Stream Segments Research Articles

Indirect Effects and Context Dependency in Stream Fish Invasions

ABSTRACTAimInvasion ecology is replete with a body of well‐supported yet contradictory evidence for numerous invasion hypotheses, likely as a result of context dependency. Context dependency in invasion studies can arise in two ways: (1) apparent, when results differ between studies solely due to methodical differences, or (2) mechanistic, when results truly differ due to ecological processes. One form of apparent context dependency occurs when causally linked factors associated with invasion success (hereafter, invasion drivers) either mask or enhance each other's effect on invasion success. Mechanistic context dependency can occur when regional scale processes modify the influence of local scale invasion processes. Together, apparent and mechanistic context dependency likely give rise to conflicting support between invasion hypotheses via confounding effects of causally related invasion drivers and region‐specific invasion processes.Location2339 stream segments in two ecoregions of the United States.MethodsUsing local scale stream fish community data for two distinct ecoregions, we constructed identical path models to estimate the direct and indirect effects of invasion drivers on nonnative richness. We chose one variable to index invasion drivers from each of the following categories: propagule pressure, natural abiotic, anthropogenic abiotic and biotic factors.ResultsWe found evidence of apparent context dependency through the presence of indirect effects, in which the effects of propagule pressure and biotic factors on nonnative richness were modulated by abiotic factors. The indirect effects of invasion drivers differed between both regions, providing evidence of mechanistic context dependency.Main ConclusionsApparent and mechanistic context dependency can lead to conflicting evidence between studies of invasion hypotheses. Accounting for indirect effects of invasion drivers is important in gaining a more general understanding of the invasion process. Furthermore, because indirect effects varied regionally, it is important to understand the large‐scale processes that contextualise local invasion processes.

A comparison of detection probabilities for the patch‐nosed salamander (Urspelerpes brucei) using six survey methods

AbstractThe patch‐nosed salamander (Urspelerpes brucei), discovered in 2007, is a small amphibian endemic to northeast Georgia (GA) and northwest South Carolina (SC), USA. Given its recent discovery, little is known about the species’ conservation status. This is especially true in SC where this species is known from 4 stream localities in total, making monitoring and inventory a current priority. We applied 6 survey methods in 3 streams known to harbor the species (1 in GA; 2 in SC) using a randomized complete block design and conducted replicate surveys using each method 5 to 6 times between August 2021 and June 2022. We used occupancy models to estimate the probability of patch‐nosed salamanders using a randomly selected 5‐m stream segment while simultaneously investigating the effects of method and conditions on detectability. We recorded a total of 90 patch‐nosed salamander detections (60 from GA; 32 from SC) across 22 of the 39 stream segments in our study. Occupancy was similar in 2 streams (SCSouth: 0.94 [0.22 to −1.00 95% CI]; GARef: 0.70 [0.41–0.89 95% CI]) where it was also 3 to 4 times higher than in a third (SCNorth: 0.16 [0.04–0.47 95% CI]), though mechanisms driving the differences remain unclear. While we detected patch‐nosed salamanders with all 6 survey methods, aquatic and terrestrial versions of both leaf‐litter bags and area‐unconstrained surveys were more effective than randomized area‐constrained searches. Terrestrial applications of each method were biased toward adult detections while aquatic applications were biased toward larvae. Patch‐nosed salamander detectability was maximized during conditions (cloudless skies, >5 cm rainfall in the prior week, soil temperatures ≥20°C) that align with spring (March–June) in the species' range. A power analysis based on detectability estimates suggests that, under ideal sampling conditions, either 5 temporally replicated area‐unconstrained searches or a survey of 5 spatially replicated leaf‐litter bags (per 5‐m segment) are necessary to confirm presence‐absence of patch‐nosed salamanders with 90% confidence. Given that the 2 SC streams included in our study represent nearly half of the species’ range in that state, but collectively yielded only about one‐third of total detections and exhibited considerable disparity in occupancy, we recommend more work to clarify resource selection patterns, subpopulation stability, and potential threats to patch‐nosed salamanders in SC specifically.

