Groundwater Systems

A. Aquifer vs. Aquiclude Aquifer = permeable layer (water can go through it) Ex. Limestone, sand, gravel, sandstone Aquiclude = impermeable layer (water cannot go through it) Ex. Clay, shale

Springs Groundwater tends to discharge at Earth’s surface where an aquifer and aquiclude meet called a Spring

Can be a trickle or an entire river coming up from the ground B. Spring Properties Can be a trickle or an entire river coming up from the ground Temperature of the water = average annual temperature of the region in which it is located Warm springs = warmer than the average annual temp Pictures = geyser

Hot springs = warmer than the human body B. Spring Properties Hot springs = warmer than the human body Geyser = hot spring that erupts at regular intervals Ex. Old Faithful in Yellowstone Pictures = geyser

Man-made hole drilled into the ground to reach water in an aquifer C. Wells Man-made hole drilled into the ground to reach water in an aquifer Wells are dug into the zone of saturation (below the water table) I had some students ask why well water doesn’t have sediment in it if there’s dirt in the zone of saturation, so I’m showing them that wells have a screen that allows water through

C. Wells (cont) III. Pumping from wells lowers the groundwater levels IV. Recharge – When the zone of saturation is refilled by precipitation and runoff. V. If recharge does not keep pace with groundwater withdrawal, wells go dry **Pollutants can easily reach the water table

D. Confined Aquifer (closed off by an impermeable layer) Artesian spring – rate of recharge is very high, keeping the aquifer under pressure, which causes water to rise above the surface of the land creating a spring

E. Threats to our Water Supply Overuse – groundwater depletion (water table drops b/c water is withdrawn faster than it is recharged) Subsidence – the dropping or sinking of land when lots of groundwater is removed Groundwater pollution – by sewage, industrial waste, chemicals from agriculture which are flushed downward by infiltrating precipitation

Salt – saltwater intrusion Chemicals – cannot easily be removed because they are not filtered by sediments Salt – saltwater intrusion Freshwater floats on top of denser sea water within the aquifer. Overpumping of wells draws the underlying saltwater into the wells and freshwater zone

F. Water Supply Protection Underground impermeable barrier can be built to protect from polluted areas Pump out and treat water before use An important part of the solution is for people to become aware of how their actions impact groundwater prevention