Shoreline Extent Change of Lake Mead, NV, 2000 - 2025 (Landsat 4 and Landsat 9 Spectral Composites)

Land/Water (5 6 4) false-color composite created from Landsat 4 and Landsat 9 imagery of Lake Mead. The Near Infrared (NIR) band, Band 5, is specifically useful in this regard due to the fact that vegetation is highly reflective in the NIR band whereas large, open bodies of water (such as Lake Mead) strongly absorbs NIR light. This creates a strong contrast between bodies of water, which show up as dark (almost black) features and vegetation showing up as shades of red as a result of that difference in absorption. Modified Normalized Difference Water Index (MNDWI) was used to identify extent of water bodies in the respective Landsat spectral composites. MNDWI utilizes the Green and Shortwave Infrared (SWIR) 1 bands from a Landsat image, which were included in both datasets (Landsat 8-9 and Landsat 4-5). The MNDWI makes up for limitations experienced from some of the other water indices, such as NDWI which can experience interference with urban areas and misidentify bodies of water with urban areas due to its use of NIR versus SQIR; as Lake Mead borders the highly urban area of Las Vegas and its surrounding suburbs, it is important to avoid that data interference. Comparing the area for both shoreline extents (2000 and 2025, as shown on the map) shows a distinct reduction in the open water area in 2025 from Lake Mead's prior extent in 2000.