River and wastewater effluent nutrient inputs into the Salish Sea model

The Salish Sea Model was developed by Pacific Northwest National Laboratories in collaboration with the Washington State Department of Ecology. The model is being used to evaluate the relative effects of human nutrient inputs and climate influences on the occurrence of low dissolved oxygen (DO) levels throughout the Salish Sea, with a focus on evaluating water quality in Puget Sound. Developing an inventory of point and nonpoint source nutrient inputs entering the Salish Sea is essential to the model’s development. This presentation will present some significant updates to nutrient inputs developed for the Salish Sea Model from wastewater treatment plants (WWTPs) and rivers. Using a combination of monitoring data and statistical methods, we now have a daily time-series of river and wastewater treatment plant effluent flow and nutrient inputs throughout the Salish Sea from 1999 through mid-2017. These nutrient loading estimates are some of most comprehensive estimates developed for the region to date, allowing us to: identify the relative contributions of nutrient loads from WWTPs and rivers, recognize spatial patterns in loads being delivered to different basins of Puget Sound, and describe the seasonal nature of these loads. We have also developed estimates of 1) reference conditions, and 2) future conditions. The reference conditions are aimed at representing, as close as is feasible, what nutrient inputs would be in the absence of local human activities within the Puget Sound region. Future conditions represent nutrient inputs in 2040 while taking into population growth and climate change. These nutrient inputs are essential in the application of the Salish Sea Model to simulate existing, reference, and future conditions in the Salish Sea and to help guide the Puget Sound Nutrient Reduction Strategy

Nitrogen in Puget Sound: a story map

“Nitrogen in Puget Sound” is an ArcGIS Online Story Map developed by scientists at the Washington State Department of Ecology (Ecology). The Story Map is an interactive communication tool that uses a combination of maps, graphics, and text showcasing the state of the science and available data and resources used to understand nitrogen in Puget Sound. It was created to appeal to a broad audience, explaining nitrogen pollution and its effects at a basic level, as well as providing more detailed information for researchers and organizations interested in exploring available data and resources. The Story Map begins with an overview of eutrophication that explains how excess nitrogen influences algal blooms and low dissolved oxygen levels in Puget Sound. The interactive interface then allows the user to explore the various sources and pathways of nitrogen into Puget Sound using a series of maps and graphics, including a visual representation quantifying wastewater treatment plant and river nitrogen loads. It describes Ecology’s nitrogen monitoring programs within Puget Sound marine waters and its watersheds. The Story Map also highlights river and marine nitrogen trends and current research efforts studying changing nitrogen levels in and around Puget Sound. This Story Map will be periodically updated with new ongoing studies and scientific findings. It will act as an evolving communication tool explaining our understanding of nitrogen and eutrophication in Puget Sound. This presentation will tell the story of nitrogen in Puget Sound by walking the audience through the Story Map itself. It will also provide the audience with an introduction on how to utilize the Story Map to explore more data and information relating to nitrogen in Puget Sound

Predicting Puget Sound\u27s organic carbon—and why we need enhanced monitoring

How much has the total organic carbon deposited into the water column and sediments of Puget Sound increased due to human activity? How has that increase impacted sediment flux rates, hypoxia and the carbonate system balance? These are two important questions with answers that are still elusive. To date, both marine and freshwater organic carbon measurements in Puget Sound are relatively sparse. In the long-term, inadequate temporal and spatial organic carbon data may lead to an incomplete and incoherent understanding of carbon cycling in the Puget Sound. The Salish Sea Model, developed by PNNL in collaboration with Department of Ecology, provides insights into the extent of organic carbon loading and concentrations in the Puget Sound. Model scenario runs indicate that autochtonous organic detritus derived from increased productivity related to human nitrogen loading, combined with allochthonous carbon from direct loading due to human activity, has resulted in an increased loading of non-algal organic carbon ranging from 20 and 25% in a significant portion of the Puget Sound’s main basin, as well as in multiple inlets. This increase in organic carbon is expected to have an impact in heterotrophic respiration rates and eutrophication. This presentation will focus on loading rates and predicted organic carbon concentrations throughout the Puget Sound using the Salish Sea Model. It will point to the need for enhanced dissolved and particulate organic carbon measurements in our region, as well as basin-scale measurements of respiration rates, to optimize the alignment of on-going, long term monitoring and modeling efforts

Salish Sea model: ocean acidification module and the response to regional anthropogenic nutrient sources

