Willamette River Bathymetric Survey --
Willamette River Water Temperature Investigation

Home | Overview | Willamette bathymetric survey | Dye studies | Width survey | N. Santiam temperature model

Overview

As part of the U.S. Geological Survey's support of the technical analyses and temperature model development for Willamette Basin streams, U.S. Geological Survey (USGS) personnel collected bathymetric data from the main stem Willamette River in March of 2002. These cross-sectional and longitudinal profile data were important in filling a large data gap and were instrumental in the creation of a representative model grid for the Willamette River. After all, to simulate temperature in the Willamette River, one must first know how much water is in the system, and the surface area through which heat is exchanged between the river and the atmosphere.

Approach

Bathymetric data form the basis of a model's representation of the river channel. Accurate bathymetric data are needed to ensure accurate and reliable streamflow and time-of-travel predictions. Some bathymetric data were available for most of the Willamette River reaches to be modeled. HEC-2 cross-sections, typically used for flood studies, were available for about half of the main stem Willamette River and for the Santiam River system, but these data were somewhat dated. Cross-sectional data also were available at streamgaging sites or from time-of-travel studies.

Detailed cross-sectional and longitudinal depth-profile data were collected, referenced to an elevation datum, in the main-stem Willamette River from Harrisburg (approximately, river mile [RM] 161) to Willamette Falls (RM 26.5), focusing on reaches where HEC-2 cross-sectional data were not available (RMs 175-121, 114-89, 77-74, 42-28). The longitudinal depth-profile data are useful in identifying all of the shallow and deep areas of the river channel, allowing interpolated cross-sections to be created for a model grid that captures these characteristics of the channel.

Cross-sectional data were collected approximately every mile along the profile of the river. Cross-sectional data were collected using an acoustic doppler current profiler (ADCP). When using an ADCP to measure streamflow, the standard protocol calls for six traversals of the river's width to minimize error in the streamflow measurement. One or two traversals, however, is adequate to define the physical cross-section and obtain a general measurement of the streamflow at each site. Detailed streamflow measurements (six passes with the ADCP) were performed every 3 to 5 miles. Also every 3 to 5 miles, the crew collected additional cross-sectional information above the river surface by surveying both river banks.

All cross-sectional and longitudinal surface profile data were referenced to a reliable and accurate elevation datum through advanced GPS and surveying techniques. A separate crew spent several days surveying about a dozen reference points along the river, before the boat crew began its work. The reference points were marked with stakes; their latitude, longitude, and elevation were logged for use by the boat crew. These reference points were surveyed using survey-grade GPS equipment and standard surveying protocols. Assistance with this task was provided by the surveying experts at the USGS Cascades Volcano Observatory. Each reference point was found and surveyed by the boat crew, so that the water surface elevation of the river and all cross-sectional data would have a reliable elevation datum.

Data Analysis

The cross-sections and longitudinal profile data were referenced to a vertical datum using the locational data at the surveyed reference points. Between these locations, the water surface of the river was assumed to decrease linearly in a downstream direction. As a result, the data are most accurate in the vicinity of the reference locations, and may err most with increasing distance from such locations.

The methods used to work up the bathymetric data are described in a methods document [PDF, 388 Kb].

Download Data

Two versions of these data are available. The first set, labeled "depths" contains just the raw depth data from the longitudinal profiles and cross-sections, as well as the discharge measurements and documentation of the methods used. The second set, labeled "elevations" are the same data after being converted to elevations, referenced to a single vertical datum. It is these elevation data that were needed to construct the grid for the Willamette River temperature model. Some people may just want the depth data, however, so those data are made available as well. Each dataset is broken into two pieces. In addition to data from the Willamette River, data were collected from the lower 6 miles of the Santiam River.

Home | Overview | Willamette bathymetric survey | Dye studies | Width survey | N. Santiam temperature model

Questions? Comments? For more information about this project, contact:

Stewart Rounds
U.S. Geological Survey
2130 SW 5th Avenue
Portland, OR 97201
503-251-3280
sarounds@usgs.gov

Oregon Water Science Center Home page
Oregon Water Science Center Hydrologic Studies page

U.S. Department of the Interior | U.S. Geological Survey URL: https://or.water.usgs.gov/projs_dir/will_tmdl/main_stem_bth.html Maintainer: Oregon Webteam Last modified Wednesday - Dec 21, 2016 at 18:57:36 EST Accessibility FOIA Privacy Policies and Notices