Water Quality Of Aquatic Ecosystems Research Articles

Assessing the sources and spatiotemporal variability of dissolved trace elements in the upper Nakdong River based on multivariate analysis

Various sources associated with mining activities adversely affect water quality in aquatic ecosystems. This study aimed to estimate the sources of dissolved trace elements (DTEs: Al, As, B, Ba, Cd, Co, Cr, Cs, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Sb, U, and Zn) affecting water chemistry in the upper Nakdong River (UNR) catchment and determine the hydrological processes associated with the inflow from anthropogenic sources. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were employed to estimate main sources affecting water chemistry and its spatiotemporal variability in the four tributaries and main channel of the UNR. Water samples were classified into four groups based on their chemistry. The spatiotemporal variations of DTEs were driven by the presence of anthropogenic sources (including smelters, AMD, mining-related sources), while running toward downstream. The correlations among PCA (and HCA), Zn as smelter impact, and deuterium excess (d-excess = δ2H – 8 × δ18O) indicated that smelters had a strong influence on water chemistry in the main channel after passing through the smelter. In the dry season, d-excess < ~12 ‰ was observed with increasing Zn levels and factor score for PC2, especially samples influenced by DTEs from smelter, indicating that groundwater affected by the smelters recharged mainly by summer rainwater impacted the spatiotemporal variability of DTEs. This multivariate study suggests that the spatiotemporal variation in DTEs is associated with the complex contributions of natural and anthropogenic sources to water chemistry, which are strongly influenced by hydrological processes and seasonality.

Rapid flotation of Microcystis wesenbergii mediated by high light exposure: implications for surface scum formation and cyanobacterial species succession.

Increasing occurrences of Microcystis surface scum have been observed in the context of global climate change and the increase in anthropogenic pollution, causing deteriorating water quality in aquatic ecosystems. Previous studies on scum formation mainly focus on the buoyancy-driven floating process of larger Microcystis colonies, neglecting other potential mechanisms. To study the non-buoyancy-driven rapid flotation of Microcystis, we here investigate the floating processes of two strains of single-cell species (Microcystis aeruginosa and Microcystis wesenbergii), which are typically buoyant, under light conditions (150 μmol photons s-1 m-2). Our results showed that M. wesenbergii exhibited fast upward migration and formed surface scum within 4 hours, while M. aeruginosa did not form visible scum throughout the experiments. To further explore the underlying mechanism of these processes, we compared the dissolved oxygen (DO), extracellular polymeric substance (EPS) content, and colony size of Microcystis in different treatments. We found supersaturated DO and the formation of micro-bubbles (50-200 µm in diameter) in M. wesenbergii treatments. M. aeruginosa produces bubbles in small quantities and small sizes. Additionally, M. wesenbergii produced more EPS and tended to aggregate into larger colonies. M. wesenbergii had much more derived-soluble extracellular proteins and polysaccharides compared to M. aeruginosa. At the same time, M. wesenbergii contains abundant functional groups, which was beneficial to the formation of agglomerates. The surface scum observed in M. wesenbergii is likely due to micro-bubbles attaching to the surface of cell aggregates or becoming trapped within the colony. Our study reveals a species-specific mechanism for the rapid floatation of Microcystis, providing novel insights into surface scum formation as well as succession of cyanobacterial species.

Role of three-dimensional vortex motions on horizontal eddies in an open-channel cavity

AbstractLateral cavities are a popular object of study in hydraulic research as they are widely found in rivers and hydraulic facilities and significantly impact flow patterns, sediment transport, and water quality in aquatic ecosystems. While the effects of open-channel cavities on various aspects including characteristics of three-dimensional structures have been extensively studied, the role of vertical flow structures in the cavity has not been focused on. This study examines the relationship between the shallowness parameter and the three-dimensional flow effects on the dynamics of an open-channel lateral cavity flow with horizontal vortex motion, comparing the conventional two-dimensional model (2DC), advanced depth-integrated models including general bottom velocity calculation method (GBVC) with the ability to consider vertical flow structures, simplified bottom velocity calculation method with the shallow water assumption (SBVC), a three-dimensional model (3DC), and experimental data. The comparison results demonstrate that the three-dimensional flow effect significantly impacts the velocity distribution and vortex evolution in the cavity. The GBVC model demonstrates a good agreement with the flow patterns by the 3DC model and experimental results in the cavity, whereas the 2DC and SBVC models are unsuitable for deep-water conditions.

