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River Loads into Puget Sound

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River Sediment and Toxic Chemical Loads into Puget Sound, WA - A Demonstration Study of the National Monitoring Network for U.S. Coastal Waters and Their Tributaries

The Puyallup River
The Puyallup River is sampled during a winter storm for sediment and toxic chemicals

Problem - Puget Sound, WA, an iconic Northwest ecosystem, is the second largest estuary in the United States. Its unique geology, climate, and nutrient-rich waters sustain biologically-productive terrestrial, coastal, and marine habitats. These same natural characteristics also contribute to a high quality of life that has led to continual growth in human population and increasing land-use change throughout the basin. Development and associated human activities have significantly degraded the Sound, causing declines in fish and wildlife populations, water-quality issues, and losses of critical habitats. Restoration of Puget Sound is recognized as an urgent national priority, resulting in multiple restoration programs coordinated by the Puget Sound Partnership. The interdisciplinary Puget Sound Ecosystem Monitoring Program (PSEMP) was initiated in 2011 to evaluate progress towards ecosystem recovery and to serve as a foundation to continually improve the scientific basis for management actions in Puget Sound. In 2014, a monitoring inventory and data gap analysis report was completed by each of the ten PSEMP workgroups. The reports summarize current Puget Sound monitoring activities including coastal water quality and also identify numerous data gaps that are critical for comprehensively assessing Puget Sound ecosystem health.

Objectives - The primary objective of this project is to develop a coastal monitoring Network for Puget Sound that meets the goals of the National Water Quality Monitoring Network for U.S. Coastal Waters and their Tributaries, while also being well aligned with existing Federal and cooperative monitoring efforts in the region. A second technical objective is to begin to fill critical monitoring gaps concerning sediment and toxic chemical loads to Puget Sound from large rivers.

The Puyallup River
Continuous-flow centrifuges are used to capture and concentrate suspended sediment from large volumes of river water

Relevance and Benefits - The study addresses the issue of the prevention, reduction and control of toxics and nutrients entering Puget Sound. This issue has been deemed critical in order to improve both human and environmental health in the Puget Sound ecosystem (Puget Sound Partnership, 2008). The study will be closely linked to the U.S. EPA National Estuary Program (NEP), the Northwest Association of Networked Ocean Observing Systems (NANOOS--the Pacific Northwest's regional association of the national Integrated Ocean Observing System IOOS) through the NANOOS Ecosystem Assessment activities related to coastal and estuarine hypoxia. The Network demonstration will be linked to various USGS programs including NAWQA, CHIPS, and the newly proposed Puget Sound Initiative for the NW Area.

Approach - In 2012, Puget Sound was selected as one of two demonstration projects for the National Water Quality Monitoring Network for U.S. Coastal Waters and their Tributaries. Through this demonstration project, and fully coordinated with PSEMP, the USGS has been comparing the monitoring activities in Puget Sound to the sampling design described by the National Water Quality Monitoring Network for U.S. Coastal Waters and their Tributaries.

One of the monitoring gaps identified by PSEMP was an improved understanding of the sediment loads and sediment-associated toxic chemical loads from large rivers to Puget Sound. To address this recognized data gap, the USGS has developed a protocol for the collection of suspended sediment for chemical analysis from large volumes of water using continuous-flow centrifuges. The USGS has been collecting suspended sediment samples from the Puyallup River, the Green/Duwamish River, and the Stillaguamish River over a range of hydrologic conditions for the analysis of suspended-sediment concentration, particle size distribution, and a suite of chemicals of concern, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), chlorinated pesticides, metals, and particulate carbon and nitrogen.

The Puyallup River
A USGS D-96 sampler is deployed on the Duwamish River to collect representative samples of water for sediment and chemical analysis

Co-located with the discrete water quality sampling stations on each river is a USGS stream gaging station transmitting continuous real-time data such as turbidity, stream velocity and discharge. Sampling activities utilize recent advances in hydroacoustic and optical technologies for suspended sediment sampling. For example, the instrumentation at one or more of these stations includes Acoustic Doppler Velocity Meters (ADVMs) for quantifying stream velocity and discharge in tidally-influenced river reaches and providing acoustic backscatter data as a potential sediment surrogate.

Regressions are being developed between the discrete water quality sampling and the continuous turbidity and discharge data to provide estimates of annual sediment loading and suspended-sediment associated chemical loading from large rivers to Puget Sound.

The sediment and chemical concentrations and loading estimates will support Puget Sound restoration efforts including the nearshore of Commencement Bay, source control efforts associated with the Lower Duwamish Waterway Superfund Site, and ecosystem monitoring of the Stillaguamish river and nearshore following the SR-530 landslide near Oso, WA. The USGS has a mobile centrifuge trailer for rapid stream-side deployment at multiple Puget Sound rivers or other water bodies of interest in Washington State.

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