A RELIABILITY-ANALYSIS OF A HYBRID RAINFA LL-RUNOFF MODEL IN THE BOLIVIAN HIGHLANDS

The sensitivity of the output to the parameter values of a hybrid mode l (HEC-1 model) with one stochastic component added is considered in t he context of the Bolivian highlands. First-order and Monte Carlo anal ysis techniques were used to establish the influence of each parameter in the model. The greatest contribution to uncertainty in the model e stimation corresponds to the initial loss (IL) and the uniform loss (C L) parameters. However, it is important to recognize that large variat ion in output may also be caused by differences in the spatial distrib ution of precipitation (a low-density network). Other parameters of th e model structure (TC and (S-R)) and the parameters defining the conce ntration of flow had less effect. If it were possible to estimate the net rainfall with greater precision the concentration parameters could easily be adjusted to meet the requirements of accurate representatio n of peak flows.