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An initial validation of Landsat 5 and 7 derived surface water temperature for U.S. lakes, reservoirs, and estuaries
Schaeffer, B., J. Iiames, J. Dwyer, E. Urquhart, W. Salls, J. Rover, AND B. Seegers. An initial validation of Landsat 5 and 7 derived surface water temperature for U.S. lakes, reservoirs, and estuaries. INTERNATIONAL JOURNAL OF REMOTE SENSING. Taylor & Francis, Inc., Philadelphia, PA, 39(22):7789-7805, (2018). https://doi.org/10.1080/01431161.2018.1471545
Water quality is a critical consideration in determining water resource availability for human consumption, aquatic life, and recreation (U.S. EPA 2013). Temperature is relevant in nearly all biological and chemical processes, where the temperature coefficient (Q10) is defined as increased process rates with every 10oC temperature increase (Lighton 2008). The physical structure of the water column also is influenced by the creation of thermoclines and changes in the Brunt–Väisälä frequency as a measure of water column stratification, where the greater the frequency the greater the stratification (Schaeffer et al. 2012). Spatial and temporal measurements of temperature are key variables in ecological forecasting models and source water tracking. In particular, phytoplankton productivity (Eppley 1972), harmful algal bloom (HAB) toxin production (Davis et al. 2009), and forecasting (Wynne et al. 2013) may be parameterized with temperature. The United States Harmful Algal Bloom and Hypoxia Research Control Act (U.S. HABHRCA) of 2014 identified the need for forecasting and monitoring HABs in lakes, reservoirs, and estuaries across the nation. The ability to provide synoptic spatial and temporal satellite measurements of temperature may improve forecast modelling efforts for HABs, although these measurements offer a broad range of applications for other environmental monitoring purposes such as detecting thermal fronts and circulation patterns (Schwab et al. 1992).
The United States Harmful Algal Bloom and Hypoxia Research Control Act of 2014 identified the need for forecasting and monitoring harmful algal blooms (HAB) in lakes, reservoirs, and estuaries across the nation. Temperature is a driver in HAB forecasting models that affects both HAB growth rates and toxin production. Therefore, temperature data derived from the U.S. Geological Survey Landsat 5 Thematic Mapper and Landsat 7 Enhanced Thematic Mapper Plus thermal band products were validated across 35 lakes and reservoirs, and 24 estuaries. In situ data from the Water Quality Portal (WQP) were used for validation. The WQP serves data collected by state, federal, and tribal groups. Discrete in situ temperature data included measurements at 11,910 U.S. lakes and reservoirs from 1980 through 2015. Landsat temperature measurements could include 170,240 lakes and reservoirs once an operational product is achieved. The Landsat-derived temperature mean absolute error was 1.34°C in lake pixels >180 m from land, 4.89°C at the land-water boundary, and 1.11°C in estuaries based on comparison against discrete surface in situ measurements. This is the first study to quantify Landsat resolvable U.S. lakes and reservoirs, and large-scale validation of an operational satellite provisional temperature climate data record algorithm. Due to the high performance of open water pixels, Landsat satellite data may supplement traditional in situ sampling by providing data for most U.S. lakes, reservoirs, and estuaries over consistent seasonal intervals (even with cloud cover) for an extended period of record of more than 35 years.