Longitudinal zonation and hydrothermal variation jointly influence the bacterioplankton community assembly in peatland rivers in the Tibetan plateau.

For centuries, streams and rivers have been altered and degraded such that the conveyance of water downstream is unnaturally efficient, often to the detriment of other biophysical processes that maintain healthy riverscapes. Structural elements, such as beaver dams, can impact hydraulics and alter downstream water conveyance. While the hydraulic, hydrologic, geomorphic, and ecological effects of beaver dams have been quantified at individual study sites, study methods are often cost-prohibitive and complicated, making them less practical for monitoring at large spatial scales and in diverse settings. We mapped inundation extent and type (free flowing, ponded, and overflowing) in beaver dam complexes in diverse hydrogeomorphic settings as a simple method to monitor beaver-influenced riverscapes based on delineating inundation patterns. Our mapping of over 75 inundation events at 37 sites suggests that, on average, under undammed conditions valley bottom inundation ranged from 2.7% - 17.4% (mean 6.8%) whereas under dammed conditions the same sites had valley bottom inundation that ranged from 9.5% - 47.5% (mean 23.2%). We observed that, when beaver dams are present, roughly half of surface water inundation is converted from a free-flowing type to ponded and overflow types. This research also reveals that the focus of most previous beaver dam studies on low gradients and low stream orders is unnecessarily restrictive. We report similar magnitudes of influence in steeper gradient riverscapes as well as in beaver-modified floodplains and anabranches of higher-order rivers that are typically considered to be too large for beaver dams. While the quantification of inundated area and type presented here is valuable as a simple metric, we postulate that delineation of inundation type and extent can be used as a practical proxy for physical processes and indicators of riverscape health such as longer and more varied water residence times (i.e., hydrologic inefficiency).

The morphometric analysis of a river basin provides critical insights into its hydrological and geomorphological characteristics, essential for effective watershed management and planning. This study presents a detailed morphometric analysis of the Gostani River Basin using Remote Sensing (RS) and Geographic Information System (GIS) techniques. High-resolution satellite imagery and topographic data, including Digital Elevation Models (DEMs), were utilized to extract drainage networks and basin boundaries. Key linear, areal, and relief morphometric parameters such as stream order, bifurcation ratio, drainage density, stream frequency, elongation ratio, and relief ratio were computed using GIS tools. The results reveal that the Gostani River Basin exhibits dendritic drainage patterns, moderate drainage density, and a sub-mature stage of geomorphic development, indicating semi-permeable sub-surface material and moderate to low relief. The analysis highlights the usefulness of RS and GIS in deriving accurate and comprehensive morphometric parameters, facilitating better understanding of basin dynamics for sustainable water resource management and environmental planning.

ABSTRACT Along the river continuum, bacterial communities in river water typically show reduced α‐ and β‐diversity and a greater relative abundance of freshwater bacteria compared to terrestrial bacteria such as those derived from soil. Yet, studies on headwaters remain limited. Furthermore, the bacterial lifestyle of being particle‐associated (PA) or free‐living (FL) and temporal changes can influence community patterns. To understand the patterns of bacterial communities along the river continuum, we investigated bacteria communities in stream water, distinguishing between PA and FL, at 29 locations, including first‐ to fifth‐order streams, in a headwater area (ca. 5 km 2 ) located in a cold‐temperate forest during three seasons: spring, summer and autumn. Bacterial communities were investigated by metabarcoding of environmental DNA (eDNA) extracted from water. PA and FL were divided based on differences in size fractions retained during filtration. Both size fractions exhibited decreases in α‐ and β‐diversity, and the relative abundance of freshwater bacteria increased with stream order depending on the season. For both size fractions, the richness and relative abundance of bacteria detected only at specific sites decreased with stream order, whereas the relative abundance of widely distributed taxa increased with increasing stream order. Patterns typical of large rivers also emerged in headwater streams. Furthermore, these shifts varied with size fraction and seasonal hydrological processes. The observed patterns in α‐ and β‐diversity likely resulted from the dilution of locally restricted taxa by widespread taxa present throughout the catchment.

