黄土丘陵沟壑区典型小流域不同空间尺度水沙变化研究

Study on water and sediment variation of the typical small watershed in loess hilly and gully region at different spatial scales

以黄土丘陵沟壑区桥沟典型小流域为依托,基于支沟-干沟1986-2020年实测径流泥沙数据,采用非参数检验、双累积曲线等方法研究不同流域尺度水沙时空变化特征及成因。结合M-K突变检验和流域土地利用类型变化,将研究期划分为治理前的1986-2001年和治理后的2002-2020年两阶段。治理前流域支沟年平均径流深和输沙模数均高于干沟。与治理前相比,治理后的支沟水沙含量减幅较干沟大,导致支沟的年平均径流深和输沙模数较干沟低。治理前流域水流泥沙与降雨量呈显著的正相关,治理后相关性消减至弱相关,人类活动成为治理后流域减水减沙的主控因素,且其对支沟减水减沙的作用略大于干沟。

A typical small watershed in loess hilly and gully region is studied.Based on the observed runoff and sediment data of branch ditch in 1986-2020,non-parametric test and double cumulative curve were used to explore the spatial-temporal variation characteristics and mechanism of water and sediment at different watershed scales.The results show that combined with the m-k mutation test and the change of watershed land use type,the runoff and sediment series can be divided into pre governance(1986-2001)and post governance(2002-2020).The annual average runoff depth and sediment transport modulus of branches were higher than those of dry ditches in the pre-governance,and the decrease of water and sediment content of branches after treatment was larger than that of dry ditches,resulting in lower annual average runoff depth and sediment transport modulus of branches than that of dry ditches.The runoff sediment volume and rainfall in the river basin before treatment show a significant positive correlation.The correlation between runoff sediment and rainfall decreased to a weak correlation in post governance.In post governance,the human activities were the main controlling factor of water and sediment reduction in the basin,and its influence on water and sediment reduction in branch ditches was slightly greater than that in trunk ditches.