Modeling the erosivity of frontal storms in the semi-arid climate of Central Chile using CLIGEN .

Gabriel Lobo, Carlos Bonilla

Friday 3 july 2015

9:30 - 9:45h at Mississippi (level 1)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 14B. Sediment - River

CLIGEN is a stochastic weather generator that produces daily estimates of precipitation and individual storm parameters, including storm durations and peak intensity. These parameters are required to run other physically based models, such as the Water Erosion Prediction Project (WEPP) model, but are also necessary for estimating the erosivity of the rainfall events for empirical models such as the Revised Universal Soil Loss Equation (RUSLE). CLIGEN has proven to be effective when predicting daily estimates, but not for the individual storm parameters. Inaccurate storm duration and peak intensity estimations have been reported in several studies, which makes erosivity estimates using CLIGEN inaccurate in many cases. Therefore, a method was developed to increase the accuracy of the CLIGEN-generated storms, which consists in calibrating the input parameter controlling the storm duration and intensity. The model was tested before and after the calibration by using 1-hour pluviograph records from 30 sites located in Central Chile, all of which exhibit frontal systems. More than 18,000 storm events were analyzed from 415 years of hourly measured data. Based on a monthly analysis, storm durations and peak intensities were over and underestimated by the model in most sites and months before the calibration, especially during the wet season. This made rainfall erosivity estimates inaccurate in 19 of the 30 sites. After the calibration, the storm patterns were simulated more accurately; the r2 of the storm durations and peak intensities increased from 0.41 to 0.65 and from 0.31 to 0.60 respectively. Because of this, CLGEN yielded accurate erosivity results in 29 of the 30 sites after the calibration. This paper explains in detail the calibration method and analyzes these and other parameters related to the individual storm generation process.