- While most of Earth's surface is covered in water, only a small fraction (less than 3%) is freshwater, with most locked up in ice caps and glaciers. Less than 1% is available for human use. - The largest reservoirs of fresh water are ice caps and glaciers (2.05%), followed by groundwater (0.68%) and lakes (0.01%). Oceans contain 97.25% of total water but it is saline. - Dams and reservoirs provide benefits like water for irrigation and hydropower but also have negative impacts such as flooding of land, disruption of fish migration, and loss of water through evaporation.