Introduction to Hydrogeology

Introduction to Hydrogeology

• Hydrogeology is the science studying groundwater occurrence, distribution, and movement.
• It combines geology, hydrology, and engineering to understand groundwater systems.
• It focuses on aquifer properties, which are geological structures storing and transmitting groundwater.
• Groundwater is essential in agriculture, industry, and public water supplies.

Groundwater Occurrence

• Groundwater is water found underground in the saturated zone of soil and rock.
• The saturated zone holds water filling all pore spaces.
• The unsaturated zone, above the water table, has partially filled pore spaces.

Aquifers

• Aquifers are geological formations storing and transmitting groundwater.
• Aquifers are categorized as unconfined (water table) or confined (artesian).
• Unconfined aquifers have water tables fluctuating with precipitation.
• Confined aquifers are bounded by less permeable layers (aquicludes).
• Aquitards hinder water flow, but don't completely block it.
• Aquicludes completely block water flow.
• Aquifer properties include porosity, specific yield, permeability, and hydraulic conductivity.

Porosity and Permeability

• Porosity is the void space percentage in rock or soil.
• High porosity means more water storage potential.
• Permeability is the material's fluid transmission ability.
• High permeability allows easy water flow.
• Porosity and permeability determine aquifer productivity.

Groundwater Flow

• Groundwater flows from high hydraulic head to low hydraulic head.
• Hydraulic head is elevation head plus pressure head.
• Factors influencing flow include hydraulic gradient, aquifer properties, and recharge.
• Groundwater flow models include Darcy's Law.

Groundwater Recharge

• Recharge is surface water replenishing groundwater.
• Recharge happens via precipitation infiltration into the soil.
• Land use impacts recharge rates.
• Recharge rates differ based on climate, vegetation, and soil type.

Groundwater Discharge

• Discharge is groundwater leaving the aquifer and returning to the surface.
• Discharge pathways include springs, wells, and stream seepage.
• Springs are natural groundwater outlets.
• Wells are man-made openings for extraction.

Groundwater Management

• Groundwater management sustainably extracts and uses resources, protecting environment and public health.
• Groundwater depletion can cause land subsidence and coastal saltwater intrusion.
• Safe use requires monitoring water levels, understanding recharge, and implementing sustainable extraction.

Groundwater Contamination

• Groundwater contamination sources include industrial waste, agricultural runoff, and leaky tanks.
• Contaminants travel through aquifers, risking human health and ecosystems.
• Remediation methods include pumping and treating, bioremediation, and others.

Hydrogeological Investigations

• Hydrogeological investigations characterize subsurface geology and groundwater flow.
• Investigations include well drilling, geophysical surveys, and aquifer testing.
• Results assess groundwater resources, manage consumption, and mitigate contamination.