hydrogeology

Hydrogeology is the science concerned with the distribution and movement of groundwater in soils and rocks of the Earth's crust. It integrates geology, hydrology, chemistry, and engineering to characterize where groundwater resides, how it flows, and how it can be managed sustainably. Hydrogeologists investigate aquifers, confining layers, recharge and discharge areas, and the interactions between groundwater and surface water.

Key concepts include hydraulic head, hydraulic conductivity, porosity, and permeability, which govern groundwater flow according to Darcy's law. Groundwater occurs in porous media such as sands and gravels or in fractured rock; aquifers store and transmit usable water, while aquitards or aquicludes impede flow. Recharge replenishes groundwater through precipitation and infiltration; discharge occurs at springs, streams, or wells. Groundwater chemistry reflects rock-water interaction, redox conditions, and source waters, informing water quality and contamination risks.

Methods include pumping tests to measure aquifer response, well logging, tracer studies, and geophysical surveys. Groundwater models simulate flow and transport under different conditions for water-supply planning and contamination risk assessment. Applications range from drinking water supply and irrigation to environmental protection and mining. Hydrogeology faces challenges such as climate variability, over-extraction, land-use change, and subsidence, requiring monitoring networks and sustainable management strategies.