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We studied the sequence of climatic and hydrological events associated with the formation of peat during the Holocene, using pollen, diatoms and environmental magnetism from peat cores at three locations in the Sacramento-San Joaquin Delta of California: Browns Island, Franks Wetland and Webb Track Levee. Our data show that peat first formed under relatively dry conditions in a freshwater environment before 6.5 ka BP. Subsequently, pollen accumulation rates were highest prior to intervals with high peat accretion rates but are inversely correlated with organic accumulation rate. Intervals of high peat accretion were preceded by pulses of terrigenous material. During intensive drainage episodes, high flows delivered abundant, coarser-grained sediment to the marshes, which inundated the existing vegetation and decreased the rate of biochemical decay. The build-up of undecomposed organic material led to the acceleration of peat accretion. Our data support the rarely discussed hypothesis that most of the peat in the Sacramento-San Joaquin Delta formed in freshwater marshes that were fed by rivers draining from the Sierra Nevada, rather than in saltwater wetlands resulting from sea level rise and estuarine submergence. This result has important implications for current attempts to remediate and restore the Delta ecosystem.

The Unazuki Reservoir is located on the Kurobe River, which is influenced by a catchment with one of the highest sediment yields in Japan. Due to a sufficiently available discharge during flood events, annual sediment flushing with full water-level drawdown (i.e., free-flow sediment flushing) is conducted to preserve the effective storage capacity of the reservoir. Nevertheless, the upstream half of the reservoir (i.e., study segment) suffers from the excessive deposition of coarser sediments. Remobilization of these coarser materials and their transportation further downstream of the reservoir is a priority of reservoir owners for sustainable reservoir functions, such as flood-risk management and hydroelectric energy generation. In this paper, an already conducted sediment-flushing operation in the Unazuki Reservoir is simulated, and its effects on sediment scouring from the study segment of the reservoir together with changes in bed morphodynamics are presented. A fully 3D numerical model using the finite volume approach in combination with a wetting/drying algorithm was utilized to reproduce the hydrodynamics and bed changes using the available onsite data. Afterwards, the effects of discharge adjustment on the morphological bed changes and flushing efficiency were analysed in the study segment using an additional single-discharge pulse supplied from upstream reservoirs. Simulation results showed that an approximately 75% increase in the average discharge during the free-flow stage changed the dominant morphological process from deposition into an erosive mode in the study segment. If the increase in discharge reaches up to 100%, the flushed volume of sediments from the target segment can increase 2.9 times compared with the initiation of the erosive mode., Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT)

Floodplain waters of Murray-Darling Basin riversrange from ephemeral puddles to semi-permanentbillabongs kilometres long and several metres deep.They may comprise >60% of the standing waters onthe floodplain, the more permanent waters provid-ing refugia for a diverse aquatic fauna in times ofdrought. There is evidence of a rich and diversemicroflora and -fauna in the larger permanent billa-bongs (BOON et al. 1990), but virtUally no informa-tion on such assemblages in the smaller ephemeralwaters, which may be only rainpools and of veryshort persistence (weeks or even days). We wereinterested in characterizing the diversiry and dynam-ics of the microfaunal communities in such habitats,in particular the adaptations of the microfauna tohabitat ephemeraliry and heterogeneiry. To providean estimate of the microfaunal species diversiry rep-resentative of ephemeral waters in the region, weundertook a qualitative survey of 112 small flood-plain pools in the wet spring of August-September1991, when all contained water (SHIEL et al. 1998),results of which are summarized here. Replicate sedi-ment samples were also taken over the summer of1998 from dry sediments of sites with differentflooding frequencies, viz. permanently flooded(Ryan's no. 1 billabong), flooded every 2-3 years(Ryan's no. 3), and flooded no more frequently thanevery 25 years (overbank region of Ryan's no. 2).From sediment cores, identifiable cysts, resting eggs,ephippia and diapausing individuals were identifiedas a prelude to flooding experiments to determinethe viabiliry of the floodplain 'eggbank' (cf. BOUL-TON & LLOYO 1992. See also DE STASIO 1989, 1990,HAIRSTON et al. 1995, HAIRSTON 1996, and refer-ences therein).

Soil erosion is a natural process, and the erosion potential of a site is the result of complex interactions among soil, vegetation, topographic position, land use and management, and climate. Soil erosion occurs when aeolian and hydrologic processes exceed a soil’s inherent resistance to these forces (figures 1 and 2). Soil erosion was recognized as a significant problem at both local and national scales in the United States in the 1920s; by 1935 soil erosion was considered a national disaster, covering over one-half of the country (Sampson and Weyl 1918; Weaver 1935), and is still a concern with 21% of the western United States degraded and vulnerable to accelerated soil erosion (Herrick et al. 2010; Weltz et al. 2014a; Duniway et al. 2019). In 1995, it was estimated that 4 × 109 t (4.4 × 109 tn) of soil was lost from US cropland (Pimentel et al. 1995). The most vulnerable areas for soil movement and thus erosion occur where annual precipitation is 100 to 400 mm y–1 (4 to 16 in yr–1), which limits soil moisture available to sustain plant growth. Anthropogenic-driven dust emissions have dramatically increased across …

Land use and land cover (LULC) changes strongly affect local hydrology and sediment yields. The current study focused on a basin in the Brazilian Amazon and had the following three objectives: (1) to perform an effective diagnosis of flow and sediment yield, (2) to evaluate the impacts of LULC changes over the last 40 years on the hydro-sedimentological variables, and (3) to investigate the impacts of the possible trends or breaking points in the flow, surface runoff, and sediment yield series. The Soil and Water Assessment Tool (SWAT) model validation showed that the simulated results were consistent with the data measured in the dynamic reproduction of flow seasonality. Furthermore, changes in LULC altered surface runoff, sediment yield, and flow according to the Mann-Kendall and Pettitt non-parametric tests. It was also observed that the sub-basins in which pastureland is predominant are more susceptible to increased surface runoff and sediment yield. According to trend and homogeneity tests, these sub-basins had break points in the time series of these variables. On the other hand, in the sub-basins whose land cover is predominantly forest, the time series is homogeneous and trendless. The current study highlighted the impacts that 40 years of LULC changes in an Amazonian basin had on hydro-sedimentological variables, which, in turn, can play an important role in changing the hydrological cycle, consequently these changes can also impact diverse human activities in the region, such as agribusiness, livestock, energy production, food security, and public water supply. Thus, it is concluded that the SWAT model is a good estimator of hydro-sedimentological processes in Amazonian basins and can be used by decision makers in the management of water and environmental resources.

