Morphometric analysis of Halda River basin, Bangladesh, using GIS and remote sensing techniques.

GIS and remote sensing techniques were effectively used to analyse the morphometric parameters including linear, geometric, basin texture (aerial) and relief aspects of the Halda River Basin, Bangladesh. Along with measuring the morphometric parameters using predetermined formulas, advanced geo-computing tools of spatial analysis, cartography, math, geoprocessing and geometric analysis were employed to carry out the spatial distribution of selected parameters, especially aerial parameters. The linear aspect indicates the basin is six-order and oval-shaped. The bifurcation ratio (4.03) and relevant parameters indicate the moderate effect of geology and structural control is evident. The mean stream length (1.27) and Rho value (ranges between 0.11 and 0.20) indicate high runoff in steep areas and hydrologic storage capacity in flat areas. The stream frequency (0.83), drainage density (1.22), drainage intensity (0.68), infiltration ratio (1.02), length of the overland flow (0.41), and constant of channel maintenance (0.82) indicate the presence of moderate hard rock, less structural disturbances and moderate to high surface runoff in the basin. Basin relief (489 m), relative relief (2.02), ruggedness number (400), Melton's ruggedness number (12.43), and mean slope (9.33%) indicate the potential of high erosion and material transfer. The spatial distribution of selected aerial aspects significantly correlated to elevation and slope. The hierarchical pattern and spatial distribution of the morphometric parameters indicate areas with high slopes and lower-order streams have a high potential to be affected by soil erosion, landslides and flash floods, elsewhere, the areas with low slopes are prone to short-duration riverine floods. The research findings will help policymakers for integrated river basin management, agricultural development, and water management. In addition, researchers of morphohydrological, geological and climatological research will be beneficiary.

Antimicrobial resistance in rural rivers: Comparative study of the Coquet (Northumberland) and Eden (Cumbria) River catchments.

Many studies have characterised resistomes in river microbial communities. However, few have compared resistomes in parallel rural catchments that have few point-source inputs of antimicrobial genes (ARGs) and organisms (i.e., AMR) - catchments where one can contrast more nebulous drivers of AMR in rural rivers. Here, we used quantitative microbial profiling (QMP) to compare resistomes and microbiomes in two rural river catchments in Northern England, the Coquet and Eden in Northumberland and Cumbria, respectively, with different hydrological and geographical conditions. The Eden has higher flow rates, higher annual surface runoff, and longer periods of soil saturation, whereas the Coquet is drier and has lower flowrates. QMP analysis showed the Eden contained significantly more abundant microbes associated with soil sources, animal faeces, and wastewater than the Coquet, which had microbiomes like less polluted rivers (Wilcoxon test, p < 0.01). The Eden also had greater ARG abundances and resistome diversity (Kruskal Wallis, p < 0.05), and higher levels of potentially clinically relevant ARGs. The Eden catchment had greater and flashier runoff and more extensive agricultural land use in its middle reach, which explains higher levels of AMR in the river. Hydrological and geographic factors drive AMR in rural rivers, which must be considered in environmental monitoring programmes.

Impact of climate change on the water resources of the Atbara River using novel hydrological models.

Rivers respond directly to climate change, as well as incorporating the effects of climate-driven changes occurring within their watersheds. In this research, climate change's impact on the Atbara River, one of the main tributaries of the Nile River, was studied. Various statistical methods of analysis were applied to study the basic characteristics of the climatic parameters that affect the discharge of the Atbara River. The three hydrological gauging stations on the Atbara River, namely, the Upper Atbara and Setit reservoirs, Khashm el-Girba reservoir, and Atbara Kilo 3 station, were included in the study. The correlation between the meteorological parameters and the hydrology of the Atbara River and the prediction of the future hydrology of the Atbara River Basin was determined. Many hydrological models were developed and tested to predict the hydrology of the river. Finally, forecasting for river hydrology was built. No significant trend was found in the precipitation in the study area. The developed model simulates the observed data with a high coefficient of determination ranging from 0.7 to 0.91 for the three hydrological gauging stations studied. Results predicted a slight decrease in river discharge in future years.

Productivity declines threaten East African soda lakes and the iconic Lesser Flamingo.

