Year Established: 2018 Start Date: 2018-03-01 End Date: 2019-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: $10,014
Principal Investigators: Xiangming Xiao, Zhenhua Zou
Abstract: The numerous open surface water bodies across Oklahoma provide ~64% of the total fresh water withdrawal in Oklahoma (USGS, 2010). High resolution maps of open surface water body are critically important to water resource management. At present, annual water body maps at 30-m spatial resolution, derived from Landsat images, are available from our research group (Zou et al., 2107) and other groups (Feng et al., 2016; Homer et al., 2015; Pekel et al., 2016). Currently, these are the highest spatial resolution satellite-image-based maps of open surface water bodies in Oklahoma. However, streams and ponds with a width smaller than 30-m were not well captured in these maps because of the spatial resolution issue. We propose to evaluate our open surface water body mapping algorithm, which was evaluated with Landsat images (Zou et al., 2017), on Sentinel 2 images, and to combine both Sentinel-2 and Landsat images to generate annual maps of open surface water body in the areas of Lake Texoma, Lake Thunderbird and Grand Lake at the spatial resolution of 10-m in 2016-2017. Chlorophyll-a (Chl-a) is one of the most commonly used indicators of water quality. Based on the Chl-a sampling data of 2014-2015 (OWRB, 2015), 6 lakes were in the hypereutrophic status and 22 lakes were in the eutrophic status, covering 7% and 88% of the total water areas sampled respectively. The reported eutrophic status of a lake was based on the annual chlorophyll-a concentration value that averaged across sampling sites and sampling quarters (OWRB, 2015). The temporary peaks of chlorophyll-a concentration during the plant growing season in specific portions of a lake may not be captured due to the low sampling frequencies and limited sampling sites. Algal blooms are likely to occur in eutrophic and hypereutrophic lakes, which could result in fish mortality and jeopardize drinking water quality. The in-situ water sampling approach for water quality monitoring is very expensive and time consuming, and thus it cannot be implemented for all lakes in the state. Landsat and Sentinel satellites can scan any location several times in a month and provide spectral images in the spatial resolution of 30m and 10m. Satellite-image based water quality detection has the potential to provide Chlorophyll-a concentration information of Oklahoma lakes in high temporal frequency and spatial resolution, which could provide an alternative and supplement to the expensive in-situ data collection. Compared with Landsat images, Sentinel 2 images have 4 additional vegetation red edge bands that can be used for Chlorophyll-a estimation. Thus, we propose to assess the potential of Sentinel-2 images with existing chlorophyll-a estimation algorithms for clear water (O'Reilly et al., 1998) and turbid water (Dall'Olmo et al., 2003; Matsushita et al., 2015) in Lake Texoma, Lake Thunderbird, and Grand Lake, based on available in-situ water sampling data and to-be-done water sampling data from collaborators, and the published data in BUMP reports (OWRB, 2015). We will combine both Sentinel-2 and Landsat images to further improve chlorophyll-a estimation algorithms, based on the available in-situ water sample data in Lake Texoma, Lake Thunderbird, and Grand Lake.