Water Quality Analysis Simulation Program Research Articles

Water quality monitoring and modeling for an urban storm drainage channel in Thane, India.

The absence of a sewer system and inadequate wastewater treatment plants results in a discharge of untreated wastewater to the urban drainage channels and pollutes receiving waters. Field visits were carried out to observe water quality parameters such as dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) in an urban drainage system (Kolshet drain) in Thane City, Mumbai Metropolitan Region, India. Dye-tracing studies using rhodamine WT dye were used for computing the velocity, discharge, and dispersion coefficient of the drain. The data analysis shows that the BOD and COD values in the drain are higher than the permissible limits (30mg L-1 for BOD and 250mg L-1 for COD), which is not suitable for disposal to any receiving water body. Also, the DO was less than the permissible limit of a minimum of 3mg L-1 (for the survival of aquatic life). It is seen that the higher BOD load significantly reduced the DO throughout the drain. The Water Quality Analysis Simulation Program (WASP 8.32, 2019) developed by the US Environmental Protection Agency (USEPA) has been used for the simulation of the DO and BOD in the drainage channel. The model simulates an appropriate estimate of the expected variation of DO and BOD at points of interest. The modeling for the Kolshet drain is expected to enable better estimates of the wastewater parameters and the pollution transport in the drain for planning purposes.

Assessing Reaeration Rate Equations for Modelling Dissolved Oxygen of Pusu River in Malaysia

Many authors reported high variability in the prediction of reaeration rates by various equations, leading to uncertainty in the estimation of the reaeration rate for a river. Due to this uncertainty, it is essential to identify a suitable equation to predict the dissolved oxygen (DO) concentration of the river in concern. Pusu River in Malaysia receives sewage discharges and suffers from land-clearing activities and stormwater-related pollution. Pusu River is a small river, but highly important in terms of demography and geographic location. As such, it is required to identify a suitable reaeration rate equation for predicting its DO concentration, which indicates the overall health of a river. The purpose of this study is to assess the suitability of reaeration rate equations to predict Dissolved Oxygen (DO) concentrations of the Pusu River. The water quality analysis simulation program (WASP) model was employed to model the DO of the Pusu River. Reaeration rates calculated from the available 31 equations were given input in the model, and errors in prediction were calculated in terms of Root Mean Square (RMS) error and R2 for every equation. It was revealed that Neguluscu and Rojanski (1969) equation using depth and velocity as the variables performed best among all the equations. It produced a minimum RMS error of 0.17 and 0.09 mg/L in calibration and validation data, respectively. R2 values for predicted-observed plots were 0.98 and 0.97 in these two data sets using the equation. Based on overall Performance Indicator Values (PIVs), reaeration rate equations with depth and velocity as the variables performed better than the other equations with more variables for Pusu River. This study provided important information to accurately model the DO of the Pusu River for future simulation of different scenarios.

Analisis daya tampung beban pencemaran sungai bedadung Jember menggunakan software wasp

The distribution of pollution sources from domestic, agricultural, and industrial activities has the potential to reduce the water quality of the Bedadung River, thereby negatively impacting its self-purification. The aim of this research is to model the parameters, specifically the values of Biochemical Oxygen Demand (BOD) and Total Suspended Solid (TSS), and to determine the river's capacity to carry the pollution load using the Water Quality Analysis Simulation Program (WASP). The input parameters for this study include BOD, TSS, and water discharge data collected at 21 monitoring points along the Bedadung River, with the river water sampling technique employing the grab sampling method. The output validation of the modeling is assessed using the Root Mean Square Error (RSME) equation, and the research results indicate that the water quality modeling with WASP software effectively reflects the dynamics of BOD and TSS parameters in the Bedadung River, as supported by an average output validation value of 9%. The pollution load capacity values for the Bedadung River in the Patrang - Ajung segment are found to be 361.48 kg/day for BOD and 5368.31 kg/day for TSS. The positive values suggest that the Bedadung River still has the capacity to naturally degrade organic pollutants.

