A random search methodology for examining parametric uncertainty in water quality models

2006 ◽  
Vol 53 (1) ◽  
pp. 33-40 ◽  
Author(s):  
O.O. Osidele ◽  
W. Zeng ◽  
M.B. Beck
Keyword(s):  
Water Quality ◽  
High Speed ◽  
Nutrient Dynamics ◽  
Nearest Neighbor ◽  
Optimal Parameter ◽  
Random Search ◽  
Parametric Uncertainty ◽  
Simulation Models ◽  
Quality Model ◽  
Rejection Algorithm

The advent of the modern high-speed digital computer has tremendously enhanced the utility of Monte Carlo methods for evaluating complex environmental simulation models. In particular, random searching is becoming popular, as thousands of model runs can now be executed quickly and with minimal effort. Indeed, the issues of computational burden and inefficiency, hitherto the bane of random searching, are now receding. This paper presents one such method, uniform covering by probabilistic rejection (UCPR), which combines a pure random search with a probabilistic rejection algorithm that significantly enhances its efficiency. Using nearest-neighbor distances, an ensemble of points in a predefined parameter sampling domain migrates to locate and define a final distribution of optimal parameter vectors, thus providing a realistic depiction of parameter uncertainty. In a prototypical case study of the Oconee River (Georgia, USA), UCPR and regionalized sensitivity analysis, are employed for identifying the parameters of sediment-transport-associated nutrient dynamics, a dynamic river water quality model. Results indicate the existence of a complex interactive parameter structure, evidenced by multiple sets of optimal points widely dispersed over a broad domain of feasible parameter values.

scholarly journals Development of an Event-Based Water Quality Model for Sparsely Gauged Catchments

2019 ◽  
Vol 11 (6) ◽  
pp. 1773
Author(s):  
Hong Nguyen ◽  
Gunter Meon ◽  
Van Nguyen
Keyword(s):  
Water Quality ◽  
Nutrient Dynamics ◽  
Water Quality Model ◽  
Data Availability ◽  
Model Complexity ◽  
Quality Model ◽  
Small Catchment ◽  
Modeling Systems ◽  
Model Components ◽  
Event Based

This paper describes an event-based water quality model for sparsely gauged catchments. The model was cultivated in a robust way to cope with practical issues, such as limited available data and error propagation. A simplified model structure and fewer input parameters are the most appealing features of this model. All model components are coupled and controlled within an Excel Spreadsheet Macro as an operational tool. Herein, the geomorphological instantaneous unit hydrograph (GIUH), the simplified process erosion and sedimentation component, the loading function, and the river routing from different existing modeling systems are adopted and linked together. Furthermore, an add-on Monte Carlo simulation tool is provided to deliver an uncertainty analysis for calibration of the output obtained from the model results. The model was successfully applied to simulate nutrient dynamics for small catchment scales during flood events in Vietnam. The success of the model application shows the ability of our model, which can adapt the model complexity to the data availability, i.e., the dominant processes in the system should be captured, whereas the minor processes may be neglected or treated in a less complex manner.

scholarly journals CE-QUAL-W2 model of dam outflow elevation impact on temperature, dissolved oxygen and nutrients in a reservoir

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Karl-Erich Lindenschmidt ◽  
Meghan K. Carr ◽  
Amir Sadeghian ◽  
Luis Morales-Marin
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Water Temperature ◽  
Nutrient Dynamics ◽  
Water Withdrawal ◽  
Quality Model ◽  
Temperature Regimes ◽  
Labile Phosphorus ◽  
Daily Water ◽  
Animal Consumption

