Hydrological Conditions Research Articles

Optimization Algorithms for Sustainable Operation of Multi-Unit Hydropower Plants

The work presented in this article concerns numerical studies on optimization methods used for the sustainable utilization of the energy potential of water, converting it into electricity in a hydropower plant equipped with more than one unit. These methods allow for maximization of production in given hydrological conditions, leading to the balanced, lossless, and environmentally friendly use of the renewable energy source that is water. Methods are selected from three groups, i.e., analytical, enumeration, and randomized. The results of calculations of optimal points of selected test functions carried out using the Broyden–Fletcher–Goldfarb–Shanno Limited-Memory Version (L-BFGS-B), Explicit Complete Enumeration (ECE), and Genetic Algorithm (GA) methods provided basic information on the features of these methods. Based on these tests, the GA method was selected to solve the problem of the optimal load distribution in a hydropower plant equipped with three identical hydro units. The defined optimization problem consisted of finding a configuration of hydro units in operation that would guarantee the maximum efficiency of the power plant under the imposed hydrological conditions. During the numerical studies, a number of calculations were performed to identify the impact of procedures and parameters characteristic of the optimization methods on the obtained results. Particular attention was paid to the GA method and penalty functions, enabling the elimination of results from the area of prohibited solutions.

Современная оценка факторов, определяющих эффективность воспроизводства рыб в низовьях р. Урал

The Aral-Caspian basin plays a crucial role in the formation of commercial fish stocks, which have been de-clining in recent years due to a decrease in the efficiency of natural reproduction due to an unfavorable hydrological regime. The results of studies carried out in 2019-2023 in the lower reaches of the Ural River on the influence of the hydrological regime and the number of producers in spawning areas on the reproduction efficiency are presented using the example of semi-migratory fish: roach, bream, walleye, carp, asp. It is shown that over the past 10 years, low- and medium-water years with a flood flow volume of 2-3 km3 prevailed, and only 3 years were high-water (more than 4 km3). Unfavorable years in terms of water content had a negative impact on the efficiency of fish reproduction in the Ural River, which led to a decrease in the number of offspring and, as a result, a reduction in commercial fish stocks in the region. It was found that in high-water years, even with a low number of producers in spawning grounds, the number of life-resistant sloping juveniles of the studied fish species was greater than in low-water years with a high number of producers. In the course of research, it was found that unfavorable hydrological conditions in the Ural River had a lesser impact on the roach and bream, and the number of juveniles of the latter has increased over the years. Commercially valuable walleye, asp and carp are in a depressed state, the number of recorded juveniles of which was ten times less than bream and roach. The state of reproduction of the carp is alarming, the number of juveniles of which reached a critical level in low-water 2019. According to the results of the study, it is recommended to implement a number of comprehensive measures of fisheries reclamation to improve the state of commercial stocks in the Ural-Caspian region.

Transport of (Micro)plastic Within a River Cross-Section—Spatio-Temporal Variations and Loads

Despite substantial research, the spatio-temporal dynamics of microplastic fluxes remain underexplored, especially in lower-order rivers. This study aims to quantify microplastic loads using a spatio-temporal sampling approach in a single cross-section of the Lahn River, a typical low-mountain river in Central Germany, over a sampling period from July 2020 to April 2021, covering varying discharge conditions, from low to high flow. A total of 198 plastic particles were detected, averaging 3.67 particles per hour, with a mean microplastic load of 0.03 ± 0.027 particles per cubic metre. Microplastic abundance varied spatially within the river cross-section, with lower concentrations found at deeper sampling positions. The data indicate that higher discharge conditions correlate with increased microplastic loads, predominantly at the water surface, suggesting that hydrological conditions significantly influence plastic transport dynamics. However, it remains unclear whether the microplastics observed at higher discharges originate from additional sources or are reactivated from river sediments. This research highlights the need for further studies to validate model assumptions and better understand the reactivation and transport mechanisms of microplastics in river systems.

