Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA.
Environ Sci Pollut Res Int. 2019 Mar;26(9):8971-8991. doi: 10.1007/s11356-019-04390-0. Epub 2019 Feb 4.
This paper presents findings on uncertainties, introduced through digital elevation model (DEM) resolution and DEM resampling, in watershed-scale flow and water quality (NO, P, and total suspended sediment) simulations. The simulations were performed using the Better Assessment Science Integrating Point and Nonpoint Sources/Hydrological Simulation Program Fortran watershed modeling system for two representative study watersheds delineated with both the original DEMs of four different resolutions (including 3.5, 10, 30, and 100 m) and the resampled DEMs of three different resolutions (including 10, 30, and 100 m), creating 14 simulation scenarios. Parameter uncertainties were quantified by means of the GLUE approach and compared to input data uncertainties. Results from the 14 simulation scenarios showed that there was a common increasing trend in errors of simulated flow and water quality parameters when the DEM resolution became coarser. The errors involved in the watershed with a mild slope were found to be substantially (up to 10 times) greater than those of the other watershed with a relatively steep slope. It was also found that sediment was the most sensitive and NO was the least sensitive parameters to the variation in DEM resolution, as evidenced by the maximum normalized root mean square error (NRMSE) of 250% in the simulated sediment concentration and 11% in the simulated NO concentration, respectively. Moreover, results achieved from the resampled (particularly coarser) DEMs were significantly different from corresponding ones from original DEMs. By comparing uncertainties from different sources, it was found that the parameter-induced uncertainties were higher than the resolution-induced uncertainties particularly in simulated NO and P concentrations for studied watersheds. The findings provide new insights into the sensitivity and uncertainty of water quality parameters and their simulation results, serving as the guidelines for developing and implementing water quality management and watershed restoration plans.
本文提出了通过数字高程模型 (DEM) 分辨率和 DEM 重采样引入的不确定性，对流域尺度的水流和水质（NO、P 和总悬浮泥沙）模拟的影响。使用 Better Assessment Science Integrating Point and Nonpoint Sources/Hydrological Simulation Program Fortran 流域建模系统，对两个具有代表性的研究流域进行了模拟，这两个流域分别使用了原始的四个不同分辨率（包括 3.5、10、30 和 100 m）和三个不同分辨率（包括 10、30 和 100 m）的重采样 DEM 进行了描绘，共创建了 14 种模拟情景。通过 GLUE 方法对参数不确定性进行了量化，并与输入数据不确定性进行了比较。结果表明，模拟水流和水质参数的误差随着 DEM 分辨率的变粗而呈普遍增加趋势。研究发现，坡度较缓的流域的误差明显（高达 10 倍）大于坡度较陡的流域的误差。还发现，泥沙是对 DEM 分辨率变化最敏感的参数，NO 是最不敏感的参数，模拟泥沙浓度的最大归一化均方根误差 (NRMSE) 为 250%，而模拟 NO 浓度的 NRMSE 为 11%。此外，重采样（特别是更粗糙）的 DEM 产生的结果与原始 DEM 的结果有显著差异。通过比较不同来源的不确定性，发现参数引起的不确定性高于分辨率引起的不确定性，特别是在所研究流域的模拟 NO 和 P 浓度方面。研究结果为水质参数及其模拟结果的敏感性和不确定性提供了新的认识，为制定和实施水质管理和流域恢复计划提供了指导。
