Effects of climate and land-use change on green-water variations in the Middle Yellow River, China

Water resources management should cover both blue water and green water. For green-water management at the river drainage basin scale, the green-water coefficient (C-gw) is adopted, defined as the ratio of annual green water to annual precipitation. Based on data from the Middle Yellow River basin, China, for the period 1950 to 2007, we studied the temporal variation in C-gw in response to some influencing factors. A decreasing trend in C-gw was found. The influence of changes in land management on C-gw, reflected by an increase in the area (A(sw)) of soil and water conservation measures, is emphasized. Using multiple regression analysis, the contributions of A(sw) and the 5-year moving averages of annual precipitation and air temperature were estimated as 51, 37 and 12%, respectively. The results may provide useful information for better management of water resources, including green and blue water flows in the Yellow River basin.