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Recycle system is commonly found in a process flowsheet. However, it is one of the systems that are difficult to achieve convergence, especially for novice in process simulation. In this chapter, strategies to converge recycle systems will be covered. Emphasis is placed on sequential modular (SM) approach, which is commonly used in commercial process simulation software. Chapter 1 discussed how SM approach is used to simulate recycle stream simulation briefly. More tips on recycle stream convergence are given in this chapter.

This study is devoted to the ability of carbon fiber material samples impregnated with various amounts of barium iodide and triethylenediamine to remove radioactive methyliodide from air streams. The main sorption characteristics of impregnated UVIS® carbon fiber were determined and the use of this material for purifying of technological gas flows at nuclear power plants was evaluated. The methyliodide trapping efficiency by samples impregnated with barium iodide, TEDA, and their mixture was 83.4 ± 0.8%; 93.1 ± 0.6% and 93.5 ± 0.7% respectively, under the same conditions. The study established a significantly higher capacity (8.3 ± 0.07 mg/cm2) of samples impregnated simultaneously with both chemical compounds toward methyliodide. Under the same test conditions, the values of this parameter for the samples impregnated separately with TEDA and BaI2 were 2.85 ± 0.05 mg/cm2 and 0.86 ± 0.04 mg/cm2, respectively.

This study consider the development of three dimensional analytical solutions for contaminant transport induced by a pumping well near a stream. The solutions were derived for both line-width and finite-width streams based on Green’s function approach. These solutions were implemented in an aquifer that was partially penetrated by the stream and were general enough to be applied to both unconfined and confined aquifers. The analytical solutions were checked to show the effect of stream width, leakance coefficient, distance from the river edge to pumping well and pumping rate on contaminant concentration. Generally, it was found that higher values of these parameters increased the contamination in the well area for both line and finite width stream. The graphical representation of the analytical solution shows that the contaminants attenuated vertically along z axis as well as horizontally along × axis. The finite width model produced more realistic estimate for the distribution of contaminants due to the effect of river width. In particular, the results shows higher contamination near the stream for finite width model. However, this impact of river width on contaminant concentration appear to be neglected if the distance between river and pumping well was more than twice the stream width.

Underground mine designs typically try to avoid extraction beneath streams and rivers of any significant size, especially when the overburden rock thickness between the stream bed and the mine is thin. Potential issues with mining beneath streams include excessive groundwater inflow to the mine, weak ground (roof, floor, and pillar) conditions, horizontal stress effects, as well as stream loss and other potential adverse environmental effects. However, there are times when crossing beneath a stream or river is necessary to move into a new area of mineral reserve without creating additional mine access points from the ground surface. Often, stream crossings are completed without thorough assessment, potentially resulting in increased costs, decreased safety, and, in some cases, failure to advance the mine. Selection of the most favorable location(s) to cross the stream must account for numerous factors and the associated assessment often requires a multi-disciplinary approach. Stream crossing investigations often require geological, hydrogeological, geotechnical, and geophysical expertise. Phases of stream crossing investigations include desktop evaluation of maps and aerial photography, stream bed observations, drilling, detailed rock core logging, downhole geophysical surveying, hydraulic conductivity testing (packer testing), geotechnical laboratory testing, assessment, and reporting. The deliverables from a stream crossing assessment typically include geological, geotechnical, and hydrogeological characterization of potential stream crossing locations, classification of favorable and unfavorable crossing locations, recommendations for entry design and pillar sizing, and recommendations for if, and how, to conduct pre-grouting activities. Examples of technical aspects of data collection and assessment are provided based on decades of industry experience conducting stream crossing assessments in various underground mining scenarios.

Tropical mountain rivers produce a disproportionately high amount of the sediment and carbon that reaches coastal regions and are often portrayed as distinct, though understudied, fluvial systems. They mostly drain uplands with limited contemporary glacier cover, but have undergone climatic changes throughout the Pleistocene, and currently receive more than 2000 mm of annual precipitation. These streams have steep reaches with numerous boulders, rapids, and waterfalls that alternate with flatter reaches flowing over weathered rock or a thin veneer of coarse alluvium. Yet it remains unclear whether and which key diagnostics could help to distinguish tropical mountain rivers from their counterparts in temperate regions. One emerging view is that their distinctiveness is grounded in high rates of chemical and physical weathering and a high frequency of significant geomorphic events rather than the size of individual floods or other geomorphic processes. Disturbances such as earthquakes, volcanic eruptions, tropical cyclones, and landslides can rapidly reshape channels and floodplains. Their bedrock reaches with abundant large and immobile boulders seem to indicate that restorative processes are less effective than in other rivers.

