Variations In Water Quality Parameters Research Articles

Variation of water quality parameters and correlation with catch per unit effort of oriental river prawn (Macrobrachium nipponense) in Anzali Lagoon, Iran

Variation of water quality parameters and correlation with catch per unit effort of oriental river prawn (Macrobrachium nipponense) in Anzali Lagoon, Iran

Water quality of a southwest Iberian coastal lagoon: Spatial and temporal variability

The present work aims to characterize Ria Formosa water quality considering its spatial, and temporal variability at two scales: short-term (among seasons) and long-term to evaluate its evolution over the past 40 years, by comparing six historical datasets with data obtained in this study. To attain these goals, four field surveys under different seasons and/or weather conditions were conducted between 2017 and 2019 at seven sites along the Ria Formosa, covering the water bodies specified for this system. In situ measurements (temperature, salinity, pH and dissolved oxygen) and water sampling for determination of nutrients, chlorophyll a and suspended solids were taken every 2 h at each site, during complete semidiurnal tidal cycles. Moreover, these data were complemented with in situ data acquired at a high frequency (every 15 min) by a real time observational station deployed at an inner area, close to a main channel, where the anthropogenic pressure is more intense. Data analysis clearly depict a spatial variability pattern along the Ria Formosa, as well as a temporal heterogeneity, influenced by the contribution of precipitation, sediments, wind and water exchanges with the adjacent ocean. Between sampling sites, the lowest variability of water quality parameters occurred at the boundary coastal station, at the main inlet, in permanent connection with the ocean, while the maximum variability was found at both the lagoon edges, mainly due to the shallowness of the water column. Temporally, the highest concentrations of nutrients were obtained during the Wet/rainy conditions survey, under the influence of runoff. The lowest concentrations of nutrients were attained during the Summer, except for phosphate, due to consumption by phytoplankton. Although the sampling frequency along time has been limited, Ria Formosa water quality data from the last 40 years shows a decreasing trend in nutrients concentration and a marginal increase of dissolved oxygen, suggesting a water quality improvement over time, in contrast with other coastal lagoons that are showing a water quality deterioration due to an increasing anthropogenic pressure. Altogether, these are relevant aspects to consider regarding Ria Formosa present and future management, including climate change and anthropogenic pressures susceptibility assessment and to use them within an international context by comparison with other similar systems.

Big Data Analysis Framework for Water Quality Indicators with Assimilation of IoT and ML

According to the United Nations, the Sustainable Development Goal ‘6’ seeks to ensure the availability and sustainable management of water for all. Digital technologies, such as big data, Internet of Things (IoT), and machine learning (ML) have a significant role and capability to meet the goal. Water quality analysis in any region is critical to identify and understand the standard of water quality and the quality of water is analyzed based on water quality parameters (WQP). Currently, water pollution and the scarcity of water are two major concerns in the region of Uttarakhand, and the analysis of water before it is supplied for human consumption has gained attention. In this study, a big data analytics framework is proposed to analyze the water quality parameters of 13 districts of Uttarakhand and find the correlation among the parameters with the assimilation of IoT and ML. During the analysis, statistical and fractal methods are implemented to understand the anomalies between the water quality parameters in 13 districts of Uttarakhand. The variation in WQP is analyzed using a random forest (RF) model, and the dataset is segmented location wise and the mean, mode, standard deviation, median, kurtosis, and skewness of time series datasets are examined. The mean of the parameters is adjusted with the coefficient of variation based on the standard values of each parameter. The turbidity in almost all the experimental sites has a normal distribution, with the lowest mean value (0.352 mg/L) and highest (11.9 mg/L) in the Pauri Garhwal and Almora districts, respectively. The pH of the water samples is observed to be in the standard range in all the experimental sites, with average and median values being nearly identical, at 7.189 and 7.20, respectively. However, the pH mode is 0.25. The Cl− concentration varies with mean values from the lowest (0.46 mg/L) to the highest (35.2 mg/L) over the experimental sites, i.e., the Bageshwar and Rudraprayag districts, respectively. Based on the analysis, it was concluded that the water samples were found to be safe to drink and in healthy condition in almost all the districts of the state Uttarakhand, except for the Haridwar district, where some increase in contaminants was observed.