Several monitoring programs indicate the presence of lower pH and related changes in carbonate system variables in the Salish Sea. This project expands the existing Salish Sea Model to evaluate carbonate system variables. This project quantifies the influences of regional nutrient sources on acidification. The model accounts for Pacific Ocean upwelled water, regional human nutrient contributions, and air emissions around the Salish Sea. This effort also identifies geographical areas and seasons experiencing greater influence from regional sources of nutrients to Salish Sea waters. Results from this effort indicate that increased dissolved inorganic nitrogen, phytoplankton biomass, and non-algal organic carbon caused by regional anthropogenic nutrient sources can constitute significant contributors to acidification in the Salish Sea

Sensitivity of the regional ocean acidification and carbonate system in Puget Sound to ocean and freshwater inputs

While ocean acidification was first investigated as a global phenomenon, coastal acidification has received significant attention in recent years, as its impacts have been felt by different socio-economic sectors (e.g., high mortality of shellfish larvae in aquaculture farms). As a region that connects land and ocean, the Salish Sea (consisting of Puget Sound and the Straits of Juan de Fuca and Georgia) receives inputs from many different sources (rivers, wastewater treatment plants, industrial waste treatment facilities, etc.), making these coastal waters vulnerable to acidification. Moreover, the lowering of pH in the Northeast Pacific Ocean also affects the Salish Sea, as more acidic waters get transported into the bottom waters of the straits and estuaries. Here, we use a numerical ocean model of the Salish Sea to improve our understanding of the carbonate system in Puget Sound; in particular, we studied the sensitivity of carbonate variables (e.g., dissolved inorganic carbon, total alkalinity, pH, saturation state of aragonite) to ocean and freshwater inputs. The model is the updated version of our FVCOM-ICM framework (Finite Volume Community Ocean Model coupled to the water-quality model CE-QUAL-ICM), now with carbonate-system and sediment modules. Sensitivity experiments altering concentrations at the open boundaries and freshwater sources indicate that not only ocean conditions entering the Strait of Juan de Fuca, but also the dilution of carbonate variables by freshwater sources, are key drivers of the carbonate system in Puget Sound. This work is an update from our presentation in the Salish Sea Conference 2016, showing the final results from our model experiments

Relative influences of human nutrient sources, the Pacific Ocean, and climate change on Salish Sea dissolved oxygen through 2070

The Department of Ecology and Pacific Northwest National Laboratory evaluated future dissolved oxygen scenarios within the Salish Sea using a circulation and water quality model of Puget Sound, the Strait of Georgia, and the Strait of Juan de Fuca. A recently published report summarizes relative contributions of human nutrient sources, the Pacific Ocean, and climate factors on dissolved oxygen both now and through 2070. Human nitrogen contributions from the U.S. and Canada to the Salish Sea have the greatest impacts on dissolved oxygen in portions of South and Central Puget Sound. Marine point sources cause greater impacts on oxygen than human influences on river inflows now and into the future. Most of the Salish Sea reflects a relatively low impact from human sources, although that will increase as loads increase. The Pacific Ocean strongly influences dissolved oxygen concentrations under both current and future conditions. If 50-year declining trends in North Pacific Ocean dissolved oxygen continue, Salish Sea dissolved oxygen would decline far more than from human nutrient loads. Climate change will alter the timing of freshwater flow reaching the Salish Sea, as provided by the University of Washington Climate Impacts Group. This would alter estuarine circulation patterns, potentially worsening impacts in some regions but lessening others. Future air temperature increases would further decrease dissolved oxygen, particularly in shallow inlets. This is the first assessment of how Salish Sea dissolved oxygen concentrations respond to population increases, ocean conditions, and climate change. Additional analyses are needed to link sediment-water interactions and increase scientific certainty

An overview of the Salish Sea model: existence of reflux mixing and recurring hypoxia

