Monitoring sediment transport and aquatic macroinvertebrate communities in the Willamette River basin
The U.S. Geological Survey is listening to rivers to understand how flows transport bedload sediment, which is fundamental to ecosystem structure and health.
A U.S. Geological Survey (USGS) hydrologist and an Assistant Professor of Electrical Engineering at Portland State University (PSU) teamed up to develop passive acoustic monitors, or hydrophones, in a novel approach to monitoring river bedload transport. Bedload is typically the sand, gravels, and cobbles that move along the riverbed. Four hydrophones were deployed in 2023 in two tributaries of the Willamette River: the North Santiam and McKenzie Rivers. Every 15 to 30 minutes, the hydrophones record 1-minute audio files of water and any bedload being moved by the current. Scientists can then analyze the specific frequencies associated with moving and colliding rocks to determine the streamflows needed to initiate the movement of gravel and cobbles in each studied reach river.
Measuring bedload transport directly is hard because it only happens during high-streamflow events and requires a crew of 3-6 people to safely operate the heavy-duty specialized equipment, which can be expensive lost or destroyed in these types of conditions. Hydrophones offer a passive and more affordable alternative to traditional bedload monitoring.
Why is monitoring bedload important?
In gravel and cobble-bed rivers, like those downstream of large dams operated by the U.S. Army Corps of Engineers (USACE) as part of the Willamette Valley Project, coarse bed sediment helps define channel form and plays a crucial role in various thermal, ecological, and chemical processes. Distribution and mobilization of coarse bed sediment is largely determined by the magnitude of streamflows, which are partially controlled by upstream dams. Understanding which streamflows mobilize bedload and how often they occur helps inform how factors like river ecology are influenced by streamflow.
One such ecological example is that bedload transport and its distribution throughout the river are key drivers in structuring aquatic macroinvertebrate communities. Aquatic macroinvertebrates are small critters without backbones that live in water, such as insects, snails, worms, and crustaceans, and they serve multiple functions in freshwater ecosystems. They eat both live and decomposing organic material, and are prey for fish, birds, and other animals. To explore the relationship between these organisms and river bedload, the USGS also implemented a macroinvertebrate monitoring program across nine locations in 2022 and 2023. During the summer, scientists sampled invertebrates in several locations in the Willamette River and its tributaries comparing their distribution to the physical properties of bedload sediment. The data collected is used to examine patterns of invertebrate communities and biomass, and how they respond to streamflow and sediment characteristics. This information can be used to develop computer models simulating how changes in streamflow impact the aquatic ecosystem.
Graph of streamflow over time at North Santiam at Greens Bridge (14184100):
Recording 1:
Recording 2:
Program information
Initial hydrophone development was funded by the USACE to help inform The Sustainable Rivers Program (SRP). The SRP is a partnership between the USACE and The Nature Conservancy to adaptively modify operations at dams with the goal of enhancing habitat conditions for the plants and animals that depend on river flows downstream. The Willamette SRP began in 2007 through a series of stakeholder-driven environmental flow workshops, which resulted in a series of environmental flow recommendations for Willamette tributaries downstream of USACE projects. Of the 63 Willamette River Basin SRP flow recommendations identified by stakeholders, 33 relate to bed sediment mobilization to achieve various ecological outcomes.
To inform the adaptive management cycle, the USGS developed and implemented this monitoring program to examine (a) flows required to mobilize and transport coarse bed sediment and (b) how sediment mobilization affects ecological indicators, specifically aquatic macroinvertebrate populations.
This work was expanded through a seed grant from the USGS-Portland State Partnership (UPP). The UPP aims to be a model partnership that redefines the way universities and federal agencies collaborate, advance scientific research, and develop the next generation of connected scientists, stewards, and advocates for our hydrologic and geologic resources. UPP Seed Grants are awarded to USGS and PSU researchers interested in pursuing innovative joint research.
The U.S. Geological Survey is listening to rivers to understand how flows transport bedload sediment, which is fundamental to ecosystem structure and health.
A U.S. Geological Survey (USGS) hydrologist and an Assistant Professor of Electrical Engineering at Portland State University (PSU) teamed up to develop passive acoustic monitors, or hydrophones, in a novel approach to monitoring river bedload transport. Bedload is typically the sand, gravels, and cobbles that move along the riverbed. Four hydrophones were deployed in 2023 in two tributaries of the Willamette River: the North Santiam and McKenzie Rivers. Every 15 to 30 minutes, the hydrophones record 1-minute audio files of water and any bedload being moved by the current. Scientists can then analyze the specific frequencies associated with moving and colliding rocks to determine the streamflows needed to initiate the movement of gravel and cobbles in each studied reach river.
Measuring bedload transport directly is hard because it only happens during high-streamflow events and requires a crew of 3-6 people to safely operate the heavy-duty specialized equipment, which can be expensive lost or destroyed in these types of conditions. Hydrophones offer a passive and more affordable alternative to traditional bedload monitoring.
Why is monitoring bedload important?
In gravel and cobble-bed rivers, like those downstream of large dams operated by the U.S. Army Corps of Engineers (USACE) as part of the Willamette Valley Project, coarse bed sediment helps define channel form and plays a crucial role in various thermal, ecological, and chemical processes. Distribution and mobilization of coarse bed sediment is largely determined by the magnitude of streamflows, which are partially controlled by upstream dams. Understanding which streamflows mobilize bedload and how often they occur helps inform how factors like river ecology are influenced by streamflow.
One such ecological example is that bedload transport and its distribution throughout the river are key drivers in structuring aquatic macroinvertebrate communities. Aquatic macroinvertebrates are small critters without backbones that live in water, such as insects, snails, worms, and crustaceans, and they serve multiple functions in freshwater ecosystems. They eat both live and decomposing organic material, and are prey for fish, birds, and other animals. To explore the relationship between these organisms and river bedload, the USGS also implemented a macroinvertebrate monitoring program across nine locations in 2022 and 2023. During the summer, scientists sampled invertebrates in several locations in the Willamette River and its tributaries comparing their distribution to the physical properties of bedload sediment. The data collected is used to examine patterns of invertebrate communities and biomass, and how they respond to streamflow and sediment characteristics. This information can be used to develop computer models simulating how changes in streamflow impact the aquatic ecosystem.
Graph of streamflow over time at North Santiam at Greens Bridge (14184100):
Recording 1:
Recording 2:
Program information
Initial hydrophone development was funded by the USACE to help inform The Sustainable Rivers Program (SRP). The SRP is a partnership between the USACE and The Nature Conservancy to adaptively modify operations at dams with the goal of enhancing habitat conditions for the plants and animals that depend on river flows downstream. The Willamette SRP began in 2007 through a series of stakeholder-driven environmental flow workshops, which resulted in a series of environmental flow recommendations for Willamette tributaries downstream of USACE projects. Of the 63 Willamette River Basin SRP flow recommendations identified by stakeholders, 33 relate to bed sediment mobilization to achieve various ecological outcomes.
To inform the adaptive management cycle, the USGS developed and implemented this monitoring program to examine (a) flows required to mobilize and transport coarse bed sediment and (b) how sediment mobilization affects ecological indicators, specifically aquatic macroinvertebrate populations.
This work was expanded through a seed grant from the USGS-Portland State Partnership (UPP). The UPP aims to be a model partnership that redefines the way universities and federal agencies collaborate, advance scientific research, and develop the next generation of connected scientists, stewards, and advocates for our hydrologic and geologic resources. UPP Seed Grants are awarded to USGS and PSU researchers interested in pursuing innovative joint research.