Dissolved organic matter (DOM) is independently stratified in thermally stratified water bodies

Thermal stratification often occurs in deep-water bodies, including oceans, lakes, and reservoirs. Dissolved organic matter (DOM) plays a critical role in regulating the dynamics of aquatic food webs and water quality in aquatic ecosystems. In the past, thermal stratification boundaries have been sometimes used exclusively to analyze the vertical distribution of DOM in thermally stratified water bodies. However, the validity of this practice has been challenged. Currently, there is limited understanding of the formation mechanism and stratification of the vertical distribution of DOM in thermally stratified water bodies, which hinders the analysis of the interactions between DOM and vertical aquatic ecological factors.To address this gap, we conducted a comprehensive study to extensively collect the vertical distribution of DOM in thermally stratified water bodies and identify the primary factors influencing this distribution. We found that DOM was independently stratified in thermally stratified water bodies (including two cases in unstratified water bodies), and that the formation mechanisms and statuses of DOM stratification were different from those of thermal stratification. The boundaries and numbers of DOM stratification were generally inconsistent with those of thermal stratification. Therefore, it is more accurate to divide DOM into different layers according to its own vertical profile, and analyze DOM characteristics of each layer based on its own stratification instead of thermal stratification. This study sheds light on the relationship between DOM and thermal stratification and provides a novel approach for analyzing DOM vertical distribution characteristics and their impact on aquatic ecosystems. This finding also holds significant implications for the design and implementation of environmental management programs aimed at preserving the health and functionality of aquatic ecosystems.

Temporal profiling of sediment microbial communities in the Three Gorges Reservoir Area discovered time-dissimilarity patterns and multiple stable states

Microbial communities play vital roles in cycling nutrients and maintaining water quality in aquatic ecosystems. To better understand the dynamics of microbial communities and to pave way to effective ecological remediation, it's essential to reveal the temporal patterns of the communities and to identify their states. However, research exploring the dynamic changes of microbial communities needs a large amount of time-series data, which could be an extravagant requirement for a single study. In this research, we overcame this challenge by conducting a meta-analysis of years of accumulations of 16S rRNA high-throughput sequencing data from the Three Gorges Reservoir Area (TGRA), an ecological and environmental hotspot. For better understanding the microbial communities time-dissimilarity dynamics, three microbial communities time-dissimilarity patterns were hypothesized, and the linear pattern in the TGRA was validated. In addition, to explore the stability of microbial communities in the TGRA, two alternative stable states were revealed, and their differences in community richness, alpha diversity indices, community composition, ecological network topological properties, and metabolic functions were demonstrated. In short, two states of microbial communities showed distinct richness and alpha diversity indices, and the communities in one state were more dominated by Halomonas and Nitrosopumilaceae genera, facilitating nitrogen cycling metabolic processes; whilst the main genera of the other state were Bathyarchaeia and Methanosaeta, which favored methane-related metabolism. Moreover, different studies and environmental differences between mainstream and tributaries were attributed as the potential inducing factors of the state division. Our study provides a comprehensive insight into the dynamics and stability of microbial communities in the TGRA, and a reference for future studies on microbial community dynamics.

Metal-organic frameworks combined with mid-infrared spectroscopy for the trace analysis of phosphates in water