Effects of Channelization on Macroinvertebrate Assemblages in a Small Stream: The Case of Awetu in Jimma City, Ethiopia

Freshwater ecosystems are increasingly modified worldwide by anthropogenic activities. Land use change is one of the leading factors responsible for stream ecosystem degradation. Physical habitat disturbance due to channelization is among the factors responsible for the loss of biodiversity and degradation of river water quality worldwide. Since 2020, Jimma City municipality has been beautifying the city and one of the activities is channelizing using concrete embankment, a part of the Awetu stream that runs through the city. The main aim of this study is to assess the effect of channelization on macroinvertebrate assemblages and the water quality of the Awetu stream. A cross-sectional study was conducted in April 2022. Macroinvertebrates, water samples, and habitat data were collected from 21 sampling sites along the three segments of the stream (upstream, channelized, and downstream). Data were analyzed for different macroinvertebrate metrics and water quality parameters. Canonical Correspondence Analysis was used to examine the overall relationship between macroinvertebrate assemblages and water quality parameters. The upstream site has better macroinvertebrate assemblages than channelized and downstream sites (p<0.05). The downstream site showed better assemblage compared to the channelized site, though it was not significant. Regarding water quality parameters, a significant variation was observed between channelized and, un-channelized sites (upstream and downstream) (p<0.05). The habitat condition score varied from 47 (poor) at channelization to 150 (suboptimal) upstream. Upstream sites were found to have relatively better macroinvertebrate assemblages, better water quality, and good habitat conditions. The downstream sites had lower macroinvertebrate assemblages, poor habitat conditions, and degraded water quality compared to the upstream sites. The channelized segment had the poorest habitat, with poor macroinvertebrate assemblages and water quality. Thus, the conservation of habitat conditions along the channelized segments of the Awetu stream is recommended to improve the water quality and macroinvertebrate assemblage.

Effects of Language Proficiency on Selective Attention Patterns at Segmenting Boundaries in English Audio Sentences.

Normative perceptual segmentation facilitates event perception, comprehension, and memory. Given that native English listeners' normative perceptual segmentation of English speech streams coexists with a highly selective attention pattern at segmentation boundaries, it is significant to test whether Chinese learners of English have a different attention pattern at boundaries, thereby checking whether they perform a normative segmentation. Thirty Chinese learners of English with relatively higher language proficiency (CLH) and 26 with relatively lower language proficiency (CLL) listened to a series of English audio sentences. Meanwhile, they were asked to press the key whenever a phonetic probe "ba" occurred. Response time to "ba" reflects the attention where "ba" is located at segmentation boundaries. The results revealed that, (1) relative to native English listeners' highly selective attention pattern, the CLH group showed a relatively selective attention pattern, while the CLL group displayed a non-selective attention pattern. (2) Both the CLH group and natives had better recognition memory than the CLL group. (3) Both the CLH group and natives' attention at segmentation boundaries was not correlated with their memory for sentences, while the CLL group's attention at boundaries was correlated with memory. These findings suggest that (1) Chinese learners of English did not perform a normative segmentation, which shows the effect of English proficiency on perceptual segmentation; (2) English proficiency has a superior effect on memory for sentences, while perceptual segmentation would come next to support memory by providing structure for memory construction if English proficiency is not high; (3) a comparison of attention patterns between Chinese learners and natives can provide a reference for potential intervention to rectify non-natives, thereby improving their perception of English speech streams.

Adaptive Optimization and Dynamic Representation Method for Asynchronous Data Based on Regional Correlation Degree.

Event cameras, as bio-inspired visual sensors, offer significant advantages in their high dynamic range and high temporal resolution for visual tasks. These capabilities enable efficient and reliable motion estimation even in the most complex scenes. However, these advantages come with certain trade-offs. For instance, current event-based vision sensors have low spatial resolution, and the process of event representation can result in varying degrees of data redundancy and incompleteness. Additionally, due to the inherent characteristics of event stream data, they cannot be utilized directly; pre-processing steps such as slicing and frame compression are required. Currently, various pre-processing algorithms exist for slicing and compressing event streams. However, these methods fall short when dealing with multiple subjects moving at different and varying speeds within the event stream, potentially exacerbating the inherent deficiencies of the event information flow. To address this longstanding issue, we propose a novel and efficient Asynchronous Spike Dynamic Metric and Slicing algorithm (ASDMS). ASDMS adaptively segments the event stream into fragments of varying lengths based on the spatiotemporal structure and polarity attributes of the events. Moreover, we introduce a new Adaptive Spatiotemporal Subject Surface Compensation algorithm (ASSSC). ASSSC compensates for missing motion information in the event stream and removes redundant information, thereby achieving better performance and effectiveness in event stream segmentation compared to existing event representation algorithms. Additionally, after compressing the processed results into frame images, the imaging quality is significantly improved. Finally, we propose a new evaluation metric, the Actual Performance Efficiency Discrepancy (APED), which combines actual distortion rate and event information entropy to quantify and compare the effectiveness of our method against other existing event representation methods. The final experimental results demonstrate that our event representation method outperforms existing approaches and addresses the shortcomings of current methods in handling event streams with multiple entities moving at varying speeds simultaneously.

