Basin Management Research Articles

Simulation of Flow and Salinity in a Large Seasonally Managed Wetland Complex

Seasonally managed wetlands in the San Joaquin River (SJR) watershed in California provide important benefits to wildlife and humans but are threatened through anthropogenic activity. Wetlands in the SJR are subject to salinity regulation, which poses challenges for wetland management. Salinity management in the SJR basin is supported by a process-based model, the Watershed Analysis Risk Management Framework (WARMF). Wetlands are simulated with a “bathtub” analog where water levels are assumed to be the same over one model compartment and the storage volume depends on depth. The complexity and extent of hydrological features pose challenges for input data acquisition. Two approaches to estimating inflow and pond depth and determining water sources were assessed. Approach 1 used mostly monitored data, while Approach 2 used wetland manager knowledge. Approach 2 predicted outflow and salinity better than Approach 1, and an important benefit was the simulation of water reuse within the wetland complex, which was previously not implemented. Approach 1 is generally suited for estimating pond depth when a model compartment represents one wetland, while Approach 2 is suited for wetlands with large spatial extent, many hydrological features, and managed flows. The improved model will support wetland management.

A WEAP-assisted agent-based modeling approach for watershed planning in a coupled human and nature system

ABSTRACT Coupled human and nature systems exhibit dynamic water demands due to diverse consumer socio-economic characteristics, resulting in inherent complexities. Modeling such systems effectively entails adopting an agent-based methodology. To enhance comprehension of water resource management in the Zarrineh-Roud Basin, northwest of Iran, a comprehensive hydrological-behavioral model has been utilized. This model consists of two primary components: An agent-based model (ABM) for simulating farmers’ decision-making processes and a water evaluation and planning (WEAP) model for simulating catchment area, cultivated area, and agricultural water consumption. Validation outcomes of the simulation model demonstrate precise estimation, particularly in the runoff estimation of the Nezam Abad hydrometric station, with statistically favorable correlation coefficient (R2) and Nash–Sutcliffe index (NS) values of 0.78 and 0.75, respectively. Analysis of different management scenarios indicates that with ample government funds, simultaneous implementation of ‘Education and increasing environmental awareness’ and ‘Alternative employment’ policies can significantly improve water resources conditions and income. In scenarios with limited financial resources, a combined implementation of ‘Water pricing,’ ‘Alternative employment,’ and ‘Education and raising environmental awareness’ emerges as the most effective strategy for managing water resources, albeit with a slight reduction in farmers’ income.

Spatiotemporal evolution and interaction of water constraints and their socio-ecological drivers in the Taihu Lake Basin

To effectively manage water constraints (WCs) within a basin, it is crucial to first scientifically delineate their spatial distribution and thoroughly understand the interactions between WCs. Investigating the complex driving mechanisms at multiple scales is also essential. In this study, a basin WC evaluation framework is constructed using a conflict risk assessment model. The spatiotemporal variations of four types of WCs across three spatial scales in the Taihu Lake Basin (TLB) are thoroughly investigated. Furthermore, the study quantifies the trade-offs, synergy effects, and bundle patterns of these water constraints. The study employs the Optimal Parameters-based Geographic Detector (OPGD) and multivariate linear regression to identify the key socio-ecological drivers of WCs. Our findings indicate that between 2010 and 2020, water resource constraint (WREC), water environment constraint (WENC), water safety constraint (WSAC), water ecology constraint (WECC), and the comprehensive WC (CWC) displayed varying degrees of heterogeneity. Particularly, the mean values of WSAC, WECC, and CWC witnessed an increase over the decade. Additionally, all WCs exhibited a strong positive spatial autocorrelation. Synergistic interactions among WCs were predominantly observed in pairs such as WREC-WSAC, WREC-WECC, and WSAC-WECC, while a weaker trade-off effect was noted in the WENC-WECC pair. At multiple scales, we identified eight types of WC bundles capable of undergoing mutual transformations, especially at the basin scale. The primary drivers of WCs varied across different stages and scales, with most factors collectively exerting a more significant impact than individually. Notably, factors like secondary and tertiary industry GDP (X2), population density (X3), precipitation (X6), and elevation (X7) were identified as core drivers influencing the evolution of WCs in the TLB. Integrating these spatiotemporal characteristics and driving mechanisms of WC interactions into basin planning and management can significantly support the alleviation of multidimensional water constraints in territorial spaces.