Detecting traces of phosphates in water is critical for monitoring water quality in aquatic ecosystems. Mid-infrared techniques are effective for label-free and quick measurements in at-line or in-line applications, but sensitivity is limited due to high water absorption. To combat this, preconcentration schemes combined with evanescent field spectroscopy can be used to enrich the analyte in the probed volume and thereby increasing sensitivity. Metal-organic frameworks (MOFs) are versatile materials with defined porosity and tuneable chemistry, which make them ideal for selective adsorption of target molecules. In this study, an NH2-MIL-88B(Fe) (= Fe3O(NH2-BDC)3) MOF-based enrichment layer was prepared on a diamond attenuated total reflection (ATR) crystal for in situ Fourier transform infrared (FTIR) spectroscopic measurements of ortho-phosphates in water. A workflow for single-use enrichment layers was established, and an automated flow system was used to apply aqueous phosphate solutions. Using internal referencing and compensating for variation in MOF film depositions, phosphate analysis reproducibility increased from 74% to 94%. The Langmuir adsorption model was used to derive a limit of detection (LOD) of 0.18 mg L-1 phosphorus in water. Overall, this work demonstrates the effectiveness of NH2-MIL-88B(Fe) MOFs as enrichment layers for aqueous phosphate sensing. Our results provide a promising avenue for the development of sensitive and selective sensors for environmental and biomedical applications.

Involvement of High School Students of General Secondary Education Institutions in Environmental Projects: Theoretical and Methodological Approaches and Practical Implementation

The article considers certain stages of formation of educational and research skills of high school students of secondary education institutions in the implementation of environmental projects. The purpose is to analyse the specifics of attracting high school students of general secondary education institutions to the implementation of environmental projects. The main methods of research were methods of systematization, statistical processing, analysis, observation, induction, deduction, and synthesis used to solve scientific and methodological problems. Results. It is established that the goal of an environmental project makes it possible to choose a range of tasks that should be implemented by a high school student, namely: the object of research and the method of achieving the final result. In accordance with the set goal, the project objectives are determined. The solution of each task is a stage of research. Tasks determine the content of the study, methods, and results obtained. They can include the formulation of a problem, the identification of new facts, the establishment of new connections, a new formulation of a known problem, original conclusions and recommendations for the implementation of the obtained experimental data. The proposed scheme is a model for conducting research on determining water quality in aquatic ecosystems. The diagram shows three stages of step-by-step research. The first one is aimed at selecting the object of research (the main selection of criteria and objects of research is revealed). The second stage is the selection of methods for conducting the experiment. The criteria for selecting experimental sites are disclosed and, accordingly, identifiers for conducting an experiment and implementing an environmental project are given. The third stage is aimed at analysing the results of the study, formulating appropriate conclusions and planning the next stages of the study. The main stages in the formation of scientific research are considered from the formation of the topic, research tasks to the discussion and formation of conclusions of an environmental project. Conclusions. In the process of implementing environmental projects, which is aimed at search activities, high school students improve their ability to perform mental actions, operate in practice with all the acquired skills and abilities. The implementation of eco-projects develops logical and ecological thinking, forms a scientific and practical style of thinking, intuition, and develops interest in natural science. Scientific literature can’t provide deep and thorough knowledge, practical skills and abilities if the acquired theoretical knowledge is not combined with research activities. During their own observations, high school students are convinced that there are close connections between living organisms and the surrounding component, i.e. the environment.

A New Technique for Resolving Benthic Solute Fluxes: Evaluation of Conditional Sampling Using Aquatic Relaxed Eddy Accumulation

AbstractSolute exchange between the sediment and the water column strongly influences water quality in aquatic ecosystems. Among the techniques available for in situ observation, only aquatic eddy covariance (AEC) can resolve the hourly dynamics of benthic fluxes, but only for few substances like oxygen. In micrometeorology, relaxed eddy accumulation (REA), a technique based on high‐frequency sampling conditioned by current direction, overcomes this limitation. We developed a portable prototype instrumentation platform to transfer REA to the sediment‐water interface of shallow aquatic ecosystems. In order to evaluate the sampling system, we configured the prototype for measuring oxygen fluxes and comparing them to simultaneous AEC measurements. In a river and two artificial lakes, at depths 1–3 m and 0.2 m above the sediment, we measured 15 oxygen flux pairs in fully developed turbulence during 8–15 min periods, ranging from −150 to 50 mmol m−2 day−1. The good agreement between REA and AEC fluxes (R2 = 0.94) shows the reliability of the conditional sampling system. REA represents a promising technique for exploring the sediment contribution to biogeochemical cycles in aquatic ecosystems.

