Ground water

Rainfall is absorbed (infiltrates)farmland soil

Because of urbanization, the rainfall cannot infiltrate, so it’s runoff,

Where does the water go???

Frequent large storms can exceed the system's ability to handle the load. This can cause mixing of sanitary and

storm sewer water that results in flooding an water back-up

If the sewer system is full or it can’t handle the rate of water flow, the rainwater has no where to go but back (up) into your household drains.

• The Deep Tunnel Project

• Begun in 1975, and at one time the nation's largest municipal water pollution control project

• It involves the construction of 109 miles (174 kilometers) of tunnels 9 to 33 feet (3 to 10 meters) in diameter.

• Excavated in limestone bedrock as much as 350 feet (107 meters) below the surface.

• These tunnels will collect any combined sanitary and storm sewer flows and send them to reservoirs for storage…

• …until the area's water reclamation plants can treat and safely discharge the water.

• The Deep Tunnel is designed to reduce and nearly eliminate the release of untreated water to streams, Lake Michigan, and people's basements.

Groundwater

Groundwater is the most abundant available source of fresh water

Rivers, lakes, streams = 1.4% of fresh water

Zone of aeration • Unsaturated zone • Pore spaces are filled

mainly with air

Zone of saturation • All pore spaces in the

material are filled with water

• Water within the pores is groundwater

Water table – the top of the zone of saturation

GroundwaterPrecipitation (rain water) that enter (infiltrates) the ground.

And is STORED in the ground in the spaces between rock particlesin aquifers.

(Groundwater is the most abundant available source of fresh water)

Factors that affect the amount of water that infiltrates the ground:

type of rock or soilclimatetopographyvegetationland use

soaks-in

Soil and vegetation allow water to slowly

infiltrate

Urban streets, concrete, asphalt roads and buildings do not allow water to infiltrate and the water quickly

runs-off

Figure 5.3

What determines if precipitation will INFILTRATE or RUN-OFF?

Porosity

•amount of pore spaces, voids, openings.

• Ground materials ability to HOLD water.

• Determines storage of groundwater.• The percent % of the total volume of material that consists of pore spaces

Porosity factors: 3-S’s• Size of particles: (large, small, fine)

• Shape of particles (rounded or angular)

• Sorting of particles: - well-sorted: all the SAME size and shape

- unsorted: mixed, DIFFERENT size and shape

• Compactness of particles

Which is well-sorted? Compacted? Un-sorted?

saRank the following as #1 for the highest porosity and #5 as the lowest porosity.

And describe factors

Good porosity

Due to:

Round shape

Same size

well-sorted

LOW porosityDue to:unsortedSmall clay particles fill-in the pore spaces between the large particles.

High porosity

Due to:

Same big size

Same shape

Well-sorted

High porosity

Due to: Big sizeBut.. unsorted and angular

Good porosity.

Due to:

Same size

Well-sorted

sand Clay soil

20 ml of water filled the spaces

What is the POROSITY of the rock?

__________%

50 cm3

of dry rock