Seasonal variation of water quality parameters of surface water in mining areas

PurposeTotal organic carbon (TOC), dissolved organic carbon (DOC) and other physicochemical parameters of the Birim River, which serves for drinking and domestic purposes for rural mining communities, were analysed to assess the suitability of water quality for human consumption.Design/methodology/approachIn total, 40 samples were collected from 20 sampling sites during the rainy season from July to September and the dry season from December to February in addition to two repeat samples and two blank samples. Samples were analysed for physiochemical parameters and the results were compared with World Health Organisation standards (WHO).FindingsData obtained for both rainy and dry seasons indicated TOC ranged from 1.1 to 7.3 mg/L and DOC 1–7.2 mg/L; pH, 5.6–8.63; temperature, 23.3–29.3°C; turbidity, <1.00–869NTU; apparent colour, <2.5–600 mg/L Pt-Co; true colour <2.5–150 mg/L Pt-Co; alkalinity, 27.8–80.4 mg/L; total suspended solids, <1.00–998 mg/L; electrical conductivity, 82–184 µS/cm; and bicarbonate, 33.9–98.1 mg/L. Particulate organic carbon (POC) was constituted between 1 and 10% of the TOC. Values for pH, turbidity, total suspended solids, and true colour indicated contamination of the river. p -value of <0.05 between seasons for the physicochemical parameters also suggests that the water is polluted.Practical implicationsWater from the Birim River is unsuitable for human consumption and may constitute a serious health risk to the consumers.Originality/valueThe paper yields immense value to inhabitant of communities using surface water affected by mining activities, policy makers in sustainability. It warns of the unsuitability of water from the Birim River for human consumption due to the potential health risk to consumers.

Seasonal variation of reservoir water quality: A case study of Kubanni reservoir, Zaria, Nigeria

Background: Reservoirs serve as fishing and domestic water resources for the people living around the catchment area. However, natural activities threaten the water quality, therefore, constant and proper monitoring of the reservoir is necessary. This study aimed to examine seasonal variation in water quality parameters of Kubanni reservoir, Zaria, Nigeria. Methods: Water quality data of Kubanni reservoir, Zaria, Nigeria, for 7 years (January 2014 to December 2020) were collected and analyzed to understand the seasonal variation. Ten water quality parameters including pH, turbidity, electrical conductivity (EC), temperature, total dissolved solids (TDS), dissolved oxygen (DO), chloride (Cl- ), total Iron, nitrate (NO3-), and manganese (Mn) were analyzed. The data were analyzed using Kolmogorov-Smirnov test to select the probability distribution which provides the best fit by EasyFit software. The functions included Weibull, Exponential, Fréchet, Gamma, Lognormal, and Normal. Seasonal variation was determined using Spearman’s rank-order correlation. Results: The results showed that pH, EC, temperature, TDS and NO3- approach the Weibull distribution. Turbidity and total Iron approach the Fréchet distribution. Mn approaches the normal distribution, while DO and Cl- approach the Gamma distribution. The output of non-parametric Spearman’s correlation coefficient and Spearman’s statistical criterion indicates a significant difference at 5% significance level between the pH and total Iron values recorded in both seasons. This suggests that season has an effect on the concentration of pH and total Iron. Conclusion: Out of the 10 parameters examined, pH and total Iron are climatologically influenced.

