English: The province of Manitoba, Canada sits near the center of the country, bordered by the provinces of Saskatchewan (west) and Ontario (east), by the territory of Nunavut to the north, and by the United States to the south. With a topography created by glacial movement and sitting in the center of the Hudson Bay drainage basin, Manitoba’s low-lying prairie land is filled with lakes—and lots of them. The abundance of waterways has given the province the nickname “land of 100,000 lakes”. Some experts say that Manitoba actually has more than that number—and suggest that somewhere near 90,000 of the smaller lakes remain nameless.

On September 28, 2021, the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite acquired a true-color image centered on three of Manitoba’s largest lakes. Lake Winnipeg, sitting in the east, stretches 271 mi (436 km) from north to south and covers an area of about 9,170 square miles (23,750 sq km), making it the 11th-largest freshwater lake on Earth. Lake Winnipegosis is oriented parallel and to the west of Winnipeg and Lake Manitoba sits south of Winnipegosis, separated only by a 1.9 mile-wide (3 km) strip of land.

Swirls of green color the waters of every lake within this image. These swirls are likely caused by algae, which frequently blooms in lakes in this region. While algae occur naturally, heavy growth is spurred by high levels of phosphorus and nitrogen that pour into the lake each year, primarily from human activity within the drainage basin. These serve as fertilizers and can fuel substantial blooms, including harmful algae blooms (HAB) which can be toxic to aquatic life and for people or animals that wish to use or drink the waters.

In a few areas, the lakes appear exceptionally bright or even silver in color. This is due to an optical phenomenon called “sunglint”, which is which is caused when sunlight reflects off the surface of the water directly back at the satellite sensor.