The records of suspended sediments and associated hydro-meteorology of the glacierized catchments are very limited in Sikkim Himalaya. Therefore, we carried out the first-ever estimate of suspended sediment transport from the meltwater stream of East Rathong Glacier for June-September during three consecutive melt seasons (2013–2015). These records were used to estimate the suspended sediment concentration (SSC), load (SSL), yield (SSY) and erosion rate (ER). The daily mean SSC was 105.75, 84.20, and 91.51 mg/l during melt seasons of 2013–2015 respectively. The monthly mean SSC of the combined melt season of 2013–2015 was 92.72, 107.14, 105.93 and 60.46 mg/l for June-September, respectively. The observation shows that July-August contributed to maximum SSC, accounting 70.45% of total SSC. Similarly, the monthly mean SSL for June-September was 55.64, 69.61, 65.75 and 25.72 tons, respectively. We observed high variability in SSL (CV = 0.54) than SSC (CV = 0.38) since the estimation of SSL depends on both discharge (Q) and SSC. The relationship between monthly mean SSC and Q was highly significant (R2 = 0.98) than daily SSC and Q (R2 = 0.25) due to reduced variability on a monthly scale. Further, mean SSY in the catchment was high during peak melting season (July-August), which substantially reduced during the end of the melting season. We estimated the mean SSY of 281.93 ton/yr km2 during the combined melt season (2013–2015). The average ER for the East Rathong Glacier basin was 1.04 mm/yr, which is lower than the ER of most of the Himalayan glaciers. We observed significant meteorological control of Tmean, Tmax and Rainfall in the transportation of suspended sediments from meltwater stream at a monthly scale. These in-situ based records on dynamics of suspended sediment and associated hydro-meteorological parameters are relevant for the planning and management of freshwater resources and planning for hydropower projects under a changing climate.

Air Quality Index is the simplest and widely used measure of overall air pollution of a region. Air Quality Assessment can be done with the help of Air Quality Index Parameter. Essentially it is used for assessing the air pollution hot spots in the region for delineating management and concrete actions. Different Methodology are adopted to assess the Quality of air for study area by taking into consideration of four pollutants synergistic effects which are PM10, PM2.5, SO2 and NO2 The average concentration recorded for PM10, PM2.5, SO2 and NO2 was recorded for six consecutive months before and after the lockdown period i.e., from 25th December 2019 till 25th June 2020. Different AQI were estimated for various months and varying results were observed ranging from good to unacceptable for the set of data. The findings of this study will provide detailed information of air pollution and AQI status before and after lockdown.

A pilot-scale multistage constructed wetland-pond (MCWP) system with a "pre-ecological oxidation pond, two-stage horizontal subsurface flow constructed wetland (HSCW) and surface flow constructed wetland (SFCW) as the core and postsubmerged plant pond" as the process was used to treat actual polluted river water in the field, and the variation in nitrogen removal from summer to winter was investigated. The results showed that the average total nitrogen (TN) removal efficiency in the MCWP was approximately 40.74%. The significant positive correlation between the daily highest temperature and the TN removal efficiency of the whole system was fitted with a nonlinear curve (R2 = 0.7192). The TN removal load rate in the HSCWs was 2.7–3.7 times that in the SFCW. The SFCW, which had high-density plants (35 plants/m2), increased the proportion of nitrogen removed by plant harvesting and microbial function. The TN transformed by Iris pseudacorus L. accounted for 54.53% in the SFCW. Furthermore, bacteria completed the nitrogen cycle in the SFCW through a variety of nitrogen removal pathways. This research not only investigated the TN removal performance in an MCWP system but also made it possible to predict the TN removal efficiency according to the daily highest temperature from summer to winter in the field.

River flood season segmentation is a significant measure for flood prevention. This study aims to carry out theoretical analysis on flood season segmentation methods and put forward a framework for proper flood season segmentation through comparison between different segmentation methods. The studied framework consists of a Fisher optimal partition method for determining the optimum numbers of the sub-seasons, an ensemble approach for segmenting a defined flood season, and a nonparametric bootstrap combined with a fuzzy optimum selection method (NPB-FOS) for testing the rationality of the flood season staging schemes. The present research findings show that different methods could result in different staging schemes. It is proved through rational analysis that the staging scheme obtained by probability change point (PCP) is superior to others. The flood season of the downstream reach of the Yellow River can be segmented into three sub-seasons, i.e. early flood season (01 June–20 July), main flood season (21 July–28 September), and late flood season (29 September–08 November). The segmentation results of the flood season should play an active role in flood prevention. HIGHLIGHTS The conjunctive use of Fisher optimal partition, ensemble approach, nonparametric bootstrap, and fuzzy optimum selection method applied to flood season segmentation.; The rational methods segment a flood season into several sub-seasons.; An optimal framework for reasonable flood season segmentation was proposed.; A case study in the Yellow River was carried out and reasonable results were obtained.

Understanding relationships between urban structure patterns and air pollutants is key to sustainable urban planning. In this study, we employ a mobile monitoring method to collect PM2.5 and BC data in the city of Philadelphia, PA during the summer of 2019 and apply the Structure of Urban Landscapes (STURLA) methodology to examine relationships between urban structure and atmospheric pollution. We find that PM2.5 and BC vary by STURLA class, and some classes exhibit significant difference in pollution concentrations. We also find that the proportions in which STURLA components are present throughout the urban landscape can be used to predict the spatial distribution of urban air pollution. Among frequently sampled STURLA classes, gpl (grass, pavement, and low-rise buildings) hosted the highest PM2.5 concentrations on average (16.60 ± 4.29 µg/m3), while tgbwp (trees, grass, bare soil, water, pavement) hosted the highest BC concentrations (2.31 ± 1.94 µg/m3). Furthermore, STURLA combined with machine learning modeling was able to correlate PM2.5 (R2= 0.68, RMSE 2.82 µg/m3) and BC (R2 = 0.64, RMSE 0.75 µg/m3) concentrations with urban landscape composition and interpolate concentrations throughout the city. These results demonstrate the efficacy of the STURLA methodology in modeling relationships between air pollution and urban structure patterns.

This study evaluates the vulnerability of aquifers to the nitrate concentration variations. Prediction of nitrate concentration using MT3DMs modeling for a period of 10 years. The results showed th...

Through water transfer, the hydrodynamic conditions of the river network can be improved, and the biochemical degradation of pollutants can be promoted, but at the same time, the endogenous release may be intensified. It is therefore possible to subdivide the response of nutrient content to water transfer into three components: (a) Direct Impact (DI) of dilution through water diversion, (b) Indirect Impact (II) by sediment release, and (c) Self Impact (SI) of nutrient degradation and attenuation of nutrients. By combining field investigation, laboratory experiment, and numerical simulation, the contribution weight of DI, II, and SI to the change of nutrient concentration was quantitatively analyzed. The results show that: (1) in the upper reaches of the river network, II plays a leading role in that the weight is more than 75%, and increasing the amount of water diversion increases the nutrient content; (2) SI plays a leading role in the tributary of the central part of the river network, the weight is more than 60%, and when the auxiliary pumping station is opened, the weight of II is less than 1%; (3) in the southeast of the river network, the nutrient release rate is sensitive to the change of hydrodynamics, and the weight of II is more than 90%. The results of this study can provide a reference for the formulation of a comprehensive hydrodynamic water quality management control scheme in the urban river network. HIGHLIGHTS Water transfer imposes direct and indirect impacts on nutrient concentration.; The response of nutrient to water transfer can be divided into three components.; The dilution weight of the downstream section is higher than that of the upstream section.; The control of endogenous pollution in Liangxi River and southeastern rivers is the key to improving the water quality of the river network.

Globally, exposure to high levels of radon gas is a known health risk. Granite commonly contains high concentrations of uranium and subsequently high exhalation of radon gas. In the Saldanha Bay ar...

