Temporal variations in water resources in the Yangtze River (Changjiang) over the Industrial Period based on reconstruction of missing monthly discharges

To evaluate the response of river discharge to anthropogenic impacts and climate variability over the Industrial Period, we reconstructed past series of monthly discharge from three gauges on the main river of the Yangtze by means of regression (making use of the cross correlation among the gauges) and analyzed the integrated data (the observed series of discharge with missing values filled by reconstructed values) for the period 1865-2008 in relation to human activities and climate variability. The correlative coefficients between observed and predicted discharges at the three stations for the gauging period are R² = 0.90-0.96 (n = 827-1557). The integrated time series of discharge to the sea shows periodicities of ∼7, ∼14, and ∼38 years, and we found significant decreasing trends in annual discharge (-11%) and monthly discharge from August to November (-47% for November) and an increasing trend in discharge in January (+30%) and February during the dry season. These trends are mainly attributed to human impacts, in particular, reservoir construction and water consumption. It is estimated that these trends will continue in the future decades of this century because of the influence of the South-to-North Water Diversion Project as well as increased water consumption and the construction of new dams within the river basin.