干旱区生态环境知识资源中心

A 15-year record for the semiarid upland Eshtemoa catchment provides a basis for estimating the efflux of water, sediment, and solutes in a type of environment for which there is a dearth of information. Average annual runoff was 5.4 mm, giving a runoff coefficient of 2.1%. Average annual yields were 275 Mg km(-2) for suspended sediment, 15.3 Mg km(-2) for bed load, and 0.6 Mg km(-2) for dissolved load, though distinct seasonal differences are identified and related to the prevalence of cellular, convectively enhanced storms in autumn and spring and frontal storms in winter. The majority of the average annual total sediment and solute yield of 291 Mg km(-2) is generated by as few as 8 of the 74 flow events of the 15-year record. The relative importance of bed load and the consequent ranking of the load components as suspended load >> bed load >> dissolved load distinguishes this dryland environment from its humid counterparts.