Assessment of Surface Water Quality of an Urban Wetland: Thalangama Wetland, Colombo, Sri Lanka

Thalangama wetland is situated within the Kelani river basin, Colombo District, Sri Lanka. It is one of the most attractive landscapes in Colombo that provides a wide range of ecological, social and economic functions. Wetland water supports aquatic life and is being prominently used for agriculture and bathing and contact recreational activities without knowing if the water quality is appropriate for such uses. This study was therefore conducted to assess the surface water quality of Thalangama wetland using key-physicochemical parameters and to examine the suitability of wetland waters for bathing and contact recreational water, aquatic life, irrigation and other agricultural activities. A total of 10 water quality parameters covering temperature, pH, salinity, TDS, EC, DO, BOD, COD, nitrate, and total phosphate were measured at eight sampling sites of the wetland. The study was conducted in August 2020. The spatial variation of water quality parameters was assessed using one-way ANOVA followed by Tukey’s pairwise comparison. Results were compared with ambient water quality standards of Sri Lanka. The study revealed that the surface water quality parameters including temperature, EC, TDS, DO, BOD, COD, nitrate and total phosphate show a significant spatial variation among the sampling sites. Surface water pH and BOD at all the sampling sites were within the ambient water quality standards for water suitable for bathing and contact recreational water and water suitable for aquatic life, irrigation and agricultural activities. EC at all the sampling sites were within the limits of water suitable for irrigation and agricultural activities. Nitrate and total phosphate concentrations at all the sampling sites were within the limits of water suitable as bathing and contact recreational water and water suitable for aquatic life. DO at six out of eight sampling sites were within the limits of water suitable as bathing and contact recreational waters and water suitable for aquatic life, irrigation and agricultural activities. COD at all the sampling sites were not within the limits of water suitable as bathing and contact recreational water and water suitable for aquatic life. The study identifies agricultural practices, livestock rearing, construction activities and urban discharges as major anthropogenic influences that degrade the surface water quality of the wetland. Hence, the study determines the necessity for effective management of the surface water of Thalangama wetland to prevent pollution and to ensure the water quality of the wetland is within the recommended standards.&#x0D; Keywords: Urban wetlands, Surface water quality, Spatial variation, Physicochemical parameters, Ambient water quality standards

Growth performance of Nile Tilapia (Oreochromis niloticus) fingerlings fed with water spinach (Ipomoea aquatica) diets

Nile tilapia (Oreochromis niloticus) are herbivores with longer coiled intestines compared to carnivores; mouth characteristics necessary for plant shredding. Hence, several studies have been conducted to replace feed ingredients in the diet of Nile tilapia considering the increasing cost. In this study, Water spinach (Ipomoea aquatica) was evaluated as a potential feed ingredient for Nile tilapia. A six months feeding trial was conducted to assess the effects of water spinach fish feed composition on the performance of Nile tilapia fingerlings. Five diets were formulated containing 0% (control diet), 5%, 10%, 15% and 20% water spinach composition. Each treatment was carried out in triplicate using 30 Nile tilapia juveniles per replicate with an initial mean weight of 2±1g. The fish were fed at 5% body weight twice per day. Water quality monitoring was done every morning before feeding. There was no significant (p &gt; 0.05) variation in water quality parameters between all the treatments. The best growth performance was recorded from a fish-fed 5% diet (180.49±0.83 g), while fish fed with a 20% diet had poor growth performance (128.98± 0.80g). The highest SGR was obtained in fish fed with a 5% diet (1.34±0.05) while the lowest was obtained in fish fed with a 20% diet (1.09±0.05). Except for SGR, WG, FL, and FW, there was no significant difference (P&gt;0.05) in other growth parameters of all the treatments. Final weight had a significant difference as determined by One-Way ANOVA (F (4,316) =6.363, P=0.00) between 15% and 20% water spinach composition compared to 5% water spinach composition. Therefore, 5% water spinach composition had the best growth performance.

Geochemical and multivariate assessment of groundwater resources of churachandpur sub-division of Manipur, India

