What is defined as a body of water flowing or contained in natural or artificial unlined depressions for a significant periods of the year?

The correct answer is surface water. Surface water is defined as water that flows or is contained in natural or artificial unlined depressions for significant parts of the year, such as rivers, lakes, ponds, and reservoirs. This type of water is directly exposed to the atmosphere and plays a crucial role in the hydrological cycle, influencing ecosystems and providing water resources for various human activities.

Subsurface water refers to water located below the Earth's surface, typically found in soil or rock layers, and is not visible like surface water. Groundwater is specifically the water that saturates the soil or rock formations below the water table, which is the upper surface of the area where the soil or rock is fully saturated with water. The water table itself delineates the boundary between the unsaturated zone above and the saturated zone below.

Understanding these distinctions is essential for septic installation, as surface water can impact the design and placement of systems to prevent contamination and ensure proper hygiene and environmental protection.