Bioethanol is the one of the most commonly-used liquid biofuels in the world and could significantly contribute to the renewable energy balance. This chapter will map the potential biowaste streams that could produce second-generation bioethanol. Organic fraction of municipal solid waste, food processing waste along with lignocellulosic residues will be quantitatively and qualitatively analyzed. This chapter will encompass up-to-date information on recent technological developments for bioethanol production. Apart from the fermentation process, all the upstream and downstream process techniques will be reviewed. In addition, the bottlenecks and barriers that impede the sustainable and viable bioethanol production, and the future trends and perspectives shall be discussed.

Headwater streams are facing increasing disturbances from human pressures worldwide, thus better knowledge about bioindicators, particularly aquatic insect responses to various pressures and stressors, are urgently needed. Multiple trait-based approaches consider species attributes filtered by the environment, allowing them to persist in ecosystems under environmental pressures. Because this approach has been minimally explored in Odonata larvae, we aimed to understand how anthropogenic stressors structure Odonata larval assemblages in neotropical savanna streams by using multiple trait-based approaches. We hypothesized that a set of stressors--such as reduced substrate heterogeneity, poor water quality, natural land cover converted to pasture and agriculture, and reduced local riparian canopy cover--select Odonata functional traits. We collected 3209 Odonata larvae from 186 neotropical savanna headwater stream sites and used 39 environmental variables and seven traits in 23 categories related to their functional roles in Odonata genera. To assess associations between trait categories and environmental variables, we applied RLQ and fourth-corner statistical analyses. We found strong relationships between environmental variables and sets of Odonata biological traits that were separated into two main groups. Zygoptera genera (Perilestes, Allopodagrion, Heliocharis, Argia, Epipleoneura, Mnesarete/Hetaerina, Psaironeura) have elongated body shapes, caudal lamellae respiration, conforming thermoregulation, and endophytic oviposition. Such traits favor assemblages in conditions similar to reference streams, including denser riparian vegetation, good water quality, and diverse flows and substrate. Therefore, they are more sensitive to changes in those conditions. On the other hand, Anisoptera genera (Gomphoides, Archaeogomphus, Macrothemis, Brechmorhoga, Gynothemis, Phyllocycla) have cylindrical body shapes, internal gill respiration, endothermic thermoregulation, and burrowing behavior. Those traits facilitate their survival in intermediate or disturbed stream sites, characterized by riparian deforestation, increased erosion and siltation, and higher levels of total dissolved solids and conductivity. Therefore, using Odonata larval traits can be a valuable tool for assessing and monitoring anthropogenic impacts on neotropical savanna streams.

Climate extremes threaten global food security, and compound events, such as late spring heavy and warmer rainfall over snow and subsequent flooding, exacerbate this vulnerability. Despite frequent occurrences in recent years, a quantitative understanding of the compound weather events' impacts remains elusive. Here, we use Synthetic Aperture Radar data from Sentinel-1 and normalized difference vegetation index data from MODIS satellites to map the spring 2019 U.S. Midwest flood extent and evaluate its impact on crop loss. We find a statistically significant association between flooded counties and those with plant greenup delay, while the correlation between flood area percent and amount of green-up delay remains weak, albeit reliable. An analysis of the stream gage time series and crop loss records shows that during the past ∼70 years, ∼43% of spring large discharges are associated with widespread crop loss. We also find an increase in streams' discharge frequency and magnitude across the Midwest, indicating the possibility of a future increase in crop loss due to spring flooding. This study highlights the importance of Earth-observing satellite data for developing climate adaptation and resilience plans.

