Chapter 10 Groundwater Hydrosphere Hydrosphere water on and

Chapter 10: Groundwater

Hydrosphere • Hydrosphere – water on and in Earth’s crust • 97% in oceans • 90% of fresh is frozen

Precipitation & Groundwater • Seawater becomes water vapor & clouds • Infiltration – precipitation becomes groundwater • Porosity - % of pore space (open holes in something)

Zone of Saturation • Zone of saturation – depth where groundwater fill ALL pores • Water table - upper boundary of zone of saturation ▫ Fluctuates with location & weather condition • Zone of aeration – above water table, mostly air

Groundwater Movement • Permeability – ability of a material to let water pass through it • Aquifer – where groundwater flows • Aquicludes – Impermeable layer

Groundwater Erosion & Deposition • Slightly acidic – carbonic acid ▫ Ca. CO 3 (calcium carbonate) major component of limestone dissolves in any acid ▫ Role in formation of limestone caves

Dissolution of Groundwater • Cave – natural underground opening with connection to Earth’s surface ▫ Form when groundwater dissolves limestone • Karst topography – surface feature produced when limestone is dissolved ▫ Sinkhole – depression in the ground from collapsed cave ▫ Sinking streams

Groundwater Deposits • Tap water may have Sulfur & Iron • Hard water – contains calcium, magnesium, and iron • Soft water – water with few dissolved ions

• Dripstone formations – water drips in caves depositing tiny amounts of Calcium Carbonate ▫ Stalactites – cone-shaped structures hanging from cave’s ceiling ▫ Stalagmites – mound-shaped deposits forming on floor of caves ▫ Dripstone columns ▫ Travertine – limestone that makes dripstone formations

Springs • Springs – natural discharges of groundwater • Temperature of water usually the average annual temperature • Hot springs – water temperatures higher than human body • Geysers – explosive hot springs that erupt at regular intervals

Wells • Wells – holes in ground that reach a reservoir of groundwater ▫ Tap into aquifers ▫ Over pumping lowers the water table • Drawdown – difference between original water table level & level in pumped well • Recharge – water from precipitation & runoff is added back to well

Confined Aquifers • Confined aquifer – found between 2 aquicludes ▫ Not easily polluted • Artesian well – well drilled in confined aquifer, water spurts above surface • Artesian spring – spring that discharges pressurized water

Threats to our Water Supply • Freshwater is Earth’s most valuable resource • Overuse occurs when the use rate is greater than the recharge rate • Subsidence – sinking of land because of withdrawal of groundwater

Groundwater Pollution Sources • Sewage, industrial wastes, landfills, agricultural chemicals • Chemical contaminants are extremely difficult to separate from groundwater • Near seas, groundwater is polluted by salt

Protecting our Water Supply • Identify & eliminate pollution sources • Chemical treatment of water at surface