Water Quality Model Research Articles

Simulation and Application of Water Environment in Highly Urbanized Areas: A Case Study in Taihu Lake Basin

In the wake of frequent and intensive human activities, highly urbanized areas consistently grapple with severe water environmental challenges. It becomes imperative to establish corresponding water environment models for simulating and forecasting regional water quality, addressing the associated environmental risks. The distributed framework water environment modeling system (DF-WEMS) incorporates fundamental principles, including the distributed concept and node concentration mass conservation. It adeptly merges point source and non-point source pollution load models with zero-dimensional, one-dimensional, and two-dimensional water quality models. This integration is specifically tailored for various Hydrological Feature Units (HFUs), encompassing lakes, reservoirs, floodplains, paddy fields, plain rivers, and hydraulic engineering structures. This holistic model enables the simulation and prediction of the water environment conditions within the watershed. In the Taihu Lake basin of China, a highly urbanized region featuring numerous rivers, lakes and gates, the DF-WEMS is meticulously constructed, calibrated, and validated based on 26 key water quality monitoring stations. The results indicate a strong alignment between the simulation of water quality indicators (WQIs) and real-world conditions, demonstrating the model’s reliability. This model proves applicable to the simulation, prediction, planning, and management of the water environment within the highly urbanized watershed.

Prediction of Sunlight- and Salinity-Driven Inactivation Kinetics of Microbial Indicators with Validation in a 3D Water Quality Model

Prediction of Sunlight- and Salinity-Driven Inactivation Kinetics of Microbial Indicators with Validation in a 3D Water Quality Model

Simulation Study on Water Quality of Paddy Field Ditches Considering the Effects of Rainfall and Sediment Release

As the main channel for the drainage of paddy fields, the water quality of canals directly affects the water quality of surrounding water bodies. Factors such as rainfall and the release of accumulated pollutants from the sediment of the canals have a direct impact on the water quality of drainage ditches. Based on the measured hydrological and water quality data, a dynamic water quality model was built to simulate the runoff and water quality changes in a paddy field for different return periods (1, 2, 5, 10, 20, and 50 years), and to consider the effects of released drainage sediment on the water quality of the paddy field. The change in water quality in paddy fields and ditches in different periods was studied. The simulation results showed that under different return periods, the total nitrogen concentration and total phosphorus concentration in the water of the paddy field and ditch increased first, and then decreased with time in June and July–September, while the pollutant concentration remained basically stable after the end of rainfall. With the increase in return period, the total nitrogen concentration and total phosphorus concentration decreased gradually. The release of nitrogen and phosphorus from the sediment of ditches resulted in an increase in the total nitrogen concentration and total phosphorus concentration in the ditches, and an increase in the pollution load. Under the influence of rainfall and fertilizer, the total nitrogen concentration and total phosphorus concentration in paddy ditch drainage were generally higher and more polluted in June than in July–September, and under the influence of released sediment, the ditch drainage was most polluted in June when the return period was one year, with the total nitrogen concentration and total phosphorus concentration at the outlet of the paddy ditch reaching 21.63 mg/L and 0.88 mg/L, respectively. The research results can provide a theoretical basis and basic support for the interception and treatment of non-point source pollution in farmland.

Numerical Simulation of the Marine Environmental Capacity of Jinpu Bay

Based on the study of the marine environmental capacity, a water quality model and a response field-based linear programming method are adopted here. Water quality control objectives are taken as the constraint conditions, according to the requirements of Jinpu Bay’s functional zoning. The pollutant response coefficient and water quality background value are combined with the values of the water concentration quality control points set in each functional area and the target value of the functional area wherein they are located. The maximum allowable emission intensity of inorganic nitrogen, phosphate and chemical oxygen demand (COD) can be calculated using the linear programming method of the maximum allowable emission of pollutants at estuaries or sewage outfall points on Jinpu Bay. The research results reveal the diffusion of marine pollutants and the marine environmental capacity of Jinpu Bay. Some rivers need to reduce the discharge intensity and some other outlets still have a certain residual capacity. Based on this, the environmental capacity of Jinpu Bay was evaluated, and a technical reference is provided for the economic development of the region and the formulation of pollutant emission control policies.

