NUMERICAL SIMULATION OF THE RAINFALL-RUNOFF PROCESS ON A DAILY BASIS.

Abstract

A DIGITAL MODEL HAS BEEN DEVELOPED FOR THE SIMULATION OF THE RAINFALL-RUNOFF OF RURAL WATERSHEDS.INPUT DATA ARE DAILY VALUES OF PRECIPITATION AND TEMPERATURE TOGETHER WITH MEAN MONTHLY POTENTIAL EVAPOTRANSPIRATION.THE MODEL PRODUCES DAILY VALUES OF STREAMFLOW AS WELL AS INFORMATION ON THE TIME VARIATION OF THE SOIL MOISTURE CONTENT.IN ALL, TEN MODEL PARAMETERS HAVE TO BE IDENTIFIED, SEVEN OF WHICH HAVE A MAJOR INFLUENCE ON THE PERFORMANCE OF THE MODEL.LTHE MODEL OPERATES BY ACCOUNTING CONTINUOUSLY FOR THE MOISTURE CONTENT IN FOUR DIFFERENT AND MUTUALLY INTERRELATED STORAGES REPRESENTING PHYSICAL ELEMENTS IN THE WATERSHED.LIT HAS BEEN APPLIED TO THREE DIFFERENT DANISH WATERSHEDS.SEVERAL STATISTICAL MEASURES OF ACCURACY HAVE BEEN UTILISED FOR A QUANTITATIVE EVALUATION OF THE SIMULATION RESULTS.THE SIMULATIONS DEMONSTRATE THAT THE MAIN SHORTCOMINGS OF THE MODEL ARE DUE TO THE LACK OF A PROCEDURE ACCOUNTING FOR FROZEN GROUND DURING EXTENDED PERIODS OF FROST, WHICH COULD IMPROVE SOME OF THE SIMULATION RESULTS DURING WINTER AND SPRING.(A)