降雨侵蚀力对河岸滩区耕地土壤养分流失的影响

河岸滩区的人类农业活动最为直接地影响着河流的水文生态.自1997年小浪底水利枢纽工程成功截流以来,下游孟津扣马黄河滩区1 955hm2的天然滨河湿地有72%常年出露.为当地农业开发提供了原生动力.在10 a期间滩区的土地利用状况也发生了明显的改变,其中28.8%转变成鱼塘-荷花塘等人工湿地,39.8%转变成小麦棉花等旱地农作物,剩下的328 hm2的河床湿地因受农业活动的影响,正发生着严重的退化和萎缩.通过野外定位观测,对孟津黄河滩区河岸耕地土壤养分随降雨径流流失的特征进行了研究.研究结果表明,次降雨侵蚀力(R)是影响径流量和土壤养分流失的重要因素.在弱侵蚀力下,产生的径流以蓄满产流为主;当降雨侵蚀力大于19.0,产生的径流以超渗产流为主.径流土壤养分流失量与次降雨侵蚀力之间存在明显的二次曲线关系.根据滩区土壤的渗透特征,在次降雨侵蚀力R=10.0～45.0之间的中等强度降雨将产生较为严重的土壤养分流失.并强调河岸带的水土保持工作应亟待加强.

Nutrient Loss From Riparian Cultivated Land Under Different Rainfall Erosivity

Agricultural activities in riparian directly influence fluvial hydrology and ecology.Since the Yellow River was dammed up by the Xiaolangdi hydro-junction in 1997,72% of the 1 955hm² riparian wetlands have been appearing perennially in Kouma floodplain of Mengjin County,which offers the primary motivation for local agricultural development.The land use type changed remarkably in the past 10 years.28.8% of riparian wetlands changed into the created wetlands,for example,fish ponds or lotus fields and 39.8% of riparian wetlands changed into dryland farms for wheat or cotton cultivation.328hm² remained natural wetlands have been degrading and shrinking severely because of agricultural activities.Based on the field experiments,the characteristics of nutrient loss by runoff in Mengjin riparian dryland farming are analyzed.Results show that rainfall erosivity(R) is an important factor to the amounts of runoff and nutrient loss.Under the condition of low rainfall erosivity,runoff is generated from overflow mostly and however,under the condition of R>19.00,runoff is generated from over-infiltration mostly.There are conic relationships between nutrient loss and rainfall erosivity.Under the condition of moderate rainfall intensity(R=10.0-45.0),nutrient loss may be severe due to the characteristics of infiltration in Kouma floodplain.So,soil and water conservation in riparian should be strengthened imperatively.