Simulation of benthic microalgae impacts on water quality in shallow water systems, Corsica River, Chesapeake Bay

Eutrophication and hypoxia represent an ever-growing stressor to estuaries and coastal ecosystems due to population growth and climate change. Understanding water quality dynamics in shallow water systems is particularly challenging due to the complex physical and biogeochemical dynamics and interactions among them. Within shallow waters, benthic microalgae can significantly contribute to autotrophic primary production, generate organic matter, increase dissolved oxygen consumption, and alter nutrient fluxes at the sediment–water interface, yet they have received little attention in modeling applications. A state-of-the-art modeling system, the Semi-Implicit Cross-Scale Hydroscience Integrated System Model (SCHISM), coupled with the Integrated Compartment Model (ICM) of water quality and benthic microalgae, has been implemented in the Corsica River estuary, a tributary to Chesapeake Bay, to study benthic microalgal impact on water quality in shallow water systems. The model simulation has revealed a broad impact of benthic microalgae, ranging from sediment–water interface fluxes to water column dynamics, and the effects are observed from near-field to far-field monitoring stations. High-frequency variability and non-linearity dominate benthic microalgal dynamics, sediment oxygen demand, and nutrient fluxes at the sediment–water interface. Resource competition and supply determine the spatial scope of benthic microalgal impacts on far-field stations and the whole estuary system. Our study shows that benthic microalgae are a significant factor in shallow water dynamics that needs adequate attention in future observation and modeling applications.

A Pragmatic Approach for Chlorine Decay Modeling in Multiple-Source Water Distribution Networks Based on Trace Analysis

Providing water with adequate quality to users is one of the main concerns for water utilities. In most countries, this is ensured through the introduction of disinfectants, such as chlorine, which are subjected to decay over time, with consequent loss of disinfection action and the possible formation of harmful by-products. In this context, water quality models can be a useful tool to support management and, thus, ensure sufficient standards in all network points, but most of these models require the input of reaction parameters which could be difficult to obtain based on the information available to water utilities, especially in the case of complex water distribution networks (WDNs) supplied by more than one source. This study proposes a pragmatic, interval-number-based method to model chlorine decay in complex WDNs by relying on the use of the network hydraulic model and the results of trace analysis, which are exploited to obtain overall reaction rates. The method is applied to the case of a real WDN supplied by water sources with different qualitative features. The results obtained highlight that the method can help water utilities in the identification of overall water quality parameters.

Evaluating the structures and arrangements of water institutions to include in‐stream modeling for water quality management and control pollution: Insights from the Awash Basin, Ethiopia

AbstractHealthy rivers and stream waters support sustainable use and protect the ecological health of water flows. Developing countries rarely include in‐stream water quality modeling in their strategic policy documents. In the sub‐Saharan regions, stream water quality is declining due to many human activities. Ethiopian is no different, and its environmental policy does not directly target the importance of impact and planning analyses. Also, it does not include decision making processes for the protection of water ecology and multiple water uses. In this study, stream water quality issues in the Awash Basin have been assessed. The key sources of land‐based pollutants have been identified, and the availability and appropriateness related data have been examined and evaluated as well as the capacity of model users of institutions. Applicable models with the capability of simulating the Awash streams are presented and the changes needed for the existing settings suggested. The model selection was undertaken using a set of criteria based on environmental assumptions to enable environmental improvement into the future. The available hydrological and monitoring information provides an opportunity to apply model analyses, while the poor capacity of the governmental model users is of concern. With limited supporting conditions in governmental water institutions, the level of in‐stream water quality modeling integration in the Awash Basin development plans is too low to make recommendations based on key areas of support. It is time to apply and capitalize on the potential opportunity of using the models in local, regional, and national institutions for planning and impact analyses and strategic policy documents. The methods described in this study can be a guidance for model practitioners of the Awash basin targeting improvement in their institutions.

A short history of the phosphorus index and Andrew Sharpley's contributions from inception through development and implementation.

