Nonlinear Filtering Effects of Reservoirs on Flood Frequency Curves at the Regional Scale

TitleNonlinear Filtering Effects of Reservoirs on Flood Frequency Curves at the Regional Scale
Publication TypeJournal Article
Year of Publication2017
AuthorsWang, Wei, Li Hong-Yi, L. Leung Ruby, Yigzaw Wondmagegn, Zhao Jianshi, Lu Hui, Deng Zhiqun, Demisie Yonas, and Bloschl Gunter
JournalWater Resources Research
Volume53
Number10
Pages8277-8292
Date Published11/2017
Abstract

Reservoir operations may alter the characteristics of Flood Frequency Curve (FFC) and challenge the basic assumption of stationarity used in flood frequency analysis. This paper presents a combined data-modeling analysis of reservoir as a nonlinear filter of runoff routing that alters the FFCs. A dimensionless Reservoir Impact Index (RII), defined as the total upstream reservoir storage capacity normalized by the annual streamflow volume, is used to quantify reservoir regulation effects. Analyses are performed for 388 river stations in the contiguous U.S. using the first two moments of the FFC, mean annual maximum flood (MAF) and coefficient of variations (CV), calculated for the pre and post-dam periods. It is found that MAF generally decreases with increasing RII but stabilizes when RII exceeds a threshold value, and CV increases with RII until a threshold value beyond which CV decreases with RII. Hence depending on the magnitude of RII, reservoir regulation acts as a filter to increase or reduce the nonlinearity of the natural runoff routing process and alters flood characteristics. The nonlinear relationships of MAF and CV with RII can be captured by three reservoir models with different levels of complexity, suggesting that they emerge from the basic flood control function of reservoirs. However, the threshold RII values in the nonlinear relationships depend on the more detailed reservoir operations and objectives that can only be captured by the more complex reservoir models. Our conceptual model may help improve flood-risk assessment and mitigation in regulated river systems at the regional scale.

URLhttp://dx.doi.org/10.1002/2017wr020871
DOI10.1002/2017wr020871
Journal: Water Resources Research
Number: 10
Volume: 53

Reservoir operations may alter the characteristics of Flood Frequency Curve (FFC) and challenge the basic assumption of stationarity used in flood frequency analysis. This paper presents a combined data-modeling analysis of reservoir as a nonlinear filter of runoff routing that alters the FFCs. A dimensionless Reservoir Impact Index (RII), defined as the total upstream reservoir storage capacity normalized by the annual streamflow volume, is used to quantify reservoir regulation effects. Analyses are performed for 388 river stations in the contiguous U.S. using the first two moments of the FFC, mean annual maximum flood (MAF) and coefficient of variations (CV), calculated for the pre and post-dam periods. It is found that MAF generally decreases with increasing RII but stabilizes when RII exceeds a threshold value, and CV increases with RII until a threshold value beyond which CV decreases with RII. Hence depending on the magnitude of RII, reservoir regulation acts as a filter to increase or reduce the nonlinearity of the natural runoff routing process and alters flood characteristics. The nonlinear relationships of MAF and CV with RII can be captured by three reservoir models with different levels of complexity, suggesting that they emerge from the basic flood control function of reservoirs. However, the threshold RII values in the nonlinear relationships depend on the more detailed reservoir operations and objectives that can only be captured by the more complex reservoir models. Our conceptual model may help improve flood-risk assessment and mitigation in regulated river systems at the regional scale.

DOI: 10.1002/2017wr020871
Year of Publication: 2017
Citation:
Wang, W, H Li, L Leung, W Yigzaw, J Zhao, H Lu, Z Deng, Y Demisie, and G Bloschl.  2017.  "Nonlinear Filtering Effects of Reservoirs on Flood Frequency Curves at the Regional Scale."  Water Resources Research 53(10): 8277-8292, doi:10.1002/2017wr020871.