An oil and gas well development process that typically involves injecting water, sand, and chemicals under high pressure into a bedrock formation via the well

Energy that can be harnessed from a continuous flow of water, such as a river. It is a renewable source of energy because the water cycle is constantly renewed by the sun

Wastewater and sewage and include faeces and the contents of pit latrines and septic tanks

Contamination derived from diffuse sources, where there are many sources or the source is unknown

Water resources that are not replenished or not for a very long time