In the 1980s, growing recognition of agricultural phosphorus (P) sources to surface water eutrophication led to scrutiny of animal feeding operations. In 1990, the USDA-Natural Resources Conservation Service (NRCS) invited prominent scientists to find a solution. It was at an initial meeting that Dr. Andrew Sharpley suggested that P assessment could be modeled after the Universal Soil Loss Equation, where a matrix of factors influencing P loss would be associated with farm nutrient management recommendations. After codifying the P assessment into the USDA-NRCS 590 Nutrient Management Standard some 10years later, 48 states chose to develop their own P Index. Sharpley, working with many others, helped develop several state P Indices. In 2000, Sharpley secured funding from the USDA-Agricultural Research Service to support the National P Research Project, which conducted in-field P runoff assessments using standardized rainfall simulated studies across 20 states; this allowed individual trials to be aggregated for agroecological regions that were then incorporated into specific state P Indices. Eventually, comparison of P Indices across state boundaries led to a white paper at the behest of USDA-NRCS that resulted in three regional projects evaluating modeling approaches to support or replace P Indices. Sharpley's national umbrella project pointed to shortcomings in water quality models, such as APEX or TBET, as a replacement for state P Indices, which remain a key part of the USDA-590 standard. As a selfless leader, capable of attracting and assembling diverse, productive interdisciplinary teams, Sharpley was essential to the inception, development, and implementation of the P Index.

Improving incomplete mixing modeling for junctions of water distribution networks

Abstract Most of the existing water quality models for water distribution networks assume complete mixing at junctions. Albeit few models offer the possibility to consider incomplete mixing (IM) at junctions, most of them were developed under laboratory conditions and for equal pipe size junctions. In real-world distribution networks, however, cross junctions of 150 × 100 × 150 × 100 mm or 100 × 150 × 150 × 150 mm are common, yet no model has been developed for these configurations. This paper presents a new equation to compute concentrations in cross junction outlets while considering IM for six cross junction configurations, including unequal pipe sizes and 150 mm pipes. For each cross junction configuration, mixing was studied under 25 flow scenarios in the laboratory and 40 simulated flow scenarios using OpenFOAM software. Two new flow rate ratios were selected as independent variables to compute different outlet concentrations. For two specific cross junctions with equal pipe sizes, the root-mean-squared error between the observed and simulated concentrations of the newly developed model was 0.02, while it was 0.05 and 0.07, respectively, for the AZRED IM model and the Shao et al. IM model.

One- and Three-Dimensional Hydrodynamic, Water Temperature, and Dissolved Oxygen Modeling Comparison

Understanding and modeling water quality in a lake/reservoir is important to the effective management of aquatic ecosystems. The advantages and disadvantages of different water quality models make it challenging to choose the most suitable model; however, direct comparison of 1-D and 3-D models for lake water quality modeling can reveal their relative performance and enable modelers and lake managers to make informed decisions. In this study, we compared the 1-D model MINLAKE and the 3-D model EFDC+ for water temperature, ice cover, and dissolved oxygen (DO) simulation in three Minnesota lakes (50-m Carlos Lake, 23.5-m Trout Lake, and 5.6-m Pearl Lake). EFDC+ performed well for water temperature and DO simulation in the open water seasons with an average root mean square error (RMSE) of 1.32 °C and 1.48 mg/L, respectively. After analyzing the ice thickness with relevant data, it was found that EFDC+ calculates a shorter ice cover period and smaller ice thickness. EFDC+ does not consider snowfall for ice thickness simulation. The results also revealed that EFDC+ considers spatial variance and allows the user to select inflow/outflow locations precisely. This is important for large lakes with complex bathymetry or lakes having multiple inlets and outlets. MINLAKE is computationally less intensive than EFDC+, allowing rapid simulation of water quality parameters over many years under a variety of climate scenarios.