Soda lakes are some of the most productive aquatic ecosystems.1 Their alkaline-saline waters sustain unique phytoplankton communities2,3 and provide vital habitats for highly specialized biodiversity including invertebrates, endemic fish species, and Lesser Flamingos (Phoeniconaias minor).1,4 More than three-quarters of Lesser Flamingos inhabit the soda lakes of East Africa5; however, populations are in decline.6 Declines could be attributed to their highly specialized diet of cyanobacteria7 and dependence on a network of soda lake feeding habitats that are highly sensitive to climate fluctuations and catchment degradation.8,9,10,11,12 However, changing habitat availability has not been assessed due to a lack of in situ water quality and hydrology data and the irregular monitoring of these waterbodies.13 Here, we combine satellite Earth observations and Lesser Flamingo abundance observations to quantify spatial and temporal trends in productivity and ecosystem health over multiple decades at 22 soda lakes across East Africa. We found that Lesser Flamingo distributions are best explained by phytoplankton biomass, an indicator of food availability. However, timeseries analyses revealed significant declines in phytoplankton biomass from 1999 to 2022, most likely driven by substantial rises in lake water levels. Declining productivity has reduced the availability of healthy soda lake ecosystems, most notably in equatorial Kenya and northern Tanzania. Our results highlight the increasing vulnerability of Lesser Flamingos and other soda lake biodiversity in East Africa, particularly with increased rainfall predicted under climate change.14,15,16 Without improved lake monitoring and catchment management practices, soda lake ecosystems could be pushed beyond their environmental tolerances. VIDEO ABSTRACT.

The role of hydraulic conductivity in the Pine Island Glacier's subglacial water distribution.

Global climate warming leads to ever-increasing glacier mass loss. Pine Island Glacier in Antarctica is one of the largest contributors to global sea level rise (SLR). One of the biggest uncertainties in the assessment of glacier contribution to SLR at present are subglacial hydrology processes which are less well known than other ice dynamical processes. We use the Glacier Drainage System (GlaDS) model which couples both distributed and channelized components to simulate the basal hydrology of Pine Island Glacier with basal sliding and meltwater production taken from a full-Stokes Elmer/Ice model fitting observed surface velocities. We find ≈100 km long Rothlisberger channels up to 26 m in diameter extending up glacier from the grounding line along the main trunk of Pine Island Glacier delivering 51 m3 s-1 of fresh water to the grounding line. Channelization occurs at high water pressure because of high basal melt rates (maximum of 1 m a-1) caused by high rates of shear heating in regions with fast ice flow (>1000 m a-1). We simulate a shallow "swamp" of 0.8 m water depth where flow transitions from a distributed system into the channels. We performed a set of 38 sensitivity experiments varying sheet and channel conductivity over 4 orders of magnitude. We find a threshold behavior in distributed sheet conductivity above which basal water pressures are unaffected by changing channel conductivities. Our findings suggest a strong need to better understand controls on basal water conductivity through the distributed system. This issue is critical to improve model-based predictive capability for the Pine Island Glacier and, more generally, the Antarctic Ice Sheet.

The exploratory dataset of isotopic composition of different water sources across Kazakhstan.

This work presents the dataset of stable water isotopes of oxygen and hydrogen measured in water samples from different sources (precipitation, surface water, groundwater, tap water) across Kazakhstan from 2017 to 2018 and from 2020 to 2023. The dataset includes results on isotopic composition of 399 water samples, namely precipitation: event-based (n = 108), cumulative monthly (n = 22); surface water: lakes, reservoirs, brooks, rivers, channels (n = 175), groundwater: shallow and artesian groundwater, spring (n = 85), tapwater (n = 9). For each sample name of the source, location, latitude, longitude and date of sampling, measurement uncertainty (one standard deviation) are available. The samples were assessed by plotting the data in dual δ18O vs. δ2H isotope space with reference to values found in the published literature and fitting a linear regression equation for Astana (event) precipitation. Overall, this is the first dataset covering wide range of sources across Kazakhstan, which could be used by global and regional water resource assessments and studies such as tracing water sources, hydrograph separation and end-member analyses, isotope mass balance, evapotranspiration partitioning, residence time analysis and groundwater recharge.

Dynamics of land cover changes and carbon emissions driven by large dams in China.

The recent surge in dam construction has sparked debates regarding their contribution to carbon neutrality and food security, focusing on trade-offs between production benefits and ecological drawbacks. However, how dams affect carbon emissions and land cover changes, including their spatial differentiations, remains unclear. We quantified spatiotemporal variations in carbon emissions and storage of 137 large dams in China from 1992 to 2020, resulting from land cover change in potentially affected areas. We observed a lesser increase in carbon emissions and a more pronounced increase in carbon storage driven by forest conservation and regeneration within dam-affected areas compared to unaffected areas. Additionally, we noticed an increased grain yield in nearby areas potentially due to increased water availability. Our findings highlight the importance of considering land cover change when assessing carbon neutrality or grain yield at regional and national scales. This study provides useful insights into optimizing dam locations to mitigate future carbon emissions effectively.

