New Mexico Geological Society Annual Spring Meeting — Abstracts

As part of a project to determine the influence of hillslope aspect and vegetation cover on the evolution of a drainage basin, paired canopy and intercanopy runoff plots were deployed on two opposing hillslopes with clear vegetation contrasts and quasiexact north facing and south facing aspects. The opposing hillslopes are located in a small first order semi-arid basin in the Sevilleta National Wildlife Refuge and exhibit sharp vegetation differences with juniper/grassland on the north facing slope (NFS) and creosote/grassland on the south facing slope (SFS). A total of eight plots were installed to measure the total runoff and sediment yield under different ground cover types and slope positions. At each slope four plots were distributed in pairs at two different elevations. Each plot-pair is arranged with a canopy covered plot (with a Juniper canopy for the NFS and Creosote canopies for the SFS) and an intercanopy plot partly covered by grasses. The objectives of this study were to determine the effects of ground cover, hillslope aspect and slope position on runoff and sediment yield. The results show higher and more frequent runoff discharges for the SFS, rendering higher sediment yields than the north-facing counterpart. Furthermore, higher sediment yields were observed in the upper slope positions of both north and south facing slopes. Similarly, three out of the four plot pairs show higher sediment yields for the pair member under canopy conditions. The results on runoff and sediment movement provide an insight on the influence of hillslope aspect and vegetation coverage, and the feedback relationships between climate-vegetation-soil and erosion that conducts the basin evolution. The results of this study will assist in land management decisions on semiarid areas.