The community-centered freshwater biogeochemistry model unified RIVE v1.0: a unified version for water column

Abstract. Research on mechanisms of organic matter degradation, bacterial activities, phytoplankton dynamics, and other processes has led to the development of numerous sophisticated water quality models. The earliest model, dating back to 1925, was based on first-order kinetics for organic matter degradation. The community-centered freshwater biogeochemistry model RIVE was initially developed in 1994 and has subsequently been integrated into several software programs such as Seneque-Riverstrahler, pyNuts-Riverstrahler, ProSe/ProSe-PA, and Barman. After 30 years of research, the use of different programming languages including QBasic, Visual Basic, Fortran, ANSI C, and Python, as well as parallel evolution and the addition of new formalisms, raises questions about their comparability. This paper presents a unified version of the RIVE model for the water column, including formalisms for bacterial communities (heterotrophic and nitrifying), primary producers, zooplankton, nutrients, inorganic carbon, and dissolved oxygen cycles. The unified RIVE model is open-source and implemented in Python 3 to create pyRIVE 1.0 and in ANSI C to create C-RIVE 0.32. The organic matter degradation module is validated by simulating batch experiments. The comparability of the pyRIVE 1.0 and C-RIVE 0.32 software is verified by modeling a river stretch case study. The case study considers the full biogeochemical cycles (microorganisms, nutrients, carbon, and oxygen) in the water column, as well as the effects of light and water temperature. The results show that the simulated concentrations of all state variables, including microorganisms and chemical species, are very similar for pyRIVE 1.0 and C-RIVE 0.32. This open-source project highly encourages contributions from the freshwater biogeochemistry community to further advance the project and achieve common objectives.

Water quality modeling-based assessment for the scope of wastewater treatment of the urban reach of River Yamuna at Delhi, India.

River water quality management is a tedious job as it comprises multiple variables. The River Yamuna, Delhi's urban reach, is highly contaminated with very low or zero freshwater flow during the non-monsoon periods. The river quality has been appraised for pre- and post-monsoon periods of 10 years of data collected from the Delhi Pollution Control Council (DPCC). A sharp declination of dissolved oxygen and acceleration of BOD have been observed after the outfalling of drain 1. The wastewater treatment plants data for 2020-2022 have been analyzed, and the removal efficiencies of BOD and COD were found between 65 and 94%. The BIOFORE technology has shown maximum removal efficiencies, around 94% and 89% for BOD and COD, respectively. The level of treatment has been evaluated by developing a water quality model with the existing QUAL2kw framework. Twelve strategies have been generated for four levels of treatment and three different flow conditions. The severely polluted reach of Yamuna has low self-purification capacity; flow augmentation has little effect on the existing load. Hence, the level of treatment required to increase. After the introduction of outfalling drain D13-D16, a sag of DO has been observed; to improve the DO concentration, external aeration is suggested before wastewater disposal into the river. The study is a novel effort to manage the river quality by developing scenarios, including the level of treatments and flow augmentation, and keeping up the desired DO concentration assigned for this river reach.

Towards a generic model evaluation metric for non-normally distributed measurements in water quality and ecosystem models

Model evaluation is a crucial process in model development and quantified model evaluation metrics play a pivotal role in model calibration and validation. However, in current water quality and ecosystem models, conventional model evaluation metrics are derived from hydrological models and often overlook the non-normal distribution of water quality and ecological state variables. In this study, we proposed a series of metrics that consider non-normal distributions by modifying components of the Kling-Gupta efficiency. Subsequently, we tested the existing metrics and newly proposed metrics using four different synthetic datasets and the actual simulation case of total phosphorus, chlorophyll a, and dissolved oxygen concentrations. The results demonstrate that the newly proposed metric, Fu-Zhang efficiency, which replaces the ratio of standard deviations with the ratio of interquartile ranges to measure dispersion similarity, is more suitable for evaluating simulation results with lots of outliers in the measurements. Our study reveals the hidden perils in conventional integrated model evaluation metrics of water quality and ecosystem models and calls for the development of comprehensive and feasible quantitative evaluation frameworks to drive the next paradigm shift.

