivated grassland fields, 65% for soybean fields and 93% for corn fields. However, land use only explained 4% (2019) and 5% (2020) of the water turbidity spatiotemporal variance, which was instead mostly driven by the sediment load coming from upstream watersheds. Our results indicate that, despite complex processes driving water mass movements in the floodplain, intensive farming practices lead to higher water turbidity compared to natural lands. This study provides evidence that intensive agriculture impacts the water quality in a critical moment for the long-term health of the Lake St-Pierre.

Introducing a new floodplain scheme in ORCHIDEE (version 7885): validation and evaluation over the Pantanal wetlands

Abstract. Adapting and improving the hydrological processes in land surface models are crucial given the increase in the resolution of the climate models to correctly represent the hydrological cycle. The present paper introduces a floodplain scheme adapted to the higher-resolution river routing of the Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface model. The scheme is based on a sub-tile parameterisation of the hydrological units – a hydrological transfer unit (HTU) concept – based on high-resolution hydrologically coherent digital elevation models, which can be used for all types of resolutions and projections. The floodplain scheme was developed and evaluated for different atmospheric forcings and resolutions (0.5∘ and 25 km) over one of the world's largest floodplains: the Pantanal, located in central South America. The floodplain scheme is validated based on the river discharge at the outflow of the Pantanal which represents the hydrological cycle over the basin, the temporal evolution of the water mass over the region assessed by the anomaly of total water storage in the Gravity Recovery And Climate Experiment (GRACE), and the temporal evaluation of the flooded areas compared to the Global Inundation Extent from Multi-Satellites version 2 (GIEMS-2) dataset. The hydrological cycle is satisfactorily simulated; however, the base flow may be underestimated. The temporal evolution of the flooded area is coherent with the observations, although the size of the area is underestimated in comparison to GIEMS-2. The presence of floodplains increases the soil moisture up to 50 % and decreases average temperature by 3 ∘C and by 6 ∘C during the dry season. The higher soil moisture increases the vegetation density, and, along with the presence of open-water surfaces due to the floodplains, it affects the surface energy budget by increasing the latent flux at the expense of the sensible flux. This is linked to the increase in the evapotranspiration related to the increased water availability. The effect of the floodplain scheme on the land surface conditions highlights that coupled simulations using the floodplain scheme may influence local and regional precipitation and regional circulation.

Multi-source remote sensing data and image fusion technology reveal significant spatiotemporal heterogeneity of inundation dynamics in a typical large floodplain lake system

Study regionThe Poyang Lake, which is located on the south bank of the middle-lower Yangtze River basin. The lake is the largest freshwater lake in China, and also a typical floodplain lake in the world. Study focusThe spatiotemporal heterogeneity of inundation dynamics of large floodplain lake system has not been paid enough attention. Based on the reconstructed high spatial and temporal resolution inundation dataset using the image fusion model and multi-source remote sensing data, this study systematically analyzed the spatiotemporal heterogeneity of inundation dynamics in the Poyang Lake- floodplain system. New hydrological insights for the regionIt is found that within the same floodplain lake, the inundated area and inundation frequency in different regions of the lake (the main lake region and the adjacent floodplain region) can have asynchronous intra-annual fluctuation and opposite inter-annual change trend. This is highly related to the hydrological complexity of the lake: the relative impacts of catchment inflow and the Yangtze River varies in different regions across the lake. The stage-area relationship at the central station along the flow direction of the lake has the highest linear correlation, which might provide more accurate estimates of lake surface/volume. In addition, this study highlights the importance of reconstructed high spatial-temporal resolution of remote sensing data for the accurate assessment of inundation dynamics in floodplain lakes. All the results enrich the understanding of complex hydrological regime of large floodplain lakes and are valuable for the practice of water resources management and ecological conservation in such lakes.

Epiphytes support aquatic consumers of a large floodplain lake ecosystem in the southern Gulf of Mexico

Epiphytes support aquatic consumers of a large floodplain lake ecosystem in the southern Gulf of Mexico

Monitoring long-term vegetation condition dynamics in persistent semi-arid wetland communities using time series of Landsat data

