HUMAN IMPACTS ON THE HYDROLOGY IN PEARL RIVER DELTA, CHINA

The Pearl River Delta (PRD) lies in the south of GuangDong province in China. It is the river networks area of the lower reaches of MaKou of West River, Sanshui of North River and ShiLong of Dongjiang River. Over the last 20 years, in order to keep sustainable development of economy, many regulations engineering to improve grade of channel from river networks to estuary was implemented in 1990's. At the same time, artificial sand excavation reached the peak level. These human activities impacted the hydrodynamic greatly than natural evolution. As a result, the morphology and hydrology of the PRD water system has been predominantly dictated by those human activities. In this paper, based on the Saint-Venant equations, a numerical model of junction-river course for the whole PRD was established by using the junction-control methods for water level. First, the river networks in the PRD are schematized as 340 main river courses, 216 nodes and 1850 cross sections. The areas of this river networks are approximately 20001km(2), and the total river length is more than 1600km., second, utilizing the transforms of the single river finite-difference equations and the mass and energy conservation at the river junction, the control equations for all junctions' water level can be written in matrix notation. The water level at all junctions are obtained by solving the irregular spare matrix equations, finally, the water level at all single river sections are gotten by the solution algorithm for the single river unsteady flow. After calibration, simulation under different topographical condition in 1990 and in 2005 respectively was made. This paper put much emphasis on comparison changes of the hydrodynamic condition in PRD in recent 20 years by numerical model and observation data. Research result shows that frequent human activities caused the change of topographical; which result in changes of the hydrodynamic, Such as the tide range in PRD shows abrupt shift and the divided flow ratio between various water courses change. More specifically, the average annual tide range at Makou was 0.32m in 1990, however; it was 0.55m in 2005. Meanwhile, the dramatic change of hydrodynamic in PRD directly results in stronger saline intrusion in recent years.