Information synthesis to identify water quality issues and select applicable in-stream water quality model for the Awash River basin in Ethiopia: A perspective from developing countries

In the sub-Saharan countries, stream water quality is declining due to many human activities. In-stream water quality models help to prepare effective planning strategy to tackle the problem and understand pollutant dynamics in the stream system. In this study, water quality issues of the Awash basin were reviewed to select an applicable in-stream model. The key sources of pollutants were considered and the availability, appropriateness and quality of related data were assessed and the capacity of model users was also evaluated. The identified opportunities and limitations were analyzed to present options of applicable models simulating the status quo in the basin's streams, and also, the changes needed for the existing settings. The model selection was done using a set of criteria based on assumptions useful for enabling environment and improvement in the future. Land covers, surficial geologies, and urban and industries along streams are found major issues to be addressed. Though the poor capacity of the governmental model users is a concern, the available hydrological, monitoring, and meteorological information are opportunities to capitalize the usage of in-stream modeling. QUAL2KW and INCA models are found more applicable for the present conditions, while in the future the WASP model may well be useful to conduct detailed analysis. The identification process applied in this study is based on the context of the Awash basin and it can be a replicated and support local model practitioners in creating improvement in water quality managements.

Estimating two time-varying reaction coefficients in a water quality model from inexact initial and boundary data

Estimating two time-varying reaction coefficients in a water quality model from inexact initial and boundary data

Quantifying seasonal to multi-decadal signals in coastal water quality using high- and low-frequency time series data

Abstract To inform water quality monitoring techniques and modeling at coastal research sites, this study investigated seasonality and trends in coastal lagoons on the eastern shore of Virginia, USA. Seasonality was quantified with harmonic analysis of low-frequency time-series, approximately 30 years of quarterly sampled data at thirteen mainland, lagoon, and ocean inlet sites, along with 4–6 years of high-frequency, 15-min resolution sonde data at two mainland sites. Temperature, dissolved oxygen, and apparent oxygen utilization (AOU) seasonality were dominated by annual harmonics, while salinity and chlorophyll-a exhibited mixed annual and semi-annual harmonics. Mainland sites had larger seasonal amplitudes and higher peak summer values for temperature, chlorophyll-a and AOU, likely from longer water residence times, shallower waters, and proximity to marshes and uplands. Based on the statistical subsampling of high-frequency data, one to several decades of low-frequency data (at quarterly sampling) were needed to quantify the climatological seasonal cycle within specified confidence intervals. Statistically significant decadal warming and increasing chlorophyll-a concentrations were found at a sub-set of mainland sites, with no distinct geographic patterns for other water quality trends. The analysis highlighted challenges in detecting long-term trends in coastal water quality at sites sampled at low frequency with large seasonal and interannual variability.

Investigation of chemical change in water quality and spatial modeling with GIS mapping: A case study from Beşgöz Lake in Konya Province of Türkiye

In this study, Beşgöz lake in Sarayönü district of Konya province, located in the Central Anatolia Region of Türkiye, was chosen as the study area. Rehabilitation work was carried out in 2020 with the resources of the State Hydraulic Works. The average depth of Beşgöz Lake was increased from 4 m to 8.5 m, and its surface area was increased from 86.000 m2 to 230.000 m2. Beşgöz Lake, located in Sarayönü district, provides water from underground sources at the bottom of the lake. These underground sources come from the gaps in the limestone in the lower parts of the lake. When looking at the geological map, it is thought that there is a connection between Beyşehir Lake and Beşgöz Lake because the land has a calcareous structure. The changes in the water quality parameters of Beşgöz Lake in different periods were examined and spatially modeled using spline interpolation techniques with Arc GIS 10.3.1 program, one of the Geography Information Systems (GIS) software. In order to determine some water quality parameters of Beşgöz Lake, water samples were taken from eight different points representing the lake in 4 different periods (Spring, Summer, Autumn, Winter). Seasonally in the water of Beşgöz Lake, water quality parameters such as pH, Electrical Conductivity (EC), Temperature, Chloride (Cl), Nitrite (NO2), Nitrate (NO3), Sulphate (SO4) Chemical Oxygen Demand (COD), Suspended Solids (TSS), Boron (B) were investigated. As a result of the research, it was found that pH values varied between 7.77–8.42, EC: 268–470 µS/cm, water temperature varied between 6.8–20 °C, Cl varied between 0.139 - 3.9 mg/L, NO2 varied between < 0 00–0.33 mg/L, NO3 varied between < 0.00 - 4.13 mg/L, SO4 varied between 0.057 − 18.4 mg/L, COD varied between 5–32, TSS: 0.60 - 31.8 and B varied between 0.05–0.093 mg/L. As a result of the study, it was seen that the water quality of Beşgöz Lake, which is the subject of the research, is class I and potable water quality.

