Using the Method of soil conservation service Curve Number (SCS-CN) Combined with the Geographic information system (GIS) to estimate the surface runoff on the Co To Island, North Vietnam

Abstract

Co To Island in the north of Vietnam is about 22 km2 in area (including Big and Small Co To Islands), of which about 51% of mountainous and hilly areas, about 49% of cultivated land.On the island, there is only the meteorological observation station, no hydrological station. Because of the demand for water resources management, rainwater harvesting and storage needs initial hydrological parameters, this study first published the results of surface flow from rainwater on Big Co To Island. The authors used the Soil Conservation Services Curves Number method (SCS - CN) in conjunction with the Geographic Information System (GIS) to estimate surface flow parameters on Big Co To Island. Two types of rainfall monitoring data that have been exploited in this study are the average annual rainfall (Rainfall Eevent 1) and the amount of rainfall during the storms (Rainfall Events 2-4). Estimated results of Qo discharge flow rate reach 0.39 m3/ s based on the 30-year rain monitoring data series with error less than 29%. The result of estimating the total surface water(Wo)generated from rain in event 1 was 13.1 x 106 m3, meanwhile, during the rainy event 2 these values reached 10.2 x 106 m3.This result confirms the potential of exploiting rainwater resources from storms on the island.SCS –CN method combined with GIS for determining exact areas, soil properties, land use ... has allowed the implementation of other calculations on the distribution of hydrological parameters at 14 sub-basins with different rain events. In the absence of any official statements about the hydrographic parameters of Big Co To Island, the findings of this study will be good references for other research and calculations involved. The SCS - CN method combined with GIS is an effective and convenient tool to evaluate the hydrological parameters of water resources on the island, especially where there is no permanent hydrological monitoring station.