Hydrogeochemical and multivariate assessment of groundwater samples of the Churachandpur sub-division of the state of Manipur was carried out to study its suitability for potable and irrigational uses. The study extensively discusses the underlying hydro-geochemistry using multivariate geostatistical tools for physicochemical parameters of 35 spatially distributed groundwater samples during pre- and post-monsoon seasons. In situ parameters (pH, TDS, DO, EC, salinity, ORP) were assessed in field conditions, and it was found that few samples exceed concentration than the prescribed standards. Both positive and negative ORP values and low DO levels of the samples indicate oxidizing and reducing aquifers due to recent unstable geologic formations. Although the concentration of Cl−, SO42−, and NO3− is well within desirable levels, the concentration of F− and As3+ of a few samples exceeds the prescribed standard. The water quality index of the groundwater samples signifies that more than 50% of samples are unsuitable for potable uses for both seasons. The geochemical analysis indicates that most of the water is Ca–Mg–Cl–HCO3 type followed by Mg–Ca–Cl–HCO3 types in both the seasons and dominated by the rock-weathering geochemical process. Multivariate analysis and geostatistical mapping highlight the spatial variability of water quality parameters and possibilities of the occurrence of geogenic contaminants in the aquifers of the study area.

Analysis of variation of water quality parameters along treatment processes in OPA waterworks, ILE-IFE, Nigeria

This study was conducted to assess the variation of water quality parameters along the treatment processes of Opa Waterworks at Obafemi Awolowo University, Ile – Ife, Nigeria. This was to ascertain how chemical and physical parameters vary along the treatment plant visits while at the same time ensuring that the influent and effluent conforms to water quality standards set by the World Health Organization.Determination of physicochemical parameters; pH, temperature, conductivity, turbidity, nitrate and chloride was done by  using standard methods while a colorimetric,  and atomic absorption spectrometry methods were used for the selected heavy metals; cadmium, zinc and copper.It was observed that for the influent, the concentration of lead was 9.44 mg/l, nitrate 0.25 mg/l, chloride 18.27 mg/l, sulphate 4.29 mg/l, copper 4.55 mg/l, zinc 0.07 mg/l and cadmium 1.10 mg/l. For the effluent, the concentration of nitrate was 0.22 mg/l, chloride 16.01 mg/l and sulphate 4.29 mg/l while that of lead, copper, zinc and cadmium was 0.00 mg/l. The overall results show that the concentrations of the water quality parameters tested conform to the World Health Organization water quality standards at the effluent points of the treatment plant. Â

Analysis of spatio-temporal variations of river water quality and construction of a novel cost-effective assessment model: a case study in Hong Kong.

Assessment of river water quality has been attracting a great deal of attention because of its important implications for the living environment of human beings and aquatic organisms. River water quality is commonly assessed using dozens of different water quality parameters. However, different parameters may contain redundant information, which could lead to the waste of monitoring efforts. Thus, this study constructed a novel cost-effective assessment model of river water quality using the 1-year monitoring data collected from 23 sampling stations in the water control zone of Tolo Harbour and Channel in Hong Kong. First, the spatio-temporal variations of water quality parameters and the overall status of river water quality were analyzed based on all 19 parameters using Kruskal-Wallis test, hierarchical cluster analysis, and the water quality index (WQI). The results indicated that most water quality parameters and overall water quality status varied significantly over space, but did not exhibit obvious seasonal differences; and 99.27% of water samples were identified to be in good or excellent status of overall WQI. Then, using principal component analysis (PCA)/factor analysis (FA) and Pearson's correlation analysis, eight parameters, including 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), ammonia-nitrogen (NH3-N), nitrate-nitrogen (NO3-N), chlorophyll-a (Chl-a), fluoride (F-), total suspended solids (TSS), and arsenic (As), were verified to be responsible for the greatest contributions to water quality, the assessment of overall water quality status. These eight crucial parameters were further employed to establish six cost-effective water quality assessment models. Using the overall WQI as the benchmark, the results of linear regression analysis demonstrated that the cost-effective model constructed based on BOD5, COD, NH3-N, NO3-N, F-, TSS, and As were the optimal water quality assessment model, which can achieve the most reliable results with reduced parameters.

