Groundwater Processes and Artesian Wells

Groundwater Process

• Groundwater is derived from precipitation and surface water recharge.
• An artesian well is a free-flowing well, named after the province of Artois in France where many such wells were found.

Subsurface Water

• Water in the soil mantle is called subsurface water.
• The saturated/groundwater zone is the space where all pores are filled with water, and the water table forms its upper limit.
• The water table is the free water surface in an unconfined aquifer.

Zones of the Water Table

• The saturated/groundwater zone has a water table as its upper limit, marking a free surface.
• A perched water table is a water table retained around a localized zone of high permeability.
• If the water table intersects the land surface, groundwater comes out to the surface as springs or seepage.

Zones of Soil Pores

• The zone of aeration is where soil pores are only partially filled with water.

Runoff Classification

• Runoff is classified into two based on time delay between precipitation and runoff: direct runoff and groundwater runoff.
• Direct runoff includes surface runoff, prompt interflow, and quick return flow.
• Surface runoff flows over the surface as overland flow and through channels as open-channel flow.

Hydrograph and Stream Flow

• High stream discharges occur during monsoon months, and low flow is maintained during the rest of the year due to base flow.
• The shape of the stream hydrograph and peak flow are controlled by the storm and physical characteristics of the basin.
• Evapotranspiration plays a minor role in this process.

Annual Runoff Volume

• The annual runoff volume of a stream is mainly controlled by the amount of rainfall and evapotranspiration contribution.

Hydrograph Characteristics

• The annual hydrograph of a stream shows a series of short-duration spikes marking flash flows in response to storms.
• The stream becomes dry soon after the end of the storm flow.
• The stream does not have a well-defined channel.
• Seasonal variation of rainfall is clearly reflected in the runoff.

This quiz covers the concepts of groundwater, including its sources, aquifers, and artesian wells.