Concentration of Heavy Metals in Water, Soil, and Vegetables Irrigated with Industrial Wastewater in Oromia Special Zone Surrounding Finfinne, Ethiopia

Background: This study sought to determine the spatial distribution of heavy metal concentrations in water, soil, and vegetables that were irrigated with industrial wastewater in Ethiopia’s Oromia Special Zone. We aimed to make recommendations for corrective actions that would reduce the negative environmental effects of untreated waste. Methods: Five sampling sites were meticulously chosen within the Sululta, Laga Tafo Laga Dadi, Galan, Sabata, and Burayu regions, taking into account the varying stressors across the upper stream, middle stream, and downstream segments of the rivers. These sampling sites were strategically selected to capture a comprehensive understanding of heavy metal aggregation within the area. The sampling encompassed the collection and analysis of 25 water and wastewater samples, 13 soil samples, and 8 vegetable samples. The distribution of sampling efforts was tailored to reflect the availability of irrigation sites within the respective areas, resulting in a harmonized amalgamation of 5, 3, and 1 samples for water and wastewater, soil, and vegetable matrices, respectively. Results: The lettuce in the Gelan area had the greatest quantity of lead, suggesting higher cancer risk. The sites of Gelan and Burayu had significant levels of chromium contamination in their lettuce, followed by their cabbage, according to the WHO/FAO and USEPA. As a result, those who eat vegetables that have high levels of heavy metal contamination may be at risk for developing cancer. Conclusion: The concerned institutions and stakeholders must work to mitigate the high concentration of heavy metals in water, soil, and vegetables by the installation of treatment plant.

Decisive significance of lineaments on groundwater occurrence in the Khapri watershed of Deccan Volcanic Province (DVP), district Dangs, Western India

This study investigates the influence of geological lineaments on groundwater occurrence in the Khapri watershed, Dangs district, Gujarat, where rugged terrain and less transmissible basaltic rocks limit infiltration despite high rainfall (2000 mm). Lineaments were mapped using IRS LISS-III satellite data and eight hill-shades generated at various azimuth angles (45°, 90°, 135°, 180°, 225°, 270°, 315°, and 360°) from Carto-Digital Elevation Model (DEM) in GIS environment to ensure maximum extraction. These lineaments, validated through Google Earth and ground-truthing, were categorized into positive (ridges, plateaus, dykes) and negative (joints, fractures, straight stream segments) based on their contribution to water infiltration. The comprehensive lineament map revealed dominant NNE-SSW and ENE-WSW orientations. Positive lineaments largely induce runoff, while negative lineaments support water infiltration. The study indicates a moderate correlation between lineament densities and the groundwater regime. Regions with high negative lineament density exhibit lower groundwater fluctuation, indicating better groundwater occurrences, while areas with high positive lineament density show greater fluctuation, indicating lesser groundwater occurrence. Linear regression analysis indicates that 48% and 50% of the variation in groundwater fluctuation is explained by positive and negative lineament density, respectively. This analysis emphasizes the importance of identifying and mapping negative lineaments for targeting groundwater resources in hard rock terrains.

Factors contributing to pesticide contamination in riverine systems: The role of wastewater and landscape sources