The successful design of a structure requires not only the proper analysis of the structure but also the careful consideration of the environment that the structure is situated in. For many waterfront structures such as those near harbors, lakes, streams, and creeks, water is especially an engineering problem. To alleviate this problem, a sheet-pile wall made of glass fiber reinforced plastics (GFRP) was introduced in a pioneering stream bank stabilization (revetment) project at the Nan-Zi-Gou creek in the Shihmen Reservoir watershed of Taiwan. This paper presents the project as a case study and describes the material experiments and the finite-element analysis of revetment stability. The final construction of the GFRP sheet-pile wall was completed successfully. It is said that this pioneering work brought many positive features of GFRP to construction and could serve as a model for future replication.

Headwater streams, as critical zones due to their proximity to terrestrial sources, emit large quantities of CO2 owing to their higher drainage density of catchments, substantial total areas, and stream lengths. Stream ecosystem metabolism (EM, i.e. photosynthesis and respiration) can significantly affect the in-stream carbon cycle. However, how stream CO2 emissions respond to ecosystem respiration (ER) is still not well known. Here we report in-situ daily observations of headwater stream gross primary production (GPP), ecosystem respiration (ER), isotopic composition of dissolved inorganic carbon (δ13CDIC) and CO2 emissions conducted in five streams in two headwater catchments of the Changjiang River in Southeastern China. The results show that δ13CDIC, pCO2, and CO2 emission rates have significant diel variations. Both the day and night δ13CDIC values were more depleted than the theoretical values in the two catchments, but the nocturnal depletion was greater. The headwater streams have high EM, with an average ER of −1.99 ± 0.82 g C m−2 d−1and GPP of 1.52 ± 0.84 g C m−2 d−1 in the two catchments. ER increases with DOC concentration but decreases with water discharge. The nocturnal pCO2 (3885 ± 2959 μatm) was significantly higher than in daytime (2525 ± 2221 μatm). The higher nocturnal CO2 emission rate (225 ± 165 mg C m−2h−1) was about 42 % higher than in daytime. DOC uptake velocity ( V f ) was 0.46 ± 0.14 m d−1, and increased with lower water discharge and lower catchment-scale DOC yield. DOC loss rate (ζ) was 0.96 ± 1.25 d−1 and declined exponentially with higher water discharge and catchment-scale DOC yield. Moreover, the removal fraction of DOC via ER was about 0.32 ± 0.14, contributing to 31 ± 16 % of the CO2 flux in streams. The re-estimated annual CO2 flux was about 14.62 ± 4.99 Tg C yr−1 from the Changjiang headwater streams network. This study emphasizes the necessity of incorporating the effects of EM into the river network's CO2 emissions and the importance of the headwater streams to river carbon cycling.

With ongoing climate change and increasing water resource pressures, the knowledge and predictability of stream drying is essential for water management. However, the hydrological data for assessing the flow regime of temporary streams are often non-existent or scarce. The flow regime strongly affects stream ecological functioning and ecosystem processes. A few biological indices have been developed in the past decade to assess community responses to flow intermittency. One of them - the Biodrought Index, used to recognise antecedent stream drying based on benthic invertebrate assemblage composition - was initially intended for deployment in the Czech Republic. Here we report on a test of how reliably this index can be used in Central Europe. We used five independent data sets of macroinvertebrate samples collected during the flowing phase in five countries: Austria, Czech Republic, Germany, Hungary and Slovakia. Altogether 89, 26 and 220 samples were assessed from intermittent, near-perennial and perennial sites, respectively. Each sample was assigned to one of three flow intermittence categories according to the Biodrought Index and then compared with the flow regime recognised by hydrological observations and gauging station data. In most cases, the Biodrought Index clearly reflected the previous flow state and identified streamflow cessation. The misidentification rate between intermittent and perennial samples was very low, ranging from 0% to 6%. Classification rate of correctly recognised samples ranged from 54% to 93% and misclassification rate between near-perennial and perennial/intermittent category was 6% to 46%. Overall, this study confirmed the robustness and the reliability of the Biodrought Index, which proved to be an effective tool in assessing the recent hydrological history of small and medium-sized streams. The index can improve the interpretation of the macroinvertebrate assemblage data collected for ecological status assessment, can help to evaluate the effectiveness of river restoration projects or identify water resource pressures. Hence, we consider the Biodrought Index a useful method for indicating antecedent stream drying in the extensive area of Central Europe and thus helpful in monitoring and managing river ecosystems.

