Variations In Water Quality Parameters Research Articles

Evaluation of water quality trends in the Maroon River Basin, Iran, from 1990 to 2010 by WQI and multivariate analyses

This research aimed to investigate the long-term spatiotemporal changes of surface water quality of the Maroon River by implementing Water Quality Index (WQI) and multivariate statistical analyses such as non-metric multidimensional scaling and cluster analyses, as complementary tools to investigate spatial variations in water quality parameters and also delineate areas in terms of water quality conditions in the period under study. The other purposes of this study were to evaluate the physicochemical properties of the Maroon River water and assess the effects of each water quality parameter on the WQI values. Relationship between quality scale of hydrochemical parameters and the resulting WQI scores was determined employing linear regression analysis. Moreover, the suitability of water quality was evaluated for irrigation purposes using conventional indices, electrical conductivity (EC), sodium adsorption ratio (SAR), and percent sodium (Na%). The monitoring stations were placed in high and very high categories according to the assessment of irrigation water quality with EC. Considering WQI, the upper (S1, S2, and S4) and lower (S3, S5, and S6) monitoring stations of the Maroon River distributed in category C3 (high salinity) and C4–C5 (very high salinity), respectively. The findings of WQI presented an increasing trend from upstream toward downstream in the Maroon River. The findings of the linear regression analysis showed no significant correlation between WQI scores with pH and SO4 2− concentrations even though the relationship is weak. These results suggest that pH and SO4 2− concentrations could be the secondary driving parameters behind the variations in WQI scores. It can be inferred that the Maroon River water is appropriate for irrigation based on Na% and SAR. However, it also exhibits high EC. Therefore, for mitigating the adverse impacts of polluted water authors recommend multidimensional management practices such as transferable discharge permit programs in the study area.

IDENTIFICATION OF WATER QUALITY SIGNIFICANT PARAMETER WITH TWO TRANSFORMATION/STANDARDIZATION METHODS ON PRINCIPAL COMPONENT ANALYSIS AND SCILAB SOFTWARE

Water quality monitoring is prone to encounter error on its recording or measuring process. The monitoring on river water quality not only aims to recognize the water quality dynamic, but also to evaluate the data to create river management policy and water pollution in order to maintain the continuity of human health/sanitation requirement, and biodiversity preservation. Evaluation on water quality monitoring needs to be started by identifying the important water quality parameter. This research objected to identify the significant parameters by using two transformation/standardization methods on water quality data, which are the river Water Quality Index, WQI (Indeks Kualitas Air, Sungai, IKAs) transformation/standardization method and transformation/standardization method with mean 0 and variance 1; so that the variability of water quality parameters could be aggregated with one another. Both of the methods were applied on the water quality monitoring data which its validity and reliability have been tested. The PCA, Principal Component Analysis (Analisa Komponen Utama, AKU), with the help of Scilab software, has been used to process the secondary data on water quality parameters of Gadjah Wong river in 2004-2013, with its validity and reliability has been tested. The Scilab result was cross examined with the result from the Excel-based Biplot Add In software. The research result showed that only 18 from total 35 water quality parameters that have passable data quality. The two transformation/standardization data methods gave different significant parameter type and amount result. On the transformation/standardization mean 0 variances 1, there were water quality significant parameter dynamic to mean concentration of each water quality parameters, which are TDS, SO4, EC, TSS, NO3N, COD, BOD5, Grease Oil and NH3N. On the river WQI transformation/standardization, the water quality significant parameter showed the level of Gadjah Wong River pollution, which are EC, DO, BOD5, COD, NH3N, Fecal Coliform, and Total Coliform. These seven parameters is the minimal amount of water quality parameters that has to be consistently measured on predetermined time and location, and also become the indicator of human health and environment health quality. The result of Scilab multivariate analysis was not different with the result from Biplot Add In multivariate analysis, in which the results of water quality significant parameter has been verified with bio-monitoring.