The evaluation of groundwater quality and geochemistry have an important role in the management of water resources in arid and semi-arid regions. In the present study, the spatio-temporal assessment of groundwater quality and hydrogeochemical processes, as well as, statistical analyses in the Azarshahr and Ajabshir plains located in the Urmia Lake basin were investigated. The results revealed that within six years (from 2014 to 2019), the value of total hardness was higher than the permissible level and the quality of groundwater for drinking was very hard and fresh in both plains. In 2019, 84 and 67% of the samples fell within the range of good to poor groundwater quality in the Azarshahr and Ajabshir plains, respectively. The temporal assessment with the help of water quality index values for both plains revealed a good groundwater quality for the Azarshahr plain and a good to poor groundwater quality for the Ajabshir plain. However, deterioration of water quality was observed in both plains from 2014 to 2019. The level of water quality for irrigation was better in the Azarshahr plain than in the Ajabshir plain, due to the presence of fewer salty sites. In addition, Ca–Mg–HCO3 and rock dominance were identified as hydrochemical facies and the controlling factor in the groundwater of both plains, respectively. Multivariate statistical analyses indicated both natural and anthropogenic sources (such as weathering, fertilizers, and wastewater) for hydrochemical parameters. It was suggested to develop a comprehensive regulation to control the entry of pollutants into the groundwater of the study area. HIGHLIGHTS The level of water quality for drinking and irrigation was better in the Azarshahr plain than in the Ajabshir plain.; Ca–Mg–HCO3 and rock dominance were identified as hydrochemical facies and the controlling factors in the groundwater of the study area.; The groundwater resources in the Urmia Lake Basin were found to be threatened by different sources of pollution.

The magnitude and variation of the sediment loads transported by rivers have important implications for the functioning of river systems and changes in the sediment loads of rivers are driven by numerous factors. In this paper, the key drivers of changes in the sediment loads of the major rivers of China are identified by reviewing recent studies of changes in their sediment loads. Except for the Songhua River, which presents no clear tendency of change in runoff or sediment load, nearly all the major rivers of China are characterized by an apparent decline in annual sediment load. The total annual sediment load of major Chinese rivers transported to the coast decreased from 2.03 billion t/yr during the period 1955–1968 to 0.50 billion t/yr during the period 1997–2010. The primary drivers of changes in the sediment loads of the rivers are dam construction, implementation of soil and water conservation measures, catchment disturbance, agricultural practices, sand mining and climate change. Examples drawn from Chinese rivers are used to demonstrate the importance of these drivers. Construction of a large number of reservoirs in the Yangtze River basin represents the primary driver for the reduced sediment load of the Yangtze River. The implementation of soil and water conservation programmes is one of the key drivers for the sharp decline in the sediment load of the Yellow River. Catchment disturbance explains why the reduction of the sediment load of the Lancang-Mekong River at the Chiang Saen gauging station was much less than that at the Gajiu gauging station upstream. A reduction in sediment load resulting from the expansion of agricultural production may be the main driver for the reduced sediment load of the Huaihe River. The decrease in the sediment load of the Pearl River has been influenced by sand mining activities. Climate change is one of the key drivers responsible for the greatly reduced sediment load of the rivers in the Haihe River Basin.

International audience; In order to optimize ship navigation in the macrotidal Gironde Estuary, a recent project funded by the port of Bordeaux aims at better understand and forecast hydrodynamic and fine sediment transport within the estuary. In the framework of this project, a two-dimensional hydro-sedimentary model is built. The model includes hydrodynamic forcings, mixed-sediment transport, and consolidation processes. The harmonic analysis of the astronomical tides reveals a strong distortion of the tidal wave inducing the growth of overtide constituents and the non-significant effect of tide-surge interactions in annual-scale prediction. Depending on hydrological conditions, river discharge can considerably alter the model accuracy due to the migration of the turbidity maximum zone modifying the bottom roughness. Comparison with measurements shows the ability of the model to reproduce suspended-sediment concentrations in the central Estuary. Sensitivity of the model to sediment features has also been discussed in regard of suspended-sediment concentrations and fluid mud deposits. The model will be further coupled with ship squat predictions and a morphodynamic model.p { margin-bottom: 0.25 cm; line-height: 115%; }

Plant residue decomposition can significantly affect the water environment of wetland ecosystems. However, little is known about the trajectory and the key drivers of the different initial mass of residue (IMR) that regulate water quality. Here, we conducted a study of 210 days with an in situ experiment to examine the impact of the change in IMR and the key decomposition parameters of Phragmites australis on the water quality in the growing season of 2019 in Baiyangdian wetland in North China. Five IMR of the Phragmites were applied, ranging from 0 to 1000 g with 250 g increments. The chemical oxygen demand (COD_W), total organic carbon (TOC_W), total nitrogen (TN_W) and total phosphorus (TP_W) of the water, and the total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), cellulose, lignin, decomposition rate (k) and the remaining mass of the Phragmites in the bag (RM) were monitored. Our results showed that the IMR of the Phragmites only marginally influenced the decomposition of itself and; the variations in the level of the water indicators were ranked as TN > TP > COD > TOC and; the impacts of IMR were longer on TOC and COD than on TP and TN and; the change in water quality was significantly influenced by the Phragmites decomposition and highly correlated with the change in TOC, cellulose and k of decomposing Phragmites residue. These results indicated that the impact of 250 g of IMR on the water was negligible after 120 days, suggesting that the optimal harvest rate of the Phragmites should be above 75% in the Baiyangdian wetland, despite the strong impact at the beginning and; the impact of change in IMR on water quality can be explained by the change in the decomposition parameters of the decomposing Phragmites residue, where such a decomposition-based explanation might be a promising tool to link wetland plant management and water quality.

Water erosion threatens large areas around the world. “Donga” is one of the witnesses of gully erosion in northern Benin, which induces serious threats to the natural habitats. This study was conducted to evaluate soil moisture content in different donga types (“microdongas”, “mesodongas”, and “megadongas”) and its variation at different topographic levels. The thermogravimetric soil moisture measurement technique was used for moisture estimation on saturated and unsaturated soil. Data were analyzed through analysis of variance test and t test with SAS software. The results showed that soil moisture content varied according to donga types. On unsaturated soil, higher difference (2.75%, p = 0.0328) was obtained in mesodongas at the middle followed by megadongas at the middle (2.6%, p = 0.034). On saturated soil, higher difference was obtained in mesodongas at the upstream (6.51%, p

Atmospheric nitrate (NO3−Atm) deposition has increased dramatically during the past ~ 150 years and contributes to ecosystem eutrophication. NO3−Atm deposition is widespread, but the role of different landscapes in modulating watershed-scale processing and export of NO3−Atm remains unclear. We measured triple oxygen isotopes (a tracer of NO3−Atm) of NO3− for 832 stream samples collected during baseflow and stormflow from 14 watersheds of varied land use throughout two years in the Chesapeake Bay watershed, and we used these data to assess the influence of land use on NO3−Atm dynamics. Watersheds with more agricultural (> 35%) and developed (> 70%) land exported more NO3−Atm than predominantly forested (> 75%) watersheds. Agricultural lands likely facilitate greater NO3−Atm export because of elevated rates of terrestrial N addition relative to rates of NO3− consumption. In contrast, developed lands likely have limited biotic processing of NO3−Atm because of greater hydrologic connectivity of overland flow pathways to channels. Our results, along with data from prior studies, can be interpreted by extending the conceptual model of kinetic N saturation to NO3−Atm streamwater export across varied land use watersheds. In this framework, elevated rates of terrestrial N inputs overwhelm NO3− sinks, allowing proportionally more NO3−Atm to leak from watersheds. Changes in watershed-scale N inputs that increase stream NO3− concentrations additively affect NO3−Atm, with agricultural watersheds, and their associated large terrestrial N inputs, increasing NO3−Atm export.

