Abstract:
Hydrological phenomena are very complex and difficult to be understood completely, so it needs a simplification in the form of model. IHACRES model is one of the well known rainfall-runoff model that have been successful in investigating the hydrological response of the various watersheds around the world. The existence of this success, it is necessary to research the reliability of the IHACRES model in Indonesia, namely in the Indragiri watershed. This model is calibrated, verified and simulated based on discharge data recording at Lubuk Ambacang station for 10 years (1995-2004) and then validated against discharge data at Pulau Berhalo station. This research was conducted by varying the length of data is grouped into scheme 1 until scheme 8. The research results show that the best scheme in calibration phase is scheme 3 (3 years calibration) with R2 value of 0,8140, while the verification phase, the best scheme is scheme 6 (6 years calibration) with R2 value of 0,5508. In the validation phase using the data in Pulau Berhalo station, scheme 7 (7 years calibration) showed better performance than scheme 3 and scheme 6 with R2 value 0.361 and bias 17.155 mm/year. Overall, the results of this research provide understanding that the success obtained in the calibration phase does not guarantee the success at verification phase.
