Abstract Title

Session S-02A: Future Salish Sea Water Quality

Proposed Abstract Title

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

Keywords

Marine Water Quality

Location

Room 615-616-617

Start Date

30-4-2014 1:30 PM

End Date

30-4-2014 3:00 PM

Description

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.

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Apr 30th, 1:30 PM Apr 30th, 3:00 PM

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

Room 615-616-617

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.