Abstract. Understanding aquatic ecosystem metabolism involves the study of two key processes: carbon fixation via primary production and organic C mineralization as total ecosystem respiration (ERtot). In streams and rivers, ERtot includes respiration in the water column (ERwc) and in the sediments (ERsed). While literature surveys suggest that ERsed is often a dominant contributor to ERtot, recent studies indicate that the relative influence of sediment-associated processes versus water column processes can fluctuate along the river continuum. Still, a comprehensive understanding of the factors contributing to these shifts within basins and across stream orders is needed. Here, we contribute to this need by measuring ERwc and aqueous chemistry across 47 sites in the Yakima River basin, Washington, USA. We find that ERwc rates vary throughout the basin during baseflow conditions, ranging from 0 to −7.38 g O2 m−3 d−1, and encompass the entire range of ERwc rates from previous work. Additionally, by comparing to ERtot estimates for rivers across the contiguous United States, we suggest that the contribution of ERwc rates to reach-scale ERtot rates across the Yakima River basin is likely highly variable, but we do not test this directly. We observe that ERwc is locally controlled by temperature, dissolved organic carbon, total dissolved nitrogen, and total suspended solids, which explains 49 % of ERwc variability across the basin using Least Absolute Shrinkage and Selection Operator (LASSO) regression. Our findings highlight the potential relevance of water column processes in aquatic ecosystem metabolism across the entire stream network and that these influences are likely not predictable simply by knowing the position in the stream network. Our results are generally congruent with previous work in terms of locally influential variables, suggesting that the observed variability and suite of associated environmental factors influencing ERwc are potentially transferable across basins.

This study evaluates the performance of various Digital Elevation Models (DEMs) and Survey of India (SOI) topographic sheets in fluvial morphometry using the upper part of the Jiadhal River basin as a case study. The primary objective is to compare and assess the interchangeability of data derived from SRTM, ASTER, AW3D, TanDEM-X, Cartosat 30m DEMs, and SOI 1:50,000 scale topographic sheets. Key morphometric parameters such as stream order, stream length, drainage density, drainage texture, basin area, perimeter, and relief aspects were derived from each dataset and compared to determine the influence of spatial resolution on hydrological studies. Results indicate that DEMs such as AW3D, Cartosat capture finer landform features better and provide added precision in stream delineation, mostly in flat terrains, as compared to other data sources. Despite variations in satellite’s spatial resolutions, parameters and sensor systems, the derived fluvial morphometric parameters and statistics from the DEMs and topographic sheets showed significant agreement overall. The study highlights that AW3D, Cartosat 30m DEM outperforms SRTM, ASTER and TanDEM-X in stream path delineation, and are recommended for future morphometric and river basin studies. This research highlights the significance of choosing appropriate DEMs based on their spatial resolutions as well as terrain characteristics of the river basin for improved morphometric and river basin analysis.

Watershed management is crucial for sustaining water resources, controlling soil erosion, and mitigating flood risks. Prior to management, it is important to understand characteristics of watershed through morphometric analysis, which lays foundation for informed decision-making, conservation strategies, and sustainable land use planning in a watershed. Despite the progress made in watershed management studies, a significant research gap exists in applying an integrated approach of morphometric and hypsometric analyses using high-resolution datasets. This study abridges such gap by integrating morphometric analysis and hypsometric analysis by applying remote sensing (RS) and geographic information system (GIS) in Koyna River basin of Maharashtra, India. Furthermore, this study prioritizes sub-watersheds for soil and water conservation using RS and GIS techniques. The watershed boundary was delineated, and key morphometric parameters, i.e., basin area, stream order, stream length, and drainage density, were derived from high-resolution digital elevation model. The basin was classified as a 6th order basin with a drainage density of 0.83 km km-², indicating a coarse drainage pattern. The elongation ratio (0.8) indicated an elongated basin shape, associated with moderate slopes and differential erosion susceptibility, particularly in the upstream regions. The hypsometric analysis (HI = 0.5) suggested a mature basin condition, reflecting an equilibrium state between erosional and depositional processes. Sub-watershed prioritization revealed that three sub-catchments, i.e., SW9, SW10, and SW5 ranked highest in vulnerability and requires immediate implementation of soil and water conservation measures, while others showed relatively stable conditions. Findings of this study highlighted that accurate watershed delineation, supported by morphometric and hypsometric evaluation in a GIS framework, is essential for effective hydrological assessment and resource management. The approach provides a scientific basis for targeted watershed prioritization, enabling site-specific interventions and supporting long-term sustainability of land and water resources.