Wastewater treatment plant (WWTP) discharges can be a source of organic contaminants, including pesticides, to rivers. An integrated model was developed for the Potomac River watershed (PRW) to determine the amount of accumulated wastewater percentage of streamflow (ACCWW) and calculate predicted environmental concentrations (PECs) for 14 pesticides in non-tidal National Hydrography Dataset Plus Version 2.1 stream segments. Predicted environmental concentrations were compared to measured environmental concentrations (MECs) from 32 stream sites that represented a range of ACCWW and land use to evaluate model performance and to assess possible non-WWTP loading sources. Statistical agreement between PECs and MECs was strongest for insecticides, followed by fungicides and herbicides. Principal component analysis utilizing optical fluorescence and ancillary water quality data identified wastewater and urban runoff sources. Pesticides that indicated relatively larger sources from WWTPs included dinotefuran, fipronil, carbendazim, thiabendazole, and prometon whereas imidacloprid, azoxystrobin, propiconazole, tebuconazole, and diuron were more related to urban runoff. In addition, PECs generally comprised a low proportion of MECs, which indicates possible dominant loading sources beyond WWTP discharges. Cumulative potential toxicity was higher for sites with greater ACCWW and/or located in developed areas. Imidacloprid, fipronil, and carbendazim accounted for the largest portion of predicted potential toxicity across sites. The chronic aquatic life toxicity benchmarks for freshwater invertebrates were exceeded for 82 % of the imidacloprid detections (n = 28) and 47 % of the fipronil detections (n = 19). These results highlight the ecological implications of pesticide contamination from WWTP discharges and also the potential legacy effects from accumulated soil and groundwater sources. Pesticide management strategies that mitigate both current and historical impacts may improve the health of aquatic ecosystems.

Design and implementation of a BigQuery dataset and application programmer interface (API) for the U.S. National Water Model

We introduce an open-source web-based Application Programming Interface (API) developed within a representational state transfer (REST) architecture framework that provides access to the operational streamflow forecasts from the U.S. National Water Model (NWM). We built this API within the Google Cloud infrastructure, taking advantage of Google's API Gateway, BigQuery, and the Google Cloud Run architecture. We ran a data transformation from netCDF to tabular formation then ingested data into BigQuery using Apache Beam parallel processing technology. The API activates functions deployed to Cloud Run that executes SQL queries within the BigQuery data warehouse. The API gives users granular control to specify queries based on forecast type, reference datetime, stream segment specifics, and forecast ensemble members. This API greatly simplifies access and use of current and historic NWM forecasts, an otherwise arduous task due to the large volume of data and unwieldy storage methods. Retrieved forecast data can be used for many critical water management applications providing actionable intelligence for, e.g., flood management, safety, recreation, agriculture, and related uses.

Event-based depth estimation with dense occlusion.

Occlusions pose a significant challenge to depth estimation in various fields, including automatic driving, remote sensing observation, and video surveillance. In this Letter, we propose a novel, to the best of our knowledge, depth estimation method for dense occlusion to estimate the depth behind occlusions. We design a comprehensive procedure using an event camera that consists of two steps: rough estimation and precise estimation. In the rough estimation, we reconstruct two segments of the event stream to remove occlusions and subsequently employ a binocular intersection measurement to estimate the rough depth. In the precise estimation, we propose a criterion that the maximum total length of edges of reconstructed images corresponds to the actual depth and search for the precise depth around the rough depth. The experimental results demonstrate that our method is implemented with relative errors of depth estimation below 1.05%.

Landscape influences on thermal sensitivity and predicted spatial variability among brook trout streams in the southeastern USA

AbstractWarming water temperatures as a result of climate change pose a major threat to coldwater organisms. However, the rate of warming is not spatially uniform due to surface‐ground‐water interactions and stream and watershed characteristics. Coldwater habitats that are most resistant to warming serve as thermal refugia and identifying their locations is critical to regional aquatic conservation planning. We quantified the thermal sensitivity of 203 streams providing current and potential habitat for brook trout (Salvelinus fontinalis) across nearly 1000 linear km of their native range in the southern and central Appalachian Mountains region, USA, and characterized their spatial variability with landscape variables available in the National Hydrography Dataset. Using the Bayesian framework, we calculated the maximum slope of the logistic function relating paired weekly mean air temperature and stream temperature as an index of stream thermal sensitivity. Streams differed greatly in thermal sensitivity and those with more resistant water temperature regimes (i.e., thermal refugia) were consistently characterized by southerly latitudes and groundwater input. Landscape variables derived from a principal component analysis explained 16% of the variation in thermal sensitivity, indicating that the existing landscape variables were modestly successful in explaining spatial thermal heterogeneity. Using our model and spatial interpolation, we predicted thermal sensitivity at 8695 stream segments potentially suitable for brook trout in the study region. Thermal refugia were more common southward presumably due to higher elevations, but elsewhere they were also clustered at finer spatial scales. Our analysis informs prioritizing habitat conservation and restoration of this native salmonid and other aquatic organisms that depend on coldwater habitats in a warming world.

