The Importance of Freshwater

About 70 percent of Earth's surface is covered in water. Of all the water on Earth 97 percent is in the oceans. That only leaves 3 percent as freshwater. Of that small amount of freshwater almost 2 percent is locked up in glaciers and ice at the North and South poles. The remaining 1 percent of freshwater is mostly groundwater, with a small fraction filling the world's lakes and rivers.

Graphic showing the amount of saltwater vs. freshwater in comparison to the size of Earth. These spheres represent all of Earth's water, Earth's liquid fresh water, and water in lakes and rivers. The largest sphere represents all of Earth's water, and its diameter is about 860 miles (the distance from Salt Lake City, Utah, to Topeka, Kansas). It would have a volume of about 332,500,000 cubic miles (mi3) (1,386,000,000 cubic kilometers (km3)). The sphere includes all the water in the oceans, ice caps, lakes, and rivers, as well as groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant.

Source: USGS
Yet freshwater is essential for life. Plants, animals, and humans all need freshwater to survive. We use for drinking water, to irrigate crops, as part of sanitation systems, and in industrial factories, to name a few.  
Water used up from groundwater, rivers and lakes is replenished by rain and snowfall. Water resource managers rely on accurate precipitation measurements to monitor their freshwater resources.