Spatial Changes In Water Quality Research Articles

Water Quality Assessment of Wenyu River with Variable Weight Cloud Model

The water resource is an important guarantee of social and economic sustainable development. The improvement of water’s ecological carbon sequestration ability is a direct response to the goal of “double carbon”. Water quality directly affects its carbon sequestration capacity. So it is necessary to understand the water quality of rivers. In view of the fuzziness and uncertainty in water quality evaluation, this paper uses the cloud model to realize the qualitative to quantitative transformation of water quality in Wenyu River. By combining moment estimation theory with critic weight, AHM weight, and variable weight theory. A water quality evaluation method integrating a variable weight cloud model is constructed. And the temporal and spatial changes in water quality in Wenyu River are studied. The results show that the combined weights balance the influence of each index while retaining the advantages of subjective and objective weights. The results of the water quality evaluation are consistent with the practice, which verifies the feasibility and applicability of the method.

Evaluating the impact of percolated reclaimed water from river-channel reservoir on groundwater using tracers in Beijing, Northern China

As an increasingly important aspect of water management, historical dry river-channels, ponds or lakes are operated for the storage of reclaimed water as a landscape with the need for reuse of water. However, the percolated reclaimed water may have an adverse effect on groundwater quality. The aims of this work are to evaluate the potential for using various groundwater constituents or characteristics as tracers of percolated reclaimed water, to clarify the groundwater hydrochemical process with the effect of the reclaimed water recharge, and to estimate the degree to which the infiltrated reclaimed water has mixed with the native groundwater. Results obtained by comparing analysis between the dry season and wet season are presented based on multivariate statistics analysis, correlation of hydrochemical elements, and stable isotopes. The groundwater with the impact of reclaimed water was clustered together with higher Cl, K and NH4–N concentrations, lower Ca concentrations and more enriched heavy isotopes using unprecedentedly 3D-biplot; The water types of the groundwater change from Ca–Mg–HCO3–Cl, via Ca–Na–Mg–HCO3–Cl to Na–Ca–Mg–Cl–HCO3 with increasing reclaimed water percolated into the groundwater; the most useful tracers for evaluation of the fate and mixing of reclaimed water are chloride ion and oxygen-18 and chloride ion is more accurate than oxygen-18 to quantify the recharge source of the groundwater from the reclaimed water; using a two-end-member mixing model to calculate the reclaimed water discharged into the groundwater, the proportion of reclaimed water in groundwater is up to 94% near the unlined riverbed and up to 43% far from it. These results demonstrate the potential of the combined application of multivariate statistics analysis, traditional hydrochemical analysis and isotopes to assess the percolated reclaimed water in the groundwater, especially using 3D-biplot to determine the spatial water quality changes defined by the different factors.

Water quality indices to assess the spatiotemporal variations of Dhaleshwari river in central Bangladesh

Abstract Different water quality indices were determined to assess the spatiotemporal variations of Dhaleshwari river, specially, where effluent from the central effluent treatment plant (CETP) of newly shifted tannery industrial park was discharged. Thirty physicochemical parameters were examined to evaluate the drinking water quality index (DWQI), irrigation water quality index (IWQI), heavy metal pollution index (HPI) and contamination index (Cd). Pearson’s correlation coefficient was also utilized to understand the interrelationship and coherence pattern among the parameters and indices. DWQI values using CCME method were within the ‘Poor’ (0–44) range (37 ​at both upstream and junction and 34 ​at the downstream) and those using W.A. method were at ‘Poor’ (51–75) and ‘Unsuitable’ ( ​> ​100) level (52 ​at upstream and 63 ​at downstream and 103 ​at the junction). IWQI values showed the ‘Excellent’ (0–25) quality status (a range of 19.2–20.3). Considering heavy metal pollution, HPI values revealed ‘Critical’ ( ​> ​100) condition of water, and Cd values ( ​> ​3) emphasized ‘High’ contamination of the river water. Temporally, water quality deteriorated in the winter season compared to the monsoon and post-monsoon season. Spatial changes in water quality in junction and downstream side clearly indicated the negative impact of tannery industrial park. Different indices were positively correlated either very strongly or strongly. This study will provide an index-based baseline data that will help the local people in the vicinity of tannery industrial park envisage the different applications of the river water and the policymakers take conservation strategies to save the river Dhaleshwari as well.