FORMATION OF THE ARCHITECTURAL AND URBAN PLANNING SPACE OF OXBOW LAKES: SCIENTIFIC AND PRACTICAL EXPERIENCE

Problem statement. Following the adoption of Law No. 1641-VIII on October 4, 2016, the Ukrainian legislation introduced the “basin management principle”. This principle entails comprehensive (integrated) management of water resources within the river basin area [1]. In the valleys of lowland rivers with numerous bends, particularly in the Dnipro, Danube, and Vistula rivers, oxbow lakes are formed, representing remnants of old river channels. Oxbow lakes are small lakes that form on floodplains due to erosion and sediment deposition. In large cities, such lakes are important centers of biological diversity, improve microclimate, act as barriers to floods, and have an attractive appearance. However, oxbow lakes are susceptible to drying up, silting, and turning into marshes. Therefore, research on oxbow lakes in the context of urban planning is highly necessary to prevent chaotic development and preserve similar ecosystems. Additionally, the consolidation of experience in the development and rehabilitation of such objects is practically significant for urban planning. Research objective. The purpose is to examine and summarize the scientific and practical experience in forming the architectural and urban planning space along oxbow lakes. Conclusion. Scientific research in the fields of hydraulic engineering, agronomy, and urban planning that can be implemented in urban planning practice to address oxbow lake issues has been identified and systematized. Using satellite imagery and analytical maps, patterns in the organization of oxbow lake spaces in the largest cities of Ukraine have been identified. Similarly, examples of planning and development of lakeside (old riverbed) territories in Europe, America, Asia, and Oceania have been found and analyzed. Successful practical solutions for the use of scientific and technical methods for preserving oxbow lakes have been identified in the aforementioned examples. Patterns and trends in organizing development and street networks around small floodplain lakes and oxbow lakes have been revealed.

How economically and environmentally viable are multiple dams in the upper Cauvery Basin, India? A hydro-economic analysis using a landscape-based hydrological model

Abstract. The construction of dams threatens the health of watershed ecosystems. The purpose of this study is to show how multiple dams in a basin can impact hydrological flow regimes and subsequently aquatic ecosystems that depend on river flows. The approach assesses the ecosystem services (ESs), including the tradeoffs between economic and ecological services due to altered flow regimes. It uses a previously developed model that integrates a landscape-based hydrological model with a reservoir operations model on a basin scale. The approach is novel because not only does it offer the analysis of alterations in ecosystem services on a daily scale when pre-dam data are unavailable but also allows for dams to be synthetically placed anywhere in the river network and the corresponding alterations in flow regimes to be simulated in a flexible manner. As a proof of concept, we analyse the economic and ecological performances of different spatial configuration of existing reservoirs instead of synthetically placed reservoirs in the upper Cauvery River basin in India. Such a study is timely and conducted for the first time, especially in light of calls to assess the cascade of reservoirs in India and regions elsewhere where pre-dam data are unavailable. The hydrological impact of different configurations of reservoirs is quantified using indicators of hydrologic alteration (IHAs). Additionally, the production of two major ecosystem services that depend on the flow regime of the river, as indicated by irrigated agricultural production and the normalized fish diversity index (NFDI), is estimated, and a tradeoff curve, i.e. a production possibility frontier, for the two services is established. Through the lens of the indices chosen for the ecosystem services, the results show that smaller reservoirs on lower-order streams are better for the basin economy and the environment than larger reservoirs. Cultivating irrigated crops of higher value can maximize the value of stored water and, with lower storage, generate a better economic value than cultivating lower-value crops while reducing hydrological alterations. The proposed approach, especially when simulating synthetic spatial configurations of reservoirs, can help water and river basin managers to understand the provision of ecosystem services in hydrologically altered basins, optimize dam operations, or even prioritize dam removals with a goal of achieving a balanced provision of ecosystem services.

Experience and Enlightenment of Russian Water Right System

This article provides a comprehensive overview of Russia's water resources, their development and utilization status, as well as the water rights system and related laws and regulations. It begins by detailing the abundant rivers, lakes, and groundwater resources in Russia. The analysis highlights that Russia has a high proportion of industrial water use, advanced water recycling technology, and significant water storage capacity in numerous reservoirs. The article also delves into the main contents of the Russian Federation Water Law, covering ownership and usage rights of water resources, and the legal responsibilities for water protection and management. Finally, it summarizes the experiences and insights from Russia's water rights system, emphasizing the importance of integrated basin management, clear water rights ownership, and the establishment of a comprehensive legal framework.

