Jan-Tai Kuo

Eutrophication modelling of reservoirs in Taiwan

Two reservoirs in Taiwan were modeled to simulate the hydrodynamics and water quality in the water column. The modelling effort was supported with data collected in the field for a 2-year period for both reservoirs. Spatial and temporal distributions of temperature in the water column of the two reservoirs were well reproduced by the hydrodynamic model. Model calculated concentrations of key water quality constituents such as nutrients, dissolved oxygen, and algal biomass matched the measured values closely in both reservoirs. Most importantly, vertical stratification of temperature and dissolved oxygen in the Tseng-Wen Reservoir was mimicked by the model throughout this 2-year period. The calibrated model was then used to simulate water quality response to various nutrient reduction scenarios. Model results reveal that a 30-55% reduction of the phosphorus loads will upgrade the existing eutrophic/mesotrophic to oligotrophic conditions in the Te-Chi Reservoir.

An intervention model for average 10 day streamflow forecast and synthesis

Abstract An intervention model which is derived from the Box-Jenkins time series model is employed in modeling the average 10 day streamflow of the Tanshui River basin in Taiwan to deal with the extraordinary phenomena caused by typhoons and other serious abnormalities of the weather. Including five types of typhoons and one serious drought as the external factors, the model is capable of describing the special hydrological time series. The intervention model is applied to streamflow forecasting and synthesis at Sanhsia gaging station in the basin. Comparing with traditional autoregressive-moving average (ARMA) models, the intervention model greatly improves the forecasting technique and successfully captures the special pattern of the streamflow when typhoons invade. In addition, the model can be used effectively to synthesize streamflows.

Modelling hydrodynamics and water quality in the separation waterway of the Yulin offshore industrial park, Taiwan

Abstract Numerical models are often used to evaluate the potential impact of human alternation of natural water bodies and to help the design of the alternation to mitigate its impacts. This paper describes a case study in which an estuarine hydrodynamic and water quality model was used to help the design of the artificial waterway for an offshore industrial park. Yulin offshore industrial park is located at the central western coast of Taiwan. To mitigate its impacts on the nearby coastal area, the industrial park is buffered by a waterway separating it from the main island. The original design of the separation waterway has a width of 500 m. However, this width has been a controversial issue for the past 10 years. Since the separation waterway receives discharges from two streams in the main island, the Shu-Chu-Liao Stream and Hsin-Hu-Wei Stream, the potential inundation during flood events and water quality conditions during low flow periods are two of the major considerations for the width of the waterway. A vertical two-dimensional, real-time model of estuarine hydrodynamics and water quality was modified and used to determine the rational width of the separation waterway. The model modification is necessary to account for the multiple outlets into the sea when the whole system of the separation waterways is completed. Model calibration and verification were conducted with current, residual velocity, salinity, and water quality variables measured in the completed portion of the waterway. The overall performance of the model was in qualitative agreement with the available field data. The model was then used to evaluate several scenarios of different widths for the yet-to-be completed system of separation waterways. Based on the model simulation results, a 200 m wide waterway, bordered by 300 m wide flood plain, is recommended for adoption. The model simulation indicated that coastal water quality standard may be attained and inundation by the 50-year flood may be avoided by such a separation waterway.

Integrating legacy components into a software system for storm sewer simulation

Abstract This paper presents an approach that integrates a legacy component into a software system for storm sewer simulation. The legacy component employed here is the Storm Water Management Model (SWMM). The Extended Transport (EXTRAN) block of the SWMM that applies the finite difference method (FDM) with explicit numerical schemes, solving the de Saint-Venant equations, is used to route the storm sewer flow. A storm sewer simulation system, named S4, that integrates SWMM-EXTRAN and implements a visualization model, has been developed to demonstrate the proposed approach. The approach makes use of the multi-thread technology to alternate the execution between SWMM-EXTRAN for flow simulation on one thread and the program controller that updates simulation state variables and displays the computed temporal water-stages at the junctions on the other thread at every time step of the FDM process. Two test examples are used to verify and demonstrate the feasibility of the proposed approach. The results show that the multi-thread technology is applied successfully for integrating legacy components, such as SWMM-EXTRAN, into a software system (in this case, S4). In addition, the proposed approach is generally applicable for integrating legacy models or components developed using FDM with explicit numerical schemes.

Using an integrated model to track the fate and transport of suspended solids and heavy metals in the tidal wetlands

Abstract An integrated two-dimensional depth-average numerical model was developed to simulate hydrodynamics and to track the fate and transport of contaminants in the Erh-Chung Flood Way wetland in northern Taiwan. The model was calibrated and verified with field data collected from Nov. 8, 2002 to April 13, 2003. The RMA2 and TOXIWASP models were configured for the wetland system to model mass transport, suspended sediment as well as heavy metals. Hydrodynamic results from the RMA2 model were used to develop mass transport for the TOXIWASP model in the wetland system. Model results mimic the field data for suspended sediment and heavy metals. Results of model sensitivity analyses show that the partition coefficient is a key parameter for the fate and transport of heavy metals in the wetland system.

