Sensitivity analysis of EUROSEM using Monte Carlo simulation II::the effect of rills and rock fragments

A sensitivity analysis of the surface and catchment characteristics in the European soil erosion model (EUROSEM) was carried out with special emphasis on rills and rock fragment cover. The analysis focused on the use of Monte Carlo simulation but was supplemented by a simple sensitivity analysis where input variables were increased and decreased by 10%. The study showed that rock fragments have a significant effect upon the static output parameters of total runoff, peak flow rate, total soil loss and peak sediment discharge, but with a high coefficient of variation. The same applied to the average hydrographs and sedigraphs although the peak of the graphs was associated with a low coefficient of variation. On average, however, the model was able to simulate the effect of rock fragment cover quite well. The sensitivity analysis through the Monte Carlo simulation showed that the model is particularly sensitive to changes in parameters describing rills and the length of the plane when no rock fragments are simulated but that the model also is sensitive to changes in the fraction of non-erodible material and interrill slope when rock fragments were embedded in the topsoil. For rock fragments resting on the surface, changes in parameter values did not affect model output significantly. The simple sensitivity analysis supported the findings from the Monte Carlo simulation and illustrates the importance when choosing input parameters to describe both rills and rock fragment cover when modelling with EUROSEM

Using Soil and Water Conservation Contests for Extension: Experiences from the Bolivian Mountain Valleys

Soil and water conservation (SWC) contests among farmer groups were organized in five rural villages in the Bolivian mountain valleys. The contests were aimed at quickly achieving widespread sustainable results. This article analyzes the effectiveness of these contests as an extension tool. Mixed results were obtained. In three villages, participation rates in the SWC activities introduced in the contests were still high even 2 years after project withdrawal. These were all villages where a solid foundation for sustainable development had been laid before the contests were held. Two years later, most families were still involved in maintenance of the SWC practices introduced in the contests, and many farmers had started to experiment with different soil management practices. However, replications of these SWC practices were not widespread, Conservation Leaders did not continue with their training activities, and the quality of maintenance of the practices was often not satisfactory. In order to become a more effective extension tool and achieve widespread impact, SWC contests must receive continued support by a catalyst agency. Moreover, other SWC contests should also be organized in which practices are not predefined. Given that SWC contests are a low-budget extension tool, local municipalities could become more actively involved

Modelling of event-based soil erosion in Costa Rica, Nicaragua and Mexico : evaluation of the EUROSEM model.

This study was undertaken as part of a larger project to evaluate the impact of soil erosion on soil productivity in Costa Rica, Nicaragua and Mexico. An important part of the overall project consists of the use of the event-based EUROSEM model (European Soil Erosion Model) to predict soil erosion rates. This paper evaluates the use of the model both for single event and yearly soil loss estimations using erosion plot data from Nicaragua and data obtained through rainfall simulator experiments in Costa Rica and Mexico. EUROSEM was calibrated based on the hydrographs followed by the sedigraphs in Costa Rica and Mexico and this was followed by a model validation. In Nicaragua, model calibration was done using total soil loss values for 1993 and the model was consecutively validated using plot data for 1994 and 1995. The study stresses the importance of calibrating the model for individual catchments, and that the total area of plant stems and soil cohesion are crucial calibration parameters when modelling grassland with cover percentages above 60%. EUROSEM generally did not perform well on single event simulations in terms of simulating hydrographs and sedigraphs. Whereas the difference between observed and simulated total soil loss was between 0.0% and 100.0%, differences in total discharge, peak run-off rate and peak soil loss ranged between 2.0% and 326.5%. The difference was attributed to the model's inability to model crusting. The application of the model for yearly soil loss predictions looks promising with simulated and observed total soil loss values in Nicaragua differing by between 2.5% and 5.0%