Geologic structure and origin of the Zadlog karst polje

In the wider Idrija area in western Slovenia, several large plains formed along the thrusts within the dolomite and at the contact of dolomite and limestone. The purpose of this paper is to present the detailed structural-geological background of one such plain, namely the Zadlog plain, and based on these findings, to provide new starting points for analyzing the genetic conditions of other karst poljes in Notranjska. The Zadloško polje was formed in a wider near-fault crushed zone at the contact of two structural units within the Upper Triassic Norian-Rhaetian dolomite, with the thrust crossing the polje in its central part. The initially lowered area at the thrust represented a morphological basis, and the crushed zones in the dolomite played a hydrological retention role inducing the stagnation of surface water and, as a result, the formation of the karst polje. Younger fault tectonics then established efficient drainage of surface water and the erosion of sediments to the karst underground. Besdies this, slope equilibration leads us to conclude that the karst polje capability of hydrologic retention is recently decreased. The example of Zadloško polje shows that the thrust structures and associated hydrological conditions are the key elements for the formation of karst poljes in the dissected karst surface. Further detailed structural-geological mapping will reveal whether similar structural-geological conditions are the basis for the formation of other karst poljes in the region.

Evaluation of the Hydrological Response of Nature-Based Solutions (NBS) in Socio-Economically Vulnerable Tropical Urban Settlements: A Case Study in La Guapil, Costa Rica, Under Climate Change Scenarios

Urbanization increases the number of impervious surfaces in watersheds, reducing infiltration and evapotranspiration, which increases runoff volumes and the risks of flooding and the pollution of water resources. Nature-based solutions (NBS) mitigate these effects by managing water volume and quality, restoring the hydrological cycle, and creating sustainable livelihoods that can promote socioeconomic equity by providing green space. In light of the aforementioned information, this study analyzes the hydrological response of NBS in La Guapil, a densely populated and socioeconomically vulnerable area of Costa Rica with approximately 80% impervious surfaces, focusing on their effectiveness in stormwater management and improving hydrological conditions. Field data from the study area’s storm drainage system, as well as hydrological analyses, were collected and processed to evaluate RCP8.5 climate change scenarios using the Clausius–Clapeyron (CC) relationship. Three scenarios were proposed: (1) the “status quo”, reflecting current conditions, (2) green roofs and green improvements, and (3) detention ponds and green improvements, evaluated using the SWMM, with the latter scenario also using the Iber model. Simulations showed that Scenario 2 achieved the greatest reduction in peak flow (53.74%) and runoff volume (57.60%) compared to Scenario 3 (peak: 28.37%; volume: 56.42%). Both scenarios demonstrate resilience to climate change projections. The results of this study provide a foundation for further research into NBS in Costa Rica and other comparable regions.

Landscape-scale drivers of spatial dynamics and genetic diversity in an emerging wildlife pathogen

Aquatic pathogens often cannot tolerate drying, and thus their spread, and diversity across a landscape may depend on interactions between hydrological conditions and the movement of infected hosts. The aquatic fungus Batrachochytrium dendrobatidis (Bd) is a nearly ubiquitous pathogen of amphibians and particular lineages have been associated with host declines. By coupling amphibian surveys with molecular pathogen detection and genotyping techniques, we characterized the spatial dynamics and genetic diversity of Bd on a landscape containing both permanent and ephemeral ponds. In doing so, we aimed to clarify how pathogen loads and prevalences vary across seasons and among habitat types, and which host species move the pathogen from place to place. At the start of spring breeding, Bd prevalence was lower on amphibians sampled from ephemeral ponds. For the remainder of the amphibian active season, prevalence was similar across both ephemeral and permanent ponds, with variation in prevalence being well-explained by a hump-shaped relationship with host body temperature. The first amphibians to arrive at these ephemeral ponds infected were species that breed in ephemeral ponds and likely emerged infected from terrestrial hibernacula. However, species from permanent ponds, most of which hibernate aquatically, later visited the ephemeral ponds and these animals had a greater prevalence and load of Bd, suggesting that migrants among ponds and pond types also move Bd across the landscape. The Bd we sampled was genetically diverse within ponds but showed little genetic structure among ponds, host species, or seasons. Taken together, our findings suggest that Bd can be diverse even at small scales and moves readily across a landscape with help from a wide variety of hosts.

