ABSTRACT
Groundwater is a significant storage component in the global water budget. Groundwater is critical source of water supply in many parts of the world, and is often important in sustaining river flows and various aquatic ecosystems during drier seasons. Rainfall that percolates through the soil zone is referred to as recharge, and the proportion of flow derived from groundwater is called baseflow. Properties of underground materials such as effective porosity and saturated hydraulic conductivity determine how much groundwater can be stored and transmitted. Direction of groundwater movement is established by knowing spatial variation in the hydraulic head, or the sum of the elevation head and the pressure head. Groundwater moves from high to low total head, perpendicular to equipotentials. The rate at which this occurs is governed by Darcy’s law, which is the product of the saturated hydraulic conductivity and the hydraulic gradient. Wells and piezometers are used to measure hydraulic head at various locations, and from which equipotentials and the potentiometric surface can be determined.
