The accurate survey is of great significance to water resources in terms of efficient utilization,ecological environment protection and resource management.However,most of the current water resource investigation researches were based on high-resolution satellite data,which cannot meet the accuracy requirement for survey of water resources in underlying surface of complex plain urban region.Here,an investigation method is proposed for water resources quantity,which is based on UAV(unmanned aerial vehicle) remote sensing,SWAT model and geographic information technology.In this method,the accurate distribution of surface water can be obtained by field investigation,and the total quantity of water resource including groundwater and duplicated amount between surface water and groundwater are estimated by the hydrological model with underlying surface data from the third National Land Survey.Then this method is applied to a plain city of Pizhou,where the river network is complex,to verify its feasibility and accuracy as well as analyze Pizhou's water resource characteristics.The results illustrate that,compared to conventional approaches,the proposed method considers more factors and has less uncertainty,thus can provide a highly reliable methodology for urban water resources investigation.