Attribution for decreasing streamflow of the Haihe River basin, northern China: Climate variability or human activities?

Summary Climate variability and human activities are regarded as the two driving factors for the hydrological cycle change. In the last several decades, there were statistically significant decreasing trends for streamflow and precipitation, but an increasing trend for mean temperature in the Haihe River basin (HRB). The attribution of climate variability and human activities for streamflow decrease was quantitatively assessed in three catchments located in different parts of the HRB. They are the Taolinkou catchment in the Luanhe River, Zhangjiafen catchment in the north of Haihe River, and Guantai catchment in the south of Haihe River. Based on the break point of streamflow, the whole period was divided into two periods: “natural period” (before the break point) and “impacted period” (after the break point). Using the Variable Infiltration Capacity (VIC) model calibrated in the “natural period”, the “natural streamflow” without the impact of human activities was reconstructed for the whole period. The differences of the “natural streamflow” between the “natural period” and “impacted period” indicated the impact of climate variability on streamflow decrease. The remaining contribution to streamflow decrease was made by human activities. The results indicated that the decrease of streamflow between the two periods could be attributed to 58.5% (41.5%), 40.1% (59.9%), and 26.1% (73.9%) from climate variability (human activities) in the Taolinkou, Zhangjiafen and Guantai catchment, respectively. That was to say, climate variability was the major driving factor for the streamflow decrease in the Taolinkou catchment; on the other hand, human activities was the main driving factor for the streamflow decrease in the Zhangjiafen and Guantai catchment.