不同雨型下紫色土区坡耕地产流产沙特征

利用遂宁水土保持试验站5个径流小区1984—2015年次降雨和径流输沙数据,基于降雨过程定量划分出4种雨型,分析了雨型对不同坡度坡耕地产流产沙的作用。结果表明:径流深与各时段最大雨强均呈极显著相关(p0.01),随着坡度的增加,最大相关系数所对应的雨强时段越短;冲刷量均与Ⅰ平均呈极显著相关,且相关系数最大。径流深、冲刷量与雨强拟合关系均为幂函数,分别为"凸型"和"凹型"增函数,且拟合度区间分别为0.79,0.88]和0.90,0.97],说明冲刷量和雨强的关系更密切。各雨型下的产流产沙量随坡度的增大而增大,同一坡度下基本表现为雨型Ⅳ(短历时、大雨强)雨型Ⅲ(中历时、中雨强)雨型Ⅱ(长历时、中雨强)雨型Ⅰ(长历时、小雨强),其中,雨型Ⅳ明显大于雨型Ⅰ且达到显著水平(p0.05),且在15°小区的响应最为明显。雨型Ⅳ是造成该区坡耕地水土流失的主要降雨类型,且径流深和冲刷量随坡度的增大而增加,故应在水土保持工作中着重采取相应措施进行防治。

Characteristics of the Runoff and Sediment Yield of Sloping Farmland in the Purple Soil Area Under Different Rainfall Patterns

Based on the data of individual rainfall,runoff and sediment yield of five runoff plots from 1984 to 2015 in Suining Soil and Water Conservation Experimental Station,68 rain processes were classified into four rainfall patterns.The effects of rainfall patterns on runoff and sediment yield of sloping farmland were analyzed for different slopes.Then the results showed that there were highly significant correlations between runoff depths and rainfall intensities of different periods (p＜0.01).With the slope gradient increasing,the period of rainfall intensity for the greatest correlation coefficient became shorter.The amount of sediment was significantly correlated with the average rainfall intensity during each individual rainfall,and the correlation coefficient was maximum.The fitting curve between runoff depth,the amount of sediment,and rainfall intensity was an increasing function of convex and concave shape,of which the fitting interval was between 0.79 and 0.88,and 0.90 and 0.97,respectively.It was indicated that the correlation between sediment yield and rainfall intensity was more affinitive than that between runoff depth and rainfall intensity.With the slope gradient increasing,runoff and soil erosion became greater.At the same slope gradient,the yields of sediment and runoff of rainfall Ⅳ (short duration,heavy rainfall) was the greatest,followed by rainfall Ⅲ (moderate duration,moderate intensity),rainfall Ⅱ (long duration,moderate intensity),and rainfall Ⅰ (long duration,light intensity).Furthermore,the difference between rainfall Ⅳ and rainfall Ⅰ was significant (p＜ 0.05).When the slope gradient was about 15°,the effects of rainfall pattern were the most obvious.Overall,runoff and sediment yield increased with increasing slope gradient.Rainfall Ⅳ was the main pattern of rainfall causing soil erosion.In the future,we should take some measures of soil and water conservation to reduce soil erosion caused by rainfall Ⅳ on sloping farmland.