Nutrient dynamics in wetland systems associated with hydrological and anthropogenic variations in the south of Samborombón Bay, Argentina.

Wetlands provide numerous ecosystem services to the environment, such as nutrient removal and storage. The aim of this work is to evaluate the nutrient dynamics in different sectors within wetland systems in the south of the Samborombón Bay (Argentina) based on hydrological and/or anthropogenic variations. For this purpose, the hydrological features of the wetland were defined through the analysis of satellite images, precipitation and tidal data, and field surveys. Three sectors were identified in the wetland: one with tidal influence, another which is dependent on rainfall, and another that receives inputs from rainfall and from a sewage effluent treatment plant. In order to analyze the nutrient dynamics, samples of surface water, groundwater, and sediments were collected from these sectors. Measurements of pH and electrical conductivity were determined in situ in water samples, while the concentration of inorganic forms of phosphorus and nitrogen, soluble reactive silica, and organic carbon were determined through laboratory analysis. Also, bioavailable phosphorus, organic matter, pH, and electrical conductivity were determined in the sediment samples collected. Statistical analysis of the data reveals differences between the sectors and allows the interpretation of the dynamics of the studied components in the wetland. Electrical conductivity distinguishes the intertidal sectors of the wetland while components associated with P and N discriminate the sectors with inputs from the sewage effluent treatment plant. On the other hand, soluble reactive silica, organic carbon, and organic matter do not seem to be influenced by the tide or effluent discharge. This study demonstrates that the studied wetland works as a nutrient retention area, providing ecosystem services to local inhabitants. Although these services can be utilized, they require a continuous monitoring over time to provide an early warning in case the variations in P and N cycles could lead to eutrophication or wetland degradation.

Water table depth and plant species determine the direction and magnitude of methane fluxes in floodplain meadow soils.

Methane (CH4) is a powerful greenhouse gas with ongoing efforts aiming to quantify and map emissions from natural and managed ecosystems. Wetlands play a significant role in the global CH4 budget, but uncertainties in their total emissions remain large, due to a combined lack of CH4 data and fuzzy boundaries between mapped ecosystem categories. European floodplain meadows are anthropogenic ecosystems that originated due to traditional management for hay cropping. These ecosystems are seasonally inundated by river water, and straddle the boundary between grassland and wetland ecosystems; however, an understanding of their CH4 function is lacking. Here, we established a replicated outdoor floodplain-meadow mesocosm experiment to test how water table depth (45, 30, 15 cm below the soil surface) and plant composition affect CH4 fluxes over an annual cycle. Water table was a major controller on CH4, with significantly higher fluxes (overall mean 9.3 mg m-2 d-1) from the high (15 cm) water table treatment. Fluxes from high water table mesocosms with bare soil were low (mean 0.4 mg m-2 d-1), demonstrating that vegetation drove high emissions. Larger emissions came from high water table mesocosms with aerenchymatous plant species (e.g. Alopecurus pratensis, mean 12.8 mg m-2 d-1), suggesting a role for plant-mediated transport. However, at low (45 cm) water tables A. pratensis mesocosms were net CH4 sinks, suggesting that there is plasticity in CH4 exchange if aerenchyma are present. Plant cutting to simulate a hay harvest had no effect on CH4, further supporting a role for plant-mediated transport. Upscaling our CH4 fluxes to a UK floodplain meadow using hydrological modelling showed that the meadow was a net CH4 source because oxic periods of uptake were outweighed by flooding-induced anoxic emissions. Our results show that floodplain meadows can be either small sources or sinks of CH4 over an annual cycle. Their CH4 exchange appears to respond to soil temperature, moisture status and community composition, all of which are likely to be modified by climate change, leading to uncertainty around the future net contribution of floodplain meadows to the CH4 cycle.

Hydro-meteorological factors and inflowing nutrients drive water quality in an impounded lake of China's South-to-North Water Diversion Project.