Water, an essential element for rainwater harvesting (RWH), plays a pivotal role in addressing water scarcity and enhancing community resilience. This study conducted a comprehensive analysis of water storage in the Pothowar region, which spans approximately 23,204 square kilometers across five districts: Islamabad, Rawalpindi, Chakwal, Attock, and Jhelum. The objective was to assess the availability, demand, and utilization of water reservoirs using GIS technology to identify potential storage sites. The study utilized advanced tools, starting with the acquisition of a 12.5m Digital Elevation Model (DEM) from ALOS PALSAR, followed by data refinement using the Fill tool. Flow direction analysis and watershed delineation in ArcGIS 10.8.2 revealed 6,508 sub-watersheds and outlets. An Analytical Hierarchy Process (AHP) model was employed to assign weights to factors such as soil, land use, rainfall, stream order, drainage density, and slope, enabling the classification of suitability classes. The results indicated that 41% of the region was classified as moderately suitable, with 3.79% rated as very highly suitable, 44.81% as highly suitable, and 10.40% as not suitable. Specific mini dam sites were proposed based on suitability, with 121 outlets classified as very highly suitable, 3,655 as highly suitable, 2,188 as moderately suitable, and 690 as not suitable. This comprehensive analysis enhances the understanding of the region's hydrological dynamics, supporting informed decision-making for sustainable water resource management aligned with both developmental and environmental objectives. By combining advanced geospatial tools and a collaborative approach, this study offers a cutting-edge framework for regional water resource management.

Notwithstanding that Otammiri river basin is one of the most important watersheds in Imo State, its hydrology is not well known. Good understanding of a basin drainage system and morphometry is fundamental for watershed management. Therefore, the aim of this study is to investigate the morpho-hydrological attributes of Otammiri watershed using geospatial technique. Landform, sub-catchment, drainage mapping, linear and areal morphometry analysis of the basin has been carried out by analyzing SRTM DEM-30 data using ArcGIS10.5 and supher11. Strahler (1964) stream order method was used for stream ordering. This study revealed that the basin is divided into 3 wings as a result of the confluence of Otammiri and Nworie river. The study area is rough and situated in surface of elevation range of 10m to 140m above mean sea level with total number of 82 streams of total length, 105 kilometers draining a landed area of approximately 113 square kilometers. The elevation of the basin decreases from north eastern part to the southern part with a large portion of the surface situated in a terrain of slope between 1 degree and 90 degrees. Results revealed that there are one (1) fourth order streams, three (3) third order streams, nineteen (19) second order streams and fifty-nine (59) first order streams. The river network revealed a dendritic pattern and a stream frequency of 0.7257, drainage density 0.9292 km-1, circulatory ratio of 0.320 and elongation ratio of 0.770. These digital derivatives attest that geospatial technique is effective in characterization of hydro-morphometric attribute of a river basin.