Freshwater biodiversity is rapidly declining due to accelerated human-induced disturbances. Increased human-induced environmental disturbances are believed not to only decrease species numbers, but to also diminish beta diversity, for instance, by the local extinction of native species and wide-spread introduction of non-native species – a process widely known as biotic homogenization. Here, we investigated whether anthropogenic impacts reduce beta diversity. We also assessed the relative roles of environmental and spatial factors in driving beta diversity. We examined relationships among macroinvertebrates beta diversity, stream status classes (reference and impacted classes), and environmental predictors in streams in Northern Nigeria. We used PERMDISP and distance-based redundancy analysis followed by variation partitioning to evaluate how beta diversity of macroinvertebrates differed between the reference and impacted sites, and what mechanisms were responsible for their responses. While beta diversity between reference and impacted sites was similar for all distance matrices, there were significant differences in composition related to turnover between the reference and impacted sites using the distance matrices. Species sorting prevailed in structuring macroinvertebrates communities in our system, while spatial variables were not relevant. Our result of beta diversity of macroinvertebrates and their responses to disturbances support the hypothesis that disturbances do not necessarily lead to biotic homogenization. We recommend that tropical streams restoration ecologists need to emphasize the study of varying condition classes in their attempt to develop effective restoration strategies based on their environmental heterogeneity.

The selection of suitable indicators is the key to the development of multi-metric bioassessment. Here, we examined how taxonomic and functional structures of macroinvertebrate communities responded to the environmental gradients in ten mountainous streams in the Weihe River and Hanjiang River basins, two subtropical biodiversity hotspots in central China. Our main objectives were: 1) to examine whether trait-based metrics performed better than taxonomic compositions in differentiating environmental gradients; 2) to test whether indicators (species and traits) were more efficient than entire communities in discriminating three site groups subjected to different levels of human disturbances. Our results showed that both taxonomic and functional trait compositions, including species- and trait-based indicators, were all sensitive to environmental disturbance. Particularly, the trait-based variables responded more sensitive to human disturbances. Indicator assemblages can be effective surrogates of entire communities in response to environmental changes. Traits- and indicators-based metrics should be considered as useful supplements in the existent bio-monitoring schemes in China. We argued that the combination of taxonomic and functional indicators should be implemented in bioassessment, as they reflect different aspects of environmental changes and anthropogenic disturbances.

This study aimed to provide datasets useful for identifying and disentangling any complex patterns in the fine spatial heterogeneity of a common nonpoint source pollutant, nitrate, as well as other related water quality metrics (temperature, dissolved oxygen, pH, and conductivity) in streams of the eastern U.S. We aimed specifically to provide a resource dataset of uniquely high spatial detail for the better understanding of how the rapid appearance or disappearance of this common nutrient at fine scales may relate to other aspects of form and function in these watersheds. To accomplish this, the low-order streams observed in this study extend across environmental gradients in urban and rural land cover, and change from free flowing to impounded water. Study streams were also observed at different levels of steam discharge, both pre and post summer storm events. Four unique 600 m stretches of two low-order creeks in Dutchess County, New York, were observed longitudinally at a fine spatial resolution (20 m). These four 600 m stretches contrasted in land cover from heavily urban channelized streams to mainly rural meandering streams with seasonally active floodplains. Data collection occurred above and below areas where impounded water was input into to the stream via a side tributary to observe the effect of adjacent impoundments, and fine scale water quality was assessed both before and after major storm events to see the influence of wet-period flow path activation on nonpoint source fluxes. Data was organized into a final data table and maps showing how water quality parameters change in regard to land use and land cover, free flowing versus impounded water, and the influence of storm events versus dry periods. Water quality data are also mapped in comparison to thresholds of concern for growth of cyanobacteria – a common constituent of harmful algal blooms in the region. Fine spatial resolution data from this study can be used as a baseline for future studies or modeling efforts at similarly fine scales to better understand why concentrations of nitrate rapidly rise or fall longitudinally at