Evaluation of water quality in the South-to-North Water Diversion Project of China using the water quality index (WQI) method

The world’s longest trans-basin water diversion project, the Middle-Route (MR) of the South-to-North Water Diversion Project of China (SNWDPC), has officially been in operation for over 5 years since December 2014. Its water quality status has always attracted special attention because it is related to the health and safety of more than 58 million people and the integrity of an ecosystem covering more than 155,000 km2. This study presented and analysed the spatio-temporal variations and trends of 16 water quality parameters, including pH, water temperature (WT), dissolved oxygen (DO), permanganate index (PI), five-day biochemical oxygen demand (BOD5), fecal coliform (F. coli), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH3−N), sulphate (SO42−), fluoride (F−), mercury (Hg), arsenic (As), selenium (Se), copper (Cu), and zinc (Zn), which were determined monthly from samples collected at 27 water quality monitoring stations in the MR of the SNWDPC from March 2016 to February 2019. The water quality index (WQI) was used to evaluate the seasonal and spatial water quality changes during the monitoring period, and a new WQImin model consisting of five crucial parameters, i.e., TP, F. coli, Hg, WT, and DO, was built by using stepwise multiple linear regression analysis. The results demonstrated that the water quality status of the MR of the SNWDPC has been steadily maintained at an “excellent” level during the monitoring period, with an overall average WQI value of 90.39 and twelve seasonal mean WQI values ranging from 87.67 to 91.82. The proposed WQImin model that uses the selected five key parameters and the weights of those parameters has exhibited excellent performance in the water quality assessment of the project, with the coefficient of determination (R2), Root Mean Square Error (RMSE), and Percentage Error (PE) values of 0.901, 2.21, 1.93%, respectively, showing that the proposed WQImin model is a useful and efficient tool to evaluate and manage the water quality. For the management department, the risk sources near certain stations with abnormally high values should be carefully inspected and strictly managed to maintain excellent water quality. The potential risks of algae proliferation in this project should be of concern in future research.

Reservoir scale reactive-transport modeling of a buoyancy-controlled CO2 plume with impurities (SO2, NO2, O2)

A demonstration project for the geological storage of CO2 is currently being considered in the deep Precipice Sandstone formation of the Surat Basin, Queensland, Australia. Because of the presence of potential fresh water resources in this formation, a reservoir-scale two-dimensional reactive-transport model was developed to assess temporal and spatial changes in water quality imposed by co-injecting CO2 with SO2, NO2, and O2 at this location. The model shows that because the injection rate is relatively low (60,000 tons/year), flow is buoyancy-dominated and under these conditions the predicted CO2 flow pattern is quite sensitive to fine-scale heterogeneities and the resolution of the numerical mesh. The model also shows that SO2 and NO2 readily partition into the aqueous phase in close vicinity of their injection point, lowering pH somewhat beyond the acidification from CO2 dissolution. Only O2 under redox disequilibrium conditions is modeled to persist in the CO2 plume away from the injection point, however at sub-ppm levels. This modeling effort demonstrates acidification near the wellbore due to the preferential stripping of gas impurities, and accumulation of CO2 around a lithostratigraphic boundary above the target formation, where relatively rapid mineral dissolution (muscovite, chlorite and calcite) and precipitation (ankerite, kaolinite and chalcedony) occur.