Variations in water quality parameters and their correlation with fish catch per unit effort of Bhini Stream, a tributary of River Ravi, Jammu and Kashmir, India

The quality of water is very critical for fish survival and growth in a water body. However, little is known about the state of the Bhini Stream’s water quality and its relationship to fish catch. The focus of this study was to evaluate water quality parameters in the Bhini Stream and see if there was a correlation between them and fish catch per unit effort. Monthly samples were gathered using a three-level stratified sampling method. Temperature, depth, transparency, pH, TDS, EC, DO, alkalinity, hardness, chloride, sulphate, phosphate, nitrate, and fish catch (CPUE) were all monitored simultaneously in each of the three strata of the stream. The water quality characteristics were within the permissible range for fish production. There were no significant differences in water quality parameter concentrations between the riverine, transitional, and lacustrine zones (p&gt;0.05). TDS and nitrates from fertilisers used on nearby fields and brought to the stream by runoff or floods were significantly and negatively correlated with CPUE (r=0.84, p&lt;0.05; r=0.71, p&lt;0.05). 13 fish species all belonging to order Cypriniformes were reported from the stream with Schistura denisoni being reported for the first time from the River Ravi.

Assessment of Water Quality in Different Inlet and Outlet Canals of Kurunegala Lake, Sri Lanka

Kurunegala Lake is one of the major drinking water supplying tanks in Kurunegala, Sri Lanka. Water quality assessment is vital for the sustainable management of drinking water resources. This study evaluated the temporal variability of water quality in different inlets and outlet canals of Kurunegala Lake. Three major inlets and one outlet canals connected to Kurunegala were identified, and one sampling location was selected from each of these canals. Water samples data were collected from each selected location in a one-month interval for three years. Water quality parameters were determined in each water sample, such as pH, Electrical Conductivity (EC), Dissolved Oxygen Level (DO), Total Dissolved Solids (TDS), Nitrate-nitrogen (NO3–N), and Available Phosphorus (Av.P) concentrations. This study showed that pH, DO, NO3–N, and Av.P of some of the water samples tested were within permissible levels according to WHO &amp; SLS drinking water standards, CEA act. The inlet and outlet canals showed a temporal and spatial variation in water quality parameters during the study period. The results conclude that there is an impact of surrounding land use on water pollution in inlet water canals connected to Kurunegala Lake. Therefore, a pollution management plan is required to prevent further pollution by conducting future research.

Spatiotemporal water quality variability in a highly loaded surface flow wastewater treatment wetland.

This study evaluates spatiotemporal relationships between water quality parameters (WQPs), nutrients, suspended solids, and biochemical oxygen demand (BOD) concentrations within an engineered wastewater treatment wetland system in the Georgia Piedmont, USA. We explored factors related to treatment efficiency within a heavily loaded 630-m2 surface flow wetland system over a 2-yr period. Relationships between temperature, dissolved oxygen (DO), and oxidation-reduction potential (ORP) were observed; relationships were also seen between these WQPs and nutrient concentrations. Because temperature, DO, and ORP affect nitrogen (N) cycling rates, seasonal trends in N forms were evident in the system. Organic N and inorganic/organic phosphorus concentrations correlated with solids concentrations in the vegetated system without exhibiting seasonal trends. Surface water within the vegetated section generally exhibited anoxic conditions, leading to removal of nitrate-N within the system; however, limited mineralization and nitrification occurred, which greatly limited overall N removal. Plant selection and lack of maintenance likely led to high solids and BOD contributions to treatment wetland surface water, which varied substantially between and along monitored transects. Because so few studies have investigated treatment dynamics within treatment wetland cells, focusing solely on influent/effluent characterization, radical spatiotemporal variability may be the norm as opposed to the commonly accepted assumptions of relatively uniform pollutant degradation across treatment wetland cells. This spatiotemporal variability in WQPs underscores the dynamic nature of treatment wetlands and the need for routine maintenance, including sludge removal and plant harvesting.