Channel changes during and after extreme floods in two catchments of the Northern Apennines (Italy)

The Nure and Trebbia catchments were affected by an extreme flood event on 13-14th September 2015. This study investigates the morphological responses to the flood of the Nure and Trebbia rivers and 18 tributaries with the aims to: i) quantify channel changes in width and pattern; (ii) identify the morphological and hydrological factors which might have driven channel response; (iii) quantify channel changes which have occurred after the flood event.Channel changes were characterized by field surveys and geomorphological analysis of multi-temporal orthophotos acquired before (2011), immediately after the flood (2015) and in 2020.In the tributaries, reach-scale channel widths after the flood reached up to 15 times their pre-flood values, whereas in the main channels the post/pre-flood width ratio attained a maximum value of 4. Augmented channel width in the main rivers was mostly associated with banks and islands erosion, whereas in the tributaries it was also due to deposition of coarse sediments onto the former floodplains. Islands were swept away in the main channels while both island erosion and formation occurred in the tributaries. In terms of channel pattern, pre-flood single-thread reaches displayed mainly multi-thread morphologies after the flood, mostly in response to a sudden input of coarse sediment supply. In the 5 yr following the flood, channels slightly narrowed but still remained wider than in 2011. The narrower reaches before the flood resulted to be the most sensitive to changes even some years after the flood.Statistical analyses between the channel width changes and a series of variables showed significant positive correlations with confinement index, channel slope, and the local storm rainfall depth. This study confirms how channel widening during large floods – usually neglected in flood hazard mapping and river basin management – is a very important process which must be considered in flood hazard assessment in mountain rivers.

Geochemical indices and sedimentation rates in the Pardo River basin, São Paulo state, Brazil

Sediment geochemical indices and sedimentation rates data from the Pardo River watershed, São Paulo State, Brazil, provide relevant reference guidelines for stakeholders to plan future actions aiming to achieve the appropriate management of that hydrographic basin. The watershed includes 20 municipalities where about 650,000 inhabitants are living and whose waters after withdrawal and treatment supply ∼300,000 people in that region. Six sediment cores provided the geochemical and radiometric dataset, which was obtained from sampling sites located in the following cities: Ourinhos, Santa Cruz do Rio Pardo, Águas de Santa Bárbara, Avaré, Botucatu, and Pardinho. The concentration data for some metals were compared with the reference values established by the Brazilian environmental legislation for sediment dredging because currently there is a lack of specific quality guidelines for marine or fluvial sediment in Brazil. Also, the entire dataset was used in the calculation of two traditional geochemical indices, i.e., the enrichment factor (EF) and contamination factor (CF). In some cores, both indices provided insight revealing possible anthropogenic inputs of magnesium oxide (MgO), potassium oxide (K2O), sulfur trioxide (SO3), vanadium oxide (V2O5), copper (II) oxide (CuO), and other constituents due to development of activities related to the crop production. The constant rate of supply (CRS) of the unsupported/excess lead 210 (210Pb) model has been successfully applied to the obtained a radiometric 210Pb dataset, yielding mean values of the mass accumulation rate (MAR) between 0.86 and 7.23 g/(cm2·y) and linear sedimentation rates (LSR) ranging from 2.9 to 7.1 cm/y. Both of these rates exhibited a significant correlation, representing physical weathering processes occurring in the basin. Chemical weathering rates reported in the literature indicate values much lower than the physical weathering rates and such findings have also been confirmed in the current study when the obtained data were compared with results from previous investigations in the Pardo River watershed. The CRS 210Pb chronological model was useful to track historical changes in the MgO and CuO concentration in the sediment cores, allowing curves to be plotted exhibiting major peaks in core 1 (1980–2010) and core 3 (2000–2010), a continuous increase from 1970 onwards until 2010 (core 4), and a sharp increase at the end of the monitoring period, 2017 (cores 5 and 6). Data available for the harvested area at a municipality located within the basin for the period 1990–2022 have indicated a more pronounced increase over the last years in the production of sugar cane, soybeans, and oranges, implying an increasing use of fertilizers and agricultural correctives for crop production, whose chemical composition would justify the trends observed for MgO and CuO concentrations in the sediment cores. The current study also revealed a wide range of significant relations involving the concentration of ferric oxide (Fe2O3) and other analyzed constituents, with iron tending to accumulate in the finer grain sizes (from 0.125 to <0.037 mm) of the sediment. The CRS 210Pb chronological model permitted evaluation of the history of the iron flux up to the present, which could represent baseline guidance levels for indicating future anthropic inputs in the basin.

