Chapter 15-16 River Systems Running Water and Groundwater

The Water Cycle

Evaporation Condensation Runoff Infiltration

What makes Earth unique?

Water

Earth as a System: The Hydrologic Cycle (Water Cycle)

    Is the single most important agent sculpturing the Earths surface Amount of water essentially constant and moves from the oceans to the air to the land and back to the oceans 100 million billion gallons of water that moves through Hydrologic Cycle Oceans account for 97% of all water, lakes and streams for only account for about 0.01%

Water Storage Reservoirs Water source

Oceans Icecaps, Glaciers Ground water Fresh-water lakes Inland seas Soil moisture Atmosphere Rivers

Total water volume Water volume, in cubic miles

317,000,000 7,000,000 2,000,000 30,000 25,000 16,000 3,100 300

326,000,000 Percent of total water

97.2400% 2.1400% 0.6100% 0.0090% 0.0080% 0.0050% 0.0010% 0.0001%

100%

Processes involved in the cycle

• • • • • Precipitation (Condensation): Sleet, Hail Rain, Snow, Evaporation: Infiltration: From ground, lakes or oceans Water seeping into the ground Runoff: rivers Water going directly into lakes and Transpiration: The release of water vapor to the atmosphere by plants

Section 1 The Water Cycle Spot Question

List the forms of precipitation.

• Precipitation is any form of water that falls to Earth from the clouds, including rain, snow, sleet, and hail.

The Water Cycle

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Section 1 The Water Cycle

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Water Budget

In Earth’s water budget, precipitation is the income. • Evapotranspiration and runoff are the expenses.

• The water budget of entire Earth is balanced – precipitation is equal to the amount of evapotranspiration and runoff.

• Local water budgets are usually not balanced.

Water budget:

• Inputs minus Outputs

Basic principles of water balance in a drainage basin

• • • • Soil is like a bucket Inputs – Mainly precipitation Outputs – Evaporation – – Transpiration Drainage Water storage depends on – Size of bucket (soil depth and texture) – Balance between inputs and outputs

Infiltration

• • Water movement into soil Depends largely on: – – – – Texture Aggregate structure Macropores made by animals and roots Impermeable layers • • Calcic layer in desert Permafrost in cold climates

Water outputs

• • • Streamflow is the “leftovers” after soil storage and evaporation are met Over long term, runoff depends on precipitation and evaporation Groundwater flow is usually a net output

Water budget = Water input +Water output

• • • •

Usage:

plants take water from the soil at a rate faster than rainfall

Deficit:

stored soil water is gone and need for moisture is greater than rainfall

Recharge:

refilling of soil water when need for moisture is less than rainfall

Surplus:

rainfall is greater than need and the soil is already saturated.

Interpreting Water Budgets

Month JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Supply 108 131 125 95 96 115 155 142 88 61 60 99 Need 15 19 45 76 124 165 181 166 129 73 26 17 Supply Minus Need +93 +112 +80 +19 -28 -50 -26 -24 -41 -12 +34 +82 Water Budget Section

S S S S U U U/D D D D R R/S

Water Use

• On average, each person in the United States uses about 95,000 L (20,890.5 gal) of water each year.

• As the population of the United States increases, so does the demand for water.

• About 90% of the water used by cities and industry is returned to rivers or to the oceans as wastewater.

• Some of this wastewater contains harmful materials, such as toxic chemicals and metals.

Conservation of Water

• Scientists have identified two ways to ensure that enough fresh water is available today and in the future.

• One way is through conservation or the wise use of water resources.

• A second way to protect the water supply is to find alternative methods of obtaining fresh water.

Conservation of Water

• Desalination a process of removing salt from ocean water • Desalination is expensive and is impractical for supplying water to large populations.

Water Use in Households

Running Water

• Many uses: – Energy – Transportation – Irrigation – Potable source

•

Chapter 16 Water Beneath the Surface GROUNDWATER 22% of all fresh water occur underground

•

Aquifer: Underground formation that holds and yields water

•

A good aquifer needs to be both porous and permeable

Aquifer

• •

Aquifer

: A rock that holds enough water and transmits it rapidly. Porous and Permeable. Sandstone and Coarse Clastic Sedimentary rocks make good aquifers

Aquiclude

: Rocks of low and very low permeability e.g., shale, slate through which water does not moves easily

Water Table

•

Water table

: the upper level of saturated zone of groundwater

Water Table

• • Ground water flows from higher elevation to lower, from areas of lower use to higher use, from wet areas to dry areas.

Follows the contour of the surface

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Movement of Groundwater

Water passes quickly through highly permeable rock and slowly through rock that is less permeable.

• The rate at which groundwater flows horizontally depends on both the permeability of the aquifer and the gradient of the water table. • The velocity of groundwater increases as the water table ’ s gradient increases.

• •

Topography and the Water Table

The depth of the water table – Topography – – – Permeability of the aquifer The amount of rainfall The rate at which humans use water.

A perched water table is a secondary water table when a layer of impermeable rock is on top of permeable rock.

Topography and the Water Table

The image below shows the water table and a surface topography.

•

Wells and Springs

Groundwater reaches Earth ’ s surface through wells and springs.

• A well is a hole that is dug to below the level of the water table and through which groundwater is brought to Earth ’ s surface.

• A spring is a natural flow of groundwater to Earth ’ s surface in places where the ground surface dips below the water table.

•

Springs

Natural flow of groundwater when the water table intersects the surface Spring

Environmental Problems

• Consequences of Ground Water Withdrawal – Lowering of Water Table – Compaction and Subsurface subsidence of land – Groundwater contamination

Lowering of Water Table

• Cone of depression: Circular lowering of water immediately around a well

Subsidence:

from pumping out water faster than replenishing

Artesian Wells and Springs

artesian formation a sloping layer of permeable rock sandwiched between two layers of impermeable rock and exposed at the surface • Water in some wells may come from as far away as hundreds of kilometers. • The permeable rock is the aquifer, and the top layer of impermeable rock is called the caprock .

Artesian System

•

Artesian Well

: a well in which the water rises above the level where it was initially encountered • Must have an aquifer confined by an aquiclude above and below (an aquifer sandwich)

Artesian System

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Hot Springs

Groundwater is heated when it passes through rock that has been heated by magma. • Groundwater that is at least 37 ° C produces a hot spring.

• Hot spring deposits minerals that form steplike terraces of calcite called travertine .

•

Hot Springs

Water 10-15 degrees F warmer than the mean air temperature of the area GGGG

Hot Springs Morning Glory Pool

Hot Springs

Hot Springs

Geysers

• Hot springs that periodically erupt from surface pools or through small vents are called geysers. • The eruption continues until most of the water and steam are emptied from the vent and chambers.

GEYSERS

GEYSERS

GGGG

Old Faithful

Hard water

• Hard Water: – – – – – Common in limestone country contains dissolved Ca and Mg; problem with soap leaves deposits in plumbing and in appliances can be cured with water softener typically ion exchange through zeolites