Water ResourcesA river runs through it…

Water: The Universal Solvent

• One of the most valuable properties of water is its ability to dissolve. This makes water an excellent solvent.

• An individual water molecule has a bent shape with a H-O-H bond angle of approximately 105 degrees.

• Water is polar thus having positive & negative partial charges on its ends.

Hydrology: The Study of Water.*The sum of all liquid water resources on Earth is found in the Hydrosphere.•The Hydrosphere interacts with the Lithosphere(land), Cryosphere (ice),Biosphere (life), Pedosphere (soil), and Atmosphere(air).

How much water is in the hydrosphere?Conventional estimate assumesa total groundwater storage of about 1,700 quadrillion gallons. This gives the estimate of hydrosphere’s total water content as 3.5x1020 gallons.

Oceans (97%)

Ice (1.2%)

Underground water (0.5%)Surface water (0.02%)

Atmosphericmoisture (0.001%)

Water Distribution:

An alternate assumption is that pores in sediments contain about 80,000 quadrillion gallons of groundwater (almost 50 times the conventional estimate). This yields an estimate of about 4x1020 gallons of water in the entire hydroshere.

Oceans (80%)

Ground-water (19%)

Groundwater (19%)

Ice (1%)Surface water (0.002%)

Atmosphere(0.001%)

Available Water sources1. Surface runoff – 2/3 lost to floods and

not available for human use.• Reliable runoff = one third

• Amount of runoff that we can count on year to year

2. Groundwater• Zone of saturation• Water table – top of zone of

saturation• Aquifer – water saturated layers of

sand, gravel or bedrock through which groundwater flows.

• Recharge slow ~ 1 meter per year

Use of Water ResourcesHumans directly or indirectly use about 54% of

reliable runoffWithdraw 34% of reliable runoff for:• Agriculture – 70%• Industry – 20%• Domestic – 10%

Leave 20% of runoff in streams for human use:transport goods, dilute pollution, sustain fisheries

Could use up to 70-90% of the reliable runoff by 2025

Freshwater Reservoirs• Rivers and Streams• Lakes• Icecaps• Groundwater

Groundwater• Much greater in volume than either lakes or streams• Non-renewable in our lifetime

• Groundwater from below the water table seeps into lakes, streams, and swamps and returns to the surface naturally at a spring. Groundwater eventually returns to the ocean, but the trip may take hundreds of years.

What is an aquifer?

• Geologic formation that possesses porosity and permeability

Water Table

• Surface below which pores and fractures of rocks and overburden are water filled

• An artesian aquifer has groundwater that is under pressure from the water at higher elevations. The pressure will cause the water to rise above the water table in a well drilled into the aquifer, becoming a flowing well if the pressure is sufficiently high.

What is a Watershed?

• An area of land, from ridge top to ridge top, that collects, stores, and releases water to a common point, such as a river or a lake

What’s in a Watershed?

• Streams • Rivers• Lakes • Wetlands• Hills • Mountains

• Farms • Cities• Houses• Humans• Animals• Plants

Watershed Functions

• COLLECT• STORE• RELEASE

Watershed – COLLECT

• Geology– Mountains, valleys, etc

• Vegetation– Interception

• Manmade surfaces

Watershed – STORE

• Wetlands, Lakes, Reservoirs• Soil• Groundwater• Snow and Ice• Biology

Watershed – RELEASE

• Streams and Rivers• Groundwater• Evaporation• Human Engineering

Hydrological (Water) Cycle• Ignoring such long-term effects as the changes

in atmospheric storage conditions, run-off filling the ocean basins etc., the hydro-logical cycle is merely the re-cycling of water between land and oceans.

Ocean Storage1,370,000,000 km3

The Hydrological Cycle

Precipitation285,000 km3

Evaporation320,000 km3

Precipitation95,000 km3

Evaporation60,000 km3

Run-off35,000 km3

Evaporation and transpiration

Evaporation

Stream

InfiltrationWater tableInfiltration

Unconfined aquifer

Confined aquifer

Lake

Well requiring a pump

Flowingartesian well

Runoff

Precipitation

ConfinedRecharge Area

Aquifer

Less permeable materialsuch as clay Confirming permeable rock layer

Water Cycle – continuously collected, purified, recycled and distributed

Water Cycle:The basic water cycle includes:•Evaporation (sometimes transpiration)•Condensation•Precipitation•Surface Runoff•Storage (oceans, rocks, groundwater, etc.)

Human uses of water:

Water is an important but precious resource. It must be carefully managed, and often conserved in order to meet human needs.