Research on the Development and Application of a Deep Learning Model for Effective Management and Response to Harmful Algal Blooms

Harmful algal blooms (HABs) caused by harmful cyanobacteria adversely impact the water quality in aquatic ecosystems and burden socioecological systems that are based on water utilization. Currently, Korea uses the Environmental Fluid Dynamics Code-National Institute of Environmental Research (EFDC-NIER) model to predict algae conditions and respond to algal blooms through the HAB alert system. This study aimed to establish an additional deep learning model to effectively respond to algal blooms. The prediction model is based on a deep neural network (DNN), which is a type of artificial neural network widely used for HAB prediction. By applying the synthetic minority over-sampling technique (SMOTE) to resolve the imbalance in the data, the DNN model showed improved performance during validation for predicting the number of cyanobacteria cells. The R-squared increased from 0.7 to 0.78, MAE decreased from 0.7 to 0.6, and RMSE decreased from 0.9 to 0.7, indicating an enhancement in the model’s performance. Furthermore, regarding the HAB alert levels, the R-squared increased from 0.18 to 0.79, MAE decreased from 0.2 to 0.1, and RMSE decreased from 0.3 to 0.2, indicating improved performance as well. According to the results, the constructed data-based model reasonably predicted algae conditions in the summer when algal bloom-induced damage occurs and accurately predicted the HAB alert levels for immediate decision-making. The main objective of this study was to develop a new technology for predicting and managing HABs in river environments, aiming for a sustainable future for the aquatic ecosystem.

Automatic Classification of Desmids using Transfer Learning

This research paper presents a novel approach to classifying microscopic images of desmids using transfer learning and convolutional neural networks (CNNs). The purpose of this study was to automate the tedious task of manually classifying microscopic algae and improve our understanding of water quality in aquatic ecosystems. To accomplish this, we utilized transfer learning to fine-tune 13 pre-trained CNN models on a dataset of five categories of desmids. We evaluated the performance of our models using several metrics, including accuracy, precision, recall, and F1-score. Our results show that transfer learning can significantly improve the classification accuracy of microscopic images of desmids, and efficient CNN models can further enhance performance. The practical implications of this research include a more efficient and accurate method for classifying microscopic algae and assessing water quality. The theoretical implications include a better understanding of the application of transfer learning and CNNs in image classification. This research contributes to both theory and practice by providing a new method for automating the classification of microscopic algae and improving our understanding of aquatic ecosystems

Modelling transformation and its impact on water quality of the wetlands of lower Gangetic plain: a geospatial approach for sustainable resource management

ABSTRACT Over the past few decades, water quality in aquatic ecosystems has been deteriorating steadily due to population growth, urbanization and industry expansion, discharge of municipal wastewater, and agricultural runoff into surface water sources. Wetlands of the Indo-Gangetic plain are disappearing continuously by several geo-genic and anthropogenic factors. The study focuses on the most important wetland ecosystems in the Malda district of the lower Gangetic plain in terms of area and socioeconomic value. The study aims to emphasize the land transformation around the selected wetlands, and to determine the current status of the water quality of the wetlands. From 2003 to 2018, the land use land cover (LULC) and land transformation of wetland areas were computed using geospatial data. The water quality of the wetlands has been measured at different sampling sites in pre- and post-monsoon seasons. The focus of the study is to identify the causal factors of the degradation and disappearance of wetlands. For the water quality index (WQI), on-site and laboratory analyses of the chosen parameters were conducted. Over the past 15 years, the built-up area increased by+98.08%, +90.32%, and +67.17%, while waterbody experienced a considerable negative change, with percentages of −21.30%, −26.83%, and −29.63% for the Chakla Beel, Chatra wetland, and Nayabandh wetland complex, respectively. The WQI revealed poor and very poor water categories at various wetland sites, under the WQI scores with 100–200 indicating “poor water” and 200–300 “very poor water.” The study analyzed the causes of the change in land use and alteration in water quality of selected wetland ecosystems.

