PARTITIONING INTERRILL SPLASH AND WASH DYNAMICS - A NOVEL LABORATORY APPROACH

With an innovative experimental device simultaneous measurement of int errill splash and wash on an Oxisol was made at 4, 9, 18, 27, and 36% slopes under a constant rainfall intensity of 65 mm h(-1) in a laborat ory setting. The specially designed runoff and sediment collection sys tem provided a means of partitioning total splash into directional com ponents (upslope, downslope, and lateral) and interrill sediment trans port into wash and splash components. Results indicate that downslope and lateral splash components increased with slope while the upslope c omponent decreased. Overall there was a linear increase of total splas h from the 0.18 m(2) plot with increasing slope. A transport-limited r egime prevailed in all studied slopes. The wash process dominated sedi ment transport at low slopes (< 9%) and was linearly related to slope with a flux at the steady state ranging from 0.65 g m(-2) min(-1) at 4 % slope to 3.15 g m(-2) min(-1) at 36% slope. Downslope splash transpo rt was dominant at high slopes (> 9%) and was best described with a po wer function model (exponent = 1.3) with a flux ranging from 0.33 g m( -2) min(-1) at 4% slope to 5.31 g m(-2) min(-1) at 36% slope. The WEPP interrill erosion model was inadequate in describing total interrill sediment delivery from the Oxisol. The practical implication of this f inding was that splash can be an important process of sediment transpo rt in interrill erosion. Failure to include splashed sediment in inter rill erosion measurements using the common ''runoff-trough'' approach may underestimate total soil loss or interrill sediment delivery to ri lls.