In this study, attempt was made to estimate the quantity of municipal solid waste (MSW) generated per annum, the generation rate in kg/capita/day as well as the quantity and the fractions of the waste streams available for energy production. The physical characterization of the waste streams into fractions was conducted. The proximate and ultimate analyses of the waste fractions were performed. Heating values of the waste streams was determined experimentally using a bomb calorimeter. It was concluded that 1% increase in carbon and sulphur will increase heating value by 79.08% and 10.83% respectively while 1% increase in hydrogen and nitrogen decrease heating value by 30.2% and 619.1% respectively. The energy potential (EPMSW) of the MSW based on the energy content of 584 tons/day MSW, is about 3,244,444 kWh or 3,244 MWh, Electrical Power (EPPMSW) of about 40555 kW or 41 MW and Power to Grid of 27 MW. Keywords: Characterization, Energy potential, Generation rate, Heating value, Municipal solid waste, Power potential

The rheophilous tadpoles of the rare and endangered Purple frog, Nasikabatrachus sahyadrensis (Biju and Bossuyt, 2003), have suctorial mouthparts that enable them to occupy a very unique microhabitat within torrential streams. In this study, we examined the influence of four stream habitat variables, i.e. water flow velocity, slope of substrate, depth of water column and water temperature, on the distribution and abundance of these tadpoles. A total of 204 measurements were recorded for all the four variables in 68 marked grids along a 100 m section of two selected streams. Statistical analysis showed that water flow velocity was the best predictor for abundance of tadpoles in both streams. When the number of tadpoles was modeled as a function of each environmental variable, the relationship ranged from linear (w.r.t water flow velocity and water temperature) to unimodal humped curves (w.r.t slope of substrate and depth of water column). The results were further assessed with respect to distribution and behavioral observations of the tadpoles in the streams as well as to the threat posed by dams and reservoirs on tadpole microhabitats. Keywords: Distribution, Microhabitat, Rheophilous, Stream, Tadpoles

The northern Pakistan is attributed with rough terrain, active seismicity, monsoon rains, and therefore hosts to variety of geohazards. Among the geohazards, landslides are the most frequent hazard with devastating impacts on economy and society. However, for most of the northern Pakistan, landslide susceptibility maps are not available which can be used for landslide hazard mitigation. This study aims to develop a remote sensing based landslide inventory, analysing their spatial distribution and develop the landslide susceptibility map. The area, selected for this study is comprised of Haramosh valley, Bagrote valley and some parts of Nagar valley, in the Central Karakoram National Park (CKNP) in Gilgit-Baltistan, northern Pakistan. The SPOT-5 satellite image was used to develop a landslide inventory which was subsequently verified in the field. The landslide causative factors of topographic attributes (slope and aspect), geology, landcover, distances from fault, road and streams were used to evaluate their influence on the spatial distribution of landslides. The study revealed that the distance to road, slope gradient has the significant influence on the spatial distribution of the landslides, followed by the geology. The derived results were used in the Frequency ratio technique to develop a landslide susceptibility map. The developed landslide susceptibility map can be utilized for landslide mitigation in the study area. Keywords: Landslides, Frequency ratio, Remote sensing, Susceptibility mapping, Northern Pakistan

Study region: The New York City water supply watersheds Study focus: This study is a modeling analysis on climate change impact on streamflow using a stochastic weather generator (SWG), a hydrologic model, and downscaled future climate scenarios. Streamflow generated using synthetic time series of precipitation and air temperature from a SWG were compared to those simulated from observed historical and projected future weather. New hydrologic insights for the region: Synthetic weather was able to mimic the observed annual streamflow cycle for the six watersheds studied, including the seasonal pattern as well as magnitude and occurrence of extreme hydrologic events. Streamflow simulations using projected climate from 20 global climate models (GCM) for one of the New York City water supply watersheds indicate the potential for changes in the hydrologic regime in this region. The models indicate a shift in the timing of spring melt runoff from a distinct peak in late March and April under historical (1950–2009) conditions towards earlier in the year for mid-century (2041–2060) period. Results indicate that the region may experience an overall increase in mean streamflow in the future due to the combined effect of decreasing spring runoff peak and increasing streamflow during other seasons. More importantly, the magnitude and frequency of extreme hydrological events are projected to increase under future scenarios. These results have implications for future operation and management of the water supply. Keywords: Climate change, Extreme events, NYC water supply, Scenarios, Water resources

