scholarly journals Sequential calibration of a water quality model using reach-specific parameter estimates

2017 ◽  
Vol 49 (4) ◽  
pp. 1042-1055 ◽  
Author(s):  
Shushobhit Chaudhary ◽  
C. T. Dhanya ◽  
Arun Kumar
Keyword(s):  
Water Quality ◽  
Oxygen Demand ◽  
Weighted Average ◽  
Sequential Estimation ◽  
Water Quality Model ◽  
Parameter Estimates ◽  
Model Parameters ◽  
Quality Model ◽  
Study Region ◽  
River Stretch

Abstract Calibration is the most critical phase in any water quality modelling process. This study proposes a sequential calibration methodology for any water quality model using reach-specific estimates of model parameters, which would aid in the improved prediction of river water quality characteristics. The proposed methodology accounts for the heterogeneity of river reaches, i.e., diverse characteristics of different reaches on the river stretch. The water quality model, QUAL2K, is coupled with MATLAB, a computing platform, to facilitate sequential estimation of reach-wise model parameters using a grid-based weighted average optimization. The Delhi segment of the Yamuna River is selected as study river stretch. Observations of water quality variables, dissolved oxygen and biochemical oxygen demand are used to calibrate and validate QUAL2K. Desirable performance measures are obtained during the calibration and the validation period. The methodology proves superior to the existing calibration methodologies applied over the study region. The proposed technique also captures the system behaviour effectively, through a systematic, efficient and user-friendly way. The proposed approach is expected to aid decision-makers in formulating better reach-wise management decisions and treatment policies by providing a simpler and efficient way to simulate water quality parameters.

scholarly journals Assessment of Water Quality Profile Using Numerical Modeling Approach in Major Climate Classes of Asia

2018 ◽  
Vol 15 (10) ◽  
pp. 2258 ◽  
Author(s):  
Muhammad Mazhar Iqbal ◽  
Muhammad Shoaib ◽  
Hafiz Umar Farid ◽  
Jung Lyul Lee
Keyword(s):  
Water Quality ◽  
Water Environment ◽  
Oxygen Demand ◽  
Surface Water Quality ◽  
Water Quality Model ◽  
Oxygen Solubility ◽  
Quality Model ◽  
Spatial Profile ◽  
Climatic Regions ◽  
Model Predictions

A river water quality spatial profile has a diverse pattern of variation over different climatic regions. To comprehend this phenomenon, our study evaluated the spatial scale variation of the Water Quality Index (WQI). The study was carried out over four main climatic classes in Asia based on the Koppen-Geiger climate classification system: tropical, temperate, cold, and arid. The one-dimensional surface water quality model, QUAL2Kw was selected and compared for water quality simulations. Calibration and validation were separately performed for the model predictions over different climate classes. The accuracy of the water quality model was assessed using different statistical analyses. The spatial profile of WQI was calculated using model predictions based on dissolved oxygen (DO), biological oxygen demand (BOD), nitrate (NO3), and pH. The results showed that there is a smaller longitudinal variation of WQI in the cold climatic regions than other regions, which does not change the status of WQI. Streams from arid, temperate, and tropical climatic regions show a decreasing trend of DO with respect to the longitudinal profiles of main river flows. Since this study found that each climate zone has the different impact on DO dynamics such as reaeration rate, reoxygenation, and oxygen solubility. The outcomes obtained in this study are expected to provide the impetus for developing a strategy for the viable improvement of the water environment.

Water quality model parameter identification of an open channel in a long distance water transfer project based on finite difference, difference evolution and Monte Carlo

2013 ◽  
Vol 69 (3) ◽  
pp. 587-594 ◽  
Author(s):  
Dongguo Shao ◽  
Haidong Yang ◽  
Yi Xiao ◽  
Biyu Liu
Keyword(s):  
Water Quality ◽  
Open Channel ◽  
Differential Evolution Algorithm ◽  
Water Transfer ◽  
Water Quality Model ◽  
Model Parameters ◽  
Quality Model ◽  
Long Distance ◽  
Mcmc Simulation ◽  
Evolution Algorithm

A new method is proposed based on the finite difference method (FDM), differential evolution algorithm and Markov Chain Monte Carlo (MCMC) simulation to identify water quality model parameters of an open channel in a long distance water transfer project. Firstly, this parameter identification problem is considered as a Bayesian estimation problem and the forward numerical model is solved by FDM, and the posterior probability density function of the parameters is deduced. Then these parameters are estimated using a sampling method with differential evolution algorithm and MCMC simulation. Finally this proposed method is compared with FDM–MCMC by a twin experiment. The results show that the proposed method can be used to identify water quality model parameters of an open channel in a long distance water transfer project under different scenarios better with fewer iterations, higher reliability and anti-noise capability compared with FDM–MCMC. Therefore, it provides a new idea and method to solve the traceability problem in sudden water pollution accidents.