Irrigation uniformity in a semi-arid climate remains one of the main factors of water use efficiency (WUE) regardless of the level of agronomic advance, since over- and under-watered parts of the field represent wasted water or wasted yield at a given irrigation dose. The aim of this study was to analyze the underlying reasons for low WUE of linear move irrigators (LMI), detected by remotely sensed crop biomass maps in the Hula Valley, Israel. Head and tail towers were equipped with high-accuracy GNSS devices, recording their movements at 0.015 m accuracy. Periodic aerial surveys, run with multi-copter mounted visible and thermal cameras, showed stable and persistent over- and under-irrigation spatial patterns. Tower movement analysis revealed a “zigzag” pattern, where each tower lags behind and then catches up intermittently; over-irrigating during lags, under-irrigating during runs at the same spatial pattern over time, explaining the biomass variability. Deviations from the average at head and tail edge towers were in the 45–50% range of over-watering and the − 30% range of under-watering, and around ± 13%, at the mid part of the field. Yield sampling found 15% (pF > 0.069) yield loss. Sunken and winding wheel tracks observed in the field may have caused that movement pattern. Low WUE means waste of water that has a severe economic impact, especially in water scarce regions. Since water shortages are expected with climate change in many agricultural regions around the world, it is imperative to improve LMI machine movement uniformity, or to enable compensating irrigation control in order to solve water waste issues.

First, the Authors are to be congratulated on their paper, in which the depressurization process in a drainage system has been analysed experimentally and numerically. The drainage system contains ...

Dynamic monitoring data of groundwater level is an important basis for understanding the current situation of groundwater development and for the utilization and planning of sustainable exploitation. Dynamic monitoring data of groundwater level are typical spatio-temporal sequence data, which have the characteristics of non-linearity and strong spatio-temporal correlation. The trend of dynamic change of groundwater level is the key factor for the optimal allocation of groundwater resources. However, most of the existing groundwater level prediction models are insufficient in considering temporal and spatial factors and their spatio-temporal correlation. Therefore, construction of a space–time prediction model of groundwater level considering space–time factors and improving the prediction accuracy of groundwater level dynamic changes is of considerable theoretical and practical importance for the sustainable development of groundwater resources utilization. Based on the analysis of spatial–temporal characteristics of groundwater level of the pore confined aquifer II of Changwu area in the Yangtze River Delta region of China, the wavelet transform method was used to remove the noise in the original data, and the K-nearest neighbor (KNN) method was used to calculate the water level. The spatial–temporal dataset and the long short-term memory (LSTM) were reconstructed by screening the spatial correlation of the monitoring wells in the study area. A spatio-temporal KNN-LSTM prediction model for groundwater level considering spatio-temporal factors was also constructed. The reliability and accuracy of KNN-LSTM, LSTM, support vector regression (SVR), and autoregressive integrated moving average (ARIMA) model were evaluated by a cross-validation algorithm. Results showed that the prediction accuracy of KNN-LSTM is 20.68%, 46.54%, and 55.34% higher than that of the other single prediction models (LSTM, SVR, and ARIMA, respectively). HIGHLIGHTS A KNN-LSTM spatio-temporal prediction model for groundwater level is proposed.; It is vital to use wavelet transform to denoise the original data before prediction.; KNN-LSTM has better applicability and accuracy than traditional single random models.

Potential evapotranspiration (PET) is an important parameter for the operation of irrigation projects and water resources management. The globally recognized PET estimation model, the FAO-56 Penman–Monteith (FAO-56 PM) model, had been criticized for its requirement of many detailed meteorological variables, but nevertheless has been accepted as the baseline model in many worldwide studies. The performances of different PET models can be found to be excellent for a specific location but may not be representative in other regions. The aim of this study is to select the most suitable PET model to estimate PET in Malaysia. Three radiation-based models and four temperature-based models were compared with the FAO-56 PM model at seven selected meteorological stations in Peninsular Malaysia. The mean bias error, relative error (Re) and normalized root-mean-square error (NRMSE) and coefficient of determination (R2) were used to evaluate the performances of the PET models. The Re values of Turc models were below 0.2 at all stations, while Priestly–Taylor, Thornthwaite, Thornthwaite-corrected and Blaney–Criddle models were above 0.2. The Makkink and Hargreaves–Samani models were below 0.2 at most of the stations. Thus, the Turc model was recommended as the best model to estimate PET in Peninsular Malaysia. HIGHLIGHTS This study applied various empirical potential evapotranspiration (PET) models to estimate the PET.; Radiation-based models and temperature-based models were compared with the FAO Penman–Monteith model.; MBE, Re, NRMSE and R2 were used to evaluate the performances of PET models.; The Turc model was found to give superior performance.; The outcomes can be used as a reference for water resources-related project design.

Carbon dioxide (CO2) emissions from aquatic ecosystems are important components of the global carbon cycle, yet the CO2 emissions from coastal reservoirs, especially in developing countries where urbanization and rapid land use change occur, are still poorly understood. In this study, the spatiotemporal variations in CO2 concentrations and fluxes were investigated in Wenwusha Reservoir located in the southeast coast of China. Overall, the mean CO2 concentration and flux across the whole reservoir were 41.85 ± 2.03 µmol/L and 2.87 ± 0.29 mmol/m2/h, respectively, and the reservoir was a consistent net CO2 source over the entire year. The land use types and urbanization levels in the reservoir catchment significantly affected the input of exogenous carbon to water. The mean CO2 flux was much higher from waters adjacent to the urban land (5.05 ± 0.87 mmol/m2/hr) than other land use types. Sites with larger input of exogenous substance via sewage discharge and upstream runoff were often the hotspots of CO2 emission in the reservoir. Our results suggested that urbanization process, agricultural activities, and large input of exogenous carbon could result in large spatial heterogeneity of CO2 emissions and alter the CO2 biogeochemical cycling in coastal reservoirs. Further studies should characterize the diurnal variations, microbial mechanisms, and impact of meteorological conditions on reservoir CO2 emissions to expand our understanding of the carbon cycle in aquatic ecosystems.

The performance of the water conservation function (WCF) affects the water supply and flood control capabilities of an ecosystem. In this study, we combined the water balance method with the Soil and Water Assessment Tool (SWAT) model to calculate the water conservation amount (WCA) upstream of the Xiong'an New Area (Zijingguan (ZJG), Zhongtangmei (ZJG) and Fuping (FP) basins) at annual and monthly scales from 2007 to 2017, and used multiple linear regression and geographic detector models to analyze the factors affecting the temporal changes and spatial pattern of the WCA. Our results reveal that the annual WCAs of the ZTM basin are all positive, while the WCAs of the ZJG and FP basins have negative values in drought years. The annual WCAs in the upstream of each basin have changed between positive and negative values. On the monthly scale, all areas of the ZJG, ZTM, and FP basins have positive and negative value changes of WCA between the rainy and non-rainy seasons. Precipitation, evapotranspiration, and their combined effects are the main factors leading to the temporal changes and spatial patterns of WCA in the study area. The above results can provide reference cases for other regions to carry out relevant research work. HIGHLIGHTS The combination of the SWAT model and water balance method can quantitatively calculate the water conservation amount (WCA) on multi-temporal scales.; The WCA has a positive-negative change between the rainy season and non-rainy season.; Precipitation, evapotranspiration, and their combined effects are the main factors leading to the temporal changes and spatial pattern of WCA.