AbstractDams are typically designed to serve as flood protection, provide water for irrigation, human and animal consumption, and harness hydropower. Despite these benefits, dam operations can have adverse effects on in-reservoir and downstream water temperature regimes, biogeochemical cycling and aquatic ecosystems. We present a water quality dataset of water withdrawal scenarios generated after implementing the 2D hydrodynamic and water quality model, CE-QUAL-W2. The scenarios explore how six water extraction scenarios, starting at 5 m above the reservoir bottom at the dam and increasing upward at 10 m intervals to 55 m, influence water quality in Lake Diefenbaker reservoir, Saskatchewan, Canada. The model simulates daily water temperature, dissolved oxygen, total phosphorus, phosphate as phosphorus, labile phosphorus, total nitrogen, nitrate as nitrogen, labile nitrogen, and ammonium at 87 horizontal segments and at 60 water depths during the 2011–2013 period. This dataset intends to facilitate a broader investigation of in-reservoir nutrient dynamics under dam operations, and to extend the understanding of reservoir nutrient dynamics globally.

Extending Uncertainty Analysis of a Hydrodynamic-Water Quality Modelling System using High Level Architecture (HLA)

2005 ◽  
Vol 40 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Karl-Erich Lindenschmidt ◽  
Jan Rauberg ◽  
Fred B. Hesser
Keyword(s):  
Water Quality ◽  
Uncertainty Analysis ◽  
Computer Architecture ◽  
Nutrient Dynamics ◽  
Simulation Software ◽  
Quality Analysis ◽  
High Level Architecture ◽  
Quality Model ◽  
High Level ◽  
The Impact

Abstract This paper illustrates the coupling of water quality model components in High Level Architecture (HLA), a computer architecture for constructing distributed simulations. HLA facilitates interoperability among different simulations and simulation types and promotes reuse of simulation software modules. It was originally developed for military applications but the platform is finding increasing applicability for civilian purposes. The models from the Water Quality Analysis Simulation Program (WASP5) were implemented in HLA to extend its Monte Carlo uncertainty analysis capabilities. The models include DYNHYD (hydrodynamics), EUTRO (phytoplankton and nutrient dynamics) and TOXI (sediment and micropollutant transport). The uncertainty analysis investigated the impact of errors in the hydrodynamic parameters (weir discharge and roughness coefficients) and boundary conditions (upstream and tributary discharge) on the uncertainty in the water quality output variables. It was found that the contribution of the hydrodynamic parameter error to the water quality output uncertainty is comparable to that obtained from the error in the water quality parameters. The error in the boundary condition input data is also an important contributor to model uncertainty.

scholarly journals Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

2017 ◽  
Vol 14 (19) ◽  
pp. 4423-4433 ◽  
Author(s):  
Yafei Zhu ◽  
Andrew McCowan ◽  
Perran L. M. Cook
Keyword(s):  
Water Quality ◽  
Primary Production ◽  
Total Phosphorus ◽  
Coastal Lagoon ◽  
Nutrient Dynamics ◽  
Nutrient Loading ◽  
Nitrogen Loading ◽  
Quality Model ◽  
Nitrogen Loads ◽  
Sediment Carbon

Abstract. The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes) were investigated using a 3-D coupled hydrodynamic biogeochemical water quality model. The study showed that primary production was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment were the main drivers for the hypoxia and subsequent sediment phosphorus release in Lake King. High primary production stimulated by large nitrogen loading brought on by a winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads), which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria). Therefore, the current study highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.

scholarly journals Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

2017 ◽  
Author(s):  
Yafei Zhu ◽  
Andrew McCowan ◽  
Perran L. M. Cook
Keyword(s):  
Water Quality ◽  
Coastal Lagoon ◽  
Nutrient Dynamics ◽  
Nutrient Loading ◽  
Phosphorus Release ◽  
Nitrogen Loading ◽  
Quality Model ◽  
Nitrogen Loads ◽  
Almost All ◽  
Sediment Carbon

Abstract. The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes) was investigated using a 3D coupled hydrodynamic biogeochemical water quality model. The study showed that primary productivity was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment are the main drivers for the hypoxia and subsequent sediment phosphorus release in the Lake King. High primary production stimulated by large nitrogen loading brought by winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads) which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria). Therefore, the current study highlighted the need to reduce both TN and TP for water quality improvement in estuarine systems.

