Topic 8Water & Climate

Water in the Earth

Water enters the atmosphere through evaporation and transpiration

Water leaves the atmosphere through condensation and precipitation

This constant circulation, called the Water Cycle or Hydrologic Cycle, maintains a dynamic equilibrium for Earth.

Precipitation can:

1. evaporate

2. run off

3. infiltrate

Water cycle song

runoff

HYDROLOGIC CYCLE

infiltration

aquifer Groundwater flow

transpiration

evaporation

precipitation

condensation

Water tableStream, spring, lake, or ocean

GROUND WATER

Groundwater is always moving --but very slowly

Porosity

All soils, and even rocks, have pores (empty spaces)

Porosity is the percentage of open space in soil or rock, compared with its total volume. Porosity is determined by:

1. Particle Shape

Loosely packed, freshly deposited = higher porosity

Rounder particles = higher porosity

2. Particle Packing

Sorted soil = higher porosity

3. Particle Sorting

How does the size of the particles affect porosity?

When considering round, tightly packed particles, size has no effect on porosity.

Average soil porosity = 35-40%

Permeability

Permeability is the rate that water can pass through a material.

This depends on pore size and whether the pores are interconnected.

some sample soils and rocks

GRAVEL Rapid

drainage

 FINE SANDModerate drainage

 CLAYSlow

drainage

PERMEABILITY

Infiltration(percolation)

Rate of infiltration depends on:

1. Porosity of the soil (how much space there is)

2. Permeability of the soil (how easily water can get through spaces)

3. Slope of the land (water will runoff a steep hill before it can infiltrate)

4. Rate of rainfall (a gentle rain gives the water time to sink in)

If the pores are already filled with water the soil is said to be saturated and the excess water becomes runoff

Zones of Subsurface Water

Water will infiltrate the soil until it reaches an impermeable layer (< 3 km), then it will begin to accumulate in the permeable rock (aquifer) and is referred to as groundwater. The top of the groundwater is called the water table.

Above the water table, pores are kept filled because of capillary action. The smaller the spaces, the greater the capillary action.

In the zone of aeration/unsaturated zone, pore spaces contain mostly air, but are also coated with water if it has recently rained.

CAPILLARITY – WATER MOVES UPWARD

• SMALLER SIZED PARTICLES INCREASE CAPILLARITY

INFILTRATION

Infiltration refers to water soaking into the ground:

Infiltration rate

Slope

Infiltration rate

Permeability

Infiltration rate

Porosity

Infiltration rate

Soil Storage Saturation

GROUND WATER - Aquifer

1. WATER INFILTRATES

2. EVENTUALLY REACHES AN IMPERMEABLE LAYER

3. ALL PORE SPACES FILLED WITH WATER – CALLED ZONE OF SATURATION – THE WATER IN THIS ZONE IS CALLED GROUNDWATER -AQUIFER

4. TOP OF SATURATED ZONE IS CALLED THE WATER TABLE

5. UNSATURATED ZONE – AIR AND WATER

6. CAPILLARY FRINGE – WATER RISES TO FEED ROOTS

WATER TABLE RISES AND FALLS ACCORDING TO

RAINFALL AND SNOWMELT

Water infiltrating the ground also flows slowly downhill below the surface, so the water table usually follows the general topography of the land above it.

A river or lake or spring is simply a place where the water table comes up to the surface.

Even during long periods without rain, most stream beds are fed by groundwater

How wells affect the water table

Groundwater contamination

Caves

Cave formation is common in limestone bedrock

A geyser is a special type of hot spring that erupts periodically. For both geysers and hot springs, groundwater circulating at depth becomes heated by the hot rock below and moves by convection, toward the surface. As it rises, it follows zones of weakness that become channels leading upward. In a geyser, these channels have constrictions which prevent the water from circulating freely to the surface where the heat would escape. The water becomes progressively hotter at depth, exceeding the surface boiling point (199° F., 93° C). Yet it will not vaporize in the geyser tube at this temperature because of the greatly increased pressure exerted by the enormous weight of the overlying water. Bubbling upward, steam expands as it nears the top of the water column until the bubbles are too large and numerous to pass freely through the tight spots. At a critical point, the confined bubbles actually lift the water above, causing the geyser to overflow. This decreases pressure on the system and violent boiling results. A tremendous volume of steam is instantly produced, forcing water explosively out of the vent in a superheated mass. The eruption begins. In an eruption, water is expelled faster than it can enter the geysers plumbing system at depth. As the eruption continues, the heat and pressure gradually decrease. The eruption stops when the water resevoir is exhausted or when the gas bubbles diminish enough to be able to rise through the water column without ejecting it. Fountain type geysers generally shoot water out in various directions, most often from a pool. Cone type geysers generally erupt in a narrow jet of water,

usually from a cone or nozzle-like formation.

Hot springs and Geysers

Hot springs and geysers

Yellowstone National Park

Water Budgets

A local water budget shows how precipitation, evapotranspiration, and soil storage of water vary throughout the year.

Ep = potential evapotranspiration (depends on the temperature)

This shows when there are possible droughts and water surpluses (flooding) in an average year.

By comparing the precipitation and temperature (Ep):

P/Ep < 0.4 arid climate

P/Ep = 0.4 – 0.8 semiarid climate

P/Ep = 0.8 – 1.2 subhumid climate

P/Ep > 1.2 humid climate

How is climate determined?

Ex/ Reno, Nevada gets 193 mm of precipitation in a year but demands 628.

193 / 628 = 0.3 arid climate

                                      

                      

Climographs are similar to water budgets and help to classify the type of climate for a location

Climate

Factors that affect climate1. Latitude – temperature decreases as latitude increases

2. Elevation – temperature decreases as elevation increases

3. Nearness to large bodies of water – coastal areas have milder temperatures and a smaller temperature range

For example, Hong Kong and Nagpur in India have almost the same latitude, but the daily temperature range is very different between the two cities. For a typical day in October, the daily temperature range in Nagpur is 12.8C while for Hong Kong it is only about 4.8 C.

Why?

Because water has a higher specific heat than land.

4. Ocean currents – water coming from higher latitudes will have a cooling effect on the land that the current encounters (lower temp. year round)

5. Mountains – The Orographic Effect

This only works, however, if there is moisture on the side of the prevailing winds

Windward side of mountain is cool and wet, leeward side is warm and dry.

How does this affect NY?

The Tug Hill Plateau holds the world record for snowfall!

6. Planetary Wind Belts

El Niño (aka: Southern Oscillation)

= An abnormal warming of surface ocean waters in the eastern tropical Pacific Under normal conditions in the Pacific, ocean water upwells from deep ocean currents along the west coast of South America. Currents are driven by strong winds created by pressure differences. This cold water is rich in oxygen and nutrients

During El Niño conditions, the atmospheric pressures reverse, which brings warmer, nutrient-depleted water to the coast. This warm water affects storm development and can cause serious droughts. Although it typically occurs around Christmas, conditions can persist for many months.

MonsoonsMonsoons are strong, often violent winds, that change direction with the season. India’s climate is dominated by monsoons.

Monsoons blow from the land toward the sea in winter, and from the sea toward land in the summer. India’s winters are hot and dry. The monsoon winds blow from the northeast and carry little moisture.

The summer monsoons roar onto the subcontinent from the southwest. The winds carry moisture from the Indian Ocean and bring heavy rains from June to September. The torrential rainstorms often cause violent landslides.

Temperature and precipitation patterns are altered by natural events such as El Niño and volcanic eruptions, but it is also important to recognize how human influence can affect them. Activities like deforestation, urbanization, and the production of greenhouse gases have huge impacts on global climate patterns.