This Week (and next) Today: –Finish Floods –Groundwater Friday: Glaciers

Finally, a flood of possibly mythic proportions “Noah’s Flood” hypothesis William Ryan & Walter Pittman (Columbia U.) Controversial, not universally accepted, but intriguing

Noah’s Flood Coming out of last ice age ~7600 years ago (=5600 B.C.), sea level was low but rising –Why? Black Sea was freshwater, surrounded by farms

Noah’s Flood Rising global sea level raised Mediterranean above the Bosporus Strait –Broke through natural dam –Water rose ~6 inches / day –Flooded lakeshore communities

some Noah’s Flood evidence Many cultures have a flood story, many can be traced to the Black Sea area Remains of houses & villages have been found on the pre-flood lakeshore But: New work finds no evidence for a sudden rise in water level of Black Sea.

Noah’s Flood More info: –book: “Noah’s Flood: The new scientific discoveries about the event that changed history”, Ryan & Pittman, 1998, Simon & Schuster

Today’s Plan: Groundwater aquifer / aquitard water table groundwater flow groundwater contamination

Groundwater: aquifers Any geologic unit through which water can move easily (i.e. it’s permeable) (= high permeability) Porosity: how much water a geologic material can hold

Opposite of an aquifer? Aquitard / aquiclude –retards the flow of groundwater (it’s almost never really zero

Groundwater: aquifers What would be the properties (porosity/permeability) of conglomerate? High porosity, high permeability

Groundwater: aquifers What would be the properties (porosity/permeability) of unfractured granite? Low porosity, low permeability

Groundwater: aquifers Can you think of a rock/sediment with high porosity and low permeability?

Groundwater: aquifers Can you think of a rock/sediment with low porosity and high permeability?

discharge=2000 ft 3 /sdischarge=4000 ft 3 /s How is this possible? No tributaries here

Ground Water and Surface Water These are almost always connected If a stream contributes water to the aquifer it’s called a “losing stream” If a stream receives water from the aquifer it’s called a “gaining stream” Same stream can be both at different places or at different times

Pumping Animation Go to animation at: urses/2003/spring/101/lectures/water _level.swfGo

Your WarmUp Answers Part B: Pumping wells That was a really cool animation but I just don’t understand what is happening. Let’s look at the situation again… go!go!

Your WarmUp Answers Part B: Pumping wells In the low permeability case the water is pumped primarily from the area directly around the well, whereas with the higher permeability the water seems to be drawn from a more broad area surrounding the well "hole". Since permeability refers to the ability of a material to let a fluid move through it, the low permeability doesn't allow the water to venture far from the path of pressure change (the "hole" of the well).

What happens when this well is heavily pumped?

Pollution of Groundwater Need a sense of ground water flow –warmup responses to The velocity of groundwater flow is dependent on: porosity and permeability 28% permeability and hydraulic gradient 61% porosity and hydraulic gradient 7% pressure gradient 4%

Groundwater Flow Groundwater velocity –Depends on permeability and hydraulic gradient (slope of water table) –Ranges from 100 m/day to mm/day –A good round number: 1 ft/day

What happens when a new well here is heavily pumped?

Flow direction can change