Freshwater lakes play a vital role in global hydrological and biogeochemical cycles, serving various functions and maintaining ecological balance. However, freshwater resources are more vulnerable to deterioration due to multiple stressors. Gaoyou Lake is one of the impounded lakes of the Eastern route of South-to-North Water Diversion Project in China, and as an important source of drinking water, the lake has been routinely monitored. Long-term monitoring of water quality in Gaoyou Lake showed that concentrations of nutrients and chlorophyll a as well as trophic state in the water column increased while water transparency decreased, indicating that the water quality has declined during the last 12 years. Specifically, there was a notable and statistically significant increase in chlorophyll a concentrations, averaging an annual rate of 9.9%. Despite a slight decline in trophic level index until 2014, subsequent years saw an upward trend, ranging from 50.7 to 56.4 and indicating a light eutrophic state. Spatially, the western area displayed higher nutrient and chlorophyll a concentrations. Changes in hydro-meteorological variables and nutrients from inflowing rivers were the main factors correlated with water quality in Gaoyou Lake. Thus, pollution source apportionment and management within Huaihe River basin should be considered to reduce the external loadings of nutrients in order to improve and sustain long-term water quality.

Long-term patterns and changes of unglaciated High Arctic stream thermal regime.

Although water temperature is one of the most important factors influencing hydrochemistry and river ecology, long-term monitoring and modelling of stream thermal temporal variability are uncommon. There is sparse research regarding the thermal regimes of Arctic rivers, especially in Svalbard, a geographical hotspot affected by extreme climate change and Arctic amplification. There is a need for improvement and better understanding of the factors influencing the stream water temperature regime. To address this research gap, we present a study of the non-glaciated arctic catchment, Fuglebekken (Spitsbergen, Svalbard). We propose methods for reconstructing the thermal regime of the Arctic stream based on available in-situ data. This study evaluates different sets of input variables with hourly time steps required to explain the variability in water temperature. The study comprises two modelling approaches, a stochastic transfer function Multiple Input Single Output and a supervised machine learning technique, Gaussian Process Regression, to simulate the water temperature in the years 2005-2022. The ground temperature at a depth of 20 cm and total solar radiation were found to be the main forcings that explain most of the water temperature variability. The outputs of both models showed similar tendencies and patterns. A diurnal warming trend of 0.5-3.5 °C per decade has been detected in stream water temperature throughout the summer season. The highest increase of 6.0 °C in the water temperature in 2005-2022 was found to be present in the second part of June. The outcomes prove that the thermal regime of the Fuglebekken stream is sensitive to ongoing climatic changes. This variability is an important factor with many environmental implications.

Recognizing Agricultural Headwaters as Critical Ecosystems.

Agricultural headwaters are positioned at the interface between terrestrial and aquatic ecosystems and, therefore, at the margins of scientific disciplines. They are deemed devoid of biodiversity and too polluted by ecologists, overlooked by hydrologists, and are perceived as a nuisance by landowners and water authorities. While agricultural streams are widespread and represent a major habitat in terms of stream length, they remain understudied and thereby undervalued. Agricultural headwater streams are significantly modified and polluted but at the same time are the critical linkages among land, air, and water ecosystems. They exhibit the largest variation in streamflow, water quality, and greenhouse gas emission with cascading effects on the entire stream networks, yet they are underrepresented in monitoring, remediation, and restoration. Therefore, we call for more intense efforts to characterize and understand the inherent variability and sensitivity of these ecosystems to global change drivers through scientific and regulatory monitoring and to improve their ecosystem conditions and functions through purposeful and evidence-based remediation.

Impact on urban river water quality and pollution control of water environmental management projects based on SMS-Mike21 coupled simulation.

To explore the impact of expanding Nanyang Sewage Purification Center (NSPC) on the main sewage discharge area of Bai River, we constructed a 2D hydrodynamic-water quality model based on surface water modeling system (SMS) and Mike21. Simulating three sewage discharge conditions in wet, normal, and dry season, we evaluated three indicators (COD, NH3-N, and BOD5) by the single-factor pollution index and provided recommendations for water environment management. The results showed that, maximum absolute error of water level was 0.08 m, percentage bias coefficient of COD, NH3-N and BOD5 were 19.3%, 16.2% and 23.1%, indicating the SMS and Mike21 coupling model was applicable; water quality of the assessment section were upgraded from the original class IV, V, V (Condition 1) to class IV, III, II (Condition 2) and class IV, III, III (Condition 3) in the wet, normal and dry season, indicating that NSPC's expansion had improved the water quality of the assessment section; as the primary pollutant, BOD5 concentration in the downstream was lower than the upstream, which was due to the dilution effect of river. Therefore, on the basis of expanding NSPC, we recommend to remediation of BOD5 by physical, chemical, and biological methods. This study broadens new ideas for the application of Mike21, and provide a reference for the prevention and improvement of river water pollution in urban areas.