Mechanical excavation of wetland habitat failed to eradicate invasive American red swamp crayfish (Procambarus clarkii) in Malta

Abstract Invasive crayfish are an important ecological concern in many freshwater ecosystems. Many efforts have been made to eradicate them, but there is very little documentation of the effectiveness of these efforts. Between 2019 and 2020, a restoration project funded by the European Regional Development Fund tried to eradicate invasive American red swamp crayfish Procambarus clarkii from the Fiddien valley system in Malta by mechanically excavating the valley's stream bed and exporting contaminated debris securely off‐site to a dry quarry. Three years post‐intervention, we systematically surveyed the valley system to explore the distribution and relative abundance of the invasive crayfish population. We placed traps in a stratified random sample of stream segments (both those that were included in the original restoration project and those that were not) and recorded catch per unit effort (crayfish caught per trap night) and the size/frequency distribution of crayfish caught. The invasive crayfish were still abundant in the upper reaches of the valley system, and, despite the excavation effort, crayfish were present at the highest relative abundance (4.3–14.8 CPUE, median = 12.3) within the restored area. Despite substantial effort and spending of more than 700,000 €, mechanical excavation did not eradicate invasive crayfish populations. We urge caution for future projects planning to attempt crayfish eradication using this approach and call for much greater impact evaluation, and at the very least post‐project monitoring, to ensure lessons can be learnt from such failures in future.

On the computation of the Basal Envelope Surface of Talwegs using the Analytic Element Method

The stream network is a major feature of a landscape, conveying water, sediment, and solute from hillslopes to the ocean. Noticeably, from a large-scale point of view, the elevation of the talwegs of perennial streams is an important head boundary condition for both surface and groundwater flow originating from hillslopes. Assuming a wireframe (1D) representation of talweg lines, the problem of interpolating elevation between talwegs has received attention for applications such as flood mapping using Height Above Nearest Drainage (HAND, [Nobre et al., 2011]), or groundwater level interpolation in low-conductivity aquifer systems. In this study we propose an alternate definition of this large-scale base level concept introduced by [Wyns et al., 2004], namely the Basal Envelope Surface of Talwegs (BEST) and the associated Height Above the Basal Envelope Surface of Talwegs (HABEST), along with a procedure to compute it using the Analytic Element Method (AEM). It can be defined as the head distribution satisfying Laplace equation (Darcy flow with vanishing divergence), with stream segments set as Dirichlet boundary conditions. The BEST is thus the real part of a complex analytic (holomorphic) function which can be modeled using analytic slit elements, with very low computational requirements and without the need for kriging, as it is often seen in the literature. This analytic model is extended to the case of a non-zero, uniform divergence flow (head distribution satisfying a Poisson equation) which can be useful to analyse groundwater levels at catchment scale.

Multi-scale habitat influences sprainting and group size of a freshwater-obligate smooth-coated otter (Lutrogale perspicillata) in Tungabhadra Otter Conservation Reserve, India

BackgroundThe impact of changing land-use patterns and associated anthropogenic threats on scale-dependent habitat use of semi-aquatic mustelids in scent-marking and social behaviour can provide important insights into the habitat ecology of smooth-coated otters (Lutrogale perspicillata).MethodsWe sampled 180 stream segments (100–400 m) as spatial replicates of 60 1-km2 sites to record indirect evidence (i.e. spraints and mass latrine sites) and group sizes of smooth-coated otters along the Tungabhadra Otter Conservation Reserve (TOCR) during the dry season. To quantify habitat, we recorded stream characteristics, riparian vegetation, and anthropogenic disturbances at the local scale, and hydro-environmental characteristics and land uses at the landscape scale. Using Markovian-chain detection and occupancy models, we assessed the multi-scale habitat use of otters in their selection of suitable areas for scent-marking based on repeated presence-absence data on spraint/latrine locations along the TOCR. We further used linear regression techniques to explore relationships between the number of individuals in smooth-coated otter group and hydro-environmental characteristics, spraint/latrine encounter rate, anthropogenic pressure, land cover, topography, and vegetation.ResultsAt the local scale, the probability of spraint deposition and group size decreased with anthropogenic disturbance while the probability of spraint detections decreased with grass cover. At the landscape scale, the probability of otter site use for spraint deposition and group sizes increased in southeast flowing streams. Spraint deposition increased with the proportion of sugarcane fields, whereas in contrast, group size decreased with proportion of sugarcane fields.ConclusionsOur findings highlight the first empirical evidence on multi-scale habitat use of a southern Indian population of smooth-coated otters in an inland freshwater ecosystem surrounded by the scrub jungle–agriculture matrix. We suggest that habitat models built from analytical approaches that account for correlated detections can avoid biased predictions when estimating occupancy and detection probability of semi-aquatic or riparian mammal communities with linear distributions. Our findings indicate that human activity can impose constraints on the choice of sites used for spraint deposition and preliminary patterns in otter groups. The study provides some crucial evidence on the need to maintain areas with minimal human interference for sustainability of freshwater reserves.