Phenotypic Plasticity, Multiple Paternity, and Shell Shape Divergence Across Lake‐Stream Habitats in a Freshwater Mussel Brood (Pyganodon grandis)

ABSTRACT Hydrodynamic forces and their absence appear to exert differential selection pressure on aquatic biodiversity in lake and stream habitats, creating a tight fit between organismal phenotypes and their environments. Ecophenotypic variants may be the result of genetic differentiation or phenotypic plasticity, where a genotype can produce multiple phenotypes dependent on the environment. Freshwater mussels possess a wide degree of morphological variation that frequently covaries with the environment, making them a good system to understand the mechanisms of ecophenotypic variation across hydrological conditions. We designed a two‐year experiment where individuals from the same Pyganodon grandis maternal brood (half and full siblings) were reared at a controlled site and four natural sites involving one lake and three streams. At the end of the experiment, shell shape was quantified for recaptured (N = 70), wild (N = 206), and zoo‐reared (N = 305) mussels. The maternal individual and 46 recaptured mussels were sequenced for genomic single nucleotide polymorphisms to test for multiple paternity and its effect on offspring morphology. Analysis of covariance found significant differences in shell shape between rearing sites, particularly between stream and lake habitats, but no shape differences were detected across the three stream sites. At two of the four sites, the shell shape of recaptured individuals was not significantly different than that of wild populations. Genomic sequencing and parentage analysis identified 11–27 different fathers among recaptured individuals. Yet no genetic differences were present between stream and lake habitats, and there was no paternal effect on shell shape. Taken together, phenotypic plasticity, over genetic differentiation, is identified as the primary mechanism of ecophenotypic variation. Plasticity is likely ubiquitous across freshwater mussels and may be a key adaptation given their high variance in habitat use. Multiple paternity may also play a role in the evolution of phenotypic plasticity, allowing more males from greater distances opportunities for fertilization, thus increasing genetic connectivity. Lastly, phenotypic plasticity and multiple paternity are convenient properties for freshwater mussel conservation and propagation. Multiple fathers increase the genetic variation of propagated broods, while plasticity may provide resilience to the release of stocked individuals across environmental heterogeneity.

Mapping of planation surfaces in the north-central Amazonia

This study aims to identify planation surfaces and their dissected reliefs in the Amazon, starting from the highlands of the border between Brazil, Venezuela and Guiana and ending near the axis of the Amazon River. Its connection with associated surface formations (regoliths) was also evaluated. The input data for the execution of the algorithm used were generated via geoprocessing techniques, which enabled the identification of five planation surfaces: a summit surface, which was associated with the Gondwana surface, from 855 to 2,745 m; a second surface (525–854 m), associated with the Post-Gondwana surface; a third surface, from 279 to 524 m, associated with the South American surface; a fourth surface, from 114 to 278 m, associated with the Velhas I surface (Early Velhas), and a fifth surface, associated with the Velhas II surface (Late Velhas). Thin soils predominate in the first three surfaces, and their presence is attributed to the erosion of the original surface formations with exposure of rock or iron crusts. The two lower surfaces present greater diversity of soils mainly due to the heterogeneity of soil hydrological conditions. In addition to Latossolos (Oxisols) and Argissolos (Ultisols), which are dominant, there are Espodossolos (Spodosols), Plintossolos (Plinthosols), Gleissolos (Gleysols) and Planossolos (Planosols).

Environmental Influences on Evapotranspiration in Wheat-Maize Rotation Systems under Diverse Hydrological Regimes in the Guanzhong Plain, China

Evapotranspiration (ET) is a crucial hydrological process in terrestrial and agricultural ecosystems, and is a key factor driving climate change dynamics. Understanding the variability of ET and how it responds to controlling factors helps describe the impact of environmental changes on agricultural ecosystems. This study analyzes long-term continuous measurements from an Eddy Covariance (EC) system in wheat-maize rotation fields in the Guanzhong Plain in China. Using structural equation modeling (SEM), we investigated the regulatory roles of environmental and biological factors on ET, and the mechanisms controlling ET for summer maize and winter wheat under varying hydrological and climatic conditions. The results indicate that the eight-year average ET during the summer maize season ranged from 259 to 348mm; during the winter wheat season, it ranged from 369 to 513mm. The adjusted SEM explained 64% of the variation in daily ET during the summer maize season and 80% during the winter wheat season. Photosynthetically active radiation (PAR) was the primary controlling factor for both seasons, with air temperature (Tair) also playing a significant role. Leaf area index (LAI) was an important mediator for ET, and had a greater effect during the winter wheat season than during the summer maize season. Vapor pressure deficit (VPD) and soil water content (SWC) had a more significant impact on ET during the summer maize season than during the winter wheat season. The ET response to environmental factors varied significantly under different hydrological and climatic conditions. Specifically, the total effect of PAR on ET increased with increased moisture availability and decreased temperature; the trend was opposite for Tair. This indicates that high temperatures and drought conditions may increase the sensitivity of ET to temperature changes, and decrease the sensitivity of ET to radiation changes. This study explains the variability of evapotranspiration in agricultural ecosystems and associated controlling factors, providing important insights about how agricultural evapotranspiration responds to vegetation phenology under future climate change scenarios. These investigations help optimize water resource utilization and allocation in agricultural fields.

