Groundwater

Groundwater The Hidden Source of Life

What is Groundwater? • the water that lies beneath the Earth’s surface • accumulates chiefly from precipitation rainfall and melting snow – and seeps through the soil

What is Groundwater? • Gravitational force pulls the water downward • Travels very slowly through rock and soil particles • Water seeps through openings then fills the pores and cracks of underground rocks and the spaces between the soil particles and becomes groundwater • The porous layer of materials that yield useful amounts of groundwater is called an aquifer. • This portion below the Earth’s surface that is saturated with water is called the saturated zone

Aquifers • underground formation of permeable rock or loose material that can produce useful quantities of water when tapped by a well • Groundwater is held within the tiny pores of the surrounding aquifer material • Aquifers can either be confined or unconfined

Confined Aquifer • exists in the confining layer where groundwater is between the boundaries of impermeable materials • obstructs water movement and impedes groundwater contamination • Confined aquifers are under high pressure so that when tapped by a well, water is forced up

Unconfined Aquifer • the upper boundary of the aquifer in which the water table is at or near atmosphere pressure • unconfined aquifer is not under high pressure • very susceptible to contamination • groundwater will eventually leave the aquifer and flow to a natural discharge area

Recharging Aquifers • naturally recharged by rainfall or surface water from streams, rivers, lake etc. • a recharge zone is constructed where permeable underground rocks and soil particles are mobilizing water for the replenishment of aquifers

Hydrologic Cycle and Groundwater

Exploration of Groundwater • almost every point in the Earth's subsurface has (at least in small amounts) water in it • The amount of groundwater to be drawn from an aquifer is dependent on the permeability of the underground layer in which it is found • Locating wells and water reserves deep beneath the earth requires a great magnitude of training and experience

Facts • Groundwater: providing an estimated 37% of agricultural use and in a broad picture, 37% of the public water supply. It provides an estimated 22% of all freshwater withdrawals and 99% of drinking water for rural regions (respectively in ratio to the totality of water supply).

Water Quality • Dissolved minerals • Hard / soft water • Acidic / basic water

Groundwater Contamination “segment of the cycle which generates and replenishes groundwater also permits for water contamination. Groundwater is most vulnerable in this process ”

Factors of Contamination • Waste Category I. These are systems designed to discharge wastewater onto the surface of the land or to the groundwater • Waste Category II. These are systems that may discharge wastewater to the land or groundwater but are not designed to do so

Factors of Contamination • Non-waste Category III. These are nonwaste systems that may discharge contamination to the land or the groundwater. • Non-waste Category IV. These are nonwaste and non-discharge sources of contamination.

Groundwater Pollution “water is said to be polluted when it contains enough impurities to make it unfit for a particular use, such as drinking, swimming, or fishing”

Environmental Issues • Overdrafting results from excessive withdrawal of groundwater from aquifers. Because of excessive groundwater withdrawal, the water table decreases drastically causing wells to dry up

Environmental Issues • Subsidence is a situation where land surface is sinking due to excessive extraction of groundwater (Overdrafting)

GW Vulnerability in M.M. • It is estimated that the population in Metro Manila alone is at least eight million (8,000,000). In Metro Manila, there are 2,216 private wells 48% of which are for domestic purposes while 9% are for commercial purposes. Maynilad also renders services with 131 wells.

GW Vulnerability in M.M. • It was concluded that shallow groundwater reservoirs occur in Paranag, Marikina and in Fairview Park, Quezon City, averaging at a depth of 0.5m to 1m.

Sustaining GW “It was concluded that shallow groundwater reservoirs occur in Paranag, Marikina and in Fairview Park, Quezon City, averaging at a depth of 0.5m to 1m.”

Conclusion • Groundwater is the “best” free thing that man can afford • Quality groundwater is threatened by various entities in the environment

Conclusion Groundwater is used extensively for small scale water supply in the expanding urban centers of the Philippines but groundwater quality is threatened by unplanned urban expansion. A consistent and rigorous national groundwater protection policy is needed. (Holman and Palmer, 1999)

BIBLIOGRAPHY: Ellis, B. (1999) Impacts of Urban Growth on Surface Water and Groundwater Quality> IAHS Publications. Holman, I. and Palmer, R. (1999) Groundwater protection incorporated into land use planning: a study from Cebu City, the Philippines. Pascual, A. Y. (1992) Determination of Groundwater Pollution Potential in Metro Manila using DRASTIC Approach. Online Resources: environmental works. (2008). In Encyclopædia Britannica. Retrieved June 29, 2008, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/189203/environmental-works http://www.water.org/waterpartners.aspx?pgID=890 http://www.wepa-db.net/policies/state/philippines/overview.htm http://sina.sharif.ac.ir/~ataie/gwsite/ http://www.groundwater.org http://www.waterencyclopedia.com/Ge-Hy/Groundwater-Supplies-Exploration-for.html http://www.eoearth.org/article/Groundwater http://water.usgs.gov/ogw/