Exploring groundwater patterns in Souss-Massa Mountainous Basin, Morocco: A fusion of fractal analysis and machine learning techniques on gravity data

Groundwater potential in Morocco’s Souss-Massa mountainous basin (SMMB) is being identified using geospatial tools and geological data. We deployed four mathematical models, namely Data-Driven Multi-index Overlay (DMIO), Geometric Average (GA), Support Vector Machine (SVM), and Logistic Regression (LR), to establish data-driven patterns among the nine influencing factors, primarily drainage density, permeability, slope, distance to rivers, elevation, lineament density, distance to lineaments, intersection node density, and rainfall. Based on the Concentration-Area (C-A) fractal approach, the findings of the four models were developed and classified into five levels of potentiality ranging from very low to very high. The regions designated as having high and very high potentialities for the DMIO, GA, SVM, and LR models, respectively, account for 22.44 %, 9.80 %, 19.36 %, and 26.77 % of the overall basin. We validated the models by calculating each model's area under the ROC curve (AUC). The estimated AUC values are more than 70 %, suggesting the model performs well. The four models' performance was compared, revealing that the SVM model outperforms the others. Gravimetric data shows that possible groundwater zones closely coincide with gravimetric lineaments. The findings of this study can provide valuable insights to decision-makers, allowing them to improve decision-making processes and develop holistic groundwater resource management in the Souss-Massa mountainous basin (SMMB).

Optimization of Manning's roughness coefficient using 1-dimensional hydrodynamic modelling in the perennial river system: A case of lower Narmada Basin, India.

This research bears significant implications for river management, flood forecasting, and ecosystem preservation in the Lower Narmada Basin. A more precise estimation of Manning's Roughness Coefficeint (n) will enhance the accuracy of hydraulic models and facilitate informed decision-making regarding flood risk management, water resource allocation, and environmental conservation efforts. Ultimately, this study aspires to contribute to the sustainable management of perennial river systems in India and beyond by offering a robust methodology for optimizing Manning's n tailored to the complex hydrological dynamics of the Lower Narmada Basin. Through a synthesis of empirical evidence and computational modelling, it seeks to empower stakeholders with actionable insights toward preserving and enhancing these invaluable natural resources. Using the new HEC-RAS v 6.0, a one-dimensional hydrodynamic model was developed to predict overbank discharge at different points along the basin. The study analyzes water levels, stream discharges, and river stage, optimizing Manning's n and required flood risk management. The model predicted a strong output agreement with R2, NSE, and RMSE for the 2020 eventas 0.83, 0.81, and 0.36, respectively, with an optimum Manning's n of 0.03. The lower Narmada Basin part near the coastal zone (validation point) appears inundated frequently. The paper aims to provide insights into optimizing Manning's coefficient, which can ultimately lead to better water flow predictions and more efficient water management in the region.

Comparative Analysis between Remote Sensing Burned Area Products in Brazil: A Case Study in an Environmentally Unstable Watershed

Forest fires can profoundly impact the hydrological response of river basins, modifying vegetation characteristics and soil infiltration. This results in a significant increase in surface flow and channel runoff. In response to these effects, many researchers from different areas of earth sciences are committed to determining emergency measures to rehabilitate river basins, intending to restore their functions and minimize damage to soil resources. This study aims to analyze the mapping detection capacity of burned areas in a river basin in Brazil based on images acquired by AMAZÔNIA-1/WFI and the AQ1KM product. The effectiveness of the AMAZÔNIA-1 satellite in this regard is evaluated, given the importance of the subject and the relatively recent introduction of the satellite. The AQ1KM data were used to analyze statistical trends and spatial patterns in the area burned from 2003 to 2023. The U-Net architecture was used for training and classification of the burned area in AMAZÔNIA-1 images. An increasing trend in burned area was observed through the Mann–Kendall test map and Sen’s slope, with the months of the second semester showing a greater occurrence of burned areas. The NIR band was found to be the most sensitive spectral resource for detecting burned areas. The AMAZÔNIA-1 satellite demonstrated superior performance in estimating thematic accuracy, with a correlation of above 0.7 achieved in regression analyses using a 10 km grid cell resolution. The findings of this study have significant implications for the application of Brazilian remote sensing products in ecology, water resources, and river basin management and monitoring applications.