Spatial Variation in Transit Time Distributions of Groundwater Discharge to a Stream Overlying the Northern High Plains Aquifer, Nebraska, USA

AbstractGroundwater transit time distributions (TTDs) describe the spectrum of flow‐weighted apparent ages of groundwater from aquifer recharge to discharge. Regional‐scale TTDs in stream baseflow are often estimated from numerical models with limited calibration from groundwater sampling and suggest much younger groundwater discharge than has been observed by discrete age‐dating techniques. We investigate both local and regional‐scale groundwater TTDs in the Upper Middle Loup watershed (5,440 km2) overlying the High Plains Aquifer in the Nebraska Sand Hills, USA. We determined flow‐weighted apparent ages of groundwater discharging through the streambed at 88 discrete points along a 99 km groundwater‐dominated stream segment using 3H, noble gases, 14C, and groundwater flux measurements at the point‐scale (&lt;7.6 cm diameter). Points were organized in transects across the stream width (3–10 points per transect) and transects were clustered in five sampling areas (10–610 m in stream length) located at increasing distances along the stream. Groundwater apparent ages ranged from 0 to 8,200 years and the mean groundwater transit time along the 99 km stream is &gt;3,000 years. TTDs from upstream sampling areas were best fit by distributions with a narrow range of apparent ages, but when older groundwater from downstream sampling areas is included, the regional TTD is scale dependent and the distribution is better described by a gamma model (α ≈ 0.4) which accommodates large fractions of millennial‐aged groundwater. Observations indicate: (a) TTDs can exhibit spatial variability within a watershed and (b) watersheds can discharge larger fractions of old groundwater (&gt;1,000 years) than commonly assumed.

Stellar Population Properties in the Stellar Streams around SPRC047

We have investigated the properties (e.g., age, metallicity) of the stellar populations of a ringlike tidal stellar stream (or streams) around the edge-on galaxy SPRC047 (z = 0.031) using spectral energy distribution (SED) fits to integrated broadband aperture flux densities. We used visual images in six different bands and Spitzer/IRAC 3.6 μm data. We have attempted to derive best-fit stellar population parameters (metallicity, age) in three noncontiguous segments of the stream. Due to the very low surface brightness of the stream, we have performed a deconvolution with a Richardson–Lucy–type algorithm of the low spatial resolution 3.6 μm IRAC image, thereby reducing the effect of the point-spread function aliased emission from the bright edge-on central galaxy at the locations of our three stream segments. Our SED fits that used several different star formation (SF) history priors, from an exponentially decaying SF burst to continuous SF, indicate that the age–metallicity–dust degeneracy is not resolved, most likely because of inadequate wavelength coverage and low signal-to-noise ratios of the low surface brightness features. We also discuss how future deep visual–near-infrared observations, combined with absolute flux calibration uncertainties at or below the 1% level, complemented by equally well absolute flux-calibrated observations in ultraviolet and mid-infrared bands, would improve the accuracy of broadband SED fitting results for low surface brightness targets, such as stellar streams around nearby galaxies that are not resolved into stars.

