Tema1

Hydrologic Cycle

Surface Water and Groundwater

Water, water everywhere

Oceans – 97.2%

Ice – 2.15%

Fresh water – 0.65%

The Hydrologic Cycle:

Processes

Evaporation

Condensation

Precipitation

Runoff

Storage

Infiltration

The Hydrologic (Water) Cycle

Describes how water continuously circulates through the

environment

Distribution of

Water

Only 2.5% of water

on earth is

freshwater

2% is in the form of

ice!

Only ~0.5% of water

on earth is available

freshwater

http://www.unep.org (United Nations Environment Programme)

Hydrologic Cycle

Energy for the Water Cycle

Sun

Gravity

Related Processes

Weathering

Erosion

Delivery of sediment to the sea

Delivery of ions to the sea

What factors determine whether

precipitation will runoff or

infiltrate? Earth materials: permeable or not

Land use/vegetation

Slope

Degree of saturation

Duration of precipitation

Intensity of precipitation

Groundwater

Precipitation infiltrates

Water resides in pore spaces or porosity

Groundwater is in communication with surface water

Exchange happens all the time

Springs bring groundwater out on the surface

Maintains stream flow without precipitation

Groundwater

Advantages

Abundant

Clean – relatively

free of pathogens

Constant temperature

More protected from

contamination

Disadvantages

Cost to drill wells

Higher TDS (“Hard

water”)

Contamination is

difficult to discover

Large volumes with

low concentrations of

contaminants are

difficult to clean

Surface Water

Oceans

Rivers and streams

Lakes and ponds

Springs – groundwater becomes surface

water

Surface Water

Advantages

Easily accessible

Easy to recognize and treat contamination

May be cheaper to produce

Lower TDS (“Soft water”)

Disadvantages

Less abundant than

groundwater

Subject to climatic

variations in

availability

Contamination is

relatively easy

Temperature varies

greatly

Problems and concerns with

surface water

Availability

Too little = drought

Too much = flood

Contamination

Elementos hidrodinámicos

principales

Precipitación

Evapotranspiración (evaporación,

sublimación, transpiración)

Escorrentía

Infiltración

Expresión del ciclo hidrológico

P = Es + Et + I

Entradas – Salidas = Variación

de la reserva

¿En que unidad se expresan?

mm = l/m2

Ejemplo: calcular el volumen de agua aportado

por una precipitación de 40 mm sobre una

superficie de 100 km2.