Quantitative assessment of runoff change and its drivers in a multi-scale framework

ABSTRACT Identifying runoff changes and quantifying the impacts of climate change and human activities are important for water resources planning and management in river basins. The impacts of climate change and human activities on runoff can be more accurately assessed through scientific hydrological modeling and data analysis methods. In this study, an integrated assessment framework was established to quantitatively separate the driving mechanisms of runoff at different time scales. The results show that the runoff of Wu River has shown a decreasing trend since 2004, with a change degree of 56%, and the monthly average flow indexes of August and September have changed significantly, both are over 90%. The NSE coefficient of the SWAT simulation effect is above 0.8, we validate the simulation results based on the LSTM model. It was found that climate change was the main factor affecting the runoff of Wu River, with the contribution rates reaching 60 and 57%, respectively. Pearson correlation analysis found that rainfall was the most important factor affecting the runoff. The results of this study are helpful to formulate effective water resources management policies and measures to ensure the sustainable utilization and management of water resources in the Wu River Basin.

Analysis of Spatio-Temporal Changes and Driving Factors of Wetland Ecosystem Health Based on the AHP-SOM-DPSR Model—A Case Study of Wetlands in the Qin-Mang River

Wetland ecosystems are vital for ecological security. However, rapid industrialization and urbanization have led to regional degradation, particularly in areas like the Qin-mang River Basin, a pivotal site in China’s ecological security strategy. Urgent measures are required to safeguard the health of its wetland ecosystems. This study employs the hierarchical analysis method-neural network-driver-pressure-state-response (AHP-SOM-DPSR) model to evaluate the ecological health of wetland ecosystems in the Qin-mang River Basin over a thirty-year period, from 1992 to 2022. Initially, the Drive-Pressure-State-Response (DPSR) model establishes a comprehensive indicator system encompassing 19 indicators spanning driving forces, pressures, states, and responses. Subsequently, a hybrid approach combining Analytic Hierarchy Process (AHP) and Self-Organizing Map (SOM) determines indicator weights to evaluate spatiotemporal ecosystem changes over the past three decades. Additionally, spatial autocorrelation theory analyzes ecosystem health in the study area. Finally, Pearson correlation coefficient analysis examines the driving factors influencing ecosystem health and their impacts. Results indicate: (1) Ecosystem health has deteriorated gradually from 1992 to 2022, underscoring the imperative for enhanced wetland management in the Qin-mang River Basin. (2) High spatial autocorrelation areas, primarily in the central-southern and northern regions, highlight priority zones for wetland ecosystem management. (3) Urbanization levels, average temperature, and total population significantly impact wetland ecosystem health in the Qin-mang River Basin. These findings offer valuable scientific insights for guiding ecological management and conservation efforts in the region.

A fine-grained dataset for sewage outfalls objective detection in natural environments

Pollution sources release contaminants into water bodies via sewage outfalls (SOs). Using high-resolution images to interpret SOs is laborious and expensive because it needs specific knowledge and must be done by hand. Integrating unmanned aerial vehicles (UAVs) and deep learning technology could assist in constructing an automated effluent SOs detection tool by gaining specialized knowledge. Achieving this objective requires high-quality image datasets for model training and testing. However, there is no satisfactory dataset of SOs. This study presents a high-quality dataset named the images for sewage outfalls objective detection (iSOOD). The 10481 images in iSOOD were captured using UAVs and handheld cameras by individuals from the river basin in China. This study has carefully annotated these images to ensure accuracy and consistency. The iSOOD has undergone technical validation utilizing the YOLOv10 series objective detection model. Our study could provide high-quality SOs datasets for enhancing deep-learning models with UAVs to achieve efficient and intelligent river basin management.

