Evaluation of HEC-HMS Model for Water Resources Management in Maha Oya Basin in Sri Lanka

Water resources are being undergoing stress due to, increased water consumption resulting from rapid population growth, development activities, and industrialization for economic prosperity. Hence, sustainable water resources management is essential to fulfill the future requirements. The main challenge in this context is the unavailability of observed streamflow series. To develop a calibrated and validated hydrological model to address the prevailing condition is crucial with a proper understanding of catchment behaviour from the hydrological point of view. Therefore, water quantification with the aid of hydrological modeling is an essential requirement, to facilitate water resource management in ungauged watersheds. This work demonstrates the development of the HEC-HMS (Version 4.3) model to Giriulla catchment (1,120 km2) to facilitate the water resources management in the Maha Oya (1,562 km²) basin. To optimize the model performance RMSE was used as an objective function, while MRAE was used as a performance indicator. Further, visual performance evaluation was used, to check timing, high and low flow simulation capability. The developed HEC-HMS model was calibrated with over 75% accuracy, while validated with 80% accuracy. The better performance during validation can be attributed to a better streamflow dataset that represents Thiessen averaged rainfall. The developed HEC-HMS model with its optimized parameters demonstrated that it can be utilised for water resources management in the Maha Oya basin.