Water quality of aquatic ecosystems of Akmola region

Currently, the issue of protecting natural resources from polluting and preventing pollution requires worldwide attention. In general, water resources are becoming an invaluable resource that explains the sustainable development of any state. Rational use and protection of water sources is becoming one of the most pressing issues in our country. Pollution of water sources, in turn, affects the deterioration of water quality, living organisms that live in water sources (algae, fish, etc.), and the health of consumers. Since water is the most important resource in the world, it is a task to protect and prevent environ mental risk. Therefore, to monitor the aquatic ecosystems of Akmola region, the research team conducted research in laboratory conditions, taking water samples from water bodies (Nura, Ishim Riversand Taldykol, Maybalyk, and Zhaltyrkol Lakes) from a practical trip organized by the research group. Research studies on water samples taken from water bodies showed that the water was polluted, and in some indicators the maximum rural concentration was exceeded. It is clear that pollutants affect water biota, although in most cases they are not the cause. According to water samples, the level of pollution of water sources was assessed. Protection of Water Resources in general from pollutants is one of the strategic tasks of the country.

Seasonal Dynamic of Physicochemical Parameters of Berach River System in Udaipur District, Rajasthan

Surface and ground water have been contaminated is a result of the improper disposal of industrial and municipal waste. Seasonal variations in human interference and natural processes particularly rainfall and temperature have an impact on the water quality of aquatic ecosystems. During the study, Sarjana tank showed the lowest average value of water temperature, 25.31ºC, whereas Gadwa pond had the maximum average value of water temperature (28.25ºC). The highest depth of visibility observed in Bada Madar tank (104cm) in winter 2019 and lowest depth of visibility observed in downstream pond (9.2cm) in monsoon 2019. Industrial pollution was responsible for comparatively low pH in the ponds of Berach river viz Upstream, Downstream, Gadwa, Daroli pond and Sarjana tank. The maximum average dissolved oxygen was found in Fatehsagar lake and minimum average dissolved oxygen found in Daroli pond. Udaisagar lake had highest alkalinity of 324.00 mg/l during winter 2018 and the lowest value of 68mg/l was observed in Down-stream pond in winter 2019. Chhota Madar tank had the lowest average hardness value of 136.61 mg/L. The highest mean conductivity (3.1018 m.mhos.) value was observed in the Down-stream pond and the lowest mean conductivity (0.3178 m.mhos.) in Chota Madar pond. Lowest TDS value (151.8 ppm) was in Bada Madar tank during the monsoon of 2018 and highest (4999.2 ppm) was in the downstream pond during winter 2018. Lowest mean chloride was found in Fatehsagar lake while highest mean chloride was found in downstream pond. Chhota Madar tank was found to be most rich in phosphates (0.4856 mg/l).

Bacterioplankton Community as a Biological Element for Reservoirs Water Quality Assessment

The Water Framework Directive (WFD) is used to evaluate the water quality of aquatic ecosystems. Phytoplankton is the only biological element considered in the reservoirs water quality assessment. In this study, we aimed to assess the use of the bacterioplankton community as an indicator of water quality, using a culture-independent assay (denaturing gradient gel electrophoresis, DGGE). Four Portuguese reservoirs (Miranda, Pocinho, Aguieira and Alqueva) were analysed in four periods (autumn 2018, spring and autumn 2019, and spring 2020). Bacterial total abundance had similar values for Miranda, Pocinho and Aguieira, and generally lower values for Alqueva. Diversity and richness values did not show a clear trend. Negative correlations were observed between some nutrients and the bacterial community. Overall, members of Actinobacteria, Bacteroidetes, Cyanobacteria, Nitrospirae and Proteobacteria were identified in all sampling sites. In Alqueva, no spatial, temporal or water body quality relationships with bacterial community were observed, which may be due to its higher size, low water velocity rate and higher residence times. However, in Miranda, Pocinho and Aguieira, a strong spatial and temporal bacterial community dynamic was observed. Furthermore, the presence of some species (e.g., Acinetobacter sp.) may reflect the poor water quality that was not detected by the WFD approach.