Water and carbon fluxes from a supra-permafrost aquifer to a stream across hydrologic states

Supra-permafrost aquifers within the active layer are present in the Arctic during summer. Permafrost thawing due to Arctic warming can liberate previously frozen particulate organic matter (POM) in soils to leach into groundwater as dissolved organic carbon (DOC). DOC transport from groundwater to surface water is poorly understood because of the unquantified variability in subsurface properties and hydrological environments. These dynamics must be better characterized because DOC transport to surface waters is critical to predict the long-term fate of recently thawed carbon in permafrost environments. Here, we used distributed Darcy’s Law calculations to quantify groundwater and DOC fluxes into Imnavait Creek, Alaska, a representative headwater stream in a continuous permafrost watershed. We developed a statistical ensemble approach to model the parameter variability and range of potential contributions of steady-state groundwater flow to the creek. We quantified the model prediction uncertainty using statistical sampling of in-situ, active-layer soil hydro-stratigraphy (water table, ice table, and soil stratigraphy), high-resolution topography data, and DOC data. Moreover, the predicted groundwater discharge values representing all possible hydrologic conditions towards the end of the thawing season were also considered given the potential variability in saturation. The model predictions were similar to and span most of the observed range of Imnavait Creek streamflow, especially during recession periods, and also during saturation excess overland flow. As the Arctic warms and supra-permafrost aquifers deepen, groundwater flow is expected to increase. This increase is expected to impact stream, river, and lake biogeochemical processes by dissolving and mobilizing more soil constituents in continuous permafrost regions. This study highlights how quantifying the uncertainty of hydro-stratigraphical input parameters helps understand and predict supra-permafrost aquifer dynamics and connectivity to aquatic systems using a simple, but scalable, modeling approach.

Medium term hydrochemical and CO2 responses to anthropogenic and environmental changes in karst headwater streams.

This study investigates the intricate effects of lithology, temperature, discharge, and land use changes on headwater stream chemistry by analysing two decades of hydrochemical data from twenty karst headwater catchments in the Garonne River basin, France. Focused on the Pyrenees and the lowland (LM) and upland (UM) regions of the Massif Central, this study identified significant regional variations and commonalities in water chemistry. The headwater streams were clustered based on their hydrological and hydrochemical profiles, revealing strong similarities between upland sites, i.e. UM and Pyrenees, despite their geographical distance. The findings revealed a predominance of water driven by calcite dissolution, with specific influences from minor lithologies. Seasonal variations in water chemistry were primarily driven by hydrological conditions. Trend analyses highlighted increased pCO2 concentration in both the Pyrenees and UM, linked to higher forest density and agricultural activities, respectively. In contrast, LM exhibited increasing Ca2+ and HCO3- concentrations alongside decreasing trends in pCO2 and discharge, and increased nitrate concentration. While overall water temperatures increase, only a few sites exhibited significant warming trends, consistent with similar studies in the region and worldwide. These findings underscore the complex interplay between land use changes and hydrochemical dynamics in karst headwaters. They reveal that rising pCO2 concentration trends in upland regions are driven by reforestation and agricultural practices, which have significant implications in CO2 emissions, and consequently for regional and global carbon budgets and carbon-related policies. In lowland areas, declining water resources and increasing ion concentrations highlight potential challenges for water management, particularly in sensitive karst catchments. This study provides a baseline for understanding how karst headwaters respond to environmental changes. Expanding this research to other karst systems worldwide, under different climates, would help validate and model these findings, and improve our understanding of the global carbon cycle.