Morphometric Analysis of Mithmumbri - Malvan Area, Sindhudurg District, West Coast of Maharashtra, India

Morphometric analysis has been carried out from the Mithmumbari to Malvan area, Western part of Maharashtra in Sindhudurg district, India. The morphometric analysis is carried out in fourteen drainage basins, viz., Achra, Pyali, Golvan, Mithmumbari, Katvan, Kamtakhudi, Gavaliwadi, Kunkeshwar, Kandalgaon, Munge, Malvan, Masura, Belachiwadi and Tambalwadi. The morphology of these basins is governed by a number of drivers including tectonic processes mainly the Vijaydurg fault, Mithbav fault, Malvan fault and lineaments, climate and lithology that influence the river system over a range of timescales. The majority of the basins are highly dissected and structurally controlled. The drainage density is low, with moderate to steep slopes within the elongated basin. The Achra, Pyali, Golvan, Gavaliwadi, Kandalgaon, Munge and Malvan basins are structurally controlled. The lower values of length of overland flow in study area reveal that stream erosion is more dominant than sheet erosion. Achra, Pyali, Mithmumbri, Golvan and Malvan basins are higher stream power, which represents higher erosion of the basin indicates high river basin management measures. Achra, Pyali, Golvan, Katvan, Kamthakhudi, Gavaliwadi, Kunkeshwar, Munge, Masura, Belachiwadi and Tambalwadi basins are rapid uplift stage of the basin. The Achra, Pyali, Golvan and Kamthakhudi basins can be inferred as SSW tilting in response to tectonic tilt. The hypsometric analysis shows eight basins (Achra, Pyali, Mithmumbari, Kamtakhudi, Kunkeshwar, Gavaliwadi, Belachiwadi and Tambalwadi) under the mature stage, five basins (Katvan, Munge, Kandalgaon, Malvan and Masura)in the youth stage and one basin (Golvan) under the old stage. The mature stage drainage basins show significant incision and entrenchment as a result of the Late Quaternary upliftment of the study area. The stages of drainage basins development in the western part of Maharashtra thus identify tectonically active and quiescent phases. Keywords: Morphometric and Hypsometric Analysis, Structural Control Basin, RS-GIS, Sindhudurg District, West Coast of Maharashtra

Exploring the Spatial Distribution of Coastal Drainage Basins in Turkey

Coastal regions are vital areas globally, serving as hubs for human habitation and economic activities. Water, being the fundamental resource for life, plays a crucial role in sustaining ecosystems and shaping coastal landscapes. The convergence of river systems in coastal zones underscores their significance in the hydrological cycle and aquatic biodiversity. However, managing these valuable yet vulnerable regions presents multifaceted challenges, necessitating robust management frameworks supported by monitoring and assessment tools. In Türkiye, a country with limited freshwater resources, the management of coastal zones is particularly complex due to increasing pressure on resources and land. This study examines the distribution and characteristics of river and coastal basins in Türkiye. Through spatial analyses on Geographical Information System and basin delineations with watershed modelling program, the study clarifies the regional differences and obstacles encountered by coastal provinces spanning the entirety of Türkiye's coastal borders. The results offer valuable understanding regarding the spatial dynamics of Türkiye's coastal areas with particular emphasis on the significance of Black Sea coastal basins and all coastal provinces. Firstly, river basin systems draining into the Black Sea constitute the majority of Türkiye's surface area. Although the Black Sea region covers only 14% of the total area, more than half of the country's surface area, excluding transboundary and endorheic basins, drains into the Black Sea. Similarly, the analysis of basin types reveals that coastal basins constitute approximately 18% of the drainage areas associated with our coastal waters, nearly one-fifth. This distinction between coastal basin and river basin boundaries differs from the traditional zoning approach in river basin management and coastal area management plans in Türkiye. Consequently, it is anticipated that this spatial evaluation, which has brought a new perspective, will significantly contribute to addressing management challenges, especially the studies that will be evaluated together with population and resource use.

Evaluation of the Water Quality of Nakdong River Using the Real-time Water Quality Index

Recently, the influx of pollutants into rivers has increased owing to the impacts of climate and environmental change, consequently accelerating the pollution of river ecosystems and aquatic habitats. Consequently, river water quality must be precisely assessed to facilitate effective management strategies by discerning different aspects of water quality deterioration and enhancement and by identifying and regulating river contaminants. Understanding water quality at a cursory glance is highly challenging, particularly for individuals lacking expertise in water pollution assessment. Hence, the present investigation utilized a domestically developed real-time water quality index (RT-WQI) to scrutinize the water quality attributes at 12 specific locations within the total pollution quantity monitoring network situated in the main channel of the Nakdong River system to render the water quality of the river easily comprehensible even to non-specialists. Furthermore, an attempt was made to detect patterns by applying the Mann–Kendall test and locally weighted scatter plot smoothing (LOWESS) using the index values for water quality assessment. To achieve this aim, extensive water quality data (averaged on a monthly basis) spanning 2004–2022 were obtained from the Water Environment Information System of the Ministry of Environment (https://water.nier.go.kr). The gathered date were then subjected to computation of descriptive statistics for individual water quality parameters to delineate the distinctive features of water quality. This study anticipates that the evaluation of water quality across diverse river systems in the future will facilitate the identification of highly polluted rivers and confirm their trends, thereby providing fundamental data for the management of river basins and the formulation of water quality policies.