In recent years, gridded precipitation data derived from satellite rainfall products have become critical data sources for hydrological applications, especially in ungauged basins where rain gauges are sparse or nonexistent. Also, in streamflow simulations, since the existing rainfall–runoff modelling methods require exogenous input with some assumptions, neural networks can be an efficient solution. In this paper, to simulate daily streamflow on the Ghare Ghieh River basin in northwestern Iran, the Levenberg–Marquardt Neural Network (LMNN) and the Particle Swarm Optimization Neural Network (PSONN) models are proposed. These models are trained and tested with different input patterns from ground-based data for water years of 1988–2008. Then, three satellite-based precipitation datasets, including TRMM-3B42V7, TRMM-3B42RT, and PERSIANN with 0.25° × 0.25° resolutions from 2003 to 2008, are used as inputs for the best-trained models which were selected in the testing step. These products are evaluated before and after calibration in streamflow simulation, and the Geographical Difference Analysis method is used to calibrate them. The results showed that the PSONN model performed better than the LMNN model. Also, in both models, before calibration of satellite precipitation products, TRMM-3B42 showed better performance in streamflow simulation, and after calibration, TRMM-3B42RT performed much better. HIGHLIGHTS Three commonly used satellite rainfall products including TRMM-3B42V7, TRMM-3B42RT, and PERSIANN are hydrologically evaluated, before and after calibration, over the Ghare Ghieh River basin.; The hybrid neural network model named PSONN is proposed for simulation of streamflow and it is compared to the basic ANN model, named LMNN.; In general, the PSONN model performed better than the LMNN model.; In both models, before calibration of satellite precipitation products, TRMM-3B42 showed better performance in streamflow simulation and after calibration using the GDA method, 3B42RT performed much better.; After calibration, in simulation with PSONN and use of TRMM-3B42, 3B42RT, and PERSIANN, the Rbias index decreased by 48, 72, and 73%, respectively.

The Lower Indus reaches – Guddu and Sukkur – are among the most complicated areas in terms of reach migration. Both climate change and human activities in recent periods along with pond system operation accelerated riverine channel morphology. A GIS-based approach using multi-temporal Landsat images (1986–2020) was employed to characterize the morphometric parameters. Results showed that width of the study reaches varied from 2.1 to 12 km. The braiding index (BI) value for Guddu reach varied from 3.47 to 7.18, and BI value for Sukkur reach varied from 2.11 to 4.92. It is observed that no erosive activity of banks occurred for peak runoff value of

Scientific and accurate prediction of river runoff is important for river flood control and sustainable use of water resources. This study evaluates the ability of a Nonlinear Auto Regressive model (NAR) in predicting runoff volume. Using the Cuntan Hydrological Station in the upper reaches of the Yangtze River as the research object, the model was established based on the runoff characteristics from 1951 to 2020 and tested by NAR. To improve the prediction efficiency, complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) preprocessing technique is used to decompose the data. The results show that the coupled CEEMDAN-NAR model has better predictive ability than the single model, with a coupled model deterministic coefficient (DC) of 0.93 and a prediction accuracy of Class A. HIGHLIGHTS Proposed a runoff prediction model using CEEMDAN-NAR hybrid approach.; Decomposition of runoff data using CEEMDAN preprocessing techniques to improve model prediction accuracy.; Using models to predict runoff in the upper Yangtze River from 2005 to 2020 and verifying their accuracy; The CEEMDAN-NAR model provides better predictions than the GRU, NAR and EEMD-NAR prediction models.

In this paper, the responses of hydro-meteorological drought to changing climate in the Be River Basin located in Southern Vietnam are investigated. Climate change scenarios for the study area were statistically downscaled using the Long Ashton Research Station Weather Generator tool, which incorporates climate projections from Coupled Model Intercomparison Project 5 (CMIP5) based on an ensemble of five general circulation models (Can-ESM2, CNRM-CM5, HadGEM2-AO, IPSL-CM5A-LR, and MPI-ESM-MR) under two Representative Concentration Pathway (RCP) scenarios (RCP4.5 and RCP8.5). The Soil and Water Assessment Tool model was employed to simulate streamflow for the baseline time period and three consecutive future 20-year periods of 2030s (2021–2040), 2050s (2041–2060), and 2070s (2061–2080). Based on the simulation results, the Standardized Precipitation Index and Standardized Discharge Index were estimated to evaluate the features of hydro-meteorological droughts. The hydrological drought has a 1-month lag time from the meteorological drought and the hydro-meteorological droughts have negative correlations with the El Niño Southern Oscillation and Pacific Decadal Oscillation. Under the climate change impacts, the trends of drought severity will decrease in the future; while the trends of drought frequency will increase in the near future period (2030s), but decrease in the following future periods (2050 and 2070s). The findings of this study can provide useful information for the policy- and decisionmakers for a better future planning and management of water resources in the study region. HIGHLIGHTS There is a lack of knowledge about how climate change will affect the hydro-meteorological drought in the tropical region.; The hydro-meteorological droughts have negative correlations with the global climate oscillation.; The drought frequency will have a rising trend in the near future period (2030s) and downward trends in the following future periods (2050 and 2070s).

Measurements of chemical persistence in natural environments can provide insight into behavior not easily replicated in laboratory studies. However, it is difficult to find environmental situations suitable for such measurements, particularly for substances with half-lives exceeding several weeks. The objective of this study was to demonstrate that a strategic postflood monitoring campaign can be used to quantify transformation half-lives on the scale of months in a real aquatic system. Water samples were collected in the upper Brisbane River estuary on 36 occasions over 37 weeks and analyzed for 127 pharmaceuticals and personal care products (PPCPs), pesticides, and perfluoroalkyl substances (PFASs). High quality time trend data were obtained for 41 substances. For many of these, data on the input of a wastewater treatment plant to the upper estuary were also obtained. A mass balance model of the estuary stretch was formulated and parametrized using PFASs as persistent benchmarking chemicals. Transformation half-life estimates were obtained for 10 PPCPs and 7 pesticides ranging from 18 to 260 days. Furthermore, insight was obtained into dominant transformation processes as well as the magnitude of chemical inputs to the estuary and their sources. The approach developed shows that under certain conditions, estuaries can be used to quantify the persistence of organic contaminants with half-lives of the order of several months., R. Álvarez-Ruiz acknowledges the Spanish Ministry of Science, Innovation and Universities and the ERDF (European Regional Development Fund) for his FPI grant BES-2016−078612. This project was supported by an Australian Research Council (ARC) Linkage grant (LP180101128) and the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 734522 (INTERWASTE project).

