Regional runoff study based on MODCYCLE distributed hydrology model

In order to analyze temporal and spatid variation law and distributed features of regional runoff on different underlaying surface, MODCYCLE model, which is a distributed hydrology model with physical mechanism and recently developed by department of water resources in IWHR, was used in a case of study of Tianjin. On the base of considering the soil, land use and precipitation characteristics, MODCYCLE model applied the revised Green-Ampt equation with pond water system to calculate runoff. Results showed that: 1) Average runoff coefficient was about 16% on whole region between 1997 and 2004 in Tianjin, but the coefficient on land area was less than 10%. 2) The runoff on land area was mainly focused on northern hilly, central urban area, and eastern coastal regions, but the runoff on water was mainly focused on central and southeast areas. 3) Between coefficients of some parts on land area, the coefficient of urban area was biggest, up to 44.1%, the coefficient of residential-low density area was also bigger, as 24.5%, but coefficients of forest and grass were less than 10%, the farm land had almost no runoff because of the field ridge.