Development of the water regime of lakes and reservoirs in the Muynak region in order to improve their hydrological and hydrobiological condition

Abstract This paper presents the results of field studies to determine the actual morphometric characteristics of water bodies of the Amudarya River delta, in particular the Mezhdurechye reservoir, Muynak and Rybachy bays. In connection with the deteriorating environmental situation and the need to stabilize it, based on the research results, the main characteristics of reservoirs were determined, in particular their actual volumes, and a watering regime for these objects was developed, as well as an assessment of the productivity of reservoirs.

Backward induction-based multi-layer approach for watershed flood management in arid regions

Managing floods in interconnected nonurban and urban areas of arid regions prone to flash floods requires a more dynamic and integrated approach than traditional linear methods. In this regard, this study proposes a novel multi-stage decision-making framework which reshapes the traditional cascade approach to flood management by addressing the interdependencies between upstream and downstream regions. The proposed cyclic decision-making process involves five main steps: First, the Hydraulic and Hydrological (H/H) conditions in urban and nonurban areas were modeled using the SWMM. Then, a multi-stage optimization framework was constructed, in the first step of which the detention dams' location and dimensions were optimized in the nonurban area. Next, to link the first and second stages of the optimization, COPRAS method was employed for selecting the critical upstream management strategies. These strategies were determined as the input for the flood network optimization in the second stage. Finally, the Backward Induction Game Theory (BIGT) method was employed to find the best management strategy, under which not only the upstream conditions were considered in downstream flood protection but also stakeholders' conflicts were totally resolved by choosing the Nash Equilibrium. Our findings revealed that the implementation of the selected scenario could reduce flood peaks at the entrance of urban areas by 60.7 % and enhance shock absorption by 81.8 %. In fact, we guarantee that it is possible to propose a scenario encompassing drainage and detention dams' characteristics that, in addition to resolving stakeholders' conflicts of interest, can reduce the risk of flooding in complex watersheds. Moreover, the framework transforms the sequential, one-way cascade decision-making process into a continuous cycle, where upstream and downstream's H/H conditions and stakeholders' preferences are evaluated in coordination to achieve an agreement. Also, this framework helps decision-makers access the most sustainable solutions considering hydrological and socio-economic points of view.

The precise implementation of the ecological water transfer project effectively promotes the enhancement of desert riparian ecosystem service value in the mainstream of Tarim River

Ecosystem service value (ESV), as a crucial indicator concerning human and regional ecological well-being, has always been a hot topic in academia. Selecting appropriate assessment factors for arid areas to comprehensively explore the spatial–temporal heterogeneity of ESV and proposing pathways for ESV enhancement are currently challenging in research. This study incorporates three driving indicators, namely, human disturbance intensity (HDI), vegetation growth status (NIRv), and hydrological wetness condition (TVDI), into ESV calculation, efficiently improving the pixel-scale spatial heterogeneity manifestation of ESV. The study was conducted in a representative desert region of the Tarim River Basin (TRB), where ecological water transfer has effectively facilitated vegetation restoration. Based on this analysis, the total ESV in the TRB grew by 12.73 % between 2000 and 2022. Among them, ESVHDI, ESVNIRv, and ESVTVDI increased by 4.10 %, 58.25 %, and 18.78 % respectively. ESV in the four source rivers and mainstream of TRB increased by 4.36 % (YR), 60.77 % (TR), 2.94 % (AR), 3.88 % (HR), and 2.11 % (KR), with the ESV enhancement areas highly coinciding (coincidence degree is as high as 60.64 % of the mainstream of TRB) with the Populus euphratica forest water transfer area. ESV in the ecological water transfer area increased by 51.27 %, especially in the mainstream of the TRB water transfer area, where ESV increased by 62.32 %. Based on the perspectives of water use benefit (ESV/ET) and efficiency (ET/NIRv), to improve the ecological water use efficiency and ESV even further, the water supply thresholds of forests, grasslands, and wetlands should be controlled within the ranges of [495.37 mm-553.45 mm], [474.25 mm-528 mm], and [1011.68 mm-1070.64 mm], respectively. This study not only provides new insights for ESV calculation in arid areas but also offers scientific guidance for precise management of arid ecosystem.