Stream restoration, such as channel reconfiguration and riparian zone revegetation, is increasing in response to aquatic impairment in agroecosystems. Though riparian zones effectively remove nitrogen (N), conditions that foster nitrate (NO3−) removal (e.g., soil saturation, low oxygen, available carbon) may facilitate the release of soluble reactive phosphorus (SRP) and greenhouse gases (GHGs—carbon dioxide [CO2], methane [CH4], and nitrous oxide [N2O]). In this study, water quality and GHG fluxes were quantified seasonally at agricultural restored, unrestored, and forested riparian zones via networks of wells and static chambers. Carbon dioxide comprised the majority of GHG emissions, and CO2 fluxes were lower at the restored site than the forested site (medians: 0.71 g C m−2 day−1 and 1.29 g C m−2 day−1, respectively). The restored site was a net CH4 source (median: 1.20 mg C m−2 day−1), while the other sites were net CH4 sinks (medians: − 1.00 to − 1.76 mg C m−2 day−1). Sites had comparable N2O emissions. Subsurface SRP was lower at the restored than unrestored agricultural sites, while median NO3− removal efficiency was higher (restored: 91%, unrestored: 35–66%). Over time, NO3− removal and CO2 fluxes increased post-restoration. Methane emissions were elevated when the restored riparian zone was a CO2 and N2O sink and NO3− removal was high. Despite variability within and between sites, seasonal conditions (temperature, water table height, precipitation) and site characteristics (geomorphology, soils) remained key explanatory variables for riparian N removal and GHG release. Overall, riparian restoration may promote N removal without increasing total GHG emissions.

Aiming at the problem of automatic classification of point cloud in the investigation of vegetation resources in the straw checkerboard barriers region, an improved random forest point cloud classification algorithm was proposed. According to the problems of decision tree redundancy and absolute majority voting in the existing random forest algorithm, first the similarity of the decision tree was calculated based on the tree edit distance, further clustered reduction based on the maximum and minimum distance algorithm, and then introduced classification accuracy of decision tree to construct weight matrix to implement weighted voting at the voting stage. Before random forest classification, based on the characteristics of point cloud data, a total of 20 point cloud single-point features and multi-point statistical features were selected to participate in point cloud classification, based on the point cloud data spatial distribution characteristics, three different scales for selecting point cloud neighborhoods were set based on the point cloud density, point cloud classification feature sets at different scales were constructed, optimizing important features of point cloud to participate in point cloud classification calculation after variable importance scored. The experimental results showed that the point cloud classification based on the optimized random forest algorithm in this paper achieved a total classification accuracy of 94.15% in dataset 1 acquired by lidar, the overall accuracy of classification on dataset 2 obtained by dense matching reaches 92.03%, both were higher than the unoptimized random forest algorithm and MRF, SVM point cloud classification method, and dimensionality reduction through feature optimization can greatly improve the efficiency of the algorithm.

Landslides are frequent occurrences in Ottawa, Canada because sensitive marine clays (also known as Leda clay or Champlain Sea clay) dominate the landscape. These landslides are often triggered by ...

Land-use practice shift in the wetland riparian zone can influence groundwater table (GWT) fluctuations and salts dynamics, potentially leading to soil salinization. The risk of soil salinization linked with high water tables could better manage using high growing capacity and deep-rooted phreatophytic vegetation via ‘biodrainage’ approach. We evaluated the impacts of short rotation willow (SRW) plantation on soil and groundwater salinity linked to shallow GWT fluctuations and compared with adjacent annual crop (AC) and pasture (PA) in a field experiment. Groundwater salinity (ECgw) along with depth to GWT and soil salinity (ECsoil at 0-60 cm depth) were measured along transects within each land-use practice in two prairie pothole region (PPR) wetland sites (A and B). The variations in ECgw were significant (p < 0.05) across land-uses; however, inconsistent between sites. The positive correlation with ECgw, ECsoil, and total dissolved salts (TDS) indicated higher salinity and salt accumulation with increased depth to GWT in both sites. The ECsoil varied significantly (p < 0.05) among land-use practices; however, no consistent land-use patterns were observed between sites. Throughout the experimentation, site B consistently exhibited higher ECsoil (two-fold) than site A. Decreasing inclinations were observed in ECsoil with increasing SRW biomass at both depths (i.e., 0-30 and 30-60 cm) and vice versa. This study refines our knowledge of SRW linked potential hydrological alteration and its implication on salinity, which provides critical context for degraded marginal riparian wetland soil management in the PPR.

Smith ED, Balika D, Kirkwood AE. 2021. Community science-based monitoring reveals the role of land use scale in driving nearshore water quality in a large, shallow, Canadian lake. Lake Reserv Manag...

The total suspended solids (TSS) concentration is a relevant parameter for stream management. A high content of TSS has a negative impact on the ecological habitats and the aquatic environment, and could also be a limitation for the exploitation of surface water. The determination of TSS concentration through water sampling and posterior laboratory analysis is a complex and economically expensive procedure. In this regard, turbidity arises as a useful surrogate measure that allows the indirect estimation of the TSS concentration in a simple and economically convenient way. In the context of a severely deteriorated water supply system, the Naposta Grande stream constitutes a valuable resource for human and industrial consumption in the City of Bahia Blanca. The general objective of the present investigation is to develop statistically based relations between the parameters involved in the suspended solids transport, in order to characterize this phenomenon through the measurement of variables of simple and straightforward field determination. The statistical relationship between the TSS concentration and turbidity and between discharge and solid flow rate was explored. In both regression analyses, the statistical correlation resulted highly significant, and therefore represent valid calibration tools for future solids transport modelling analysis and prediction as well as for sedimentological balances. A comparative analysis of the solids transport between the closure of the medium drainage basin and at the outer limit of the suburban area of Bahia Blanca City, suggests the existence of erosive processes affecting the stream bed and its margins at the section between both sites.

Accurate simulations of wastewater quality and quantity, particularly in saline and semi-arid areas, are important in agricultural water management. In this study, a system dynamics (SD) approach was proposed to simulate drainage water and groundwater salinities, water table fluctuation, and drainage discharge at field scale. The results of the SD approach were compared with results from DRAINMOD-S, a computer simulation model. For model validation, earlier experimental data from two field units were used. The field units each contained three rows of piezometers. During irrigation, daily water table fluctuation, drainage discharge, irrigation and drainage water salinity, and the salinity in each piezometer, were measured. The SD approach simulated these parameters more accurately than DRAINMOD-S for both units. HIGHLIGHTS The SD approach and DRAINMOD-S model are proposed to simulate drainage water and groundwater salinities, water table fluctuation, and drainage discharge at the field scale.; For model validation, experimental data collected from farms are used.; Adjustment between measured and predicted values, using statistical parameters.; Results showed that the SD approach simulated more accurately than the DRAINMOD-S model.

Meandering rivers have dynamic evolution characteristics of lateral migration and longitudinal creeping movement, and studies on the migration rate of meandering rivers have both scientific and practical significance for understanding the evolution process. A river source region often is sparsely populated and lacks long-term monitoring data, making it difficult to estimate the migration rate of river bends. In the source region of the Yellow River, located in the northeastern part of the Qinghai-Tibet Plateau, China, meandering rivers have extensively developed. Combined with field investigation and sampling in the source region in 2016 and 2017, 9 river bends in the middle Baihe River were selected to attempt estimation of migration rates of the river bends using tree ring analysis. The tree core and disc samples were collected using an increment borer and a crosscut saw, and the ages of the trees were estimated based on tree ring analysis. A method for estimating the migration rate of river bends based on the relation between positions and ages of trees grown on the point bars in inner banks is proposed. The estimated migration rates of the 9 river bends of the Baihe River ranged 0.38–6.10 m/yr, and the migration rates were found to be related to the flow rate, channel slope, height of the outer bank, and width of the river valley. The maximum migration rate was determined to be at the No. 9 River Bend where the ratio of the meander-bend radius to the channel width (R/W) was 2.31, which is consistent with previous findings that the bend migration is most rapid in the ‘migration phase’. The proposed method for estimating the migration rate of river bends provides a potential alternative option for future study on the morphodynamic process of a meandering river.

