The long-term water level dynamics during urbanization in plain catchment in Yangtze River Delta

Numerous aquatic problems have been produced by the extensive urbanization especially in last decades in eastern China. This paper presents an evaluation of water level alteration induced by urbanization in the Lower Qinhuai river basin, Yangtz River delta in the last half century. Analyses were conducted using Range of Variability Approach, based on the indicator system of hydrologic alteration including 31 water level related parameters. By contrasting the overall alteration range and that of each parameter in 1960–1979 (pre-impact period) and 1980–2008 (post-impact period) the hydrological impact of urbanization was revealed. The results indicate that, 1 the urbanization in 1980s-2010s lead to an expansion of impervious area by 8 times and a sever simplification of river network structure; 2 the average monthly water level increased considerably from the pre-impact to post-impact period due to the urbanization; 3 the low water level is more sensitive to the interference of urbanization, both the magnitude of water level in dry season and minimum low water pulse increased distinctly; 4the Lower Qinhuai river basin was changed with moderate intensity by the urbanization process, with and overall change degree of 42.5%. In conclusion, water level is a remarkable indicator of the river regime response to urbanization in plain river network area. The results of the study would provide support in water resources management in urban development, opening new perspective of the hydrological process evaluation in high urbanized plain catchment.