Water quality simulation using the WASP model for eutrophication control in a South Indian Reservoir

Abstract The study focused on analysing the eutrophication indicators of the Krishnagiri Reservoir Project (KRP) using the Water Quality Analysis Simulation Program (WASP). The reservoir was divided into six segments to simulate the indicators, and field measurements from 2015 to 2018 were used to calibrate the model while 2019 to 2022 were used to validate it. The results showed that the model predictions were in good agreement with the measured values, indicating the reliability of the model. The study assessed the impact of nutrient loads on dissolved oxygen, nitrate, phosphate, and chlorophyll-a. Four nutrient loading scenarios were simulated, and the most effective scenario (Scenario 4) involved a 75% reduction in nutrient load, which increased the reaeration rate by 1.47% and decreased chlorophyll-a concentrations by 88%. The study concluded that maintaining nitrates below 2.5 mg/L and phosphates below 0.75 mg/L could help restore the KRP reservoir's trophic status from hypereutrophic to mesotrophic. Overall, the study demonstrated the use of the WASP model in developing nutrient loading scenarios to manage reservoir water quality effectively. The findings could help policymakers and managers make informed decisions about reducing nutrient loads and restoring the trophic status of eutrophicated reservoirs.

Analysis of Total Maximum Daily Loads of Winongo River, Special Region of Yogyakarta, Using Water Quality Analysis Simulation Program (WASP)

A total maximum daily load (TMDL) is the amount of a pollutant load that a waterbody can accommodate without exceeding the water quality standard for that particular pollutant. The research aimed to measure pollutant loads in the Winongo River, TMDLs, and pollutant reduction needed if pollutant loads were higher than TMDLs. The Water Quality Analysis Simulation Program (WASP) model was used to determine water quality responses to the potential amounts of pollutants discharged into the river, resulting in information on existing pollutant loads. After testing the water quality parameters, it was found that pH and BOD at points 2–7 and TDS at all the sampling points meet the standards for Class 1 water per the Governor Regulation No. 20 of 2008. The WASP model showed a total pollutant load of 51,78 kg/day and a TMDL of 139,08 kg/day. Segment 1 had the lowest pollutant load of 2.57 kg/day, then the TMDL was 4.56 kg/day. The highest pollutant load measured was found in segment 6 of 20.11 kg/day, then the TMDL was 79.13 kg/day. Based on the results, the Winongo River can accommodate the pollutant loads while maintaining the water quality.

Applicability of the WASP Model in an Assessment of the Impact of Anthropogenic Pollution on Water Quality—Dunajec River Case Study

This article covers the analysis of the impact of agricultural and municipal pollution on surface waters in a selected pilot section of the Dunajec River in Poland. The analysis was performed using the dynamic Water Quality Analysis Simulation Program (WASP) model. The operational use of the WASP allows the assessment of current and future changes in water quality and the planning of measures to reduce adverse impacts on surface waters. Based on the acquired and processed data, the model simulated the impact of the pollutant supply on the water quality in the selected section. The simulations were carried out in three developed scenarios. The results of the simulations of the spread of pollutants in the riverbed show that the adopted scenarios, including an increased supply of pollutants and unfavorable hydrological conditions, will not adversely affect the operation and efficiency of the water intake. Thus in the considered cases, the risk will not reach an unacceptable level. However, a serious threat may be caused by the failure of the sewage treatment plant located in the vicinity of a water intake. The conducted analyses indicate that the WASP may have significant application potential in the risk assessment for surface water intakes.

Modelling Transport and Fate of Copper and Nickel across the South Saskatchewan River Using WASP—TOXI

