Which of the following statements regarding surface and groundwater is true?

Surface and groundwater are essential components of our water supply, and their safety and quality are influenced by various environmental factors.

The statement that all surface water must be considered unsanitary unless given adequate treatment is based on the understanding that surface water is often exposed to contaminants from the environment, such as runoff from agricultural fields, urban areas, or wildlife. Thus, untreated surface water is usually not safe for drinking, and proper treatment processes, such as filtration and disinfection, are necessary to ensure its safety for human consumption.

Additionally, the importance of surveying the entire watershed when considering surface water cannot be overstated. A watershed encompasses all the land that drains into a particular body of water, meaning any activities within the watershed can directly affect the water quality of the surface water. By surveying the watershed, potential sources of contamination can be identified, and appropriate measures can be implemented to protect and manage water resources effectively.

Both of these elements underscore the necessity of thorough assessment and management of surface water sources, making the combination of these two statements true. Therefore, recognizing the unsanitary nature of untreated surface water and the need to survey entire watersheds is crucial in ensuring safe water quality for human use.