Identification of a water quality indicator for urban roof runoff

Control and management of stormwater volume and water quality is an important concern in Iran and there is little or insufficient scientific information in assessing domestic roof harvested rainwater quality by suitable indicators. The objectives of this study were (1) to determine water quality factors which vary significantly with roof materials and first flush, (2) to select an indicator from these factors that can be used for water quality monitoring in roof runoff and (3) to find out whether a relationship exists between the resulting roof runoff water quality (WQI) and air quality parameters. Factor analysis (FA) was used to identify water quality factors and discriminant analysis (DA) was used to determine the factors and an indicator most sensitive to first flush and posterior roof runoff within mosaic tile and bitumen roofing material. Therefore, seven water quality parameters were measured in 28 runoff samples collected from two mosaic tile and bitumen roofs in seven rainfall events. FA identified three factors that explained 82.8% of the variation in water quality parameters. Discriminant analysis selected phosphate and nitrate as the most sensitive parameters in domestic roof harvested rainwater. Correlation analysis of the resulting roof runoff WQI with the air quality parameters showed that the indicator has significant correlation with most air quality parameters. Forward stepwise general regression model revealed that the roof water quality indicator values were explained by air SO2. This suggests that domestic roof harvested rainwater quality could be controlled by air quality characteristics.

Spatial and temporal dynamics of water quality in Batticaloa lagoon in Sri Lanka

The present study was undertaken to characterise the spatial and temporal dynamics of physico-chemical parameters of the Batticaloa Lagoon in Sri Lanka during November 2012 to October 2013. Eighteen sampling locations were clustered based on their positions from the Palameenmadu bar mouth. Physico-chemical parameters like temperature, electrical conductivity (EC), total dissolved solids (TDS), pH, salinity, dissolved oxygen (DO), turbidity, nitrate, phosphate and total suspended solids (TSS) were measured 15-30 cm below the water surface. The study revealed that the water temperature of the lagoon varied between 26.1-33.6°C; EC 0.24-36.6 dS/m; TDS 0.1-18.3 ppt; pH 7.32- 8.87; salinity 1.6-34 ppt; DO 3.98-11.98 mg/l; turbidity 3-41 FAU; nitrate 0.8-8.3 mg/l; phosphate 0.04-1.56 mg/l and TSS 562-6021 mg/l. High values of salinity were observed in the lagoon water near the barmouth, and during the dry months. Rainfall and the distance from sea play a major role in the variation of salinity of the lagoon. Decreasing trend in salinity was observed from the distance from barmouth to the West, North and Southern part of the lagoon. High nutrient concentration at the lagoon was observed in the locations near to the farms and cultivation areas. The water quality parameters are favourable to the production of brackish water fish and prawns during dry months. However, it contains high salt and suspended particles, thus not suitable for drinking. The results are important in understanding the pattern of variation of water quality parameters so as to assist relevant agencies to plan, protect and aid in the management of the lagoon water for different uses.

Variation of Some Water Quality Parameters from Winter to Summer Period in Chittagong Karnafully River of Bangladesh

A study has been conducted to investigate the variation of water quality parameters during January to June of 2014 in Karnafully River of Chittagong, Bangladesh. Water samples were collected from January to June 2014 of each month in 5th day. Samples of water from three points of Karnafully Rive were collected and brought in laboratory for analysis and analyzed by using different standard prescribed methods. Total eight water quality parameters were measured like as pH, EC, TDS, Total Hardness, Fe, Cl-, As and Turbidity. All the water quality parameters were attenuated from January (winter) to June (summer) except pH. Another important fact was most of the parameter’s values exceeded the permissible limit recommended by WHO. It is a concerning event for ecology and environment of this catchment area. Our findings will convey a sound message for the government body and policy maker to set up rules and regulation in order to keep ecological balance as well as save our environment and this research will be helpful for public awareness. An immediate attention from the concerning body is mandatory in order to protect the aquatic environment of Karnafully River as well as food chain contamination.