The South Saskatchewan River (SSR) is one of the most important river systems in Saskatchewan and, arguably, in Canada. Most of the Saskatchewan residents, industries, and powerplants depend on the SSR for their water requirements. An established 1D modelling approach was chosen and coupled with the Hydrologic Engineering Center’s River Analysis System (HEC-RAS). The WASP (Water Quality Analysis Simulation Program) stream transport module, TOXI, is coupled with flow routing for free-flow streams, ponded segments, and backwater reaches and is capable of calculating the flow of water, sediment, and dissolved constituents across branched and ponded segments. Copper and nickel were chosen as two metals with predominantly anthropogenic (agriculture, mining, and municipal and industrial waste management) and geogenic (natural weathering and erosion) sources, respectively. Analysis was carried out at ten different sites along the South Saskatchewan River, both upstream and downstream of the City of Saskatoon, in the years 2020 and 2021. Model performance was evaluated by comparing model predictions with concentrations of copper and nickel measured in a previously published study. The model performed well in estimating the concentrations of copper and nickel in water samples and worked reasonably well for sediment samples. The model underestimated the concentration values at certain segments in both water and sediment samples. In order to calibrate the model more accurately, extra diffusive contaminant loads were added. While several default parameter values had to be used due to the unavailability of primary historical data, our study demonstrates the predictive power of combining WASP—TOXI and HEC-RAS models for the prediction of contaminant loading. Future studies, including those on the impacts of global climate change on water quality on the Canadian prairies, will benefit from this proof-of-concept study.

How do inorganic nitrogen processing pathways change quantitatively at daily, seasonal, and multiannual scales in a large agricultural stream?

Abstract. Large agricultural streams receive excessive inputs of nitrogen. However, quantifying the role of these streams in nitrogen processing remains limited because continuous direct measurements of the interacting and highly time-varying nitrogen processing pathways in larger streams and rivers are very complex. Therefore, we employed a monitoring-driven modelling approach with high-frequency in situ data and the river water quality model Water Quality Analysis Simulation Program (WASP) 7.5.2 in the 27.4 km reach of the sixth-order agricultural stream called Lower Bode (central Germany) for a 5-year period (2014–2018). Paired high-frequency sensor data (15 min interval) of discharge, nitrate, dissolved oxygen, and chlorophyll a at upstream and downstream stations were used as model boundaries and for setting model constraints. The WASP model simulated 15 min intervals of discharge, nitrate, and dissolved oxygen with Nash–Sutcliffe efficiency values higher than 0.9 for calibration and validation, enabling the calculation of gross and net dissolved inorganic nitrogen uptake and pathway rates on a daily, seasonal, and multiannual scale. Results showed daily net uptake rate of dissolved inorganic nitrogen ranged from −17.4 to 553.9 mgNm-2d-1. The highest daily net uptake could reach almost 30 % of the total input loading, which occurred at extreme low flow in summer 2018. The growing season (spring and summer) accounted for 91 % of the average net annual uptake of dissolved inorganic nitrogen in the measured period. In spring, both the DIN gross and net uptake were dominated by the phytoplankton uptake pathway. In summer, benthic algae assimilation dominated the gross uptake of dissolved inorganic nitrogen. Conversely, the reach became a net source of dissolved inorganic nitrogen with negative daily net uptake values in autumn and winter, mainly because the release from benthic algae surpassed uptake processes. Over the 5 years, average gross and net uptake rates of dissolved inorganic nitrogen were 124.1 and 56.8 mgNm-2d-1, which accounted for only 2.7 % and 1.2 % of the total loadings in the Lower Bode, respectively. The 5-year average gross DIN uptake decreased from assimilation by benthic algae through assimilation by phytoplankton to denitrification. Our study highlights the value of combining river water quality modelling with high-frequency data to obtain a reliable budget of instream dissolved inorganic nitrogen processing which facilitates our ability to manage nitrogen in aquatic systems. This study provides a methodology that can be applied to any large stream to quantify nitrogen processing pathway dynamics and complete our understanding of nitrogen cycling.

Assessing wastewater pollution from outdoor night markets and its impacts on river quality.