The present study aims to demonstrate the prioritization of micro-watersheds in morphometric analysis using remote sensing and GIS-based approaches. Geographical Information System (GIS) and remote sensing are effective tools for managing water resources and identifying drainage patterns. GIS and image processing tools have been used to identify and analyze morphological aspects of basins. Mathematical formulas were used to calculate morphometric characteristics including linear, aerial, and relief parameters. The desired outcome is to find an enhanced comprehension of the geological, geomorphological and hydrogeological factors of the sub- basin. Twenty metrics have been gathered to gain a better understanding of the features of the basin. The Amaravathi sub-basin originates in a valley near Munnar in Kerala’s Western Ghats area. The river flows from the Anaimalai Hills to the Palani Hills before entering the Cauvery River in Karur district. The Amaravathi sub-basin is a stream of the eighth-order. The 8th-order basin comprises 48 micro-watersheds, including 37 5th-order micro-watersheds, 8 6th-order micro-watersheds, 27th-order micro-watersheds, and 1 8th-order micro-watershed. The study found that a first-order stream has the greatest stream length due to the basin’s complicated geostructural structure. The Amaravathi sub-basin’s drainage pattern is dendritic in the higher zone and sub-dendritic in the surface region. The Amaravathi sub-basin covers 8,549.8 square kilometers and is located in Tamil Nadu’s districts of Karur, Dindigul, Thiruppur, and Coimbatore. The basin’s borders have been obtained through Survey of India (SOI) toposheets, and the digital elevation model and maps were generated with ArcGIS 10.2.2 software. Several morphometric approaches were used to determine linear, relief, and area characteristics. The research focuses on measurements of shape and structure, such as stream order (Nu), stream length (Lu), bifurcation ratio (Rb), drainage density (Dd), stream frequency (Fs), texture ratio (T), elongation ratio (Re), circularity ratio (Rc), and form factor (Rf) and so on. The results of the various parameters show the features of the Amaravathi sub-basin. This method is crucial for sustainable water resource management, land use, and scientific assessment of micro-watersheds in data-inadequate areas.

The geological processes influence the Al-Najaf-Karbala Plateau. The objective is to evaluate each fan's hydrological characteristics, such as drainage system, structural elements, and surface water flow patterns. It integrates satellite imagery and field data into a GIS framework using remote sensing methods. According to a hydrological study, the Al-Najaf-Karbala plateau drainage network primarily flows from southwest to northeast. The fan may be divided into six different watersheds, each with five stream orders, using morphometric analysis. Wsh1 has many stream orders, whereas Wsh 2 has the lowest. Floodwaters are expected to flow more quickly at Watershed 2's lowest point. Watershed 4 has the largest bifurcation ratio, indicating steep slopes and rocks with low permeability. The drainage texture value in the Al-Najaf-Karbala Plateau ranges from coarse to extremely coarse due to large and resistant rocks in the area. Watershed 1's increased stream frequency indicates lower infiltration rates and stronger surface runoff. All watersheds have extended or fern-shaped basins, which suggests a decrease in flow rate that necessitated a longer time for water to accumulate. In terms of basin relief, watershed 6 has the highest relief value among all the watersheds under study, whereas watershed 1 has the lowest relief value. Watershed 4 features longer streams and a softer gradient than Watershed 3, which is steeper.

Sorowako and surrounding areas are geologically influenced by Sulawesi’s microcontinent movement, which has produced several geological phenomena. Morphometry is one of the parameter that can reveal geological condition of particular area. Morphometric analysis of water catchment area in Sorowako and surrounding areas using Bifurcation Ratio (Rb) and Drainage Density (Dd) can provide comprehensive information on level of deformation in Sorowako region. Analysis result of Bifurcation Ratio Index (Rb) on water catchment area reveals that Rb<3 value is dominant and equally spread in Sorowako region, it varies from 0.094 to 2.888. However in several place the value of Bifurcation Ratio (Rb) index is more than 5 (Rb>5) with varies from 5.142 to 10.250. Drainage Density (Dd) value ranges from 0.907 to 8.422 with an average value is 4.125 describes impact of erosion and tectonic on Sorowako region. Based on morphometric analysis of two parameters, Sorowako and surroundings area have been heavily impacted by tectonic activity on Sulawesi island. In western, eastern and northern regions on water catchment area, level of deformation tends to be higher compared to southern region. This can be seen on analysis result of water catchment area 43, water catchment area 196, and water catchment area 302 that have relatively larger number of stream orders, and also have Bifurcation Ratio’s value less than three (Rb<3). Information of tectonic deformation level on Sorowako region through morphometric analysis is important to further use as a basis for water catchment area management planning, so that it can identify areas prone to geological disasters. This fairly high level of tectonic deformation also believed to be a controlling factor for nickel grade contained in Sorowako and surrounding areas which allow supergene enrichment to occurs in rocks.