Quantification of metals in macrophytes in an aquaculture area of the itaipu binational reservoir

The macrophytes in natural conditions perform an important role in the maintenance and balance of aquatic environments with a capacity of absorbing the excess of nutrients and pollutants serving as bioindicators of water quality in aquatic ecosystems. The objective was to evaluate the levels of trace metals in three species of macrophytes (Egeria densa - submerged and Eichhornia crassipes and Salvinia auriculata - floating) collected around an aquaculture area of cages in the Itaipu Binational reservoir, during the four seasons of the year. The macrophyte samples were submitted of nitroperchloric digestion. Subsequently, the quantification of metals (Cu, Zn, Fe, Mn, Pb, Cd and Cr) was carried out by flame atomic absorption spectrometry analytical method. The concentration of Cu, Fe and Mn in E. densa and S. auriculata was higher (P&lt;0.05) than in E. crassipes. The samples of S. auriculata and E. crassipes had the lowest concentrations (P&lt;0.05) of Pb. The lowest metal pollution index (MPI) was determined in E. crassipes. There was greater bioaccumulation of metals in the root concerning the stem and leaves of E. crassipes (P&lt;0.05). The results obtained in this study show the influence of seasonal variation in the levels of Fe and Zn and the species analyzed on the concentration of Fe, Zn and Mn accumulated in aquatic macrophytes. The macrophytes E. crassipes and E. densa can be considered efficient accumulators of metals, indicating the exposure of the concentration of trace metals around the aquaculture area intended for the fish production in cages.

Diatom Communities as Bioindicators of Human Disturbances on Suburban Soil Quality in Arid Marrakesh Area (Morocco)

Diatoms, unicellular siliceous microalgae, are one of the most known groups of eukaryotic algae, commonly used as bioindicators for assessing water quality in aquatic ecosystems. Conversely, studies on terrestrial diatoms as potential bioindicators of soil quality are rather scarce. This study aims to assess the arid suburban soils quality of Marrakesh disturbed by various anthropogenic activities using diatom communities as bioindicators. The sampling of soil and physicochemical measurements were carried out at six sites with different land use. A total of 26 diatom taxa has been identified with 13 genera. The highest species richness and algal biomass were recorded in agricultural irrigated soils with treated wastewater dominated by pollution-tolerant species of Nitzschia (71.43%). In canonical correspondence analysis, suburban soils were subdivided into three groups depending on the chemical properties and diatom composition. The diatom diversity was significantly correlated with the total organic carbon (TOC), P-PO4, and N-NH4+ contents. While diversity and biomass were significantly lower in the soils affected by municipal and mining solid wastes, the input of organic matter and nutrients from treated wastewater appears to have a positive impact on the soil microflora and its richness. This first exploratory survey showed that diatom communities were more sensitive to the anthropic disturbances on urban soil and could be used as bioindicators of the quality and soils conditions.

Limnological analysis and survey of planctonic chlorophyce in the supply weir and in an effluent from the fish farming center Carlos Eduardo Matiazze in Presidente Médici, RO, Brazil

The phytoplankton consists of a diverse set of algae that are important for the water quality of aquatic ecosystems. Studies have revealed that various organisms are directly dependent on microalgae, as well as being primary producers, they are irreplaceable sources of food. Therefore, the aimed of the study was to evaluate the limnological conditions and carry out a survey of planktonic microalgae in the Chlorophyta division of the Chlorophyceae class of the supply weir and an effluent from the Carlos Eduardo Matiazze Fish Farming Center, Presidente Médici, RO, Brazil. For that, the physical-chemical parameters temperature, oxygen dissolved in water (ODA), pH, transparency, alkalinity, hardness, electrical conductivity in water (CEA), carbon dioxide and total ammonia concentration (CAT) were analyzed. The results were compared with the norms established by CONAMA Resolution 357, of 2005 fresh waters, especially class 2. And also, the survey of chlorophytes was carried out, and the analyzes of the samples were carried out by means of slide preparations for immediate reading through the observation under the binocular optical microscope. The microalgae species of the Chlorophyta division of the Chlorophyceae class were identified in a taxonomic category of order, family, genus and species. The weir water showed acceptable values, according to CONAMA, for the parameters analyzed here for most of the year. The effluent also expressed acceptable values ​​according to the legislation, with the exception of dissolved oxygen with a value of 1.7 mg/L. Concerning the survey of chlorophytes, it was observed that the weir is rich and diversified, which can be an indicator of pollutants and contamination since the weir is exposed to a large amount of effluents.