Night markets are attractive tourist sites in Asian cities. However, the outdoor activities produce different types of pollutants. Air pollution and solid waste in night markets have received much attention, but wastewater pollution from night markets has rarely been examined. The untreated wastewater are discharged into roadside gutters and might contaminate receiving waterbodies. In this study, night markets in Taipei city, Taiwan, were surveyed to clarify the characteristics of wastewater. The sampled wastewater showed high levels of organic substances, oil and grease, and phosphorous but low levels of nitrogen compounds. In addition, the unit pollution loads in night market stalls were obtained. The BOD load of each stall in the night markets was 2,509 g/day, which is higher than the sewage emissions of 50 people. In order to know the impacts of night market wastewater on the receiving waterbody, a water quality model, the Water Quality Analysis Simulation Program (WASP), was used in the studied river, Keelung River. If night market wastewater could be collected (not discharged), the BOD concentration could be reduced by 9.8%, but the NH3-N and DO concentration could be reduced by less than 1%.

Simulation of the Environmental Fate and Transformation of Nano Copper Oxide in a Freshwater Environment.

Production of engineered nanomaterials (ENMs) has rapidly increased, yet uncertainty exists regarding the full extent of their environmental implications. This study investigates the fate, transformation, and speciation of nano copper oxide (nanoCuO) released into Lake Waccamaw, North Carolina, over 101 years. Using the Advanced Toxicant module of the Water Quality Analysis Simulation Program (WASP8), we assessed the accumulation and mass proportions of nanoCuO and Cu2+ (the product of nanoCuO’s dissolution) in the water column and sediments. Our simulations suggest that when nanoCuO is released into Lake Waccamaw, the highest concentrations of both nanoCuO and Cu2+ are found in the surface sediments, followed by the subsurface sediments and the water column. Simulating different heteroaggregation attachment efficiencies of nanoCuO suggested that increases in attachment efficiency increased nanoCuO concentrations and mass proportions in the water column and sediments, while Cu2+ exhibited the opposite trends. After 101 years, most nanoCuO in the sediments was attached to particulate organic matter and clay particles at all attachment efficiencies, while low attachment efficiency slowed aggregate formation in the water column. Our results highlight the influence that heteroaggregation has on the behavior of nanoCuO inputs and suggest the potential for legacy contamination of nanoCuO and Cu2+ in sediments.

A numerical modeling framework for simulating the key in-stream fate processes of PAH decay in Muskeg River Watershed, Alberta, Canada

Most previous water quality studies oversimplified in-stream processes for modeling the fate and transport of critical organic contaminants, such as Polycyclic Aromatic Hydrocarbons (PAHs). Taking four selected PAHs as representative organic contaminants, we developed a numerical modeling framework using a Water Quality Analysis Simulation Program 8 (WASP8) and a well-established watershed model, i.e., Soil and Water Assessment Tool (SWAT) to: (1) address the influence of in-stream processes, including direct photolysis, volatilization, partitioning of PAHs to suspended solids, and DOC complexation processes on PAH concentrations; and (2) establish relationships between spatiotemporal distribution of environmental factors (e.g., ice coverage, water temperature, wind, and light attenuation), in-stream processes, and PAH concentrations at a watershed scale. Using calibrated SWAT and WASP8 models, we evaluated the impacts of seasonal changes in environmental factors on in-stream processes in the Muskeg River watershed, which is part of the Athabasca Oil Sands Region (AOSR), the third-largest crude oil reserves of the world in western Canada. Among four selected PAHs, simulation results suggest that Naphthalene primarily decay in the water through volatilization or direct photolysis. For Phenanthrene, Pyrene, and Chrysene, DOC complexation, volatilization, and direct photolysis all contribute to their decay in the water, with a strong dependence on seasonality. Model simulations indicated that direct photolysis and volatilization rates are meager in cold seasons, mainly due to low river temperature and ice coverage. However, these processes gradually resume when entering the warm season. In summary, the model simulation results suggest that critical in-stream processes such as direct photolysis, volatilization, and partitioning and their relationship with environmental factors should be considered when simulating the fate and transport of organic contaminants in the river systems. Our results also reveal that the relationship between environmental factors and fate processes affecting PAH concentrations can vary across a watershed and in different seasons.