Motivated by the UN Global Sustainable Development Goals on achieving sustainable freshwater ecosystem, this study was undertaken to examine two important water bodies in north central Nigeria (Baka Jeba and Penyan Rivers) protected locally by the rural community and serving as sources of water supply, for biodiversity conservation and protection. The status of macroinvertebrate biodiversity as important variable in assessing the environmental health and suitability of the water quality of the rivers was evaluated for a period of 8 months, between February and September 2017 using standard methods. The mean values of Physicochemical variables recorded during the study period revealed that the nutrient loads (nitrites and phosphates levels) was relatively low for both streams as well as conductivity levels ( ​0.05) among the sampling stations with number of individuals caught ranging between 1208 and 1728 per station. Of the major faunal groups, Ephemeroptera contributed the highest percentage of individuals (>29%) in both streams. Generally, Beka Jeba Stream contained more diverse taxa of macroinvertebrates compared to Penyan Stream. The Ephemeroptera- Trichoptera-Odonata (ETO) were the dominant groups collected in the river systems indicating fairly good water quality conditions. The Chironomids and other tolerant macroinvertebrate larvae were only sporadically present. Overall, the values of the physical and chemical parameters (low BOD, low nutrient levels and high dissolved oxygen) obtained for the two rivers and the wide diversity of sensitive macroinvertebrates portends the water body to be of good quality. Therefore utmost care should be taken to conserve and preserve these species as indicators of water quality by reducing the impact of key drivers of declines in macroinvertebrate biodiversity, including habitat degradation and pollution.

Rare Earth Elements (REEs) are used in increasing amounts in technical applications and consumer products. However, to date, the contribution of industrial sources to the loads of individual REEs in wastewater streams have not been quantified. Here, we determine the REE contents in sludge collected from 63 wastewater treatment plants (WWTPs) across Switzerland. To quantify the industrial fraction of individual REEs in the sewage sludge, we develop two complementary approaches, based on REE ratios and REE pattern fitting. Unspecific (background) inputs, with REE patterns similar to the averaged REE pattern of soils collected across Switzerland, dominate the REE budget of most WWTPs. A few WWTPs receive significant REE inputs from specific industrial sources. Based on population equivalents of Switzerland, we estimate a total annual load of 4200 kg Cerium (Ce, 0.5 g Ce year-1 capita-1), with an industrial contribution of 2000 kg year-1. The latter agrees with estimates of probabilistic mass flow models for engineered nanoscale CeO2 particles discharged to the sewer network. About 7 kg year-1 of Samarium (Sm,total for Switzerland: 184 kg year-1 or 0.02 g Sm year-1 capita-1) and 3 kg year-1 of Europium (Eu,total for Switzerland: 44 kg year-1 or 0.005 g Eu year-1 capita-1) are assigned to industrial inputs from single WWTPs. Gadolinium (Gd) is used in the form of a stable complex as contrast agent in magnetic resonance imaging. Assuming 10% removal of Gd during wastewater treatment, we calculate an annual discharge of 90 kg of Gd from one individual WWTP to surface waters. WWTPs with exceptionally high industrial inputs of specific REEs warrant detailed investigations to identify the respective sources and to assess whether REE concentrations in effluents are elevated to the same degree., Water Research X, 11, ISSN:2589-9147

Acid deposition, resulting from the atmospheric transport of acidifying compounds emitted during the combustion of fossil fuels, has historically resulted in stream acidification in many headwater streams in the eastern United States, including streams in Shenandoah National Park (SHEN). Though restrictions on these emissions were established by an amendment to the Clean Air Act in 1990, reductions in stream acidification have not been observed in all regions of SHEN due to variations in the geological composition of SHEN watersheds. Before the implementation of these restrictions, fish assemblages were strongly controlled by a stream’s acid neutralizing capacity (ANC), which is the ability of a watershed to buffer acid inputs. This study investigated changes in the relationship between fish assemblages and ANC within SHEN 21 years after implementation of more stringent restrictions on the emission of sulfur and nitrogen oxides in 1995. Results indicated that recovery trends in water chemistry were observed in some SHEN watersheds; however, fish species richness and total fish biomass continue to be influenced by the legacy of acid deposition in acid sensitive watersheds. Temporal trend analysis indicated little change in ANC within acid sensitive watersheds and minor decreases in stream sulfate concentrations. These findings indicate a persistent impact from previously deposited sulfur oxides and the continued influence of these compounds on fish assemblages within SHEN. Though no further loss of fish species, and in some cases, increases in species richness, suggest the early stages of recovery, many SHEN streams remain as susceptible to acidification as they were over two decades ago, highlighting the need for continued regulation of acidifying emissions and conservation efforts in headwater streams.