Thermal stratification and mixing of dam reservoirs in Iran

Although numerical water quality models offer valuable insights into thermal stratification (TSn) and mixing dynamics in lakes, they are often resource and time consuming, limiting their applications for investigating a large number of lakes over a wide geographical area. An alternative approach is using well-known thermal classification systems, which require minimum data to provide acceptable information on TSn and mixing patterns in lakes. This study investigates the TSn and mixing regimes in 198 dam reservoirs located in Iran, using Lewis’s method for analysis. The results highlight that all 198 investigated reservoirs in Iran can be represented by six out of eight possible thermal classifications. The majority of the northeastern reservoirs are categorized as “warm monomictic”. For the reservoirs located in the north and northwest regions, all six thermal classes are observed. However, in the southern part of Iran, only the reservoirs of “continuous warm polymictic”, “warm monomictic”, and “discontinuous cold polymictic” types are located. Our findings reveal that 35.4%, 21.2%, 17.2%, 13.1%, 6.6%, and 5.6% of the investigated reservoirs were classified as “warm monomictic”, “discontinuous cold polymictic”, “continuous cold polymictic”, “dimictic”, “discontinuous warm polymictic”, and “continuous warm polymictic”, respectively. Our results can provide authorities with initial insights for further in-depth studies and decision-making into water quality management in Iran and enhancement strategies for the reservoirs in the country.

Perspectivas de redução do aporte de carga orgânica em bacia hidrográfica com relevante ocupação urbana

ABSTRACT The prospects for reducing organic load in water basins must be evaluated considering the self-purification capacities of the water bodies into which the raw or treated effluent will be discharged. The aim of this work was to evaluate the reduction of the organic load contribution to the Poti River, a watercourse that crosses the city of Teresina, Piauí, Brazil, considering different conditions for the final disposal of domestic sewage. To estimate the levels of reduction of the organic load contribution, the Water Quality Model Qual-UFMG and Nonlinear Programming were used in a combined manner. Three scenarios of final effluent disposal were modeled. For the appropriation of the reductions in organic load contributions, two different optimization models were used, models that incorporated restrictions based on the environmental quality standards indicated by the Brazilian Environment Council (CONAMA) Resolutions No. 357/2005 and 430/2011. The results indicated that the estimated effort for removal of organic load based on the optimization model that does not employ an equity measure among discharges was lower, regardless of the scenario analyzed. Additionally, in the simulation scenarios in which the quality standards for effluent were not considered, the efforts for removing organic load were lower, regardless of the optimization model used.

Feasible Application of PCLake Model to Predict Water Quality in Tropical Reservoirs

The PCLake model has not previously been used for tropical reservoirs. This study attempted to apply the PCLake model to predict the chlorophyll a concentrations (Chl-a) in a tropical reservoir in Thailand. Sensitivity analyses were performed for the constants affecting the prediction of Chl-a in the phytoplankton module. The model calibration was performed by using the adjusted value of the most sensitive constant with the observed data from July to December 2020. The effects of the initial trophic state of the reservoir on the simulated Chl-a were evaluated. The results showed that Chl-a were sensitive to six constants. Among these constants, the value of the specific extinction of detritus (cExtSpDet) was adjusted using the calculated values from the typical limnological parameters of the studied reservoir. Statistical analyses of the results of calibration and the subsequent validation with the observed data from February to September 2022 were listed as follows: NSE=0.55 and 0.37, RSR=0.67 and 0.79, and PBIAS=27% and 9%, respectively. The initial trophic state of the reservoir had no influence on the long-term prediction of Chl-a. This preliminary effort indicates that the PCLake model can be used to predict Chl-a, which is representative of algal biomass in tropical reservoirs and is essential to water quality models, without complex modifications.