Application of the WASP Model for Assessment of Aeration Impact on Water Quality of Porsuk River, Turkey

Porsuk Stream is the longest branch of the Sakarya Basin which originates from Murat Mountain and bypasses the provinces of Kutahya and Eskisehir. Based on recent increasing pollution concentrations reported in the literature, the main river is experiencing problems with decreased water quality. In this study, hydrodynamics and water quality parameters are simulated in the Porsuk River via the application of the Water Quality Analysis Simulation Program (WASP) using the available flow and meteorological data. After the validation of the hydrodynamics along the main river, water quality parameters are simulated using the eutrophication module. Simulation of dissolved oxygen concentrations pointed out hypoxia, especially at two locations; Kutahya-Reservoir1 and Alpu-Guroluk segments where dissolved oxygen values stayed well below the standard limits throughout the year. As a mitigation option, aeration applications at these two stations are proposed and the effects of aeration on the simulated parameters of dissolved oxygen, phosphorus and nitrate concentrations are investigated. Aeration at two segments has significantly improved the dissolved oxygen concentrations (from ~3 mg/l to >14 mg/l) whereas it has a more subtle effect on nitrate and phosphorus concentrations.

Research on Water Quality Simulation and Water Environmental Capacity in Lushui River Based on WASP Model

In recent years, the severe deterioration of water quality and eutrophication in the Yangtze River has brought much trouble to people’s lives. Because of this, numerous management departments have paid more and more attention to the treatment of the water environment. In order to respond to water environmental protection policy and provide management departments with a basis for refining water quality, this paper takes the Zhuzhou section of Yangtze River-Lushui watershed as its research object. First, we used the Water Quality Analysis Simulation Program (WASP) model as a tool, and obtained the pollution load using the FLUX method formula. During the calibration process, the sensitivity analysis method, the orthogonal design method, and the trial and error method were used. Then, we verified the results by using water quality monitoring data published by Zhuzhou Ecological Environment Bureau. Following that, the water environmental capacity of the Lushui River in normal, wet and dry periods was calculated using the WASP model: the chemical oxygen demand (COD) was 14,072.94 tons/yr, 17,147.7 tons/yr and 10,998.18 tons/yr, respectively; ammonia nitrogen (AN) was 469.098 tons/yr, 571.59 tons/yr and 366.606 tons/yr, respectively; and total phosphorus (TP) was 93.8196 tons/yr, 114.318 tons/yr and 73.3212 tons/yr, respectively. The results show that the WASP model is applicable and reliable and can be used as an effective tool for water quality prediction and management in this area.

A coupled hydrodynamic (HEC-RAS 2D) and water quality model (WASP) for simulating flood-induced soil, sediment, and contaminant transport.

Increased intensity and frequency of floods raise concerns about the release and transport of contaminated soil and sediment to and from rivers and streams. To model these processes during flooding events, we developed an External Coupler in Python to link the Hydrologic Engineering Center-River Analysis System (HEC-RAS) 2D hydrodynamic model to the Water Quality Analysis Simulation Program (WASP). Accurate data transfer from a hydrodynamic model to a water quality model is critical. Our test results showed the External Coupler successfully linked HEC-RAS and WASP and addressed technical challenges in aggregating flow data and conserving mass during the flood event. We ran the coupled models for a 100-year flood event to calculate flood-induced transport of sediment-associated arsenic in Woodbridge Creek, NJ. Change in surface sediment and arsenic at the end of 48-h flood simulation ranged from a net loss of 13.5 cm to a net gain of 11.6 cm, and 16.2 to 2.9 mg/kg, respectively, per model segment, which demonstrates the capability of the coupled model for simulating sediment and contaminant transport in flood.

