Runoff simulations using water and energy balance equations in the lower reaches of the Heihe River, northwest China

Methods for reconstruction of river runoff have been an important component of paleo-climatology and paleo-hydrology. The lower Heihe River was studied from 2002 to 2008 to reconstruct the annual average runoff at the Zhengyi Gorges hydrological station using measured data and improved water and energy balance equations. The results indicate that the reconstructed annual runoff and the measured runoff values are not equivalent. However, the difference between reconstructed and measured runoff values is within 10 %, which suggests that water and energy balance models can successfully reconstruct runoff from rivers in arid regions. Regional differences imply that parameters must be corrected when applying water and energy balance equations to prevent large errors. In addition, the latent heat of evaporation in arid lakes is greater than their net radiation, according to latent and sensible heat calculations, which demonstrates the existence of the “cold island effect”.