Prospection of faults on the Southern Erftscholle (Germany) with individually and jointly inverted refraction seismics and electrical resistivity tomography

As part of the Lower Rhein Embayment (LRE), the Southern Erft block is characterized by a complex tectonic setting that influences hydrological and geological conditions on a local as well as regional level. The study area is located in the south of North Rhine-Westphalia and traversed by several NW-SE-oriented fault structures. Since the tectonic structures were located by past studies based on a sparse foundation of geological data, the positions include considerable uncertainties. Therefore, it was decided to re-evaluate and refine the assumed fault locations by conducting geophysical measurements. Seismic Refraction Tomography (SRT) as well as Electrical Resistivity Tomography (ERT) was performed along seven measurement profiles with a length of up to 1.1 km. In addition to compiling individual resistivity and velocity models for all deduced measurements, ERT and SRT datasets were cooperatively inverted using the Structurally Coupled Cooperative Inversion (SCCI). This algorithm strengthens structural similarities between velocity and resistivity by adapting the individual regularizations after each model iteration. Previously assumed locations of the tectonic structures diverge from the new evidence based on ERT and SRT surveys. Especially in the western and eastern parts of the research area, differences between the survey results and formerly assumed locations are in the order of 100 m. Seismic and geoelectric measurements further indicate a fault structure in the southern part of the area, which remained undetected by past studies. The cooperative inversions do not improve the geophysical models qualitatively, since the individually inverted datasets already provide results of good quality and resolution.

Hydrological drought assessment of the Yellow River Basin based on non-stationary model

Study Regionthe Yellow River Basin Study FocusNon-stationary hydrological conditions are becoming increasingly common due to climate change and human activities, and pose a novel challenge to the management of water resources and related risks, especially for large basins. However, prevalent research on drought assessment often ignores the non-stationary characteristics of hydrological processes. In this study, we investigated the stationarity of the runoff of the Yellow River Basin (YRB), the second-longest basin in China. We used an approach for assessing non-stationary droughts based on the generalized additive model for location, scale, and shape to establish a standardized runoff index containing covariates (SRI_cov) to identify hydrological droughts in the basin from 1986 to 2015. New Hydrological Insights for the RegionThe results show that the runoff was non-stationary in the YRB. Based on SRI_cov, hydrological drought predominantly occurred in the entire YRB in spring. From 1986, the number of months in which droughts occurred in the YRB exhibited a general trend of increase and peaked around 2002. After that, the total number of droughts significantly decreased but extreme droughts had become more prominent since 2005. The drought was more severe in the middle reaches of the Yellow River, and was characterized by a high frequency, intensity, and severity. Our analysis enhances the understanding of hydrological modeling and drought assessment under non-stationary conditions.

Applying a coupled model framework to assess global climate change impacts on the river-type algal blooms in the middle and lower reaches of the Hanjiang River, China

Global climate change (GCC), characterized by warming, affects the hydrological conditions at the basin scale and whether harmful algal blooms (HABs) occur at the scale of river ecological systems. Research on HABs mainly focuses on oceans and lakes, and there is still less research on the effects of GCC on river-type HABs that differ from oceans and lakes in hydrodynamic, water temperature, and nutrient conditions. This study constructed a coupled model framework that includes the GCC model, downscaling model, hydrological model, hydrodynamic model, and eutrophication model, analyzing and exploring the effect of changes in the aquatic ecological environment caused by GCC on river-type HABs in the middle and lower reaches of the Hanjiang River (MLHR). Firstly, based on the three GCC models and statistical downscaling model in CMIP6, high-precision meteorological factors such as future precipitation and temperature were obtained. Secondly, a coupled model based on SWAT and MIKE21-ECOLab was used with the digital elevation model (DEM), land use, soil, meteorological, pollution source, and measured terrain data in the MLHR Basin, which was validated by observed data. Thirdly, there has not been a significant increase in Chl-a, and the impact of GCC has not fundamentally changed the temporal and spatial distribution of HABs. Fourthly, this study proposes to use 0.2 m/s (Corresponding discharge 1160 m3/s) as the hydrodynamic condition for preventing and controlling HABs in the Shayang section.