Water quality modeling of a hypoxic stream.

The WASP/EUTRO model was used to model a low dissolved oxygen (DO) stream in Taiwan as part of the water quality management effort to restore the stream. The low DO is the result of industrial wastewater discharges causing significant oxygen consumption due to carbonaceous and nitrogenous biochemical oxygen demand in the receiving water. The modeling effort was supported by a field monitoring program including two water quality surveys of the stream. The model calibrated with these two data sets, and also used unit response analysis to calculate the DO deficit contributed by individual loads. The calibrated model was used to evaluate wastewater management alternatives to restore the stream.

Modeling estuarine hydrodynamics and salinity for wetland restoration

Abstract A vertical two‐dimensional estuarine hydrodynamic and salinity model is developed to simulate the hydrodynamic characteristics and salinity distribution of the tide‐influenced wetland. The Kuan‐Du plain, an alluvial fan with vast wetlands and transition of fresh‐salt water, situated at the confluence of the main Tanshui River and Keelung River in northern Taiwan is selected as the study case. For the purpose of land development, 85% of the wetlands in the Kuan‐Du plain was carved out by a tidal dike constructed in 1968. The municipal government of Taipei recently decided to downgrade the plain of land development and to restore a portion of the carved‐out wetland. Thus, the aim of the study is to provide information to help planning wetland restoration, and to evaluate hydraulic impact of wetland restoration with removal of the tidal dike. The model is first calibrated and verified by the existing reliable measurement data. Simulations are conducted for various combinations of tidal conditions an...

Water quality modeling of the Tanshui estuarine system in northern Taiwan

Abstract A vertical two‐dimensional numerical model was developed to simulate water quality processes in branched estuarine systems. The model consists of hydrodynamic and water quality submodels. The model was applied to the Tanshui estuarine system of northern Taiwan, and calibrated and verified using field data collected from 1994 to 1996. Favorable model calibration and verification results were obtained. After calibration and verification, the model was used to predict future water quality conditions under various hydrological conditions as the result of the Tanshui River estuarine system clean‐up project which is being implemented. Due to the clean‐up project by the interception of a large amount of wastewater to the ocean outfall system, the freshwater flow in the estuarine system will decrease. On the basis of the model prediction the daily minimum dissolved oxygen (DO) concentration in the Tanshui River‐Tahan Stream and Keelung River will not meet the water quality standard under low freshwater f...

Application of fuzzy theory to satellite data for determining eutrophic status

Generally, eutrophic status of a water body is determined by a limited number of water samples. Statistically, we have not sufficient confidence with the overall eutrophic status by using point-basis water sampling which is usually executed under a physical and financial limitation. Also, a crisp determination of traditional eutrophic indices often causes debated argument. This paper proposed to apply fuzzy set theory to describe the classification of eutrophication. Multi-spectral satellite images were converted into water quality variables, such as phosphorus, Secchi depth, and chlorophyll that are the major affecting factors of eutrophication. Fuzzy synthetic evaluation for the eutrophication status was developed for OECD index and applied to satellite-derived two-dimensional water variables. The approach was experimented on the Feitsui Reservoir which is the most important water supply for the great Taipei area, Taiwan

Linking watershed and receiving water models for eutrophication analysis of Tseng‐Wen Reservoir, Taiwan

Abstract Eutrophication has been one of the most serious water quality problems for Taiwans reservoir in recent years. As the water quality of a reservoir is closely related to its watershed development, the fate and transport of pollutants in a watershed is a key consideration to water quality studies in reservoirs. The Tseng‐Wen Reservoir, located in southern Taiwan, features the largest storage volume of impoundments on the island. The watershed of the Tseng‐Wen Reservoir has significant agricultural activities, such as cultivation of tea, mustard, and betel palm. Fertilizer use for these crops in the watershed is very popular, thereby discharging significant nutrient loads into the reservoir. This study uses a watershed model, BASINS, to simulate the flows and nutrient loads from the watershed; BASINS then drives the CE‐QUAL‐W2 model for water quality predictions in the reservoir. The watershed model results are compared with data measured at the Dapu Check Dam, in the main stem of the Tseng‐Wen Creek. Model results show that significant nutrient and sediment loads are generated from the watershed during storms. The verified model was used to simulate the water quality response to various nutrient reduction scenarios. Both watershed and reservoir models offer a very useful tool for water quality management in the Reservoir.