Assessment of groundwater quality in Jaisamand catchment for drinking purpose using geographical information system

The present study focuses on a GIS-based assessment and characterization of groundwater quality using pre monsoon and post monsoon groundwater quality data. Spatio-temporal variations of water quality parameters in the study area were analysed by using GIS techniques. Maximum area of Jaisamand catchment showed the drinking water quality within permissible limit. EC somewhat extent within permissible limit during pre monsoon period. Sulphate content also exceeded from permissible limit some extent in pre monsoon period but in post monsoon period it was within permissible range. The maximum total dissolved solids were found in western site of study area during pre monsoon period whereas in post monsoon period maximum area showed total dissolved solids within permissible range.

Relationship of Microbiota and Cyanobacterial Secondary Metabolites in Planktothricoides-Dominated Bloom.

The identification of phytoplankton species and microbial biodiversity is necessary to assess water ecosystem health and the quality of water resources. We investigated the short-term (2 days) vertical and diel variations in bacterial community structure and microbially derived secondary metabolites during a cyanobacterial bloom that emerged in a highly urbanized tropical reservoir. The waterbody was largely dominated by the cyanobacteria Planktothricoides spp., together with the Synechococcus, Pseudanabaena, Prochlorothrix, and Limnothrix. Spatial differences (i.e., water depth) rather than temporal differences (i.e., day versus night) better-explained the short-term variability in water quality parameters and bacterial community composition. Difference in bacterial structure suggested a resource-driven distribution pattern for the community. We found that the freshwater bacterial community associated with cyanobacterial blooms is largely conserved at the phylum level, with Proteobacteria (β-proteobateria), Bacteroidetes, and Actinobacteria as the main taxa despite the cyanobacterial species present and geographical (Asia, Europe, Australia, and North America) or climatic distinctions. Through multivariate statistical analyses of the bacterial community, environmental parameters, and secondary metabolite concentrations, we observed positive relationships between the occurrences of cyanobacterial groups and off-flavor compounds (2-methyisoborneol and β-ionone), suggesting a cyanobacterial origin. This study demonstrates the potential of 16S rRNA gene amplicon sequencing as a supporting tool in algal bloom monitoring or water-resource management.

Spatio-temporal variations of water quality in Nova Ponte Reservoir, Araguari River Basin, Brazil

Multivariate techniques, like cluster analysis (CA) and principal component analysis (PCA), were used to evaluate the spatial and temporal variability of surface water quality in a large neotropical hydroelectric reservoir (Nova Ponte Reservoir). The dataset, obtained during the period of 1995–2011 from the Energy Company of Minas Gerais State (CEMIG), contains 14 parameters surveyed quarterly in 14 sites, at different depths. The CA grouped the 14 sites in three main groups: lotic sites, half of the photic zone sites and bottom sites. Statistical tests showed that only three parameters (total dissolved solids, nitrate and chemical oxygen demand) have no significant difference between cluster groups. The PCA results showed temporal changes of the water quality in all groups, illustrating modifications to the importance of the parameters over time. PCA also revealed the major causes of water deterioration from 1995 to 2005 were related to agricultural and livestock activities. Currently, the water quality parameters related to organic pollution are also highlighted. Generally, this study shows that possible optimization of the monitoring network should consider temporal variation of water quality parameters.

Temporal variations in water quality in a brackish tidal pond: Implications for governing processes and management strategies

Brackish tidal ponds have been constructed along coastal areas in many parts of the world for aquaculture, including some Ramsar Sites. Such ponds are considered a sustainable, wise use of wetlands if managed properly, but they can also pose serious environmental problems if mismanaged. To understand the governing processes and to promote sustainable management strategies, this study examines the different temporal variations in water quality parameters in a brackish tidal pond located within the wetland complex of the Mai Po Ramsar Site in Hong Kong, China. The variations are compared with those of the receiving bay, and the water channel that connects the pond and the bay. Equations are then developed to link the dissolved oxygen (DO) concentrations in the pond with the governing processes, and to analyze their relative contributions to DO levels. Field data show seasonal patterns in water temperature and salinity in response to the seasonal variations in solar radiation and rainfall. For the pond and the channel, DO, chlorophyll and pH exhibit fortnightly variations due to the bi-weekly water exchange between the pond and the bay. There were also diurnal variations in water temperature and DO in response to changes in solar radiation for both locations, and the tidal flushing for the water channel. Analysis of the findings indicates that water exchange influences the DO concentration more strongly than solar radiation. The DO equation links pond water quality with the time of day, and the time in a water exchange cycle, and thus provides some guidance for determining water exchange and water sampling schedules. The study sheds light on the governing processes and management strategies related to the sustainable management of a brackish tidal pond. The results are thus beneficial in elucidating and promoting the sustainable management and wise use of wetlands in other locations.