Improved dynamic simulation technique for hydrodynamics and water quality of river-connected lakes

2020 ◽  
Vol 20 (8) ◽  
pp. 3752-3767
Author(s):  
Bojun Liu ◽  
Jun Xia ◽  
Libin Yang ◽  
Changyong Cui ◽  
Linwei Wang ◽  
...  
Keyword(s):  
Water Quality ◽  
Latin Hypercube Sampling ◽  
Resistance Coefficient ◽  
Water Quality Model ◽  
Roughness Coefficient ◽  
Model Parameters ◽  
State Variables ◽  
Quality Model ◽  
Rank Regression ◽  
Hongze Lake

Abstract In this study, a two-dimensional hydrodynamic water-quality model is proposed for river-connected lakes in an effort to improve calibration accuracy and reduce computational burden. To achieve this, the sensitivity of parameters involved in the hydrodynamic model is analyzed using stepwise rank regression and Latin hypercube sampling (LHS), and the roughness coefficient, wind drag coefficient and wind resistance coefficient are identified as the most important parameters affecting the hydrodynamics of the Hongze Lake. Then, the ensemble Kalman filter (EnKF) is used to assimilate observations to the proposed hydrodynamic and water quality model. It is found that assimilation of both state variables and model parameters results in a significant improvement of the simulation of the water level, flow velocity and pollutant concentration in the Hongze Lake.

scholarly journals Extension of the River Water Quality Model No. 1 with the fate of pesticides

2011 ◽  
Vol 14 (1) ◽  
pp. 48-64 ◽  
Author(s):  
Veerle C. J. De Schepper ◽  
Katrijn M. A. Holvoet ◽  
Lorenzo Benedetti ◽  
Piet Seuntjens ◽  
Peter A. Vanrolleghem
Keyword(s):  
Water Quality ◽  
Water Column ◽  
River Water ◽  
Bulk Water ◽  
Transport Processes ◽  
Water Quality Model ◽  
River Water Quality ◽  
Model Parameters ◽  
Quality Model ◽  
Run Off

The existing River Water Quality Model No. 1 (RWQM1) was extended with processes determining the fate of non-volatile pesticides in the water phase and sediments. The exchange of pesticides between the water column and the sediment is described by three transport processes: diffusion, sedimentation and resuspension. Burial of sediments is also included. The modified model was used to simulate the concentrations of diuron and chloridazon in the river Nil. A good agreement was found between the simulated pesticide concentrations and measured values resulting from a four-month intensive monitoring campaign. The simulation results indicate that pesticide concentrations in the bulk water are not sensitive to the selected biochemical model parameters. It seems that these concentrations are mainly determined by the imposed upstream concentrations, run-off and direct losses. The high concentrations in the bulk water were not observed in the sediment pore water due to a limited exchange between the water column and the sediment. According to a sensitivity analysis, the observed pesticide concentrations are highly sensitive to the diffusion and sorption coefficients. Therefore, model users should determine these parameters with accuracy in order to reduce the degree of uncertainty in their results.

scholarly journals Development and identification of a multi-species water quality model for reclaimed water distribution systems

2015 ◽  
Vol 5 (3) ◽  
pp. 360-371
Author(s):  
Shun Li ◽  
Fu Sun ◽  
Siyu Zeng ◽  
Xin Dong ◽  
Pengfei Du
Keyword(s):  
Water Quality ◽  
Distribution Systems ◽  
Water Distribution ◽  
Reclaimed Water ◽  
Water Distribution Systems ◽  
Water Quality Model ◽  
Bulk Liquid ◽  
Model Parameters ◽  
Quality Model ◽  
Long Distance

With the rapid development of a centralized wastewater reuse scheme in China, water quality concerns arise considering the long-distance transport of reclaimed water in distribution systems from wastewater treatment plants to points of use. To this end, a multi-species water quality model for reclaimed water distribution systems (RWDSs) was developed and validated against the data from part of a full-scale RWDS in Beijing. The model could simulate organics, ammonia nitrogen, residual chlorine, inert particles, and six microbial species, i.e. fecal coliforms, Enterococcus spp., Salmonella spp., Mycobacterium spp., and other heterotrophic and autotrophic bacteria, in both the bulk liquid and the biofilm. Altogether, 56 reaction processes were involved, and 37 model parameters and seven initial values were identified. Despite the limited monitoring data and the associated gross uncertainty, the model could simulate the reclaimed water quality in the RWDS with acceptable accuracy. Regional sensitivity analysis suggested that the model had a balanced structure with a large proportion of sensitive parameters, and the sensitivity of model parameters could be reasonably interpreted by current knowledge or observation. Furthermore, the most sensitive model parameters could generally be well identified with uncertainties significantly reduced, which also favored the trustworthiness of the model. Finally, future plans to improve and apply the model were also discussed.

scholarly journals Towards benchmarking an in-stream water quality model

2007 ◽  
Vol 11 (1) ◽  
pp. 623-633 ◽  
Author(s):  
D. B. Boorman
Keyword(s):  
Water Quality ◽  
Stream Water ◽  
A Priori ◽  
Oxygen Demand ◽  
Water Quality Model ◽  
Test Model ◽  
Stream Water Quality ◽  
Quality Model ◽  
Benchmark Model ◽  
Model Code

Abstract. A method of model evaluation is presented which utilises a comparison with a benchmark model. The proposed benchmarking concept is one that can be applied to many hydrological models but, in this instance, is implemented in the context of an in-stream water quality model. The benchmark model is defined in such a way that it is easily implemented within the framework of the test model, i.e. the approach relies on two applications of the same model code rather than the application of two separate model codes. This is illustrated using two case studies from the UK, the Rivers Aire and Ouse, with the objective of simulating a water quality classification, general quality assessment (GQA), which is based on dissolved oxygen, biochemical oxygen demand and ammonium. Comparisons between the benchmark and test models are made based on GQA, as well as a step-wise assessment against the components required in its derivation. The benchmarking process yields a great deal of important information about the performance of the test model and raises issues about a priori definition of the assessment criteria.

Sign in / Sign up

Export Citation Format

Share Document