Tidal variability of water quality parameters in a mesotidal estuary (Sado Estuary, Portugal)

To establish effective water quality monitoring strategies in estuaries, it is imperative to identify and understand the main drivers for the variation of water quality parameters. The tidal effect is an important factor of the daily and fortnightly variability in several estuaries. However, the extent of that influence on the different physicochemical and biological parameters is still overlooked in some estuarine systems, such as the Sado Estuary, a mesotidal estuary located on the west coast of Portugal. The main objective of this study was to determine how the water quality parameters of the Sado Estuary varied with the fortnightly and the semidiurnal tidal variation. To achieve this goal, sampling campaigns were conducted in May/18, Nov/18 and Jun/19, under neap and spring tidal conditions, with data collection over the tidal cycle. Results were observed to be significantly influenced by the tidal variation, in a large area of the estuary. Flood seemed to mitigate possible effects of nutrient enrichment in the water column. Additionally, significant differences were also observed when considering the different sampling stations. Temperature, Suspended Particulate Matter (SPM) and nutrients showed the highest values at low water. Lastly, the implications of the tidal variability in the evaluation of the water quality according to Water Framework Directive were also discussed, highlighting the importance of studying short-time scale variations and the worst-case scenario to ensure water quality is maintained. These findings are relevant for the implementation of regional management plans and to promote sustainable development.

Spatial and temporal variations in water quality of Todos Santos Bay, northwestern Baja California, Mexico

Coastal pollution levels in Todos Santos Bay (TSB) recreational beaches have increased in recent years due to the uncontrolled disposal of wastewater and pollutants to the coast by human activities (urbanization and tourism). In this work, the concentration of water quality parameters along the coast of TSB was evaluated from February 2012 to January 2013. Sampling was carried out at monthly intervals on 29 beach locations. Results showed that the maximum values of all parameters were always found close to the treated wastewater discharge area at Arroyo El Gallo station. Temporally, both nutrients and biochemical oxygen demand reached notably high levels in winter-spring and close to wastewater discharges. During summer, maximum counts of total coliforms and parasite eggs were detected close to wastewater discharges. Overall, our study provides a diagnostic approach on the spatiotemporal variability of water quality parameters for future studies along the coastal waters of TSB.

Assessment of Temporal Variation of Water Quality Parameters and the Trophic State Index in a Subtropical Water Reservoir of Bangladesh

This study was conducted to determine the suitability of water quality for fisheries management in Kaptai Lake from February 2019 to January 2020. Results showed that the temperature, transparency, TDS, pH, DO, EC, alkalinity and hardness were 20.9 to 31.8°C, 17 to 303 cm, 40 to 105 mg/L, 6.82 to 7.96, 6.1 to 7.65 mg/L, 75.33 to 172.33 µS/cm, 37 to 83 mg/L and 35 to 190 mg/L, respectively. However, nutrients as NH3, NO3-, NO2-, PO43- and SO42- were 0.01 to 0.05, 0.03 to 2.21, 36 to 96, 0.01 to 0.04 and 0.3 to 1.9 mg/L, respectively. Chlorophyll a and trophic state index (TSI) were 0.70 to 2.12 µg/L and 27.43 to 37.79, respectively. Study revealed that SO42-, DO and TDS were higher than the standard of ECR. On the other hand, NH3, NO3-, NO2-, PO43-, temperature, transparency, pH, EC, total hardness, total alkalinity, Chlorophyll a and TSI were within the standard levels. Concentrations of NO3-, NO2-, PO43-, Chlorophyll a and TSI (CHL) showed no significant variation with seasons. Conversely, TDS, transparency, EC, alkalinity, hardness, and SO42- were lower in monsoon compared to pre-monsoon and post-monsoon seasons. Besides, temperature, NH3, DO and TSI (SD) were higher in monsoon season. Results concluded that the Kaptai Lake is in mesotrophic condition with TSI (CHL) less than 40, and prominently there was a positive relationship between Chlorophyll a and Trophic State Index (TSI). In this regard, major nutrients and Chlorophyll a concentration in the Kaptai Lake may have an impact on the aquatic environment.

