English: Lake Tahoe, along the California-Nevada border, is one of the clearest lakes in the world. Since 1965 scientists have been monitoring the water's clarity, and have discovered a 50% reduction in the last 35 years. This is attributed to increased algal growth, more sediment washed in from the surrounding areas, and urban growth and development. The ASTER image, on the left, was acquired November 7, 2000, and covers an area of 23 x 38 km. The colors show vegetation in red. The right image was created from ASTER band 1, and is color coded to show the bottom of the lake around the shore-line. Where the data are black, the bottom cannot be seen. These data can be used to determine spatial variations in clarity which complement the point clarity measurements made from boats. Continued monitoring of Lake Tahoe with ASTER data will assist scientists to understand changes in water clarity. The image is centered at 39.1 degrees north latitude, 120 degrees west longitude.