Unraveling the carbon fraction heterogeneity in China's Rivers: Hydrology, nutrients, and dam regulation.

This study presents an assessment of hydrological diversity (hydrodiversity) in Rio Grande do Norte, Brazil, aiming to identify potential correlations between hydrodiversity and hydrological features of geoheritage. The methodology applied a quantitative approach based on mean annual precipitation, river discharge, reservoir distribution, and stream order. These variables were analyzed within a 5.5 km grid using GIS tools. The four resulting sub-indices were normalized through the Maximum Possible Value method to ensure equal weighting in the final Hydrodiversity Index, which classifies areas into four levels: low, medium, high, and very high. Results show the highest hydrodiversity values in the eastern region and along the Apodi–Mossoró River, where rainfall and drainage density are greatest. The Hydrodiversity Index map was examined alongside land use data and the distribution of 22 previously identified hydrological sites (hydrosites). A greater concentration of anthropogenic land use was noted in areas with medium to high hydrodiversity, especially in the east and along the northern coast, emphasizing the role of water resources in territorial dynamics. The findings indicate that no hydrosites are located within areas of Very High Hydrodiversity; however, more than 50% of the hydrosites correspond to areas classified as High Hydrodiversity. While further research is required to better elucidate the relationship between geodiversity and geoheritage, these results underscore both the complexity of the link between hydrodiversity and water-related geoheritage, as well as the importance of employing an index to inform conservation and management strategies.

Vegetation is one of the factors that play a significant role in determining the rate of soil erodibility or susceptibility to erosion. The study is aimed at examining effect of vegetation and organic matter on erodibility status of soil in Ukpom Abak River Basin of Akwa Ibom State, Nigeria. Data were collected with used of systematic belt transects and the simple random sampling technique. Quadrats of 5m X 120m dimensions were established with twenty-four (24) quadrats of 5m by 5m. Thereafter 20 quadrats were randomly selected. Soil samples were collected from each stream order at a depth of 0-15cm and were analysed for soil physical and chemical properties. Pearson’s product correlation, stepwise multiple regression and ANOVA were the analytical tool employed for data analysis. The results revealed that soils in study area showed low K-factor. Vegetation result revealed that stems of herbaceous species enumerated (herbaceous cover) were high (66%), while the density of shrub was low (25%). In addition, density of herbs (r = -0.401, p>0.05) and herbaceous cover (r = -0.011, p>0.05) were inversely related to the K-factor of the River Basin, while density of shrub (r = 0.241, p>0.05) was positively related to K-factor. There was a positive correlation between organic matter and K-factor (r = 0.942, p<0.05). Based on the findings, the study discourage any form of illegal logging activities and deforestation, because vegetation added organic matter that bind soil aggregate, thus reduces erosion and soil loss.

Pesticide pollution and its impact on biota: Contrasting shrimp-based biomonitoring results between headwater and middle-course streams.

This study conducts a comparative morphometric analysis of the Alo and Molamahu sub-watersheds, located in the upstream Limboto Watershed, Gorontalo Province, Indonesia, to assess flood risk. Using the National Digital Elevation Model (DEMNAS) with an 8-m spatial resolution, classical morphometric parameters were derived through remote sensing and Geographic Information System (GIS) techniques. Both sub-watersheds share a maximum stream order of 4 and exhibit relatively high drainage density and stream frequency, indicating rapid surface runoff. However, the Molamahu sub-watershed is larger, steeper, and has a higher ruggedness number than Alo, suggesting greater erosion potential and higher susceptibility to landslides and flash floods. In contrast, Alo shows gentler slopes but remains flood-prone due to short overland flow paths. The analysis demonstrates that morphometric characteristics directly influence flood dynamics, highlighting the need for tailored watershed management. Recommended strategies include erosion control and slope stabilization in Molamahu, and water retention measures in Alo, supported by broader reforestation efforts across the Limboto system.