Wetlands in arid and semi-arid regions are characterized by dry- and wet-phase vegetation expression which responds to variable water resources. Monitoring condition trends in these wetlands is challenging because transitions may be rapid and short-lived, and identification of meaningful condition change requires longitudinal study. Remotely-sensed data provide cost effective, multi-decadal information with sufficient temporal and spatial scale to explore wetland condition. In this study, we used a time series of Enhanced Vegetation Index (EVI) derived from 34 years (1988–2021) of Landsat imagery, to investigate the long-term condition dynamics of six broad vegetation groups (communities) in a large floodplain wetland system, the Macquarie Marshes in Australia. These communities were persistently mapped as River Red Gum wetland, Black Box/Coolibah woodland, Lignum shrubland, Semi-permanent wetland, Terrestrial grassland and Terrestrial woodland. We used generalized additive models (GAM) to explore the response of vegetation to seasonality, river flow and climatic conditions. We found that EVI was a useful metric to monitor both wetland condition and response to climatic and hydrological drivers. Wetland communities were particularly responsive to river flow and seasonality, while terrestrial communities were responsive to climate and seasonality. Our results indicate asymptotic condition responses, and therefore evidence of hydrological thresholds, by some wetland communities to river flows. We did not observe a long-term trend of declining condition although an apparent increase in condition variability towards the end of the time series requires continued monitoring. Our remotely-sensed, landscape-scale monitoring approach merits further ground validation. We discuss how it can be used to provide a management tool which continuously assesses short and long-term wetland condition and informs conservation decisions about water management for environmental flows.

The Problem of Effective Evacuation of the Population from Floodplains under Threat of Flooding: Algorithmic and Software Support with Shortage of Resources

Extreme flooding of the floodplains of large lowland rivers poses a danger to the population due to the vastness of the flooded areas. This requires the organization of safe evacuation in conditions of a shortage of temporary and transport resources due to significant differences in the moments of flooding of different spatial parts. We consider the case of a shortage of evacuation vehicles, in which the safe evacuation of the entire population to permanent evacuation points is impossible. Therefore, the evacuation is divided into two stages with the organization of temporary evacuation points on evacuation routes. Our goal is to develop a method for analyzing the minimum resource requirement for the safe evacuation of the population of floodplain territories based on a mathematical model of flood dynamics and minimizing the number of vehicles on a set of safe evacuation schedules. The core of the approach is a numerical hydrodynamic model in shallow water approximation. Modeling the hydrological regime of a real water body requires a multi-layer geoinformation model of the territory with layers of relief, channel structure, and social infrastructure. High-performance computing is performed on GPUs using CUDA. The optimization problem is a variant of the resource investment problem of scheduling theory with deadlines for completing work and is solved on the basis of a heuristic algorithm. We use the results of numerical simulation of floods for the Northern part of the Volga-Akhtuba floodplain to plot the dependence of the minimum number of vehicles that ensure the safe evacuation of the population. The minimum transport resources depend on the water discharge in the Volga river, the start of the evacuation, and the localization of temporary evacuation points. The developed algorithm constructs a set of safe evacuation schedules for the minimum allowable number of vehicles in various flood scenarios. The population evacuation schedules constructed for the Volga-Akhtuba floodplain can be used in practice for various vast river valleys.

Insights from a comparison of two hydrological modelling approaches in the Kwando (Cuando) River and the western tributaries of the Zambezi River basin

Study Region: The Kwando (Cuando) River and the western headwaters of the Zambezi River, which are data-scarce basins of southern Africa. Study Focus: A comparative analysis of the performance of two fundamentally different hydrological modelling approaches (a conceptual model and a theory guided machine learning model) in a data-sparse region. New Hydrological Insights for the Region: The machine learning model (HydroForecast) generally performs better – in terms of statistical fit between simulated and observed flows – than the conceptual model (Pitman). For the Kwando River, the conceptual model explicitly simulates the expected attenuation effects of a large floodplain, while the machine learning model represents this and other processes implicitly. The two models quantify the Kwando sub-basin flow contributions differently, with the conceptual model calibrated manually to align with the available qualitative information that suggests that the majority of the runoff is generated in the upstream sub-basin and then attenuated in the downstream floodplain. Generally, this work offers insight into how the two very different models can simulate historical flows in a large basin when streamflow observations and the forcing rainfall data are limited and of unknown quality, and suggests that a machine learning model better leverages information from multiple training parameters to reproduce the measured streamflows.

Influence of Seasonal Water Level Fluctuations on Food Web Structure of a Large Floodplain Lake in China

Seasonal shifts in hydrology are known to alter the abundance and diversity of basal production resources and habitats and hence strongly influence the structure and function of river ecosystems. However, equivalent knowledge of natural lake ecosystems in floodplain regions is lacking. Here, we used stable isotope ratios of carbon and nitrogen to assess available primary production sources and consumer taxa during the dry and wet seasons in a large floodplain lake connected to the Yangtze River. Fish species showed distinct δ13C values between two hydrological periods but only small changes in δ15N values. Most of the fish species had higher estimated trophic levels in the dry season, likely indicating greater carnivory. Results of Bayesian mixing models revealed that benthic algae and benthic organic matter (BOM), combined with C3 vegetation, were the principal food sources supporting the biomass of most fish species during the low-water period, whereas benthic algae and seston were the most important carbon sources during the flood period. Overall, these findings demonstrate that seasonal hydrological changes, such as water-level fluctuations, can affect the trophic structure and ecosystem functioning of floodplain lake food webs in the subtropical zone.