Sequential Uncertainty Fitting Version 2 Research Articles

Modeling pesticide diuron loading from the San Joaquin watershed into the Sacramento-San Joaquin Delta using SWAT

Quantifying pesticide loading into the Sacramento-San Joaquin Delta of northern California is critical for water quality management in the region, and potentially useful for biological weed control planning. In this study, the Soil and Water Assessment Tool (SWAT) was applied to model streamflow, sediment, and pesticide diuron loading in the San Joaquin watershed, a major contributing area to the elevated pesticide levels in the downstream Delta. The Sequential Uncertainty Fitting version 2 (SUFI-2) algorithm was employed to perform calibration and uncertainty analysis. A combination of performance measures (PMs) and standardized performance evaluation criteria (PEC) was applied to evaluate model performance, while prediction uncertainty was quantified by 95% prediction uncertainty band (95PPU). Results showed that streamflow simulation was at least “satisfactory” at most stations, with more than 50% of the observed data bracketed by the 95PPU. Sediment simulation was rated as at least “satisfactory” based on two PMs, and diuron simulation was judged as “good” by all PMs. The 95PPU of sediment and diuron bracketed about 40% and 30% of the observed data, respectively. Significant correlations were observed between the diuron loads, and precipitation, streamflow, and the current and antecedent pesticide use. Results also showed that the majority (>70%) of agricultural diuron was transported during winter months, when direct exposure of biocontrol agents to diuron runoff is limited. However, exposure in the dry season could be a concern because diuron is relatively persistent in aquatic system. This study not only provides valuable information for the development of biological weed control plan in the Delta, but also serves as a foundation for the continued research on calibration, evaluation, and uncertainty analysis of spatially distributed, physically based hydrologic models.

Modelling the hydrology and water quality of 3S river system (Sekong, Sesan and Srepok)

The objective of this study was to simulate the hydrologic characteristic and water quality of 3S rivers system (Sekong, Sesan and Srepok) using SWAT model (Soil and Water Analysis Tool). Agriculture and forest are the main land use types in this basin accounting for more than 80 % of the total area. Therfore, nitrogen and phosphorus were selected to be parameters for water quality assessment. SWAT-CUP model was applied to calibrate the model for stream flow and water quality based on SUFI-2 (Sequential Uncertainty Fitting version 2) method. The model performance has been assessed by three statistical indices, including coefficient corellation (R2), Nash-Sutcliffe efficient coefficience (NSE) and percentage Bias (PBIAS). The results showed that SWAT model was well calibrated for simulating the streamflow and water quality with the values of R2 greater than 0.5 except for the Attapeu and Kontum stations, and of PBIAS less than 10 % and 35 % for streamflow and water quality, respectively. The well-calibrated SWAT model can be applied in predicting the hydrology and water quality for other application. Furthermore, it is a tool supporting the policy makers to offer a suitable decisions regarding the sustainable river basin management.