Using self-organizing map for coastal water quality classification: Towards a better understanding of patterns and processes

Self-organizing map (SOM) was used to explore the spatial characteristics of water quality in the middle and southern Fujian coastal area. Nineteen water quality variables (temperature, salinity, pH, dissolved oxygen, alkalinity, chemical oxygen demand, nutrients NH4-N, H2SiO3, PO4−, NO2−, and NO3−, heavy metals/metalloid Cu, Zn, As, Cd, Pb, Hg, and Cr6+, and oil) were measured in the surface, middle, and bottom water layers at 94 different sampling sites. Patterns of water quality variables were visualized by the SOM planes, and similar patterns were observed for those variables that correlated with each other, indicating a common source. pH, COD, As, Hg, Pb, and Cr6+ likely originated from industries, while nutrients NH4-N, NO2−, NO3−, and PO43− were mainly attributed to agriculture and aquaculture. The k-means clustering in the SOM grouped the water quality data into nine clusters, which revealed three representative water types, ranging from low salinity to high salinity with different levels of heavy metal/metalloid pollution and nutrient pollution. Spatial changes in water quality reflected the impacts of natural factors (riverine outflows, tides, and alongshore currents), as well as anthropogenic activities (mariculture, industrial and urban discharges, and agricultural effluents). Principal component analysis (PCA) confirmed the clustering results obtained by SOM, while the latter provides a more detailed classification and additional information about the dominant variables governing the classification processes. The results of this study suggest that SOM is an effective tool for a better understanding of patterns and processes driving water quality.

Application of multivariate statistical techniques in the water quality assessment of Danube river, Serbia

AbstractThe aim of this article is to evaluate the quality of the Danube River in its course through Serbia as well as to demonstrate the possibilities for using three statistical methods: Principal Component Analysis (PCA), Factor Analysis (FA) and Cluster Analysis (CA) in the surface water quality management. Given that the Danube is an important trans-boundary river, thorough water quality monitoring by sampling at different distances during shorter and longer periods of time is not only ecological, but also a political issue. Monitoring was carried out at monthly intervals from January to December 2011, at 17 sampling sites. The obtained data set was treated by multivariate techniques in order, firstly, to identify the similarities and differences between sampling periods and locations, secondly, to recognize variables that affect the temporal and spatial water quality changes and thirdly, to present the anthropogenic impact on water quality parameters.

Simulating the saturation threshold of a water environment’s response to tourist activities: A case study in the Liupan mountain eco-tourism area

The effect of tourism on water environments has received a high degree of interest in the study of eco-tourism. Based on the analysis of the relationship between tourist activities and the water environment in the Liupan Mountain eco-tourism zone, the case study area, a Water Environment of Tourism Area Model (WETAM) is built to simulate the temporal and spatial changes in water quality and the response saturation thresholds under four sewage treatment scenarios. The results imply the following: (1) WETAM performs well in modeling a water environment to represent the dynamic process of water quality change in response to tourist activities. (2) Under four sewage treatment scenarios (fundamental, low, medium, and high), the threshold shows an obvious uptrend. (3) The response threshold of water quality with respect to the interference of tourist activities fluctuates seasonally due to changes in tourist density. (4) The thresholds differ significantly among five tourism functional areas. According to the response saturation threshold of the water environment, effective control based on the scale and intensity of tourist activities is important for a successful transformation of this tourism destination’s development strategies. Therefore, the integrated management of water pollution in tourism areas plays a crucial role in sustainable tourism development.

Application of multivariate statistical methods in determining spatial changes in water quality in the Austrian part of Neusiedler See

The aim of the present study was to distinguish areas with different chemical properties in Neusiedler See, to determine which background processes are responsible for this pattern, and to discover their spatial distribution. Uni- and multivariate data analysis was applied to the data concerning 13 mainly chemical and some biological parameters for the time period 2000–2009 from 33 sampling sites. The sampling sites were first clustered then grouped. Besides reed belt and open water areas, smaller localities, which are influenced by water inputs (the treatment plant, the river Wulka, the channels of weekend houses) were also distinguished. Using Wilks’ lambda distribution it was determined that the main components (ions) have a greater effect on forming the cluster groups than those parameters which stand in close relation to biological processes. These results concurred with those obtained from the principal component analysis (PCA) conducted on the whole lake and on the groups as well. It can be stated that most of the variance in the dataset can be explained by the main components (ions). The spatial distribution of the principal component scores was visualized with isoline maps. The results of this research lead us to the view that Neusiedler See cannot be treated as one homogeneous system. This exceptional variability originates from the lake's shallow water depth, its unstable water balance, and anthropogenic activity (agriculture, tourism, sewage treatment) in the lake's vicinity.

