Abstract
Abstract. The streamflow of the Yellow River (YR) is strongly affected by human activities like irrigation and dam operation. Many attribution studies have focused on the long-term trends of streamflows, yet the contributions of these anthropogenic factors to streamflow fluctuations have not been well quantified with fully mechanistic models. This study aims to (1) demonstrate whether the mechanistic global land surface model ORCHIDEE (ORganizing Carbon and Hydrology in Dynamic EcosystEms) is able to simulate the streamflows of this complex rivers with human activities using a generic parameterization for human activities and (2) preliminarily quantify the roles of irrigation and dam operation in monthly streamflow fluctuations of the YR from 1982 to 2014 with a newly developed irrigation module and an offline dam operation model. Validations with observed streamflows near the outlet of the YR demonstrated that model performances improved notably with incrementally considering irrigation (mean square error (MSE) decreased by 56.9 %) and dam operation (MSE decreased by another 30.5 %). Irrigation withdrawals were found to substantially reduce the river streamflows by approximately 242.8±27.8×108 m3 yr−1 in line with independent census data (231.4±31.6×108 m3 yr−1). Dam operation does not change the mean streamflows in our model, but it impacts streamflow seasonality, more than the seasonal change of precipitation. By only considering generic operation schemes, our dam model is able to reproduce the water storage changes of the two large reservoirs, LongYangXia and LiuJiaXia (correlation coefficient of ∼ 0.9). Moreover, other commonly neglected factors, such as the large operation contribution from multiple medium/small reservoirs, the dominance of large irrigation districts for streamflows (e.g., the Hetao Plateau), and special management policies during extreme years, are highlighted in this study. Related processes should be integrated into models to better project future YR water resources under climate change and optimize adaption strategies.
Highlights
More than 60 % of all rivers in the world are disturbed by human activities (Grill et al, 2019), contributing altogether to approximately 63 % of surface water withdrawal (Hanasaki et al, 2018)
Except for R1 where cropland is rare, ETIR accounts for an amount representing more than 80 % of PGSWP3 in the Yellow River basin (YRB), with a maximum value of 96.5 % in R3
This study shows that ORCHIDEE land surface model with crops, irrigation, and our simple dam operation model can reproduce streamflow mean levels, inter-annual variations, and the seasonal cycle in different sub-catchments of the YRB correctly
Summary
More than 60 % of all rivers in the world are disturbed by human activities (Grill et al, 2019), contributing altogether to approximately 63 % of surface water withdrawal (Hanasaki et al, 2018). In order to meet the fast-growing water demand in populated areas and to control floods (Wada et al, 2014), reservoirs have been built for regulating the temporal distribution of river water (Biemans et al, 2011; Hanasaki et al, 2006), leading to a massive perturbation of the seasonality and year-to-year variations of streamflows. Adapting river management is a crucial question for sustainable development, which requires comprehensive understanding of the impacts of human activities on river flow dynamics„ in regions under high water stress (Liu et al, 2017; Wada et al, 2016)
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