Analysis of the Carrying Capacity and the Total Maximum Daily Loads of the Karang Mumus Sub-watershed in Samarinda City Using the WASP Method

Watershed is a multi-aspect ecological system, which functions as a source of water resources, in order to meet daily needs. It also motivates both economical and life matters, as well as serve as a sanitary channel for the surrounding community. Watershed also generates pollutants, which are known to potentially cause a decrease in river water quality. The degradation of river habitats that are caused by high pollutants penetration into the water body, decreases the capacity to carry out self-purification of toxic loads. The water pollutant load-carrying capacity is then calculated through various methods, one of which is the use of a computerized numerical modeling simulation called WASP (Water Quality Analysis Simulation Program). This method was developed by the ES-EPA, in order to process TMDLs (Total Maximum Daily Loads) data on river bodies, as well as examine each part of the water quality, based on spatial and temporal inputs. This study was conducted at the Karang Mumus Sub-watershed flowing through the centre of Samarinda City, with aims to determine the pollutants' carrying capacity, existing load, and toxic waste allocation, via the use of the BOD (Biological Oxygen Demand) technique as a parameter of water quality. The calculation was carried out by segmenting the river into five parts, based on the number of districts it passes through, during pollutant loads inventory. The WASP modeling simulation showed that the total pollutant load-carrying capacity of the whole segments was 5,670 kg/day. It also showed the existing loads of about 3,605 kg/day, with the margin having the ability to receive pollutants at 2,065 kg/day. Moreover, the allocation of pollutant loads varies for each segment, with 2, 3, and 4 observed to reduce the pollutant by 390, 220, and 10 kg/day, respectively. However, segments 1 and 5 were still allowed to receive pollutant loads up to 1,740 and 945 kg/day, respectively.

Methylmercury Production and Degradation under Light and Dark Conditions in the Water Column of the Hells Canyon Reservoirs, USA.

Methylmercury (MeHg) is a highly toxic form of mercury that can bioaccumulate in fish tissue. Methylmercury is produced by anaerobic bacteria, many of which are also capable of MeHg degradation. In addition, demethylation in surface waters can occur via abiotic sunlight-mediated processes. The goal of the present study was to understand the relative importance of microbial Hg methylation/demethylation and abiotic photodemethylation that govern the mass of MeHg within an aquatic system. The study location was the Hells Canyon complex of 3 reservoirs on the Idaho-Oregon border, USA, that has fish consumption advisories as a result of elevated MeHg concentrations. Our study utilized stable isotope addition experiments to trace MeHg formation and degradation within the water column of the reservoirs to understand the relative importance of these processes on the mass of MeHg using the Water Quality Analysis Simulation Program. The results showed that rates of MeHg production and degradation within the water column were relatively low (<0.07 d-1 ) but sufficient to account for most of the MeHg observed with the system. Most MeHg production within the water column appeared to occur in the spring when much of the water column was in the processes of becoming anoxic. In the surface waters, rates of photodemethylation were relatively large (up to -0.25 d-1 ) but quickly decreased at depths >0.5 m below the surface. These results can be used to identify the relative importance of MeHg processes that can help guide reservoir management decisions. Environ Toxicol Chem 2021;40:1829-1839. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Modeling transmission of hexavalent chromium concentration and its health cost with a water quality analysis simulation program

In this study, the Water Quality Analysis Simulation Program (WASP7) was used to evaluate the transmission of hexavalent chromium (Cr(VI)) contamination in a water-sediment system and its flux into cultivated soils. The agricultural areas adjacent to the Wu River in Taiwan were taken as the study area, as these soils were heavily polluted with Cr(VI) concentrations of 2,173-3,271 μg/kg. The rates of accumulation of Cr(VI) are affected by the distance from the source of contamination and the size and type of cultivated areas. The highest concentrations of Cr(VI) (4.27 mg/kg) were detected in soil from Changhua city, and correlated with the greater risk of gastric cancer in residents. Specifically, the risk of gastric cancer due to Cr(VI) contamination of agricultural soil was 3×10-7 - 15.2×10-6 in Taichung city (upstream) and 1.3×10-6 -76.3×10-6 in Changhua county (downstream). The values of statistical life-years (VSLYs) were US$6.2-10 million for rice, US$42-60 million for corn, and US$360-580 million for other vegetables, respectively, each year. It is critical that techniques other than source reduction are used to reduce human exposure to Cr(VI), such as chemical oxidation or ion-exchange treatment to remove Cr(VI) from factory wastewaters, prior to their discharge into rivers.

