SMOOTHING OF A UNITGRAPH VIA CROSS-VALIDATION

Recently, it has been shown that quadratic programming techniques with a smoothing constraint controlled by a single parameter lambda provid e a framework in which the reconstruction of a unit hydrogra ph from n oisy excess rainfall and runoff data can be easily implemented. Howeve r, a remaining problem in this approach is on the choice of an optimal value lambda of the smoothing parameter lambda so that lambda is not too small, with as a result a unit hydrograph overly sensitive to nois e in the rainfall and runoff data, or not too large, with as a result information loss in the estimated unit hydrograph. In this paper, the use of cross-validation for computing a lambda is investigated and ill ustrated with rainfall-runoff data published in the literature.