Using seasonal variability of water quality parameters to assess the risk of aquatic pollution from rainbow trout fish farms in Greece

Using seasonal variability of water quality parameters to assess the risk of aquatic pollution from rainbow trout fish farms in Greece

Water quality trend analysis in a citywide water distribution system

Abstract Rapid urbanization poses challenges to meet the increased water supply demands. Apart from the quantity, the distributed water quality often fails to meet the permissible level. This study aimed to conduct a citywide spatio-temporal variation of water quality parameters. Water sampling points were selected by applying the Analytical Hierarchical Process (AHP) technique using ArcGIS considering pipe leakage, source water quality, pipe age, and pipe materials. The Chattogram city comprises 397 km of pipes; pipe material distribution shows 71.28% PVC, 20.94% asbestos, 5.16% mild steel, 2.17% ductile, and 0.45% cast iron. The citywide pipe network was established in 1963; 20.87% of pipes aged over 30 years, 15.07% 20–30 years, 26.38% 10–20 years, and 37.68% pipelines are relatively new, i.e., within 0–10 years. Eight water quality parameters, i.e., pH, temperature, turbidity, biochemical oxygen demand after five days (BOD5), total coliform, fecal coliform, chloride, and residual chlorine, were collected from the secondary source cross-checked by field survey. Computation of the Water Quality Index (WQI) was interpolated using Inverse Distance Weighted (IDW) method to generate a WQI map. Thus, this study could be a basis to improve the treatment system and proper distribution network maintenance.

Variation of water quality parameters and correlation among them and fish catch per unit effort of the Tono Reservoir in Northern Ghana

Water quality is essential for fish survival and growth in reservoirs. However, little information is known about the water quality status and its relation with fish production in the Tono Reservoir. This study sought to assess water quality parameters and examine association among them as well as determine the correlation between the water quality parameters and fish catch per unit effort of the Tono Reservoir. A three-level stratified sampling was adopted and samples were collected on a monthly basis. Water quality parameters such as water level, temperature, pH, electrical conductivity, transparency, turbidity, dissolved oxygen, chloride, sulphate, phosphate-phosphorus, silica, nitrate-nitrogen, nitrite-nitrogen, chlorophyll-a, and fish catches were measured simultaneously from each of the three strata of the reservoir. The water quality parameters of the reservoir fell within the recommended range for fish production. Concentrations of water quality parameters for the riverine, transitional and lacustrine zones showed no significant difference (p > 0.05). Catch per unit effort correlated significantly positive with only chloride (r = 0.61, p < 0.05) attributable to fertilisers used on surrounding farm lands and carried by runoff or floods to the reservoir. The reservoir could be classified as mesotrophic based on chlorophyll-a concentration. It was recommended that the reservoir water quality should be monitored quarterly by the Ministry of Fisheries and Aquaculture Development to ensure safe fish production.

Assessment of Trophic Responses of a Reservoir to Seasonal and Annual Variations in Monsoon

The variations in water quality parameters and trophic status of a multipurpose reservoir in response to changing intensity of monsoon rain was investigated by applying a trophic state index deviation (TSID) analysis and an empirical regression model to the data collected in two periods from 2014 to 2017. The reservoir in general maintained mesotrophic conditions, and Carlson’s trophic state index (TSIc) was affected most by TSITP. Nutrient concentrations, particularly phosphorus, did not show strong correlations with precipitation, particularly in the period with weak monsoon, and a significant increase in total phosphorus (TP) was observed in Spring 2015, indicating the possibility of internal phosphorus loading under decreased depth and stability of water body due to a lack of precipitation. TSIChl was higher than TSISD in most data in period 1 when a negligible increase in precipitation was observed in the monsoon season while a significant fraction in period 2 showed the opposite trend. Phytoplankton growth was not limited by nutrient limitation although nutrient ratios (N/P) of most samples were significantly higher than 20, indicating phosphorus-limited condition. TSID and regression analysis indicated that phytoplankton growth was limited by zooplankton grazing in the Spring, and that cell concentrations and community structure in the monsoon and post-monsoon season were controlled by the changing intensity of the monsoon, as evidenced by the positive and negative relationships between community size and cyanobacterial population with the amount of precipitation in the Summer, respectively. The possibility of contribution from internal loading and an increase in cyanobacterial population associated with weak monsoon, in addition to potential for nutrient enrichment in the post-monsoon season, implies a need for the application of more stringent water quality management in the reservoir that can handle all potential scenarios of eutrophication.