平凉市纸坊沟小流域近50年径流对降水的响应分析

根据纸坊沟小流域1955—2002年降水、径流观测资料，采用时间序列分析法和统计回归分析法对降雨及径流的响应情况进行了分析，结果表明:降水量在年内分配不均，凸显单一峰值；降水在年际上呈平水年—干旱年—平水年（较丰水年）周期性变化；流域月径流变化基本与月降水量变化趋势相吻合，在同一周期中径流量峰值推后于降水量峰值一个时段，流域径流年变化幅度很大；径流深在季节分配上也有很大差异，主要集中在夏、秋季，占年总值的86.2%，而春、冬季仅占13.8%；径流距平值变化无论是季节上还是月度上均呈下降趋势；当年降水量增加或减小10%，20%，30%时，年径流深表现出分别增加或减少23.29%，46.59%，69.88%的正响应；随着时间的推移和流域治理程度的提高，流域径流量和径流深相应减小，径流深总体呈下降趋势。

Response of Runoff to Precipitation in Zhifanggou Small Watershed of Pingliang City in Recent 50 Years

In accordance with the observation information of annual precipitation and runoff during 1955—2002 in the Zhifanggou small watershed, the response of runoff to rainfall was analyzed by the ways of time series analysis and statistical regression analysis. The results indicate that:① distribution of precipitation is uneven during a year, highlighting the single peak value; ② precipitation in inter-annual-year shows as cyclical changes as flat water years-years of drought-flat water years compared with wet years; ③ monthly runoff change is basically consistent with the monthly change trend of precipitation, the peak value of runoff emerges more later in a short period than the maximum precipitation in the same cycle period and runoff varies widely in years; ④ runoff depth on the seasonal distribution is quite different, mainly concentrating in summer and autumn, accounting for 86.2% of the annual total value, only 13.8% of that in spring and winter; ⑤ average values of runoff show a downward trend whether seasonal or monthly; ⑥ when annual precipitation increases or reduces by 10% or 20% or 30%, annual runoff depth shows positive response of increasing or a decreasing by 23.29%, 46.59%, 69.88%,respectively; ⑦ with the passage of time and the improvement in the level of watershed management, watershed runoff and runoff depth are going to reduce accordingly and runoff depth shows a downward trend overall as well.