GROUNDWATER

Anup Ghimire

Groundwater

Two thirds of the world’s fresh water 99% of the usable water

Confined and Unconfined

Confined Aquifer: groundwater between impermeable layers of rock

with less movement of water and replenished by rain or stream water

some distance away from the aquifer

(www.tas.gov)

Confined and Unconfined

Unconfined Aquifer: direct contact with the atmosphere through the porous soil or rock layer and replenished directly

by rain or stream water from the porous layer.

 (www.tas.gov)

Porosity

Percentage of the openings or pores in a given volume of the rock which

contain water 

(www.who.int)

Specific Yield

The ratio of the volume of water that can be extracted to the total saturated volume 

(www.who.int)

Chemical Composition

Inorganic constituents: bicarbonate, calcium, chloride, magnesium, silicon, sodium, sulphate and carbonic acid 

(www.eolss.net)

Chemical Composition

Trace Constituents: boron, carbonate, fluoride, iron, nitrate, potassium and

strontium

(www.eolss.net)

Groundwater chemistry and quality affected by:

evapotranspiration, dissolution, and precipitation of soluble minerals, acid

base reactions, ion-exchange and sorption and oxidation reduction

reactions(www.dec.na.gov)

Chemical behaviour of groundwater affected by:

temperature, ionic strength, pH and Eh 

(www.dec.na.gov)

Mineralogy of the rock types forming catchments or aquifers, overlying land uses, proximity to the coast, source of recharge water, soil type and aquifer

structure affects groundwater chemistry.

Land use activities such as soil cultivation, fertilizer application, animal

grazing and wastewater disposal has important role in the availability of

nutrients such as nitrogen and phosphorous in groundwater.

Microbes

free of microbial contamination because of long vertical transport for

microbes to reach aquifers

Microbial Contamination

 leakage from sanitation systems, disposal systems, underground storage

tanks and accidental waste water discharge

(www.acatech.de)

Common pathogens

Bacteria : Escherichia coli, Salmonella species, Shigella species, Vibrio Cholerae and Legionella species

(www.acatech.de)

Common pathogens

Viruses :Piconaviridae, Caliciviridae, Reoviridae, Adenoviridae and Coronaviridae

(www.acatech.de)

Common pathogens

Protozoans: Crptospiridium pavum, Giardia lambia, Taxoplasma gondii and Entamoeba histolytica 

(www.acatech.de)

Microbial transport and survivalAffected by advection, dispersion, diffusion, size exclusion, retention and release from solid-water or air-water interfaces

Physio-chemical, biological and hydrodynamic factors