Start of the notes for the final exam

Discussion:

Hydrologic Cycle - Keynote pdf
Rain - Keynote pdf
Water Resources - Keynote pdf
Groundwater Recharge - Keynote pdf
Water Table - Keynote pdf

Water

Hydrologic Cycle

The hydrologic cycle describes the cycling of water at Earth's surface.
The hydrologic cycle is driven by solar energy.

97% of water at Earth's surface is in the ocean.
Most of the rest, 2%, is in the polar ice caps.

Water entering the ocean is recycled sea water:

1. Most water is removed from the ocean by evaporation
2. 90% of the evaporated water returns to the ocean as rain
3. The remaining 10% precipitates on land and flows back into the ocean

Then the cycle begins again.
Water runnng into the ocean from the land is called runoff.

Rain

Each volcano has a wet and a dry side.
The windward side of a volcano is wet, and the leeward side is dry.

Windward side is wet because the Northeast Trades come from the northeast.
Warm air holds more moisture than cold air.
Warm, wet winds run into the island and are forced to ascend.
As the wind ascends it cools, and loses moisture (precipitation).
As the cool, dry air descends it warms and takes on moisture (evaporation)

This process is called orographic precipitation.

Water Resources

The primary source of water is groundwater.
In Hawaii, groundwater occurs in two modes:

1. Basal groundwater
2. High-level groundwater

Basal groundwater - groundwater floating on and displacing seawater.
Read about Ghyben-Herzberg Lenses at this link: The Ghyben-Herzberg Model
Calculate H, if h is 3 meters.

Two types of high-level groundwater:

1. Perched
2. Dike confined

Dike confined groundwater is impounded within compartments formed by impermeable dikes.
Perched groundwater forms on low-permeable layer such as ash beds, buried soil horizons, or dense cores of 'a'a flows.

Basal groundwater is much more abundant.
Most dike-confined water is in the rift system at the center of a shield volcano.

Groundwater Recharge

Source of water for the Hawaiian Islands is rainfall.
Recharge - addition of water to the groundwater system.

The primary areas of recharge are watersheds:
Two main watersheds on O'ahu:

1. Ko'olau
2. Wai anae

Runoff and infiltration in Hawaii are approximately equal.
The high infiltration rate is related to the high permeability of the lava flows and the sponge effect of the rainforest.
The vegetation holds the water and provides time for the water to infiltrate.

Most of the water transmitting structures form near the top of lava flows.
e.g. 'a'a clinker, lava tubes, irregular surface contacts, vesicles.
Generally, these structures result in greater permeability in lateral direction.

Water Table

Can classify subsurface into two regions:

1. Vadose zone
2. Phreatic zone

Vadose zone - upper part of ground where the pores are partially filled with air.
Oxidation occurs in the vadose zone.

Phreatic zone - part of ground where the pores are saturated with water.
The water in the phreatic zone is what geologists call groundwater.
Water table - the upper surface of the groundwater.

The notes for the final exam are continued in Aquatic Pollution