Биологические факторы качества воды в мезотрофной экосистеме

Dissolved organic matter (DOM) is one of the important parameters of water quality in aquatic ecosystems. In the experiments, phyto- and bacterioplankton actively consumed 14C-labeled chlorella hydrolyzate. Removal (by filtration) of cyanobacteria from the aquatic environment leads to an increase in the rate of DOM consumption by bacteria. This indicates the possibility of a negative effect of cyanobacterial metabolites on the physiological processes of bacterioplankton.

Estimation of Suspended Sediment Concentration from Remote Sensing and In Situ Measurement over Lake Tana, Ethiopia

Discharge from basins joining a lake is the main factor determining the lake volume and sediment inflow to the lake. Suspended sediment is an important parameter for describing the water quality of aquatic ecosystems. Lake Tana is an important and the largest lake in Ethiopia for the local ecological system. However, environmental change and anthropogenic activities in the area threaten its water quality. The conventional methods of suspended sediment concentration (SSC) observation are unable to determine and compare spatial and temporal SSC patterns for the lake over a period of years. Remote sensing methods have made it possible to map SSC. The objective of this study is to characterize the spatial and temporal distribution of suspended sediment of Lake Tana using in situ measurement and remote sensing applications and specifically to develop a relationship between in situ and remote sensing observation to retrieve suspended sediment concentration and map the spatal distribution of SSC. This study used MODIS‐Terra and in situ data to characterize the spatial and temporal distribution of SSC in the rainy season. Four sampling campaigns (20 samples per campaign) were carried out on Lake Tana, and the first three sampled campaigns on May 11–13, 2018, June 08–10, 2018, and July 15–17, 2018, were used for calibration of regression models. MODIS‐Terra reflectance in NIR was found best related to in situ water quality data and varies linearly with SSC (r2 = 0.81) and turbidity (r2 = 0.85). Secchi disc depth (SDD) found the best fit for a power relation with NIR band reflectance (r2 = 0.74). The MODIS‐Terra reflectance in red was found to be poorly related to in situ measurements. The relation in NIR reflectance was validated using the LOOCV (leave‐one‐out‐cross‐validation) technique and the fourth sampled data set collected on August 12–14, 2018. Developed models are validated with RMSE of 42.96 mg/l, 14.6 NTU, and 0.17 m, ARE of 23.3%, 27.6%, and 12.4%, and RRMSE of 25.1%, 44.5%, and 29.6% for SSC, turbidity, and SDD, respectively, using LOOCV. The equation was also validated using August 2018 collected data sets with RMSE of 87.6 mg/l, 11.7 NTU, 0.08 m, ARE of 20.8%, 25.9%, and 28.8%, and RRMSE of 17.8%, 20.5%, and 27.9% for SSC, turbidity, and SDD, respectively. Applying the developed regression model, a 10‐year time series of SSC from 2008–2017 for May‐August was estimated and the trend was tested using the Mann–Kendall trend test. It was found that an increasing trend was observed from the period 2008 to 2017. The result shows that satellite data like the MODIS‐Terra imagery could be used to monitor and obtain past records of SSC with the developed equation. The increasing SSC can be reduced by implementing selected management practices in the surrounding watersheds of the lake to reduce nutrient and sediment inflow.

Development of a Water Quality Assessment Index for the Chania River, Kenya

Human-related activities are known to have deleterious effects on the water quality of aquatic ecosystems, but there is limited information on the impact of these on rivers in tropical regions, such as the Chania River in Kenya. The Chania River is an important source of water for humans and animals and provides habitat for a variety of flora and fauna. This study used a Water Quality Index (WQI) to assess the suitability of the water for human use based on selected physico-chemical parameters (nitrates, Total Dissolved solids (TDS), potassium, sulphates, chlorides, copper, manganese, pH and phosphates). Sample collection was done between October 2018 and February 2019 over the dry and the wet seasons. Generally, the WQI indicated that water quality was fair to good in the dry season (19.67 to 30.10) but fair to poor in the wet season (23.17 to 89.15). It is recommended that the riparian zone of the Chania River be protected from anthropogenic disturbances in the County Kiambu.