2001 Progress Report: Application of Remotely-sensed Data To Regional Analysis and Assessment of Stream Temperature in the Pacific NorthwestEPA Grant Number: R827675
Title: Application of Remotely-sensed Data To Regional Analysis and Assessment of Stream Temperature in the Pacific Northwest
Investigators: Burges, Stephen J. , Booth, Derek B. , Gillespie, Alan R.
Institution: University of Washington - Seattle
EPA Project Officer: Packard, Benjamin H
Project Period: April 1, 2000 through March 31, 2003 (Extended to March 31, 2004)
Project Period Covered by this Report: April 1, 2001 through March 31, 2002
Project Amount: $998,395
RFA: Regional Scale Analysis and Assessment (1999) RFA Text | Recipients Lists
Research Category: Ecosystems , Ecological Indicators/Assessment/Restoration
The objectives of this research project are to: (1) develop efficient methods for regional assessments of stream temperature; and (2) demonstrate how these methods can be applied to assess effects of land use on stream temperature.
During the second year of the project, the number of in situ temperature monitoring sites was expanded, and a large volume of thermal infrared images was collected from plane and satellite-based imagers. Extra ground observations were collected in conjunction with the remote sensing images to provide ground truth for the purpose of calibration and validation. Processing and analysis of both the remote sensing and ground-based observations is in progress.
Field Analyses. Linear interpolations have been used to apply the logged temperatures along the stream network (see Figure 1a). A similar plot was created based on an independent survey of temperatures in the Puget Sound Drainage Basin (see Figure 1b). This involved more measurement sites in Soos Creek, but collected temperatures for only 1 day. Differences in the observed temperature pattern will be explored with further field observations to identify possible causes.
Statistical analysis of the water temperature time-series and their spatial relationships also is underway on the data collected from Soos Creek. It is possible that diurnal or monthly anomalies in the temperature cycle at a given location may help identify regions of increased importance for understanding the basin controls on stream temperatures.
Remotely Sensed Imagery. Preliminary work is underway to extract along-stream temperatures from Modis/Aster (MASTER) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. Difficulties in this process can be seen in Figure 2, where the Green River through Flaming Geyser State Park is clearly visible in the 5 meter resolution MASTER image. It is much more difficult to identify the river in the 90 meter resolution ASTER image. Minimal effort has been put into georeferencing the images, as can be seen from the differences between the orthophoto and the MASTER image. Because georeferencing can change the data in the thermal image by averaging and resampling, most of our processing will make use of the raw images. The finished product will be georeferenced if the spatial location data is critical to the study.
Figure 1. Linearly Interpolated Stream Temperatures for Soos Creek on August 1, 2001. Temperatures are based on (a) in situ data loggers and (b) independent survey. Figure 1 (c) Shows the distribution of temperature differences logger minus survey values. Black circles indicate measurement locations.
Kay (2002) conducted a study of various methods of correcting ASTER and MASTER data for the effects of atmospheric moisture. The study made use of ground truth observations and images collected during the Summer 2001. Kay found that atmospheric moisture fields from the MM5 regional atmosphere model provided a better correction than any of our in-field measurement techniques. The atmospheric correction techniques developed and applied in her thesis will be used for all thermal infrared images in this study.
Figure 2. Images of Flaming Geyser State Park. Figure (a) ASTER 90 meter resolution uncorrected radiant temperatures, (b) MASTER 5 meters resolution uncorrected radiant temperatures, and (c) USGS orthophoto with two in-situ logger locations marked. Thin white and red lines bound the approximate stream path by +/- 200 meters.
Fieldwork for the next reporting period will focus on areas of interest or concern identified through the in situ logger data and the thermal infrared images. Remote sensing analysis will focus on obtaining usable maps of stream temperatures. Some of the steps involved include:
· An intensive survey of stream temperatures in the Soos Creek Basin to identify areas of significant groundwater recharge.
· An intensive survey of temperatures and river conditions in the Yakima River Canyon region to help interpret and analyze the MASTER images.
· Collection of one or two images from the Hanford Reach on the Columbia to demonstrate the applicability of ASTER TIR images when the stream is sufficiently wide to contain full pixels.
· Processing the Green River MASTER images into a coherent regional map from which stream temperatures can be derived. The methods used for this processing will be applied to data from the Yakima and Cedar Rivers.
· Continued work on subpixel unmixing to identify the minimum stream width required to determine water temperatures from ASTER images.
· Continued work on the effects of scale on the observed radiance. This will involve rescaling the fine resolution to the courser resolution of ASTER.
· Further analysis of error propagation through the observed system: ground observations through satellite images.