Coastal wetlands reclamation is facing the problem of salinization. Along with the alternation of ecosystem status, studying the following effect on soil properties becomes emergency. Here we reported the pH, salinity and elemental content (mainly metals) variation affected by the vegetation situations, water sources and geographic positions. The results showed that vegetation could lead the pH and salinity of seawater zones closer to that of freshwater zones in both spatial and time scales. Spartina alterniflora (SA) was the most efficient species among the investigated plants, causing decreases of 0.15–0.69 in pH and 2.250–3.821 in salinity. This result might be caused by the absorption of Ca and K from salt marshes by SA and Suaeda salsa (SS), due to the fact that the component content of calcium (all reduced to approximate one-third) and potassium (reduced in some samples) both decreased. Meanwhile, vegetation could improve soil in seawater zones in Fe content with no extra negative influences in elemental analysis. Thus, ecological engineered vegetation indicated great potential in alternating coastal salt marshes to favorable wetlands or farmlands with almost primitive ecosystem. The results might be significant for ecological engineering and agricultural management in future.

Knowledge on spatio-temporal variations in planform, hydraulic geometry, and bed-level variations of alluvial streams is required for planning and development of hydraulic structures and bank protection works. In the current study, a Geographic Information System (GIS) has been used to analyze topographical maps, multi-temporal remotely sensed imagery, and hydrologic and hydraulic data to extract the morphological parameters of the Upper Tapi River, India. The river has been found to have consistent migration towards the northern direction, with erosion/deposition on right/left banks. The river has not experienced any major meander except in the lower reaches of the Upper Tapi Gorge and minor braiding conditions at the location where the river emerges from mountainous topography to the plain region. The analyzed river cross sections were found to be depth dominated, and contain large flows within the channel banks. The cross-sections exhibited moderate channel bed adjustments in 1994, 2006, and 2007 wherein excessive sediment flux and stream power were capable of causing morphological changes in the river. High intensity rainfall in the subcatchment resulted in high sediment flux into the river during 1994, which was reported to cause significant aggradation at the downgauging station. The analysis of sediment flux into the river in conjunction with decadal land use land cover, revealed that sediment yield from the catchment was reduced during 2000–2010 due to an increase in water bodies in the form of minor hydraulic structures. The entry of comparatively less sediment laden water into the river, resulted in moderate bed degradation especially in 2006 and 2007 as observed at the downstream station. The methodology applied in the current study is generic in nature and can be applied to other rivers to identify their morphological issues.

Excessive phosphorus is an important cause of eutrophication. For river basin management, source identification and control of nonpoint source (NPS) pollution are difficult. In this study, to explore influences of hydrological conditions on phosphorus, the Soil and Water Assessment Tool (SWAT) model is applied to the Luanhe River basin in North China. Moreover, influences of the spatial scale of the livestock and poultry amount data on estimations of phosphorus loads are also discussed. The results show that applying town-level livestock and poultry amount data allows the model to perform better when estimating phosphorus loads, indicating that using data at a finer administrative level is necessary. For the typical wet year, the estimated annual phosphorus load was 2.6 times that in the typical dry year. Meanwhile, the contribution of pollution in summer to the annual load is greater in the wet year than that in the dry year. The spatial distributions of subbasins with high unit loads of phosphorus differ under different hydrological conditions, meaning that critical areas for pollution control vary with the wetness of each year. All these findings indicate that for pollution control at basin scale, considering the seasonal and interannual variabilities in hydrological conditions is highly demanded. HIGHLIGHTS The influences of hydrological condition on phosphorus load at basin scale analyzed.; The SWAT hydrological model applied to analyze the scale effect of non-point source pollution data.; Livestock and poultry amount data of finer resolution performs better.; Contribution of summer season to annual phosphorus load varies with wetness of the year.; Critical area for phosphorus load varies with hydrological condition.

Across the Afrotropical ecosystems human activities are increasingly modifying natural flow regimes, nutrient and organic matter loading and processing in streams and rivers with implications on ecosystem structure and functioning. The Mara River Basin has undergone extensive land-use change, but influences of these changes on water quality and aquatic communities are not well understood. This study investigated changes in water quality and macroinvertebrate assemblages across a disturbance gradient arising from rural human activities in nineteen sites; grouped into three condition categories (reference undisturbed (n = 7), moderately disturbed (n = 6) and disturbed (n = 6)). Temperature, dissolved oxygen, total dissolved solids, pH and electrical conductivity were measured in situ at each sampling site, and samples collected for analysis of nutrients and total suspended solids. Sampled macroinvertebrates were identified mainly to family level for analysis of structural and functional composition. There were significant spatial variations in water quality variables across the disturbance gradient (p

In most of the basins, due to the lack of sedimentation stations, there is no accurate information on sediment deposition and soil erosion. In such basins, empirical models are used to estimate the sediment rate. At the basin scale, the applicability of these models is troublesome. The objectives of this study were to determine the erosion status of the Zarivar lake basin and to evaluate the efficiency of the Factorial Scoring Model, FSM, in estimating the sediment rate. Physiological and hydrological characteristics of 10 sub-basins of Zarivar lake were obtained using field measurements and aerial data in the GIS environment. The specific weight of the sediments was calculated in the laboratory and used to determine the weight of sediments. The sediment rate in sub-basins was measured in situ. Furthermore, by determining the effective parameters, the sediment rate for each sub-basin was obtained using FSM, and the results were compared with the measured rate. For the whole basin, the average, minimum, and maximum rate of observed sediment were 0.28, 0.007, and 1.17 m3/ha.yr, respectively. However, these rates were obtained by FSM as 103.70, 20.90, and 365 m3/ha.yr, respectively, which differed from the observed values. Based on the results, the model is not sufficiently efficient to evaluate the sediment rate in the studied sub-basins.

The paper deals with the long-term and seasonal variability of low flows using the example of a mountain river. The study covers the Laborec River in the eastern part of Slovakia, and the main aim of the research is to identify and establish long-term fluctuations of low flows on this river. The analysis aims to indicate trends of low flows and seasonal variability of outflows based on various measures and research methods as well as the links between them. Basic data on daily flow and precipitation series were collected from 1980 to 2019. Low flow periods were identified in relation to the fitting of the threshold level method to the 70th and 95th percentile on the flow duration curve as a constant, multi-annual cut-off (Q70%, Q95%). The longest lasting flows were those below q70%, which were determined in the shallow cut-offs that occurred for most of the year, i.e. from June to December and in January. The greatest culmination of flows below q95% was in August and September. The range of minimal unit outflow is the smallest in the summer-autumn period and results from long periods without precipitation and with increased evapotranspiration. The highest range of unit outflow was recorded from December to April. Knowledge of low river flows should be one of the important elements of advanced planning, which in the future may help to reduce conflicts between water users during the peak demand period.

