Groundwater

GROUNDWATER

What is Groundwater? It is water that is found underground in the cracks and spaces in soil, sand and rock. ●

It is stored in--and moves slowly through--layers of soil, sand and rocks called aquifers.

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Aquifers - gravel, sand, sandstone, or fractured rock, like limestone. speed of groundwater flow - depends on the spaces in the soil or rock and how well the spaces are connected

Groundwater

Groundwater & the Hydrologic Cycle ●

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Condensation- water vapor condensing in the air to form clouds. Precipitation-water falling from the clouds (rain, sleet or snow).

Groundwater & the Hydrologic cycle ●

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Runoff- water running downhill to lower ground. Infiltration/Rechargerainwater seeping to the ground and filling the aquifer. Evapotranspirationwater being warmed and evaporating into the atmosphere.

The Water Table ●

Water table - the level below which soil and rock are saturated with water; upper surface of the saturation zone.

The Water Table Zone of Aeration – suspended water; contains air and water. −

1.) belt of soil moisture

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2.) intermediate belt

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3.) capillary fringe

Zone of Saturation - pore spaces contain water. - GROUNDWATER!

The Water Table ●

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Precipitation – water table rises during high rain, drops during droughts. Groundwater withdrawal – water table lowers around pumped wells.

The Water Table

Groundwater Movement ●

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Groundwater generally moves very slowly because it must travel through the pore spaces of rock and soil. Average groundwater velocities are a few cm/day. Porosity - determines the amount of water a rock can hold. Void space can be from fractures, vesicles, dissolution channels, or pore spaces between elastic grains.

Groundwater Movement ●

Permeability - ability to transmit water (a measure of the connectivity of the pore spaces). ●

Clay may have a high porosity, but has low permeability because the pore spaces are isolated.

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Aquifers - good porosity and permeability; for drinking.

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Aquicludes - low permeability and restrict the movement of water.

Springs, Water Wells, and Artesian Systems ●

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Springs - natural discharge of groundwater; water table intersects the Earth's surface; perched water table causes Water to move laterally until it reaches the surface. Wells - artificial openings dug or drilled into the zone of saturation; groundwater is pumped to the surface; cone of depression.

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Artesian systems - groundwater under pressure rises above the surface of the aquifer; flow without pumping.

Groundwater recharge Naturally, by precipitation. Factors affecting natural recharge: Amount of moisture used by vegetation.

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Nature of precipitation event.

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Presence of any subsurface barriers to now.

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Amount of groundwater used by humans

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Groundwater recharge

Features produced by groundwater Hot springs - springs that bring water to the surface that is at least 6.5 degrees C higher than the mean air temperature. ●

Geysers - hot springs which periodically emit columns of water

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and steam with great force; water eventually boils under great pressure and forces its way to the surface; Cooler groundwater seeps back in, and the cycle is repeated.

Problems ●

Lowering of the water table occurs where groundwater is withdrawn faster than it can be recharged. It can cause wells to dry up.

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Saltwater incursion involves contamination of freshwater aquifers with saltwater.

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too much fresh water is removed, a cone of depression is created in the fresh water lens; lowering the water table by 1 foot results in raising the level of salt water by 40 feet.

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Land subsidence occurs where excessive pumping of groundwater removes ground support. Removal of water causes sediment compaction. The weight of buildings can also cause compaction and subsidence.

Problems

Problems POLLUTION!!!

Solutions ●

Water Resources Management Act

the Philippines increase annual water sector investments about ten-fold around P40 billion. increased wastewater treatment capacity, increased coverage of water sector services, greater water conservation, and effective implementation of the Clean Water Act. ●

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reducing groundwater withdrawal.

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reinjecting treated wastewater into recharge wells.

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construction of recharge ponds.