The significance of long-term biodiversity monitoring studies for the protection of natural biodiversity and human well-being is well recognised by the Turkish scientific community. Despite understanding the ecological importance of freshwater ecosystems, spatially or temporally congruent studies using high resolution biodiversity monitoring data from Turkish freshwater resources remain scarce. To determine a biodiversity baseline for future studies, biological and environmental sampling was carried out in 15 different locations from the highly anthropogenically impacted Bakırçay River and its catchment in Western Anatolia between 2017 and 2018. A total of 17 fish species from 10 families were recorded, belonging mainly to the Cyprinidae and Leuciscidae families. These included six non-native, six regionally endemic, and five native species. The endangered endemic Alburnus attalus was the most widespread species, whereas several non-native species were restricted to single sites. Patterns in community composition were primarily associated with pH and stream order. However, community metrics such as species richness, Pielou’s evenness, and the Shannon-Wiener diversity index were not significant. Intensifying anthropogenic activity within the Bakırçay basin suggests that sources of pollution and other detrimental stressors like non-native species should be managed to protect riverine biodiversity and maintain the provision of ecosystem services. Our findings therefore not only present a baseline for future studies on fish biodiversity and community composition, but also the possible onset of future monitoring studies in the region. Our findings underline the importance of long-term biomonitoring studies for the conservation of Türkiye’s freshwater ecosystems to monitor changes occurring over time.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-14709-2.

ABSTRACT Accurate detection data are imperative to assess distributions and habitat‐associations for species of conservation need. Environmental DNA (eDNA) sampling is an effective tool to obtain detection data across large geographic scales; however, most eDNA studies do not account for environmental variation that could influence detection. Hierarchical modelling can be used to identify factors important to species occurrence while accounting for such factors. Local extirpations and significant population declines have been documented across the range of the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) due to water quality and habitat degradation, but a paucity of information on the current distribution and status of hellbenders remains for certain regions. We conducted a state‐wide eDNA survey to (1) investigate the current distribution of hellbenders in Kentucky, a state which lacks extensive hellbender occurrence information, (2) evaluate habitat associations for hellbenders in this region and (3) identify environmental factors that influence eDNA detection. Environmental DNA samples, water chemistry and habitat data were collected from 90 sites state‐wide, 27 of which had historic records. We ran multiscale Bayesian occupancy models to determine occupancy and detection probabilities at each site, and to identify water chemistry, local habitat and landscape factors associated with hellbender occupancy and eDNA detection. Hellbender eDNA was detected at 22 sites total, including 12 (44%) historic locations. We found that total organic carbon in the stream significantly hindered eDNA detection and that local habitat quality was more important for hellbender presence than water chemistry or upstream catchment land cover. Hellbender occupancy was positively associated with the percent cobble, gravel and bedrock in the streambed and stream order, and negatively associated with the percent fine sediment in the streambed. Our results indicate that hellbender populations have significantly declined in Kentucky, and the quality of available stream substrate is critical for hellbender presence. This study demonstrates that by applying hierarchical modelling to large‐scale eDNA sampling, we were able to make robust inferences about factors associated with hellbender occurrence and eDNA detection.

ABSTRACTBased on data collected from 31 sampling sites during June and August 2018 in the three ordered rivers (the tributaries of the Anning River, the Anning River, and the lower Yalong River), fish assemblages in the region were investigated regarding their spatial variations and their relationship with environmental factors. Totally, 48 species were collected, with 47 being native and one being exotic. Among them, one was classified as endangered. Fish species diversity increased first and then decreased, reaching its peak in the mid‐order river. Obvious variations were found in fish assemblages depending on the stream order. There were three site groups: one covering the tributaries of the Anning River, one covering the Anning River, and one covering the lower Yalong River. From low‐ to high‐order rivers, the alterations of key species within the fish communities exhibited a turnover pattern. The fish assemblages in the low‐order river were primarily dominated by Nemacheilida, whereas the mid‐order river and the high‐order river displayed a dominance of Gobioninae and Cultrinae, respectively. These spatial variations might be primarily impacted by water depth and turbidity. Moreover, this study highlights the critical role of mid‐order rivers in sustaining fish diversity within dendritic stream networks of mountain rivers.