Evaluation of Spatial-Temporal Variations of Water Quality and Plankton Assemblages and Its Relationship to Water Use in Kulekhani Multipurpose Reservoir, Nepal

Spatial and temporal variation in planktons and water quality parameters were investigated in order to determine the effects of seasonal water use on reservoir water quality and planktons’ diversity in Kulekhani Multipurpose Reservoir, Nepal. This study also focuses on interactions among various water quality parameters with planktons and how such interactions can affect the second major utility, the fish farming in the reservoir. The analyses of seasonal water samples collected from three different sampling locations in the reservoir showed that select water quality parameters varied significantly (P < 0.05) with sampling seasons (transparency: 30 - 250 cm, pH: 7 - 7.5, alkalinity: 30 - 120 mg/L, DO: 6 - 11.5 mg/L, CO2: 0.1 - 1.1 mg/L) and sampling locations (phosphate: 0.1 - 0.25 mg/L, nitrate 0.01 - 0.19 mg/L) in the reservoir. Three groups of zooplankton and four classes of phytoplankton, respectively with eleven and twelve genera, were identified and quantified in the reservoir. Among them, Cyclops, Asplanchana, and Keratella were most dominant zooplanktons while Synedra, Melosira and Peridinum were the most dominant phytoplankton in the reservoir water. The abundance of select zooplanktons (Cyclops, Keratella, Polyanthra), and phytoplankton (Navicula, Melosira, Amphora, Chroococcus, Staurastrum, Scendesmus) showed significant interaction between sampling sites and sampling seasons, while the other varied only with sampling seasons and/or sites. These results showed that seasonal water level fluctuations, along with the variation of water quality parameters, change the abundance and diversity of planktons’ in the reservoir. Such changes can negatively impact the fish in cage culture, affecting the livelihood of people extensively relying on these fish farming.

Stream hydrology and geochemistry along a rural to urban land use gradient

High frequency monitoring of water quality and stable isotopes quantify large hydrological and geochemical differences across a rural to urban land use gradient that includes three watersheds and two of their subbasins. Following precipitation events, floods on a rural stream feature hydrographs with low peak discharges and long lag times, high baseflow contributions, and small geochemical variations. In contrast, the flows of an urban stream and its tributary respond in a flashy manner, with average lag times decreasing by at least 55% compared to the rural stream. We also observed that baseflow contributions during floods decreased by an average of 40% in the urban streams. Importantly, we find that reduced baseflow as a function of increasing impervious surface area is not a linear trend among the streams, and suburban streams are less impacted than would be predicted by impervious surface area alone. The urban streams also exhibit large variations in water quality parameters during flooding events, often with five times the variability of the rural end-member. These differences are observed among all physical and geochemical characteristics that were monitored, including flow magnitude, stable isotope ratios, temperature, dissolved oxygen (DO), pH, turbidity, specific conductivity, concentrations of Cl− and nutrients, and bacterial loads. The great variability of urban streams following storms is paralleled by their larger diurnal and seasonal oscillations. Collectively, the extreme variations in the physical and geochemical character of urban streams have negative consequences to environmental quality and aquatic life.

