Groundwater Discharge
Groundwater discharge is the natural release of subsurface water from underground aquifers, or bodies of rock, composed of densely compacted material that may include clay layers, sand, and gravel. Groundwater is typically released in areas where the aquifer is exposed on the surface, such as in natural streams and rivers, or in man-made land features such as lakes and reservoirs.
Groundwater discharge is an important factor in determining the water budgets of a given area. Water budgets, also known as water balance calculations, measure the amount of water brought into an area via precipitation, runoff, surface flow, and groundwater discharge, as well as the amount of water removed from an area via evapotranspiration and irrigation. By understanding how much water is released from the ground, water managers are better able to assess how much groundwater is available for agricultural, industrial, and other uses.
Groundwater discharge is divided into two primary types: base flow and non-base flow. Base flow is defined as the continuous release of groundwater that usually occurs during dry and wet periods. Base flow is typically associated with streams and rivers, and is typically considered to be the most reliable source of water because it does not vary greatly over time. Non-base flow is defined as the sporadic, episodic release of groundwater that typically occurs during periods of large amounts of precipitation. Non-base flow can be an important source of water during times of heavy rainfall, flooding, and drought.
Groundwater is often discharged into the environment without the intervention of humans. In many cases, this can be beneficial, as natural groundwater discharge can help to replenish and maintain surface water supplies. For example, in areas where surface water has been over-allocated and consumed, natural groundwater discharge can be used as an important source of water to help meet demands. Natural groundwater discharge can also help to remove excess nutrients and pollutants from the environment and provide aquatic habitats for wildlife.
In some cases, however, human interference can affect the rate at which groundwater is released from aquifers. This interference can come from a variety of sources, such as the development of well systems that can draw down groundwater levels or the implementation of water management strategies such as artificial recharge or groundwater pumping. Additionally, potential artificial interference with aquifers can come from activities such as mining, agricultural activities, or urbanization. These activities can result in changes to an aquifer’s hydrologic properties, including an increase or decrease in the rate of aquifer recharge, or an alteration of the natural flow of groundwater.
Ultimately, it is important to understand how groundwater discharge works and the potential consequences it can have on the environment. In doing so, water managers, scientists, and engineers can work to ensure that groundwater resources are used sustainably and effectively, and that natural resources remain available for future generations.