Comparative analysis of regional water quality in Canada using the Water Quality Index

The Canadian Council of Ministers for the Environment (CCME) has developed a Water Quality Index (WQI) to simplify the reporting of complex water quality data. This science-based communication tool tests multi-variable water data against numeric water quality guidelines and/or objectives to produce a single unit-less number that represents overall water quality. The CCME WQI has been used to rate overall water quality in spatial and temporal comparisons of site(s). However, it has not been used in a comparative-analysis of exposure sites to reference sites downstream of point source discharges. This study evaluated the ability of the CCME WQI to differentiate water quality from metal mines across Canada at exposure sites from reference sites using two different types of numeric water quality objectives: (1) the water quality guidelines (WQG) for the protection of freshwater aquatic life and (2) water quality objectives determined using regional reference data termed Region-Specific Objectives (RSO). The application of WQG to the CCME WQI was found to be a good tool to assess absolute water quality as it relates to national water quality guidelines for the protection of aquatic life, but had more limited use when evaluating spatial changes in water quality downstream of point source discharges. The application of the RSO to the CCME WQI resulted in assessment of spatial changes in water quality downstream of point source discharges relative to upstream reference conditions.

Multivariate statistical techniques for the evaluation of spatial and temporal variations in water quality of Gomti River (India)—a case study

This case study reports different multivariate statistical techniques applied for evaluation of temporal/spatial variations and interpretation of a large complex water-quality data set obtained during monitoring of Gomti River in Northern part of India. Water quality of the Gomti River, a major tributary of the Ganga River was monitored at eight different sites selected in relatively low, moderate and high pollution regions, regularly over a period of 5 years (1994–1998) for 24 parameters. The complex data matrix (17,790 observations) was treated with different multivariate techniques such as cluster analysis, factor analysis/principal component analysis (FA/PCA) and discriminant analysis (DA). Cluster analysis (CA) showed good results rendering three different groups of similarity between the sampling sites reflecting the different water-quality parameters of the river system. FA/PCA identified six factors, which are responsible for the data structure explaining 71% of the total variance of the data set and allowed to group the selected parameters according to common features as well as to evaluate the incidence of each group on the overall variation in water quality. However, significant data reduction was not achieved, as it needed 14 parameters to explain 71% of both the temporal and spatial changes in water quality. Discriminant analysis showed the best results for data reduction and pattern recognition during both temporal and spatial analysis. Discriminant analysis showed five parameters (pH, temperature, conductivity, total alkalinity and magnesium) affording more than 88% right assignations in temporal analysis, while nine parameters (pH, temperature, alkalinity, Ca-hardness, DO, BOD, chloride, sulfate and TKN) to afford 91% right assignations in spatial analysis of three different regions in the basin. Thus, DA allowed reduction in dimensionality of the large data set, delineating a few indicator parameters responsible for large variations in water quality. This study presents necessity and usefulness of multivariate statistical techniques for evaluation and interpretation of large complex data sets with a view to get better information about the water quality and design of monitoring network for effective management of water resources.

Phytoplankton of a small lowland stream related to water quality and hydraulic discontinuities

The structure and dynamics of the phytoplankton related to water quality and hydraulic characteristics were studied in a 12km reach of the Rodriguez Stream, a tributary of the Rio de la Plata, in Argentina. This stream includes a small artificial pond. Samples were taken seasonally along a year at three sites at the stream and once at the pond. Water quality according to physical and chemical parameters was better at site 1 than at downstream sites. Changes in phytoplankton assemblages descriptors were observed with increasing nutrients and water residence time. The spatial water quality changes are coincident with the hydraulic discontinuity. This situation suggests a synergic effect among the phytoplanktonic descriptors that were analyzed. There was a high percentage of species belonging to euglenoids followed by green algae and diatoms. Loricated euglenoids were dominant at site 1, clorococcalean greens dominated at the pond and decreased progressively downstream, at sites 2 and 3. Gomphonema parvulum, Nitzchia palea and N. umbonata were abundant in the latter sites, where current velocity increased. Our results also show the integrating character of the phytoplankton in this small stream where it can reach considerable development due to the low gradient (<10 -3 ). and specially to the presence of the pond.