An integrated numerical framework for water quality modelling in cold-region rivers: A case of the lower Athabasca River

There is a great deal of interest to determine the state and variations of water quality parameters in the lower Athabasca River (LAR) ecosystem, northern Alberta, Canada, due to industrial developments in the region. As a cold region river, the annual cycle of ice cover formation and breakup play a key role in water quality transformation and transportation processes. An integrated deterministic numerical modelling framework is developed and applied for long-term and detailed simulation of the state and variation (spatial and temporal) of major water quality constituents both in open-water and ice covered conditions in the lower Athabasca River (LAR). The framework is based on the a 1D and a 2D hydrodynamic and water quality models externally coupled with the 1D river ice process models to account for the cold season effects. The models are calibrated/validated using available measured data and applied for simulation of dissolved oxygen (DO) and nutrients (i.e., nitrogen and phosphorus). The results show the effect of winter ice cover on reducing the DO concentration, and a fluctuating temporal trend for DO and nutrients during summer periods with substantial differences in concentration between the main channel and flood plains. This numerical frame work can be the basis for future water quality scenario-based studies in the LAR.

VARIATION OF WATER QUALITY IN NHA TRANG BAY

Based on survey data in the period of 2013 - 2015 and historical data between 1996 - 1998, the paper showed the variation of water quality parameters by time. The concentration of total suspended sediment, chlorophyll-a, dissolved inorganic nitrogen, dissolved inorganic phosphorus and ratio of N:P changed significantly by season. The results of assessing water quality by UNTRIX (integrated concentration of Chlorophyll-a, dissolved inorganic nitrogen, dissolved inorganic phosphorus and level of saturated oxygen) indicated the quality levels were increased from meso-eutrophication in 1996 (average UNTRIX: 4.54 ± 0.76) to oligo-eutrophication in the period of 2013 - 2015 (average UNTRIX from 2.62 ± 0.66 to 3.81 ± 0.45).

Water quality of Nilwala River, Sri Lanka in relation to land use practices

The Nilwala River is the third largest in the southern province of Sri Lanka which runs through 72 km along its cause. Conversion of forest lands to agricultural lands, expansion of urban areas and clearing of land for construction purposes in the catchment are major issues affecting water quality in Nilwala River. The water quality of the Nilwala River lower basin at 16 locations was estimated for 4 months from September2010 to December 2010 in two-week intervals. Water quality parameters pH, Electrical conductivity(EC), Dissolved oxygen (DO), Biochemical Oxygen demand (BOD5), turbidity, colour, Total Dissolved Solids (TDS), total hardness, alkalinity, Nitrite-N (NO2--N), Nitrate -N (NO3--N), Phosphate (PO43- -P), Sulphate (SO43-), Total Fe, Ca2+, F- and Cl- were evaluated in the sampling locations. The spatial and temporal variation of water quality associated with different land use categories were analyzed using Two-way ANOVA. Principal Component Analysis (PCA) and Cluster Analysis (CA) were also conducted to determine the association between water quality variation and land use impacts of the catchment. A significant (p &lt;0.05) spatial variation of water quality parameters, except the hardness, Fluoride and Ca+2among sites were observed to be associated with different land use categories. No significant (p &gt;0.05) temporal variability in water quality parameters except Nitrite and hardness was detected. PCA and CA also indicated a strong association between the water quality variables and the land use types of the river basin. Urban impacts, land clearance in the catchment and sand mining activities of the river bed were found to be the most significant impacts to the water quality of the river and areas with forest cover having positive impact to the water quality. These findings emphasize the need of better catchment management approaches and remediation of urban impacts on river water quality.

Developing a Comprehensive Spectral-Biogeochemical Database of Midwestern Rivers for Water Quality Retrieval Using Remote Sensing Data: A Case Study of the Wabash River and Its Tributary, Indiana

