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• 1. [Article] Effects of Climate Change on Water Quality in the Yaquina Estuary, Oregon

  As part of a larger study to examine the effect of climate change (CC) on estuarine resources, we simulated the effect of rising sea level, alterations in river discharge, and increasing atmospheric temperatures ...

  Citation × Citation Citation Abstract Copy Title: Effects of Climate Change on Water Quality in the Yaquina Estuary, Oregon Author: Brown, Cheryl A., Sharp, Darrin, Chang, Heejun, Steele, Madeline Year: 2011 As part of a larger study to examine the effect of climate change (CC) on estuarine resources, we simulated the effect of rising sea level, alterations in river discharge, and increasing atmospheric temperatures on water quality in the Yaquina Estuary. Due to uncertainty in the effects of climate change, initial model simulations were performed for different steady river discharge rates that span the historical range in inflow, and for a range of increases in sea level and atmospheric temperature. Model simulations suggest that in the central portion of the estuary (19 km from mouth), a 60-cm increase in sea level will result in a 2-3 psu change in salinity across a broad range of river discharges. For the oligohaline portion of the estuary, salinity increases associated with a rise in sea level of 60 cm are only apparent at low river discharge rates (< 50 m3 s-1). Simulations suggest that the water temperatures near the mouth of the estuary will decrease due to rising sea level, while water temperatures in upriver portions of the estuary will increase due to rising atmospheric temperatures. We present results which demonstrate how the interaction of changes in river discharge, rising sea level, and atmospheric temperature associated with climate change produce non-linear patterns in the response of estuarine salinity and temperature, which vary with location inside the estuary and season. We also will discuss the importance of presenting results in a manner that incorporates uncertainty in climate projections. Title: Effects of Climate Change on Water Quality in the Yaquina Estuary, Oregon Author: Brown, Cheryl A., Sharp, Darrin, Chang, Heejun, Steele, Madeline Year: 2011 As part of a larger study to examine the effect of climate change (CC) on estuarine resources, we simulated the effect of rising sea level, alterations in river discharge, and increasing atmospheric temperatures on water quality in the Yaquina Estuary. Due to uncertainty in the effects of climate change, initial model simulations were performed for different steady river discharge rates that span the historical range in inflow, and for a range of increases in sea level and atmospheric temperature. Model simulations suggest that in the central portion of the estuary (19 km from mouth), a 60-cm increase in sea level will result in a 2-3 psu change in salinity across a broad range of river discharges. For the oligohaline portion of the estuary, salinity increases associated with a rise in sea level of 60 cm are only apparent at low river discharge rates (< 50 m3 s-1). Simulations suggest that the water temperatures near the mouth of the estuary will decrease due to rising sea level, while water temperatures in upriver portions of the estuary will increase due to rising atmospheric temperatures. We present results which demonstrate how the interaction of changes in river discharge, rising sea level, and atmospheric temperature associated with climate change produce non-linear patterns in the response of estuarine salinity and temperature, which vary with location inside the estuary and season. We also will discuss the importance of presenting results in a manner that incorporates uncertainty in climate projections. Close

• 2. [Article] Climate Change Impact on Drought Risk and Uncertainty in the Willamette River Basin

  Climate change due to global warming could induce more frequent droughts in the Willamette River Basin because less snowfall in winter and earlier snowmelt due to temperature increase may lead to decreases ...