Seasonal and spatial water quality changes in the outflow plume of the Atchafalaya River, Louisiana, USA

The objective of this study was to examine the interaction between the Atchafalaya River and the Atchafalaya Delta estuarine complex. Measurements of suspended sediments, inorganic nutrients (NO3 −, NH4 +, PO4 3−), chlorophylla (chla), and-salinity were taken monthly from December 1996 to January 1998. These data were compiled by season, and the Atchafalaya River plume data were also analyzed using the Generalized Additive Model technique. There were significant decreases in NO3 − concentrations during summer, fall, and winter as river water passed through the estuary, that were attributable to chemical and biological processes rather than dilution with ambient water. In some regions there were higher chla concentrations during summer and fall compared to winter and spring, when river discharge and the introduction of inorganic nutrients were highest, suggesting biological processes were active during this study. The presence of NH4 +, as a percentage of available dissolved inorganic nitrogen, increased with distance from the Atchafalaya River, indicative of remineralization processes and NO3 − reduction. Mean PO4 3− concentrations were often higher in the estuarine regions compared to the Atchafalaya River. During summer total suspended solid (TSS) concentrations increased with distance from the river mouth, suggesting a turbidity maximum. Highest chla concentrations were found in the bayous and shallow water bodies of the Terrebonne marshes, as were the lowest TSS concentrations. The low chla concentrations found in other areas of this study, despite high inorganic nutrient concentrations, suggest light limitation as the major control of phytoplankton growth. Salinity reached near seawater concentrations at the outer edge of the Atchafalaya River plume, but much lower salinities (<10 psu) were observed at all other regions. The Atchafalaya Delta estuarine complex buffers the impact of the Atchafalaya River on the Louisiana coastal shelf zone, with a 41% of 47% decrease in Atchafalaya River NO3 − concentrations before reaching Gulf waters.

RESEARCH: Are Recent Watershed Disturbances Associated with Temporal and Spatial Changes in Water Quality of Lake George, New York, USA?

/ Lake George, a mesooligotrophic lake, is a historically important recreational site in northeastern New York, USA. A preliminary analysis of the data, collected during 1980-1990, suggested that the indicators of primary productivity have increased, particularly in the southern basin of the lake. This change was attributed to the recent increases in the urbanization and development of the southern shorelines. The suggestion of temporal and spatial degradation in lakewater quality has caused substantial concerns among the decision makers and the public alike. The main objective of this study is to evaluate possible eutrophication of the lake by quantification of temporal and spatial trends in concentrations of total phosphorus (TP), chlorophyll a (Chl a), silica (Si), and chloride (Cl) through the use of proper statistical techniques. Results indicate no statistically significant changes in the concentrations of TP, Chl a, or Si in the spring or summer from 1981 to 1993. A significant temporal trend of increase in Cl concentration is, however, detected. This is perhaps the strongest evidence that the development of the Lake George watershed has affected lakewater chemistry. In spring, the concentrations of TP, Chl a, Si, and Cl, averaged over all 13 years, were higher in the south basin, but differences are not statistically significant (i.e., P > 0.05). In summer, Si was slightly but significantly lower, and Cl was nonsignificantly higher in the south basin. Significant interactions between temporal and spatial changes are detected based only on summer values of TP and Chl a, indicating differential trends of change for these two variables in the south and north basins during the last 13 years.KEY WORDS: Repeated-measures ANOVA; Split-plot design; Lakewater chemistry; Lake George