鹦鹉沟小流域天然降雨条件下水土及养分流失特征

Characteristics of Soil and Nutrient Losses Under Natural Rainfall in Yingwugou Small Watershed

为研究丹江流域在不同土地利用类型下水土及养分的流失特征并提供科学有效的农业非点源污染防控依据,以南水北调中线工程中丹江流域的鹦鹉沟小流域为研究对象,建立径流小区,分析了2019—2020年天然降雨条件下耕地、林地、草地3种小区的水土及养分的流失特征。结果表明:在各小区中的水土及养分流失量均与坡度、降雨量、降雨强度呈正相关关系,其降雨—径流(泥沙)回归方程均具有良好的相关性(R^(2)>0.85),后期可用于产流、产沙量的估算预测当中。在不同的土地利用类型下,水土及养分流失量排序均为:耕地>草地>林地。各形态养分的流失趋势特征相似,其中硝氮和正磷分别在总氮和总磷中流失占比最大,并且氮素的流失量远大于磷素的流失量。相关性分析表明,各影响因素对养分流失的影响整体表现为:径流>泥沙>降雨,并且磷素的流失程度与降雨量、径流量及产沙量之间的相关性均高于氮素。

In order to study the characteristics of soil erosion and nutrient losses under different land use types in Danjiang Basin, and provide scientific and effective basis for the prevention and control of agricultural non-point sources, taking Yingwugou small watershed which belongs to the Danjiang River Basin in the Middle Route of the South-to-North Water Transfer Project as the research object, the runoff plots were established to analyze the runoff sediment, nitrogen and phosphorus loss characteristics of cultivated land, forest land and grassland under the natural precipitation conditions from 2019 to 2020. The results showed that the water, soil and nutrient losses in each plot were positively correlated with slope, precipitation and rainfall intensity, and the regression equation of precipitation and runoff(sediment) had a good correlation(R^(2)>0.85), which could be used for the estimation and prediction of current and sediment yield in the later stage. Under different land use types, soil, water and nutrient losses decreased in the order: cultivated land>grassland>forest land. The trend of nitrogen and phosphorus losses in all forms was similar, among which nitrate and orthophosphate accounted for the largest proportion in total nitrogen and total phosphorus, respectively, and the output of nitrogen was far greater than that of phosphorus. The correlation analysis showed that the overall influences of various factors on nutrient losses was in the sequence: runoff>sediment>precipitation, and the correlation of phosphorus loss with rainfall, runoff and sediment was higher than that of nitrogen.