SWAT 모형의 매개변수와 유역의 지형학적 특성 관계

섬강 시험유역의 지형학적 특성 매개변수와 SWAT-CUP의 SUFI-2 알고리즘을 이용한 SWAT 모형 매개변수와의 상관관계와 이들의 관계식을 개발하였다. 개발한 상관 관계식을 이용하여 속사천 유역의 SWAT 모형의 매개변수를 추정하였다. 아울러, 속사천 유역의 2000 - 2007년의 강우-유출 자료를 대상으로 SWAT-CUP의 SUFI-2 알고리즘을 이용하여 SWAT 모형의 매개변수를 추정하였다. 개발한 식에 의해 산정한 각 매개변수의 적용성을 검토하기 위해 2000 - 2007년의 속사천 시험유역 자료를 이용하여 SWAT 모형의 유출모의를 실시하였다. 실측자료와 지형학적 특성 매개변수의 상관관계 분석으로 산정된 매개변수를 이용하여 속사천에 적용한 유출 모의결과와의 RMSE (root mean square error)는 <TEX>$1.09m^3/s$</TEX>이고, SWAT-CUP의 SUFI-2 최적 매개변수를 적용한 유출 모의결과와의 RMSE는 <TEX>$0.93m^3/s$</TEX>으로 나타났다. 따라서 지형학적 특성 매개변수를 이용한 SWAT 모형의 매개변수 추정이 적용성이 있다고 판단된다. The correlation relationships and their corresponding equations between the geomorphological parameters and the Soil Water Assessment Tool (SWAT) model parameters by Sequential Uncertainty Fitting - version 2 (SUFI-2) algorithm of SWAT Calibration and Uncertainty Programs (SWAT-CUP) were developed at the Seom-river experimental watershed. The parameters of the SWAT model at the Soksa-river experimental watershed were estimated by the developed equations. The SWAT model parameters were estimated by SUFI-2 algorithm of SWAT-CUP with rainfall-runoff data from the Soksa-river experimental watershed from 2000 to 2007. Rainfall-runoff simulation of the SWAT model was carried out at the Soksa-river experimental watershed from 2000 to 2007 for the applicability of the estimated parameters by the developed equations. The root mean square errors (RMSE) between the observed and the simulated rainfall-runoffs using the estimated parameters by developed equations of correlation analysis and the optimum parameters by SUFI-2 of SWAT-CUP were <TEX>$1.09m^3/s$</TEX> and <TEX>$0.93m^3/s$</TEX> respectively at the Soksa-river experimental watershed from 2000 to 2007. Therefore, it is considered that the parameter estimation of the SWAT model by the geomorphological characteristics parameters has applicability.

Modelling of discharge, nitrate and phosphate loads from the Reda catchment to the Puck Lagoon using SWAT

AbstractModelling of discharge, nitrate and phosphate loads from the Reda catchment to the Puck Lagoon using SWAT. This study presents an application of the SWAT model (Soil and Water Assessment Tool) in an agricultural, coastal catchment situated in northern Poland, draining an area of 482 km2 (the Reda catchment). The main objective of this study was calibration and validation of the model against daily discharge and water quality parameters (bi-monthly total suspended solids [TSS], nitrate nitrogen [N-NO3] and phosphate phosphorus [P-PO4] loads). Calibration and validation were conducted using the SWAT-CUP program and SUFI-2 (Sequential Uncertainty Fitting Version 2) algorithm. The Nash- -Sutcliffe efficiency, which was set as an objective function in calibration of all variables, was equal for discharge to 0.75 and 0.61 for calibration and validation periods, respectively. For TSS, N-NO3 and P-PO4 loads NSE was equal to 0.56, 0.62 and 0.53 in calibration period, and 0.22, 0.64 and -1.78 in validation period, respectively. For the calibration period all the results are satisfactory or good, while for the validation period the results for TSS and P-PO4 loads are rather poor, which is related mainly to the lack of homogeneity between calibration and validation periods. These results demonstrate that SWAT is an appropriate tool for quantification of nutrient loads in Polish agricultural catchments, in particular for N-NO3. The model can therefore be applied for water resources management, for quantification of scenarios of climate and land use change, and for estimation of the Best Management Practices efficiency

A comparison of single- and multi-gauge based calibrations for hydrological modeling of the Upper Daning River Watershed in China's Three Gorges Reservoir Region

Many parameters in hydrological models cannot be measured directly and should be estimated through calibration. In this study, four separate calibration schemes, including a multi-gauge and three single-gauge ones, were conducted to simulate the daily stream flow of the Upper Daning River in China's Three Gorges Reservoir Region using the Soil and Water Assessment Tool (SWAT). A highly efficient calibration technique – the Sequential Uncertainty Fitting version-2 (SUFI-2) procedure – was utilized in the calibration and validation. Results indicated that all four schemes could obtain satisfactory parameter sets, and there were no obvious differences between the simulation results obtained by the multi- and single-gauge calibration schemes in terms of Nash–Sutcliffe efficiency value (ENS). This might be attributed to the uniformly distributed land uses, similar topography variations and the low resolution of soil type map of the study area.