A comprehensive spectral-biogeochemical database was developed for the Wabash River and the Tippecanoe River in Indiana, United States. This database includes spectral measurements of river water, coincident in situ measurements of water quality parameters (chlorophyll (chl), non-algal particles (NAP), and colored dissolved organic matter (CDOM)), nutrients (total nitrogen (TN), total phosphorus (TP), and dissolved organic carbon (DOC)), water-column inherent optical properties (IOPs), water depths, substrate types, and bottom reflectance spectra collected in summer 2014. With this dataset, the temporal variability of water quality observations was first analyzed and studied. Second, radiative transfer models were inverted to retrieve water quality parameters using a look-up table (LUT) based spectrum matching methodology. Results found that the temporal variability of water quality parameters and nutrients in the Wabash River was closely associated with hydrologic conditions. Meanwhile, there were no significant correlations found between these parameters and streamflow for the Tippecanoe River, due to the two upstream reservoirs, which increase the settling of sediment and uptake of nutrients. The poor relationship between CDOM and DOC indicates that most DOC in the rivers was from human sources such as wastewater. It was also found that the source of water (surface runoff or combined sewer overflow (CSO)), water temperature, and nutrients were important factors controlling instream concentrations of phytoplankton. The LUT retrieved NAP concentrations were in good agreement with field measurements with slope close to 1.0 and the average estimation error was 4.1% of independently obtained lab measurements. The error for chl estimation was larger (37.7%), which is attributed to the fact that the specific absorption spectrum of chl was not well represented in this study. The LUT retrievals for CDOM experienced large variability, probably due to the small data range collected in this study and the insensitivity of Rrs to CDOM change. It is concluded that the success of the LUT method requires accurate spectral measurements and enough a priori information of the environment to construct a representative database for water quality retrieval. Therefore, future work will focus on continuing data collection in other seasons of the year and better characterization of the study area.

Present status of naturally occurring seaweed flora and their utilization in Bangladesh

A survey was conducted to know the present status of naturally occurring seaweed flora and their utilization in Bangladesh by interviews of scientific officers of MFTS (Marine Fisheries and Technology Station, Bangladesh Fisheries Research Institute, Cox’s Bazar), NGO officials associated with seaweed research project, local seaweed food products manufacturer, seaweed collectors and Mog or Rakhyine tribal community of Cox’s Bazar and St. Martin Island. Lack of knowledge on availability, distribution, seasonal variation, utilization status is causing impediment on utilization (e.g. seaweeds as human food, hydrocolloids, animal feed, fertilizer, cosmetic products, etc.) of available seaweeds naturally occurring in Bangladesh. Seaweeds are available along the whole Bangladeshi coast, mostly in St. Martin Island, Cox’s Bazar and Sundarbans Mangrove forest. Total 193seaweed species including 19 commercially important species, belonging to 94 genera are found. Approximately, 5,000 metric ton of seaweed biomass is available. Due to seasonal variation in water quality parameters, generally seaweeds are available from October to April, but highest abundance occurs from January to March. Seaweed salad and sauce has been utilizing by Mog people as food. About 400 seaweed collectors at St. Martin Island annually harvested 6-9 metric tons of wet seaweeds (Hypnea spp.) for smuggling to Myanmar. Different value added food, functional food and personal care products have prepared by Govt. institution, NGO and in private sector. Considering the economic importance and potentials of seaweeds, for effective and environmentally sustainable utilization, special concern is required by both government and private organizations.Res. Agric., Livest. Fish.3(1): 203-216, April 2016

Water quality estimation of River plumes in Southern Lake Michigan using Hyperion

Abstract This study focuses on the calibration of an existing bio-geo-optical model for studying the spatial variability of water quality parameters including chlorophyll (CHL), non-algal particles (NAP), and colored dissolved organic matter (CDOM) in episodic river plumes. The geographic focus is the St. Joseph River plume in southern Lake Michigan. One set of EO-1 Hyperion imagery and one set of boat-based spectrometer measurements were successfully acquired to capture episodic plume events. Coincident water quality measurements were also collected during these plume events. In this study, a database of inherent optical properties (IOPs) measurements and spectral signatures was generated and used to calibrate the bio-geo-optical model. Field measured concentrations of NAP and CDOM at 67% of the sampled sites fall within one standard deviation of the retrieved means using the spectrometer measurements. The percentage of sites, 88%, is higher for the estimation of CHL concentrations. Despite the dynamic nature of the observed plume and the time lag during field sampling, 77% of the sampled sites show field measured CHL and NAP concentrations falling within one standard deviation of the Hyperion derived values. The spatial maps of water quality parameters generated from the Hyperion image provided a synoptic view of water quality conditions. Results show that concentrations of NAP, CHL, and CDOM were more than three times higher in conjunction with river outflow, and inside the river plumes, than in ambient water. It is concluded that the storm-initiated plume is a significant source of sediments, carbon and chlorophyll to Lake Michigan.