Anthropogenic transformations of the catchment area and river bed are responsible for the changes in the geomorphology of the river valleys, the hydrological regime of rivers, the river continuum, as well as the river ecosystems. Transformed valleys offer ecological niches that are different from the natural ones, which are inhabited by organisms that should not be present in a high density in rivers or streams. We aimed to answer the question of whether the communities of microinvertebrates are indicative of anthropogenic transformations taking place in the river bed and in the catchment area. For this purpose, the study was conducted on the six upland rivers in the drainage of the Douro River, Northern Portugal. According to our results, for the diversity and abundance of microinvertebrate communities (Rotifera, Cladocera, and Copepoda), the characteristics of the catchment area are not as important as the transformation of the riverbed. The abundance of microinvertebrates is related to natural processes that are described in the river continuum concept; however, dams higher than 10 m drastically reorganized communities from benthic to typically pelagic. Large dams (>10 m) built on small rivers caused an apparent increase in species richness, as these species are the same as those found in large rivers. Therefore, the river networks were homogenized both in relation to microinvertebrate abundance and taxa. Less transformation of the riverbed (lack of impoundments) favors the greater Simpson diversity of microinvertebrates, but the density is then very low. Our results show that dams have a large influence on the communities of microinvertebrates in the river, which in turn can cause cascading spatial changes to the river ecosystem.

Tropical freshwaters support an immense diversity of fishes and invertebrates but are understudied in comparison to temperate systems. This is especially true of headwater streams, as only a small number of studies has assessed the trophic dynamics underpinning food web structure in these streams. We used stable isotopes of carbon, nitrogen and hydrogen to determine the resource use of dominant invertebrate guild and fishes in seven headwater streams in Eastern and Western Thailand, and assessed the functional and trophic diversity of each community using isotope food web metrics. Benthic invertebrates (95% credibility interval: 37–85%) and fishes (39–79%) obtained most of their resources from autochthonous sources in each stream but allochthonous and autochthonous specialists were evident in each community. We observed an increase in isotopic diversity of fishes associated with increasing stream size, but this was primarily driven by an increase in the range of isotope ratios of allochthonous and autochthonous food web endmembers rather than an increase in functional diversity. Maximum trophic position did increase with stream size. The snakehead, Channa gachua, was enriched in 2H relative to all other fishes, possibly reflecting facultative air breathing by this species. Fish communities in the headwater streams analysed filled a variety of trophic niches, predominantly fuelled by autochthonous primary production.

Fluoroprobes, such as BenthoTorch, offer a relatively rapid in situ method for monitoring benthic algae, provide new opportunities for aquatic ecological research, and enable early warning of algal proliferation in municipal water supplies. Currently, however, BenthoTorch is limited for the measurement of heterogeneous samples, and homogenizing samples is rather difficult. In this study, we compared chlorophyll-a (Chl-a) measurements between BenthoTorch and standard laboratory methods to quantify and describe the biomass and biovolume proportion of benthic algae growing on artificial and natural substrates. We used the difference in Chl-a measurements between these methods (n = 359) to evaluate the effects of environmental variables. Moreover, we used artificial and natural substrates to determine whether either of them reduced variation in BenthoTorch measurements. There was a general concordance in measurements between the two methods, but this agreement was stronger for artificial substrates. Artificial substrates also led to significantly less variation in BenthoTorch readings compared with natural substrates. This may be attributed to the formation of relatively thin algal mats on artificial substrates. To enable early warning of algal proliferation in an aquatic ecosystem, we recommend the use of BenthoTorch and artificial substrates combined with appropriate calibration using standard laboratory methods. The ability of BenthoTorch to produce instantaneous results facilitates replicate collection, which reduces sampling error and increases sampling area on the same day. Despite substantial variation in readings on natural substrates, BenthoTorch enables relatively rapid measurements, facilitating easy monitoring of large areas. Therefore, BenthoTorch may be worth incorporating into aquatic ecosystem studies, depending on the specific research questions.