Spatial Functional Outlier Detection in Multivariate Spatial Functional Data

Multivariate spatial functional data consists of multiple functions of time-dependent attributes observed at each spatial point. This study focuses on detecting spatial outliers in spatial functional data. Firstly, we develop a new method called Mahalanobis Distance Spatial Outlier (MDSO) to detect functional outliers in the data. The method introduces the multivariate functional Mahalanobis semi-distance and multivariate pairwise functional Mahalanobis semi-distance metrics based on the multivariate functional principal components analysis to calculate the dissimilarity between functions at each spatial point. Via simulation, we show that MDSO performs better than the other competing methods. Secondly, MDSO has been extended to detect spatial functional outliers as well. The functional outliers can now be categorized as global or/and local functional outliers. The appropriate number of neighbors and the cut-off point for the degree of isolation are determined via simulation. Finally, we demonstrate the application of the MDSO on a water quality data set obtained from Sungai Klang basin in Malaysia. The results can be used to support the authority in making better decisions on the management of the river basin or other spatial data with time-independent attributes.

Detection of soil salinity distribution and its change in the Yellow River Delta comparing 2006 and 2022

AbstractThe Yellow River Delta (YRD) has the world's highest land formation rate. However, soil salinization has caused severe land degradation in the region. Understanding the distribution of soil salinity and its variation is essential for saline soil management. This study combined soil salinity sampling data, remote sensing imagery, and layers of geographic environmental factors. Three different models, including Ordinary Kriging (OK), Geographically Weighted Regression (GWR), and Bayesian Maximum Entropy (BME), were used and compared to predict the soil salinity of two soil layers in 2006 and 2022. Then the spatial distribution characteristics and development trends of soil salinity in the YRD were analyzed. The results indicated that (1) The BME model is an optimal salinity prediction model that integrates soft data from multiple sources to perform nonlinear estimates. Compared to the OK and GWR models, the RMSE was reduced by up to 25% and 13%, respectively, and the greatest improvement in R2 was increased from 0.0534 and 0.2718 to 0.5569, respectively. (2) Soil salinity in the YRD shows a spatially increasing trend from the southwestern inland to the northeastern coast. Over the past 16 years, the salinization pattern has become more complex: soil salinization has been mitigated in the central and southern regions, with the average salinity decreasing from 1.03% to 0.86% and the salinization rate decreasing from 99% to 88%; and it has significantly intensified in the northern part of the study area near the old Yellow River channel and the Gubei Reservoir, and in some scattered inland areas. Continuous water and sediment regulation in the Yellow River basin and ecological management of natural reserves can generally alleviate soil salinization, but the risk of soil salinization can be increased by seawater erosion, inappropriate land use, and resource exploitation.

Hydrologic connectivity and dynamics of solute transport in a mountain stream: Insights from a long-term tracer test and multiscale transport modeling informed by machine learning

The movement of solutes in a watershed is a complex process with multiple interactions and feedbacks across spatial and temporal scales. Modeling the dynamics of solute transport along diverse hydrologic pathways within watersheds – from hillslopes to stream channels and in and out of the hyporheic zones – is challenging but critically important, as these processes integrate and contribute to the biogeochemical functioning of the river corridor up to the river network scale. Here we use results from a long-term network-scale tracer test at the H.J. Andrews experimental forest in western Cascade Mountains, Oregon, USA to inform a multiscale framework for transport in stream corridors. The framework uses a Lagrangian-based subgrid model to represent the effects of hyporheic exchange flow and advective transport at stream network scales. The spatially and temporally resolved stream discharge needed for the transport model is imputed across the river system by an entity-aware long short-term memory network. Modeled concentrations show good agreements with the observations and exhibit power scaling laws indicative of a very wide range of timescales over which hyporheic exchange flow occurs. Our results demonstrate a data-informed modeling framework that links dynamical processes occurring at small scales to a network context to help understand how changes at reach scale cascade into network-scale effects, providing a useful tool for sustainable river basin management.