Event based modeling studying three sub-basins in the Kenai River watershed

Abstract

Streams in the Kenai River watershed are characterized by a fish-rich environment, with competing interests between commercial industry and recreational users. Resource managers strive to balance the needs of both these user groups while maintaining the sustainability of the resource. The ability to estimate future river conditions could help maintain the resource, and a strong, sustainable economy on the Kenai Peninsula. This research used the U.S. Army Corps of Engineers Hydrological Modeling System (HMS), which transforms rainfall to river discharge. The main goal was to define a set of parameters that were calibrated using an event based strategy, and concurrent rainfall and discharge data. The model was calibrated and validated in three sub-basins located in different environmental settings (i.e. lowlands, mid, and high elevation). In addition, the Kenai River watershed, as a whole, was modeled. Due to limited concurrent datasets, a combination of current and historic rainfall and discharge data was used in the calibration. Over the period of time between the historic data and the current data, no major changes in the watershed were detected. Model results at the sub-basin and watershed scale provided reasonable results over the modeling period. Each sub-basin maintained errors below 10% for the calibration and only slight increase in the error for the verification trials. It was found that during an extreme precipitation event, the model did not perform within reasonable bounds.