Characteristics of Green and Blue Water Flow of Hydrological Landscapes of Upper Heihe in Northwest China

Blue water and green water are of great importance for food production and maintenance of ecosystem. Blue/green water flow on landscape scale and its seasonal variation remains unclear. This study attempt to analyze characteristics of green and blue water flow on landscape scale.In this study, FLEX-Topo model was adopted. And upstream of Heihe River Basin (UHB) was selected as the study area, which was divided through topographic information into four landscapes, such as riparian area, grass hillslope, forest hillslope and bare soil/rock. Based on the analysis of the simulation during the period of 1979-2015, characteristics of green and blue water flow of the four landscapes was presented. The results showed that (1) FLEX-Topo proved to be an efficient approach for catchment hydrological process simulation as well as for green and blue water study; (2) Annual green water flow(GWF) of riparian area was 325.19 mm/a while its blue water flow(BWF) was 151.92 mm/a. GWF and BWF of grass hillslope was 270.50 mm/a and 199.91 mm/a, respectively; GWF of forest hillslope was 424.75 mm/a which is much greater than its BWF (42.11mm/a);as for bare soil/rock, GWF (227.96 mm/a) was a litter smaller than BWF (295.32 mm/a). From the results, its can be concluded that:(1)on annual scale, majority of precipitation and water reserve in riparian area, grass hillslope, forest hillslope became green water flow, especially in forest hillslope. More than half of precipitation in bare soil/rock turn to blue water flow; (3) seasonal variation of both green water flow and green water flow of the four hydrological landscapes synchronized with precipitation.