  Citation × Citation Citation Abstract Copy Title: Climate Change Impact on Drought Risk and Uncertainty in the Willamette River Basin Author: Chang, Heejun, Jung, Il-Won Year: 2011 Climate change due to global warming could induce more frequent droughts in the Willamette River Basin because less snowfall in winter and earlier snowmelt due to temperature increase may lead to decreases in spring and summer streamflow. This study examines possible changes in drought risk using two drought indices, Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI). SPI represents a climatological drought index that considers only precipitation change, while SRI is a hydrological drought index that considers water balance change. In rainfall-dominated regions in the Willamette Valley, SPI is a useful drought index. In snow-dominated regions in the High Cascades, SRI can show more realistic drought risk change because SRI can represent snowmelt and geology effects. Our results show that the Willamette Valley is more vulnerable to drought risk than the High Cascades in the 21st century. SPI shows increasing frequency and intensity of short-term drought over the whole Willamette River basin due to summer precipitation decrease, while SRI in the High Cascades shows no change because the High Cascades have young permeable volcanic rocks and gentle slopes, which create a deep groundwater system. Additionally, the frequency of short-term extreme drought, such as droughts lasting 1 to 3 months, is projected to increase in the Willamette Valley, but long-term extreme droughts are not expected to change significantly. The increase in short-term extreme droughts is attributed to decreases in summer precipitation, and the lack of change in long-term extreme droughts is caused by increased winter runoff prompted by earlier snowmelt and winter precipitation increases. Title: Climate Change Impact on Drought Risk and Uncertainty in the Willamette River Basin Author: Chang, Heejun, Jung, Il-Won Year: 2011 Climate change due to global warming could induce more frequent droughts in the Willamette River Basin because less snowfall in winter and earlier snowmelt due to temperature increase may lead to decreases in spring and summer streamflow. This study examines possible changes in drought risk using two drought indices, Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI). SPI represents a climatological drought index that considers only precipitation change, while SRI is a hydrological drought index that considers water balance change. In rainfall-dominated regions in the Willamette Valley, SPI is a useful drought index. In snow-dominated regions in the High Cascades, SRI can show more realistic drought risk change because SRI can represent snowmelt and geology effects. Our results show that the Willamette Valley is more vulnerable to drought risk than the High Cascades in the 21st century. SPI shows increasing frequency and intensity of short-term drought over the whole Willamette River basin due to summer precipitation decrease, while SRI in the High Cascades shows no change because the High Cascades have young permeable volcanic rocks and gentle slopes, which create a deep groundwater system. Additionally, the frequency of short-term extreme drought, such as droughts lasting 1 to 3 months, is projected to increase in the Willamette Valley, but long-term extreme droughts are not expected to change significantly. The increase in short-term extreme droughts is attributed to decreases in summer precipitation, and the lack of change in long-term extreme droughts is caused by increased winter runoff prompted by earlier snowmelt and winter precipitation increases. Close

• 3. [Article] Climate Change and Shifts in Water Related Ecosystem Services in the Tualatin and Yamhill River Basins

  Water related ecosystem services (WES), such as flow regulation, drinking water supply, temperature regulation, and water recreational activities, are affected by anthropogenic climate change. Forecasting ...

  Citation × Citation Citation Abstract Copy Title: Climate Change and Shifts in Water Related Ecosystem Services in the Tualatin and Yamhill River Basins Author: Chang, Heejun, Anthony, Terrance, Ennaanay, Driss, Sharma, Manu Year: 2011 Water related ecosystem services (WES), such as flow regulation, drinking water supply, temperature regulation, and water recreational activities, are affected by anthropogenic climate change. Forecasting potential shifts in such WES is critical to identifying the form and magnitude of likely impacts. We quantified the levels and values of WES under multiple climate change scenarios in the two watersheds located in the Portland metropolitan area, Oregon, USA using the combination of a hydrologic model Better Assessment Science Integrating point and Non-point Sources - Soil and Water Assessment Tool (BASINS-SWAT) and an ecosystem evaluation model ? Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). Using the Intergovernmental Panel on Climate Change?s AR4 climate change simulation results, we found that there is a slight relative increase in annual water yield, sediment yield, and dissolved phosphorus, but storm peak management does not change substantially by the 2050s. Spatial analysis shows that the locations of hot and cold spots remain relatively stable. It is also shown that there are high spatial and temporal uncertainties associated with climate change projections due to variations in precipitation projections toward the middle of the 21st century. The findings of our study provide useful information for water and land managers in identifying target areas for conservation to best sustain WES provision, use, and value under a range of climate change scenarios. Title: Climate Change and Shifts in Water Related Ecosystem Services in the Tualatin and Yamhill River Basins Author: Chang, Heejun, Anthony, Terrance, Ennaanay, Driss, Sharma, Manu Year: 2011 Water related ecosystem services (WES), such as flow regulation, drinking water supply, temperature regulation, and water recreational activities, are affected by anthropogenic climate change. Forecasting potential shifts in such WES is critical to identifying the form and magnitude of likely impacts. We quantified the levels and values of WES under multiple climate change scenarios in the two watersheds located in the Portland metropolitan area, Oregon, USA using the combination of a hydrologic model Better Assessment Science Integrating point and Non-point Sources - Soil and Water Assessment Tool (BASINS-SWAT) and an ecosystem evaluation model ? Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). Using the Intergovernmental Panel on Climate Change?s AR4 climate change simulation results, we found that there is a slight relative increase in annual water yield, sediment yield, and dissolved phosphorus, but storm peak management does not change substantially by the 2050s. Spatial analysis shows that the locations of hot and cold spots remain relatively stable. It is also shown that there are high spatial and temporal uncertainties associated with climate change projections due to variations in precipitation projections toward the middle of the 21st century. The findings of our study provide useful information for water and land managers in identifying target areas for conservation to best sustain WES provision, use, and value under a range of climate change scenarios. Close

• 4. [Article] Spatial and Temporal Patterns in the Influence of Land Use on Water Quality in Five Portland Area Creeks Representing Differing Levels of Urbanization

  While the negative effects of urban development on freshwater systems are well documented, impacts of human disturbance on water quality vary depending on land cover, local climate, and temporal and spatial ...

