Using Vetiver grass technology for mitigating sediment loads in the Talakhaya Watershed areas in Rota, CNMI

摘要

Talakhaya watershed in Rota is identified as a Coral Reef Management Priority site for CNMI (Commonwealth of Northern Mariana Islands). In 2010 federal and jurisdictional partners developed a Conservation Action Plan (CAP) for the Talakhaya Watershed. The goal of this initial Watershed Soil Loss Assessment therefore, was to assist in evaluating the re-vegetation objectives of ‘Mitigating Sediment Load’ in the Talakhaya watershed by making a thorough characterization of its main river systems. The objectives of this project were to reach those goals by measuring the hydrological parameters following the installation and the use of water meters, barometric level loggers, turbidity meters and rain gauges. The water flow as well as the turbidity level of each stream leading to the ocean from the Talakhaya Watershed was measured and sedimentation level was assessed accordingly. The results from the monitoring of the watershed conducted during the project timeline reported here show that all four rivers under study have statistically different stage-discharge curves. The river's relationship between time and turbidity also vary especially in the summer months of the first-year observations. Linear and convex polynomial relationships were sometimes observed in the different rainfall groupings for the four river systems, however relationships were often not significant. This-being-said, Quantile Regressions suggest that when data from all four river systems are combined for cases where there is some detectable rainfall, a maximum possible turbidity level can be defined.