北洛河上游径流变化特征及其驱动因素研究

Characteristics and driving factors of runoff changes in the upper reach of the Beiluo River basin

研究人类活动及降水变化对北洛河上游径流的影响,分析径流变化的主要驱动因子,为北洛河上游及相类似的其他流域水土保持、水资源合理利用提供决策依据。采用累积距平法、Mann-Kendall趋势检验法、降水-径流双累积曲线法对北洛河上游1971—2014的年降水量和径流量变化进行趋势分析与变异点诊断,并采用双累积曲线法和线性回归模型量化分析降水变化和人类活动对年径流、汛期径流变化的影响程度。结果表明:2003年大规模退耕还林实施后,北洛河上游降水-径流关系发生突变,突变后的年径流和汛期径流显著低于突变前;年径流变化主要是汛期径流减少造成的;人类活动相比降水对年和汛期的贡献率分别为106%和114%;突变后植被调节径流的能力显著增加,日径流量> 100、> 1. 15和<0. 5 m3/s所占比例分别为0. 27%,59. 2%,和8%,径流变化对降水变化的敏感性降低。认为:大规模化植被恢复是北洛河源区径流量减少的直接因素,而退耕还林(草)、水土保持政策是核心驱动力;同时,随着退耕还林时间的延长,北洛河径流不会持续减少,未来将维持在相对低而稳定的水平。

[ Background ]Studying the impact of human activities and precipitation changes on runoff and analyzing the main driving factors of the runoff changes in the upper reach of the Beiluo River basin could provide decision-making basis for water and soil conservation and rational use of water resources in the upper reaches of the Beiluo River basin and similar watersheds.[ Methods ]Based on the daily precipitation data and runoff data of Wuqi meteorological station in the upper reach of the Beiluo River basin from 1971 to 2014, the study uses the cumulative anomaly method, Mann-Kendall trend test, and precipitation-runoff double mass curve method to analyze the changes in trends and diagnosis the variation point of the annual precipitation and runoff changes in the upper reaches of the Beiluo River during 1971-2014. The double mass curve method and linear regression model are used to quantify the impact of climate change and human activities on precipitation and runoff changes in the annual scale and flood season.[ Results ]The results show that after the implementation of the Grain for Green Program in 2003, the precipitation-runoff relationship in the upper reach of the Beiluo River changed abruptly. The annual runoff and the flood season runoff after the mutation were significantly lower than those before the mutation, and the annual runoff changes were mainly caused by the reduction of the flood season runoff. Before 2003, the average daily runoff >100 m 3 /s, >1.15 m 3 /s, and <0.5 m 3 /s were 0.27%, 59.2%, and 8%, respectively, decreased to 0.07%, 44.9%, and 0.048 after 2003. The contribution of human activities to the annual runoff and the reduction of runoff during the flood season was 106% and 114% respectively. The capacity of vegetation to regulate runoff is significantly increases a few years after the implementation of the Grain for Green Program due to the increase in the area of forest land and the reduction of farmland area. The number of the days that have extreme runoff has decreased obviously after 2003. The proportion of the non-flood season runoff accounts for annual runoff has decreased in recent years. At the same time, the ratio of moderate flow after the mutation increased compared to the previous years. Changes in runoff are less sensitive to changes in precipitation.[ Conclusions ]Large-scale of the vegetation restoration is a direct factor for the decrease of runoff in the Beiluo River's source area, and the policy of Grain for Green Program and soil and water conservation is the core driving force. At the same time, with the extension of the time for Grain for Green Program, the runoff in the upper reach of Beiluo River will not continue to decrease, and will remain at a relatively low and stable level in the future.