  Citation × Citation Citation Abstract Copy Title: Spatial and Temporal Patterns in the Influence of Land Use on Water Quality in Five Portland Area Creeks Representing Differing Levels of Urbanization Author: Chang, Heejun, Steele, Madeline, Bonak, Zoe Year: 2011 While the negative effects of urban development on freshwater systems are well documented, impacts of human disturbance on water quality vary depending on land cover, local climate, and temporal and spatial scales of analysis. To better understand this variation, we analyzed water quality data for a total of 15 sites from six Portland, Oregon area creeks at multiple spatial and temporal scales. The creeks are characterized by differing levels of urban development, from relatively pristine to highly developed. More than ten years of monthly data gathered by the Portland Bureau of Environmental Services were used to analyze temporal trends, and five years of these data were used to analyze spatial patterns. Analytes of interest were specific conductivity, dissolved oxygen, nitrate, phosphorus, total suspended solids, and temperature. These variables were compared to contributing area land use metrics at three scales: full contributing sub-basin, 100-meter riparian corridor, and 50-meter riparian corridor. We calculated seven land use metrics: population density, street density, Green Streets density, percent low density development, percent high density development, percent forested area, and percent agriculture. We found Spearman?s Rank Correlation Coefficient between the water quality parameters for annual, wet, and dry seasons and the land use metrics at each spatial scale for each parameter. The same water quality data were also analyzed for correlations to same day as well as 3-, 5-, and 7-day antecedent precipitation to examine relationships between water quality and environmental moisture conditions. Additionally, we used a Seasonal Kendall test to search for temporal trends. For each site included in the temporal analysis, changes in population density and street density metrics from 2000 to 2010 were compared to changes in water quality. Results vary across space, but generally confirm that urban development has negatively impacted the creeks. Specific conductivity, total suspended solids and nitrate are particularly sensitive to the level of urban development, especially following rain events. This work will help to better understand and mitigate urbanization impacts on freshwater systems. Title: Spatial and Temporal Patterns in the Influence of Land Use on Water Quality in Five Portland Area Creeks Representing Differing Levels of Urbanization Author: Chang, Heejun, Steele, Madeline, Bonak, Zoe Year: 2011 While the negative effects of urban development on freshwater systems are well documented, impacts of human disturbance on water quality vary depending on land cover, local climate, and temporal and spatial scales of analysis. To better understand this variation, we analyzed water quality data for a total of 15 sites from six Portland, Oregon area creeks at multiple spatial and temporal scales. The creeks are characterized by differing levels of urban development, from relatively pristine to highly developed. More than ten years of monthly data gathered by the Portland Bureau of Environmental Services were used to analyze temporal trends, and five years of these data were used to analyze spatial patterns. Analytes of interest were specific conductivity, dissolved oxygen, nitrate, phosphorus, total suspended solids, and temperature. These variables were compared to contributing area land use metrics at three scales: full contributing sub-basin, 100-meter riparian corridor, and 50-meter riparian corridor. We calculated seven land use metrics: population density, street density, Green Streets density, percent low density development, percent high density development, percent forested area, and percent agriculture. We found Spearman?s Rank Correlation Coefficient between the water quality parameters for annual, wet, and dry seasons and the land use metrics at each spatial scale for each parameter. The same water quality data were also analyzed for correlations to same day as well as 3-, 5-, and 7-day antecedent precipitation to examine relationships between water quality and environmental moisture conditions. Additionally, we used a Seasonal Kendall test to search for temporal trends. For each site included in the temporal analysis, changes in population density and street density metrics from 2000 to 2010 were compared to changes in water quality. Results vary across space, but generally confirm that urban development has negatively impacted the creeks. Specific conductivity, total suspended solids and nitrate are particularly sensitive to the level of urban development, especially following rain events. This work will help to better understand and mitigate urbanization impacts on freshwater systems. Close