干旱区生态环境知识资源中心

Intermittent channel networks pose particular challenges for monitoring the extent of material transport and retention in arid river basins as a result of pulsed and highly variable rainfall-runoff dynamics. Here, we examine how rainfall characteristics influence hydrological connectivity along a terrestrial-aquatic flowpath from upland hillslopes to low order intermittent channel networks. In addition, we explore the implications for nitrogen loss via denitrification as a function of variable flowpath length and soil water conditions associated with intermittent flow. The size, timing and intensity of storms influenced the extent of hydrological connectivity and highest order channel flow. During summer monsoons, highest order channel flow increased most strongly with storm size, while in winter, the combination of days since last storm and storm intensity provided the best model; however, models containing storm size were also highly ranked. Riparian terrace and vegetated hillslope soils had the highest denitrification potential; however, rates in channel sediments also were appreciable. Deep channel sediments dried slowly and may therefore remain biologically active for longer periods, increasing the potential for N losses via denitrification. The extent of N transport, storage and denitrification is in large part driven by the frequency, intensity and duration of individual rainfall events. Individual storm characteristics influence the magnitude of vertical and horizontal hydrological connectivity in the catchment, and therefore, the magnitude of transport, solute storage and biogeochemical processing in intermittent channel basins.