Using uncertainty approach to determine the contribution of sediment sources (Case Study: Tange bostanak watershed, Fars province)

Soil erosion and sediment yield are one of the most destructive phenomena that was cause a lot of damages in different regions. In order to combat  with increasing sediment loads, informed of the nature and sediment sources in watershed scale is essential. Soil conservation projects and for effective sediment control strategies, need to knowledge of sediment sources throughout a catchment environment. The main aims of this study are to apply tracers to determine relative contributions of sediment sources with six mixing models and to use Monte Carlo -mixing model that estimates contributions of sources to associated the uncertainty estimation in sediment fingerprinting in the land uses(rangelands, forests, cultivation and gardens)and geology information(Razak, Kashkan, Bakhtyari, Quaternary, Pabedeh Gorpi and Asmary) of  Tange Bostanak catchment, in Fars province. Multivariate discriminant function analysis was subsequently used to identify the best composite fingerprint incorporating a number of these tracers. Four tracers(C, Cu, Si, Ti) verify  ability to discriminate between land use  source categories and four tracers(Nd143/144, Cu, Si, Ti) verify  ability to discriminate between geology information’s  source categories. The application of six commonly used mixing models(Collins, MCollins, Landwehr, MLandwehr, Motha, Slattery) to Monte Carlo Simulation identified all outputs remained in the acceptable range of contributions  defined by the Monte Carlo uncertainties. Mean relative contribution (percentile 5%, percentile 50% and percentile 95%, respectively) of sediment samples resulting from the Monte Carlo mixing model uncertainty approach. The best explanatory parameters provided by the Collins model based on GOF index(99.3)was best model for land uses and the best explanatory parameters provided by the Modified Collins model based on GOF index(99.98)was best model for geology information. The relative contributions from areas of range lands with 58.76%(42.5%-75.65%)  and Asmary inrormation with 53.63%(46.7%- 60.11%) are highest, respectively. Pabedeh Gorpi and Bakhtyari information’s with 0.24 and 0.27  are the lowest relative importance, also gardens  and range lands  with 3.73 and 3.5  are the highest  relative importance, respectively.