An improved version of a diagnostic hydrodynamic and biogeochemical model (nutrients, phytoplankton, carbon, dissolved oxygen, pH) of the Salish Sea has been developed with the ability to simulate characteristic circulation and water quality features. Notable improvements include expansion of the model domain beyond the Salish Sea, encompassing Vancouver Island and out to the continental shelf boundary. In this talk we present an overview of the model setup describing the model domain coverage, modeling framework, development of boundary conditions, and tidal, riverine, wastewater, and meteorological inputs. Ability of the model to reproduce known circulation features within the Salish Sea is highlighted. The existence of a strong circulation cell between Admiralty Inlet and Tacoma Narrows sills is discussed reflecting on the implications of reflux flow back into Central Puget Sound. Simulation of sediment diagenesis processes and coupling to the water column provides improved model performance that is responsive to land based and oceanic nutrient loads. This coupling is also credited with the improvements in simulation of hypoxia in selected sub-basins within the Salish Sea such as Hood Canal, Penn Cove, and East Sound. Using tidally averaged velocity profiles from the Salish Sea Model, we demonstrate that Hood Canal sub-basin, with a sill near the mouth, a deep channel configuration, and a freshwater source at its landward end, behaves like a classic-fjord. The dominant and notable feature is that circulation and exchange in the inner basin of Hood Canal occurs in the upper 40% of the water column while the lower 60% remains poorly mixed and relatively isolated from the exchange. This results in conditions well suited for the settling of organic matter and long residence times \u3e230 days, and causes recurring hypoxia in the inner regions of Hood Canal in late fall

Future Nitrogen Loading to the Salish Sea: Population Growth, Land Use Change, and Climate Change

Estimates of future nitrogen loading to the Salish Sea from watershed inflows and marine point sources were developed for 2020, 2040 and 2070. This is the first compilation of future nitrogen loads to the Salish Sea, taking into account population growth, land use change, and climate change. Future nitrogen loading estimates were used as forcings for a three-dimensional circulation and dissolved oxygen model developed by Pacific Northwest National Laboratories and the Washington State Department of Ecology. Future nitrogen loads from watershed inflows are estimated to increase due to a general shift in land use across the region in the form of decreasing forested and agricultural land and increasing developed land. Future watershed nitrogen loads will also be influenced by changes in streamflows due to the effects of climate change on regional hydrology. These changes include increases in peak streamflow and decreases in summer baseflow for some rivers, resulting in changes in the magnitude and timing of nitrogen delivery to the Salish Sea. Future nitrogen loads from marine point sources, primarily wastewater treatment plants, are expected to double by 2070 due to regional population growth. The adoption of biological nutrient removal treatment technologies has the potential to more than offset this increase in loading by reducing effluent nitrogen concentrations. Limited long-term historic data suggests declining oxygen and increasing nitrogen levels in the Pacific Ocean near the open boundary. Since future estimates of Pacific Ocean conditions do not exist, we extrapolated these historic trends into the future to estimate future conditions at the open boundary, but this estimate remains highly uncertain. When applied to model scenarios, these future loading estimates allowed us to evaluate the relative effects of future human nutrient loads, climate influences, and Pacific Ocean conditions on the occurrence of low dissolved oxygen levels throughout the Salish Sea

Virtual simulations of potential vessel discharges in Puget Sound and the Puget Sound No Discharge Zone

The Washington State Department of Ecology (Ecology) evaluated the potential transport, dispersion and dilution of potential vessel sewer discharges within the draft proposed Puget Sound No Discharge Zone (NDZ). These model simulations included potential vessel sewer discharges at six locations in Puget Sound along major shipping routes. Results are presented as virtual animations of surface concentrations, allowing us to visualize the transport, circulation, and dilution of these discharges over the course of several days. Ecology and Pacific Northwest National Laboratory jointly developed a three-dimensional hydrodynamic FVCOM (Finite Volume Coastal Ocean Model) computer model of the Salish Sea. This model is forced by tides at the mouth of the Strait of Juan de Fuca, meteorological boundary conditions, and freshwater inputs from the US and Canada that induce estuarine circulation. The model has been calibrated to water surface elevations and profiles for the year 2006. Potential discharges were simulated using the sediment module of the model, with zero settling velocity. The model allows us to evaluate connectivity between points of discharge and other parts of Puget Sound, and calculate the degree of dilution that has occurred before discharges reach specific geographic points of interest. Model simulations show the strong influence of tidal cycles on the movement of vessel sewer discharge. At some locations, freshwater inflows into Puget Sound from rivers also influence the movement and dilution. We found that there are several periods when fecal coliform bacteria concentrations typical of raw sewage would not meet the water quality standard based on dilution alone. Since its development, Ecology has used the model for a number of applications to evaluate how potential point and nonpoint source discharges (e.g. wastewater facilities, vessel sewage discharges, and rivers) circulate once released into marine waters

Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

Abstract Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid FiniteVolume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5-20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. By late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific Ocean