Meng Lu, Chris Renschler

The long-term dense precipitation records provide important information to understand rainfall erosivity and soil erosion in semi-arid rangelands. This paper investigates the temporal trends of changes in rainfall, rainfall erosivity, and the responses of runoff and sediment on the WS103 watershed, a small semiarid rangeland watershed in the Walnut gulch Experimental Watershed, Tombstone, Arizona. A difficulty of analyzing long-term time series of rainfall characters and soil erosion indicators lies in the analogue-to-digital changing of rainfall gauge system in 1999. Extending from a previous research that compares the influence of system alteration to annual rainfall records and peak rainfall intensity, our study further compares event statistics: rainfall characters and rainfall erosivity per event, as well as number of events and significant events. After determining the influence of the digital-to-analogue system alteration to time series analysis, the time series structural stability is analyzed with a parametric and a non-parametric time series structural change detection methods. Finally, the trends of the time series of rainfall characters and theirs effects to soil erosion are quantified with the GLS (general least square) model.