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.