黄土高塬沟壑区砚瓦川流域水沙关系及其对流域治理的响应

选取黄土高塬沟壑区砚瓦川流域作为研究对象,分析综合治理前后年水沙关系及次降雨水沙关系变化及其对流域治理的响应,研究结果表明：1997年为砚瓦川流域减水减沙作用明显生效的转折年。治理期（1998-2009年）与基准期（1981-1997年）相比,无论年尺度还是次降雨尺度上,径流深与输沙模数间的关系均发生显著变化,其单位径流输沙量显著降低。其中在次降雨尺度上水沙关系趋于稳定的临界径流深为3 mm;当降雨量<50 mm、雨强<4 mm/h或历时>3 h 时,治理期较基准期水沙关系变化显著。水土保持综合治理是造成年尺度和次降雨尺度上水沙关系变化显著的原因,并且可以显著降低中低降雨量、中低雨强和中长历时降雨的单位径流输沙量。

The Flow-sediment Relationship and Its Response to Watershed Management in Yanwachuan Watershed,Loess Plateau Gully Region,China

In this study, we investigated the variation of flow-sediment relationship before and after comprehensive management and its response to the management in Yanwachuan Watershed of Loess Plateau gully region. Results showed that the runoff and sediment underwent a significant shift in 1997, and the human activities, which had positive influences on controlling soil erosion, were enhanced in the watershed after 1997. Thus, the whole period was divided into two sub-periods, the base period (1981-1997) and the management period (1998-2009). Whether at annual scale or single rainfall event scale, the flow-sediment relationship between runoff depth and sediment transport modulus varied significantly in the management period comparing with that in the base period. The sediment discharge at unit runoff depth in the management period was significantly lower than that in the base period. At single rainfall scale, the flow-sediment relationship tended to be stable when the flow discharge exceeded a critical value of 3 mm. When precipitation was less than 50 mm, rainfall intensity was lower than 4 mm/h or rainfall duration was longer than 3 h, the flow-sediment relationship in the management period showd significant variation. The comprehensive management of soil and water conservation had altered the flow-sediment relationship significantly at annual scale and single rainfall scale. The sediment discharge at unit runoff depth of individual rainfall under condition of medium-low precipitation, medium-low rainfall intensity or medium-long rainfall duration would be significantly decreased by the comprehensive control measures.