Assessment of spatial and temporal patterns of green and blue water flows in inland river basins in Northwest China

Abstract

In arid and semi-arid regions freshwater resources have become scarcer with increasing demands from socio-economic development and population growth. Until recently, water research and management in these has mainly focused on blue water but ignored green water. Here we report on spatial and temporal patterns of both blue and green water flows simulated by the Soil and Water Assessment Tool (SWAT) for the Heihe river basin, the second largest inland river basin in Northwest China. Calibration and validation at two hydrological stations show good performance of the SWAT model in modelling hydrological processes. The total green and blue water flows were 22.09 billion m<sup>3</sup> in the 2000s for the Heihe river basin. Blue water flows are larger in upstream sub-basins than in downstream sub-basins mainly due to high precipitation and large areas of glaciers in upstream. Green water flows are distributed more homogeneously among different sub-basins. The green water coefficient was 88.0% in the 2000s for the entire river basin, varying from around 80–90% in up- and mid-stream sub-basins to above 95% in downstream sub-basins. This is much higher than reported green water coefficient in many other river basins. The spatial patterns of green water coefficient were closely linked to dominant land covers (e.g. glaciers in upstream and desert in downstream) and climate conditions (e.g. high precipitation in upstream and low precipitation in downstream). There are no clear consistent historical trends of change in green and blue water flows and green water coefficient at both the river basin and sub-basin levels. This study provides insights into green and blue water endowments for the entire Heihe river basin at sub-basin level. The results are helpful for formulating reasonable water policies to improve water resources management in the inland river basins of China

Assessing water footprint at river basin level: a case study for the Heihe River Basin in northwest China

“…EFR stands for environmental flow requirements. The annual and monthly natural runoff in the HRB is obtained from Zang et al (2012), who simulate surface and groundwater flows under the natural conditions with a Soil and Water Assessment Tool (SWAT) (Arnold et al, 1994). It is often assumed that EFR accounts for a certain share of the natural runoff.…”