Linking the Flow Regime of Papyrus‐Dominated Wetlands to Biologically Relevant Hydrologic Attributes

ABSTRACTThe dominant plant species in many African wetlands is Cyperus papyrus. Its adaptation to saturated and low‐oxygen conditions and its dense structure and height provide breeding and feeding grounds for unique flora and fauna. As a keystone species adapted to local hydrology, the flooding regime of papyrus offers the full range of hydrologic conditions and events essential to ecosystem health. However, no study has attempted to link papyrus wetlands' flow regimes to their biologically relevant hydrologic attributes. This study assesses hydrologic alterations of a papyrus wetland's flow regime due to rice irrigation. We develop a conceptual ecological model linking papyrus to hydrologic attributes to determine the consequences of changed environmental flow components (EFCs) on papyrus as a habitat. We find that agricultural water management considerably alters the magnitude, duration, timing and rate of change of EFCs, which could affect productivity (seed dispersal, germination and establishment; rhizome spreading; papyrus distribution across transects; and dispersal of floating mats) in papyrus wetlands. However, the effect on the papyrus wetlands' natural pulsed regime is negligible when the ratio of irrigated area to catchment area is no greater than 1:150. Overall, a better understanding of the threats of water diversion for agriculture is made by linking papyrus' flow regimes to biologically relevant hydrologic attributes. Knowledge of the roles of the various EFCs could provide opportunities for conserving and protecting papyrus wetlands, especially for systems at risk of altered flows.

The phosphorus export coefficients variability of specific land-use and the threshold response relationship with watershed characteristics in a subtropical hilly region

The magnitude of land-use phosphorus (P) export in subtropical hilly watersheds is subject to the collective influence of various watershed characteristics. However, the spatiotemporal dynamics of key watershed characteristics and their impacts on P exports remain unclear. Total phosphorus export coefficients (TPECs) can quantify the contribution of different land-use types to P exports. Here, we employed continuous observation data of typical subtropical hilly areas in the Laodao River watershed, China, from 2012 to 2019, as well as an enhanced export coefficient model combined with Bayesian statistical methods, to quantify the spatiotemporal variability and uncertainty of TPECs under various hydrological conditions in different land-use types (forest, cropland, and tea plantation). We then determined the key watershed characteristic factors influencing TPECs and threshold responses of TPECs to these factors. The three land-use types exhibited significant spatiotemporal differences in TPECs, i.e., under different hydrological regimes and within each catchment. Watershed characteristic factors explained 68.5–74.1 % and 33.3–50.4 % of TPEC variations under medium- and low-flow regimes, respectively, but only 1.9–3.8 % under the high-flow regime. Compared to topography and soil factors, landscape patterns had a higher individual impact on TPECs. Threshold response relationships existed between TPECs and key influencing factors under both medium- and low-flow regimes. Moreover, the thresholds corresponding to abrupt TPEC change points were comparatively consistent under medium- and low-flow regimes. These findings have practical applications for rapidly characterising critical P pollution source areas and formulating basin-scale land-use plans for water quality protection.

The ADDRESS of a grain: Sediment particle tracking as an approach to assessing ecosystem quality in dammed reservoirs

The study integrates hydrodynamic modelling and geospatial analysis methods to describe the dynamic transport and sedimentation conditions of suspended solids (SS) in large lowland reservoirs. The method was tested on a dam reservoir on the Vistula River (Poland). Stochastic particle tracking was used with a Lagrangian approach, then geostatistical analyses to interpret the simulation results.It is shown that, excluding the backwater, SS sedimentation is greatest in distal parts of the reservoir's lacustrine and river sections. The reservoir retains an average of 79 % of inflowing SS. The primary process affecting the sedimentation of SS is a dam-wards increasing fineness of settling grains. Hydrodynamic simulation results showed deposition of clay fraction to also be possible in the reservoir's upper part, even during floods. Moreover, sand grains entered the dam even during very low flows. Interpretation of Particle Tracking Model (PTM) simulation results and geostatistical modelling reveals that the submerged bed of the pre-dam river still has a transport function, while fine SS accumulates in slow-flowing areas outside it. The anastomosing pre-dam riverbed still influences flow conditions and SS deposition in the upper and middle reservoir. PTM modelling and geostatistical analyses determined the influence of hydrodynamic conditions on the spatial variability of SS sedimentation in terms of the quantity and grain-size distribution of sedimenting matter.An original indicator (ADDRESS [A]; Accumulation or Discharge of Dam REservoir Suspended Solids) was developed determining the ability of polymictic reservoirs to either retain SS of different diameters or allow them through the reservoir to be discharged through the dam. The indicator quickly and simply determines particle behaviour under given hydrological conditions. Information on whether all or only some of grains of specific diameters will flow through the dam is important for explaining many natural processes affecting the reservoir ecosystem and the river ecosystem below the dam.