Spatio-temporal analysis of geomorphic recovery along an altered ephemeral stream using automated image processing

Ephemeral rivers in the Mediterranean region have been exposed to significant human disturbance over the last century. Recently, there has been a growing interest in restoring their morpho-sedimentary condition, backed by the European Water Framework Directive. Previous research has highlighted the severe geomorphic impacts of sediment extraction, such as reduced channel width and riverbed incision, but the recovery of these channels during annual flows remains poorly understood. This study presents a methodological framework to investigate geomorphologic recovery (signs of landform change) and constraints in the Rambla de Cervera (eastern Spain) from 2018 to 2021. Aerial imagery, LiDAR topography, and field surveys were used for stream segmentation, fluvial landform classification, temporal landform change, and comparison with flow characteristics from a 2D hydraulic model. The study identified three groups of segments with different channel types and recovery mechanisms. Upstream (G1), unconfined valley settings showed minor changes, indicating morphological stability. Middle segments in confined valleys (G2) showed greater alluvial channel recovery and vegetation encroachment in response to flood/no-flood periods. Downstream segments (G3), incised on cemented gravel, were highly responsive to floods but lacked landform stability due to high energy conditions. The findings suggest that channel recovery during annual floods is slow and occurs mainly downstream in degraded areas (G3). Increased sediment flux from upstream and additional sediment storage in new forms are required to recover these channels. This analysis underscores the challenge of interpreting short-term morpho-dynamic changes for long-term river recovery, but provides insight into the morpho-sedimentary conditions required to accelerate recovery of ephemeral streams.

Probabilistic monitoring of meteorological drought impacts on water quality of major rivers in South Korea using copula models

The impacts of drought range from water supply for humans to ecosystems. Drought affects river water quality by disturbing the hydrological regime in a variety of ways, and can degrade water quality by reducing surface and groundwater availability. In particular, drought-induced low flows, reduced nutrient dilution, and extreme increases in water temperature affect various water quality parameters in streams. Furthermore, the effects of drought on stream water quality may vary from season to season and from stream segment to stream segment, which requires careful investigation. In this study, Environmental Drought Condition Index - water quality (EDCI-wq) is proposed using a bivariate copula joint probability model between meteorological drought index and river water quality. Using this, environmental drought with respect to water quality is defined, and it is confirmed that environmental drought with respect to water quality can be routinely monitored through time series analysis and mapping of the proposed EDCI-wq. In addition, in order to express the environmental drought condition more explicitly to the general public, the environmental drought condition is graded into four classes based on the EDCI-wq. Furthermore, the sensitivity of river water quality to meteorological drought was estimated using the copula joint probability model, which allowed us to identify river segments that are relatively more sensitive to meteorological drought events.

Ecological Significance of Aquatic Macroinvertebrates in Headwater Streams

Headwater streams are the starting points of river ecosystems, that consist of an array of unique microhabitats. Most of these stream segments are first-order streams and these aquatic ecosystems provide habitats for many macroinvertebrates including arthropods, mollusks, annelids, nematodes, and turbellarians. These species play a significant role in maintaining the ecological integrity of the river ecosystem. Specifically, their feeding habits of scraping, collecting, shuddering, and predating make a significant contribution to maintaining stable food webs within the stream ecosystems. These macroinvertebrates are highly sensitive to environmental changes and consequently, they have been used as indicators of environmental quality. Although the aquatic macroinvertebrates play a crucial role in headwater streams, they face stresses caused either by nature itself or man leading to their extinction on certain occasions. Global warming, acidification, deforestation, forest fires, industrialization, intensive agriculture, and livestock farming practices have been identified as potential stresses behind the extinction and biodiversity losses of macroinvertebrates in headwater streams. Therefore, the abundance and distribution of macroinvertebrates in headwater streams need to be critically considered in developing criteria for development projects, agricultural practices, and other environmental management strategies to protect and conserve these unique environmental creatures.

Morphometric Status of River Mu Sub-Basin in Makurdi South, Nigeria

River Mu drainage basin morphometric status is assessed against the backdrop of its characteristics and implication on hydrologic processes operating within the watershed. Geospatial techniques of GIS and Remote Sensing was deployed in the analysis and characterization of the basin morphometric attributes. The result showed Mu drainage basin has an area of 1259.26km2, basin perimeter 240.96km, form factor 0.22, circulatory ration 0.27, and drainage texture 0.51. Mu drainage basin is of 4th order with a dendritic pattern of drainage system indicating the homogeneity in texture and lack of structural control. The stream frequency 0.10 stream segments per square kilometer, drainage density (Dd) 0.40km/km2, bifurcation ratio of 4.62 and length of overland flow of 1.25km. The drainage density, bifurcation ratio and circularity ratio value indicate that the basin is of gentle slope, elongated, high infiltration capacity, low run off and may have longer duration of flow peaks, less susceptible to flooding.