Objectives To explore the algal floral diversity and its role to determine water quality. Methods The regular monthly collection of algal and water samples was made during 2018. Unicellular algae were preserved in 2 to 3% formalin while macroalgae in 4% formalin. Microphotographs of algae were taken at the biotechnological Lab of PCSIR Lahore, Pakistan. Palmer pollution index was used to determine water quality. Results The study identified 201 algal species distributed among 57 genera, 42 families, 25 orders, 10 classes and 7 divisions. The total score of Algal Genus Pollution Index of Banjosa Lake, Ali Sojal Dam, Dothan Dam, Drake Dam and Rawalakot Nullah (city) were 14, 9, 10, 18 and 25 respectively. It was revealed that Banjosa Lake has probable organic pollution, Ali Sojal Dam and Dothan Dam showed lack of organic pollution, Drake Dam indicated moderate pollution while Rawalakot Nullah (City) indicated confirm high organic pollution. Conclusion We strongly recommend the conservation and managed status of algal species for sustainable resource of algal- derived products in future. It was revealed that the water quality of Banjosa Lake, Drak Dam and Rawalakot Nullah was affected from anthropogenic activities and needs to be managed.

The construction of the Three Gorges Dam (TGD) at the end of the upper reach of the Yangtze River results in a great belt-shape of the Three Gorges Reservoir (TGR) in China. Thus the atmospheric problems related to the TGR have attracted substantial interest from most meteorologists around the world. To understand the regional temperature changes in the TGR area since the impoundment of the TGD in June 2003, temperature data from 32 meteorological stations in the TGR area during 1961—2014 period were collected, and the trends in the temperature changes in the past 20 years, including years before and after impoundment of the TGD, were analysed by the methods of cumulative anomaly analysis, moving average, and linear regression analysis. The results showed that the annual mean temperature over the TGR area showed a slight overall upward trend in the past 54 years, and the temperature rose substantially at the period between 1985 and 2014. After impoundment, a warming trend was obvious in the TGR area. The monthly mean temperature after impoundment was higher than that before impoundment.

Severe soil erosion occurs on the Loess Plateau in China, which makes the Yellow River the most sediment-laden river in the world. Construction of about 60,000 sediment check dams has remarkably controlled soil erosion on the Loess Plateau and reduced the sediment load of the middle and lower Yellow River. Nonetheless, little is known about the mechanism of erosion control and vegetation development of sediment check dams. The function of a single check dam mainly is trapping sediment, while the function of a train of check dams comprising dozens of or over hundreds of check dams in a gully encompasses controlling bed incision and reducing erosion energy. A formula was proposed to calculate the potential energy of bank failure and slope failure in a gully, which essentially constitutes the erosion energy. The erosion energy increases when gully incision occurs, which is induced by the incision of the Yellow River and its tributaries on the Loess Plateau. Sediment deposition in many gullies due to construction of check dams reduces the erosion energy to almost zero, which in turn greatly reduces soil erosion and sediment yield. Construction of check dams promotes vegetation development. The vegetation-erosion dynamics model was used to study the effect of check dams on vegetation development. Simulation results show that reforestation without check dam construction might result in an increase of vegetation cover in the first ten years and then a drop of vegetation cover to less than 10% in the later years. The check dams provide a foundation for vegetation development.

Using a simulation program and video census data (2004–2018) from the Bois Brule River fishway, Wisconsin, USA, we compared alternative sampling designs to estimate spawning run abundances of steelhead, coho salmon, Chinook salmon, and brown trout. We evaluated two types of two-stage sampling designs, comprising varying numbers of days sampled within a year (1st stage samples) and varying numbers of hours sampled within a day (2nd stage samples). While days were sampled using stratified random sampling under both types of sampling designs, hours were sampled using uniform (1/24) or non-uniform (proportional to hourly runs) selection probabilities under the first and second types of sampling designs, respectively. Number of days sampled within a year, comprising three strata, varied from 30 to 200 days in 10-day increments, and number of hours sampled within a day varied from 2 to 24 h in 2-hour increments. Spawning run sizes of the salmonids could be estimated with a relative root mean square error (RMSE) of less than 10% on average by employing a two-stage sampling design with samples of 100 days·yr−1 and 8 hrs·day−1, i.e., 800 hrs·yr−1; by contrast, full census involved reviewing 250 days·yr−1 and 24 hrs·day−1, i.e., 6000 hrs·yr−1, of video. Sampling more days (>100) resulted in greater reductions in estimation error than sampling more hours (>8). Non-uniform (vs. uniform) selection probabilities for hours sampled slightly reduced error of estimates. Our results underscore that optimal sampling designs could ensure a considerable reduction in survey resources while maintaining relatively low error in estimation of salmonid abundances.

Riparian vegetation provides a wide range of ecosystem services including water quality regulation, flooding avoidance, and the natural control of stream temperatures. Changes in land use and the increase of anthropogenic activities in the proximity of rivers affect the growth and development of riparian buffers. The aim of the work was to assess the effects of riparian vegetation on the evapotranspiration processes and the water quality of small plain streams using remote sensing resources and in-situ monitoring. The area of study considered two neighboring basins of small plain streams (Glavacioc and Ilfov) from Romania. The data obtained from in-situ monitoring performed in 2019 was used in the Penman-Monteith algorithm to calculate the potential evapotranspiration (PET) based on a series of specific parameters. The Green Normalized Difference Vegetation Index (GNDVI), computed from LANDSAT 8 images, has been used to assess the vegetation status at the basin scale. The GNDVI fluctuations were linked to the variations in precipitation regimes and land use modifications. Remote sensing data have shown changes in GNDVI between June and September 2019 in both riparian areas resulting in an intense spread of cattail (Typha spp.). Surface waters arriving at the entrance control sections had a basic pH and were loaded with nitrates and ammonium ion (NH4+), which had decreased at the downstream section after passing the cattail phytosociological associations and the riparian patches, thus acting as buffer areas. The current anthropogenic pressures on the riparian areas might have degenerative effects on the integrity of the vegetation structure. Thus, for effective and sustainable management, it is essential to identify the main stressors and to assess to what extent they affect the riparian ecosystem as a whole.

The paper concerns the impact of the diverse land use in the Silnica river catchment, within the city of Kielce, on the size and dynamics of concentration and load of transported suspended solids, and the variability of the mineral particles mean grain size, during various flood types. This small river flows through the centre of Kielce, the city of 200,000 population in Poland. In its course, the river flows through areas of various land use. In the upper reaches, the catchment is dominated by forests, in the middle the river flows through a reservoir and the lower – through an urban area. Hydrological measurements and transport of the suspended solids were carried out simultaneously in three hydrometric cross-sections of the Silnica, which close the sub-catchments of the land use as mentioned above. The investigations were carried out during floods of various origins: induced by snowmelt, torrential rainfall and frontal rainfall. The analysis indicates that the two rainfall-induced flood types, characteristic for the summer season, show high runoff dynamics. In contrast, snowmelt-induced floods show high concentration and load of the transported suspended solids. In the section of the watercourse flowing through the city, there is an abrupt increase in runoff and suspended solids concentration. Thus, there may be periodic threats to fish and invertebrates, leading to a reduction in the population of living organisms.