APPLICATION OF COUPLED HEC-HMS AND US EPA WASP FOR TRANSPORT MODELLING OF MERCURY IN THE MINING-IMPACTED AMBALANGA RIVER

This study provides a simulation of mercury (Hg) transport in water and sediments in the mining-impacted Ambalanga River located in Upper Agno Subbasin in the Philippines. The Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS) and Water Quality Analysis Simulation Program (WASP) of the US Environmental Protection Agency (EPA) were coupled to handle both hydrologic modelling and total Hg transport processes, respectively, for 12 months in the year 2014. Watershed delineation from Digital Elevation Model, rainfall and streamflow data from the local weather bureau, and dam operational data were used to develop the hydrological model. The calibrated HEC-HMS model satisfactorily simulated the flow in the river and its tributaries, which is then used as an input to the Hg transport model. The Ambalanga subbasin was conceptually divided into 29 segments in WASP to represent the water column and the surface benthic sediment. Time-variable sediment and Hg load were applied to the upstream of Ambalanga River. Total Hg concentration in water and sediments at five sampling locations along the Ambalanga River and two sampling locations along the Upper Agno River were measured in 2014-2015, in addition to the Hg monitoring data from the local environmental bureau. The gathered data were used to validate the WASP model, and results show that it was able to reasonably simulate the Hg fate and transport. Simulation results showed a downward trend in Hg concentration in surface water and sediments from upstream to downstream, while Hg in sediments was observed to stabilize over time. The model was further utilized to come up with exceedance curves of Hg in water and sediments as a result of the river’s response to different Hg loading from the known point sources. The exceedance curves derived from the model were used to determine the maximum permissible Hg loading to the river and identify pollution load reduction measures for river rehabilitation.

Water quality characteristics and modeling of Tasik Aman, USM, Penang

Tasik Aman was constructed in 1990 as a flood retention pond in the Universiti Sains Malaysia, Main Campus, Penang, Malaysia. Tasik Aman has been experiencing accumulation of excess nutrients from the surrounding area mainly from Sungai Gambir, causing high algae population in the water body. Thus, a study was carried out in December 2019, focusing on the current water quality determination of Tasik Aman, to predict the future water quality condition of the lake. Four sites were designated to conduct water quality analysis comprising of water temperature, dissolved oxygen (DO), pH, transparency, biological oxygen demand (BOD), total dissolved solids, total suspended solids, conductivity, orthophosphate, chlorophyll-a, total phosphorus, ammonia, nitrite, and nitrate. Some physico-chemical parameters were measured in-situ while some were measured in the lab by analyzing the water samples collected in the field in accordance with APHA (2005). DO and BOD data were modeled using Water Quality Analysis Simulation Program (WASP). Tasik Aman showed high readings in temperature, TSS, TDS, conductivity, DO, BOD, chlorophyll-a, and nitrate-nitrogen. One-way ANOVA further revealed significant differences of DO, TDS, conductivity, transparency, orthophosphate, nitrate, and chlorophyll-a among the stations of Tasik Aman (p<0.05). Based on WASP analysis, simulated graphs produced for Tasik Aman showed a decrease in DO and an increase in BOD level proving that the lake contain high nutrient content that may exacerbate the eutrophication.

Choosing an appropriate water quality model-a review.

Water quality models are quite complex to use even for scientists, requiring knowledge in different areas such as biology, chemistry, physics, and engineering. Hence, the use of these models by a non-specialist is quite complicated, demanding considerable time and research, particularly to choose which model is the most appropriate for a given situation. In this study, a comparative guide is suggested, which can help users select the appropriate water quality model for certain systems and variables. Five models were considered as follows: AQUATOX, CE-QUAL-W2, Spatially Referenced Regression Model on Watershed Attributes (SPARROW), Soil and Water Assessment Tool (SWAT), and Water Quality Analysis Simulation Program 7 (WASP7), which have been widely used during the last 5 years. All of these selected models are free and easily available. It was verified that each model has its particularities and applications; however, the AQUATOX model has several advantages compared with the other models analyzed. In addition, to illustrate the availability of the proposed comparative guide, a case study was carried out to demonstrating the selection process of the selected models.