Seasonal Variation of Water Quality Parameters of Zobe Reservoir Dutsinma Katsina State, Nigeria

Study was conducted on the physico-chemical water properties of Zobe reservor Dutsinma, Katsina State Nigeria. Water samples were collected from four different sample stations i.e., Makera, Badole, Garhi and Bagaggadi respectively, for the period of one year (May 2015 to April 2016). Samples for Conductivity, pH, Dissolved Oxygen (DO), Temperature, Alkalinity, Turbidity, Hardness, Chloride, and Nitrate were collected during the morning hours, between 7:00 am to 9:00 am. The result showed variations in the monthly mean values of all the water quality parameters tested. The water is too turbid most especially during the beginning of raining season, despite this variation some of the values were within the tolerable range of the majority of tropical fresh water fish species. But the water cannot be used for domestic use unless it undergoes intensive treatment.

Water quality prediction capabilities of WASP model for a tropical lake system

AbstractWater quality modelling facilitates our better understanding of the processes taking place in a lake system, and conservation plans to address them. The water quality analysis simulation programme (WASP) was used in this study to predict daily variations in water quality parameters, namely dissolved oxygen, nitrate, phosphate and chlorophyll‐a and biochemical oxygen demand concentrations in a tropical lake system. The lake was divided into eight segments with the respective morphological, environmental and flow details being model inputs. The monthly concentration of each water quality parameter also comprised model input. The model output was daily spatiotemporal variation in these parameters over a period of 476 days. This study also indicated that the occurrence of precipitation plays a major role in defining the water quality of a tropical lake. The heavy precipitation after a long gap, especially during the summer season, results in a large quantity of organic matter entering the lake through drains, thereby increasing the organic matter and phosphate in the water body, and subsequently resulting in high chlorophyll‐a concentrations in the lake. A reduced chlorophyll‐a concentration was observed during the heavy rains. The water quality fluctuations are more pronounced with precipitation, especially where polluted drains enter the lake. An improved water quality can be observed downstream, including increased dissolved oxygen and nitrate concentrations. Improved water quality was observed during the postmonsoon period, with increased salinity and dissolved oxygen concentrations, a finding that confirms generalized and specific conclusions can be achieved with the use of the WASP model.

Seasonal variation of water quality parameters in different geomorphic Channels of the upper Malwathu Oya in Anuradhapura, Sri Lanka

Malwathu Oya is a perennial river in the Dry Zone of Sri Lanka. Water of the nearby paddy lands is diverted to the river from different locations during cultivation seasons. These anthropogenic activities cause stresses on Malwathu Oya by impairing the quality of its water. The main objective of this study was to assess the seasonal fluctuation of nitrate, phosphate, chloride, dissolved oxygen (DO) and turbidity of river water in different locations of Malwathu Oya. The study was carried out in the upper part of Malwathu Oya from Ritigala to Nachchaduwa in the Anuradhapura District. Data were collected continuously for twelve months from March 2012 to February 2013. Factorial analysis was carried out to study the interactions among different factors (study site location, climatic season, channel geomorphic unit and river segment). The mean nitrate, phosphate, chloride and DO concentrations ranged from 1.05 to 5.28, 0.004 to 0.043, 2.63 to 8.72, 3.11 to 8.50 mg/L, respectively, and the mean turbidity level ranged from 81.75 to 256.10 NTU. The nitrate, phosphate and chloride concentrations were significantly higher (p 0.05) in DO and turbidity in paddy and non-paddy areas. The results concluded that the water quality parameters except turbidity in the investigated area of Malwathu Oya were within the threshold limits for dinking purposes. Tropical Agricultural Research Vol. 25 (2): 158 – 170 (2014)