Mixed Layer Models and Their Application to Water Quality Problems

1994 ◽  
Vol 29 (2-3) ◽  
pp. 221-232
Author(s):  
M.J. McCormick
Keyword(s):  
Water Quality ◽  
Mixed Layer ◽  
Thermal Structure ◽  
Mass Conservation ◽  
Eddy Diffusion ◽  
Rate Of Change ◽  
Surface Mixed Layer ◽  
Storm Events ◽  
Quality Model ◽  
Mixing Processes

Abstract Four one-dimensional models which have been used to characterize surface mixed layer (ML) processes and the thermal structure are described. Although most any model can be calibrated to mimic surface water temperatures, it does not imply that the corresponding mixing processes are well described. Eddy diffusion or "K" models can exhibit this problem. If a ML model is to be useful for water quality applications, then it must be able to resolve storm events and, therefore, be able to simulate the ML depth, h, and its time rate of change, dh/dt. A general water quality model is derived from mass conservation principles to demonstrate how ML models can be used in a physically meaningful way to address water quality issues.

Applying the Soil Water Assessment Tool to 5th Canadian Division Support Base Gagetown

2014 ◽  
Vol 49 (4) ◽  
pp. 372-385
Author(s):  
Shawn Burdett ◽  
Michael Hulley ◽  
Andy Smith
Keyword(s):  
Water Quality ◽  
Soil Water ◽  
Land Management ◽  
Management Practices ◽  
Assessment Tool ◽  
Anthropogenic Activities ◽  
Quality Model ◽  
Sediment Yields ◽  
Soil Water Assessment Tool ◽  
Water Assessment

A hydrologic and water quality model is sought to establish an approach to land management decisions for a Canadian Army training base. Training areas are subjected to high levels of persistent activity creating unique land cover and land-use disturbances. Deforestation, complex road networks, off-road manoeuvres, and vehicle stream crossings are among major anthropogenic activities observed to affect these landscapes. Expanding, preserving and improving the quality of these areas to host training activities for future generations is critical to maintain operational effectiveness. Inclusive to this objective is minimizing resultant environmental degradation, principally in the form of hydrologic fluctuations, excess erosion, and sedimentation of aquatic environments. Application of the Soil Water Assessment Tool (SWAT) was assessed for its ability to simulate hydrologic and water quality conditions observed in military landscapes at 5th Canadian Division Support Base (5 CDSB) Gagetown, New Brunswick. Despite some limitations, this model adequately simulated three partial years of daily watershed outflow (NSE = 0.47–0.79, R2 = 0.50–0.88) and adequately predicted suspended sediment yields during the observation periods (%d = 6–47%) for one highly disturbed sub-watershed in Gagetown. Further development of this model may help guide decisions to develop or decommission training areas, guide land management practices and prioritize select landscape mitigation efforts.

Application of Expert Systems Technology in Water Quality Modeling

1989 ◽  
Vol 21 (8-9) ◽  
pp. 1045-1056 ◽  
Author(s):  
Thomas O. Barnwell ◽  
Linfield C. Brown ◽  
Wiktor Marek
Keyword(s):  
Water Quality ◽  
Expert Systems ◽  
Knowledge Engineering ◽  
Stream Water ◽  
Environmental Modeling ◽  
Water Quality Modeling ◽  
Stream Water Quality ◽  
Quality Model ◽  
Knowledge Based ◽  
Available Technology

Computerized modeling is becoming an integral part of decision making in water pollution control. Expert systems is an innovative methodology that can assist in building, using, and interpreting the output of these models. This paper reviews the use and evaluates the potential of expert systems technology in environmental modeling and describes elements of an expert advisor for the stream water quality model QUAL2E. Some general conclusions are presented about the tools available to develop this system, the level of available technology in knowledge-based engineering, and the value of approaching problems from a knowledge engineering perspective.

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