WATER RESOURCES, POLLUTION AND MANAGEMENT

 

As we probe other planets and ask if life exists elsewhere in the universe, one prime factor scientists look for is Water. Without water, there will be no life.

 

WATER’S IMPORTANT QUALITIES

·       Water is the most common compound on the surface of Earth.

·       It possesses unusual heat characteristics. Liquid water can absorb large amount of heat.

·       Part of earth’s uniqueness is because water exists naturally in all three states—solid, liquid, and gas—owing to earth’s surface temperate.

·       The polarity of the water molecule (positive charge for the 2 atoms of hydrogen and negative charge for the oxygen atom) explains why water dissolves many other molecules. Because of its solvent power, pure water is rare. The bonding between water molecules is termed hydrogen bonding which is responsible for surface tension.

·       Water filters out wavelengths of ultraviolet radiation (UV rays) that could harm some aquatic organisms

·       As water cools, it contracts in volume like all other compounds reaching its greatest density at 4oC (39oF). Below this temperature, water behaves differently from other compounds. It begins to expand as more hydrogen bonds form among the slower-moving molecules creating the hexagonal structures of snow and ice. This expansion continues to a temperature of -20oF (-29oC), with up to 9% increase in volume possible. This explains why an ice is less dense than liquid water and also why ice floats on liquid water. 

PHASES OF WATER

A change from one state of water to another is called a phase change. The change from solid to vapor is called - sublimation; from liquid to solid - freezing; from solid to liquid - melting; from vapor to liquid - condensation; and from liquid to vapor - vaporization, or evaporation. For water to change from one state to another (solid, liquid, gas) heat energy must be added to it or released from it. The heat energy required for water to change phase is termed latent heat, because, once absorbed, it is hidden within the structure of the water, ice, or water vapor.

FORMS OF HUMAN USES OF WATER

 

1.   Water withdrawal, remove water from the supply, use it, and then return it to the stream.

2.   Consumptive uses remove water from a stream but do not return it, so the water is not available for a second or third use.

3.   Nonconsumptive Uses: Americans in the 48 contiguous states withdraw approximately one-third of the available surplus runoff for irrigation, industry, and municipal uses.

 

How much Freshwater water is available?

 

About 70% of the earth's surface is covered with water but only a tiny fraction is available to us as freshwater.

 

97.4% of all water found on the earth’s surface is contained in the oceans and seas and is therefore too salty for domestic use. The remaining 2.6% is Freshwater but most of the freshwater is locked up in ice caps or glaciers (93%) or is in groundwater (11.02), soil moisture (0.18%) too deep or salty to be used.

 

Only about 0.014% of earth’s total volume of water is easily available to us as soil moisture, usable groundwater water vapor, lakes, ponds, rivers and streams.

 

Of the tiny freshwater available on the earth, human beings compete with plants, animals and other species for its use. Luckily, freshwater is continuously supplied through the solar-powered hydrological cycle but human activity and possibly global warming have disrupted the cycle.

 

WATER’S IMPORTANCE

 

a) In the Human Body:

Ÿ         The body of an average human adult contains 50 liters (110lbs) of water. If the body looses about 12% of this water, the individual will die

Ÿ         Water is a principal component of blood.

Ÿ         Water is a transportation medium for many substances including vitamins, hormones, enzymes, oxygen and minerals required for growth

Ÿ         Water is also a medium for getting rid of waste from the body (through sweat and urine)

 

b) Within an ecosystem:

Ÿ         No Plant or animal can survive without it. All organisms are composed of water. A tree is about 60% water by weight and most animals are 50%-65% by weight.

Ÿ         There are no substitutes for most of its uses.

Ÿ         Water plays a major role in shaping the earth’s surface relief, moderating climates and diluting pollutants.

 

WHY SHORTAGES IN FRESHWATER SUPPLY?

 

1.  Dry climate

2.  Drought

3.  Rapidly increasing population:

4.  Increases in Agricultural uses of water: 

5.  Expansion in Industrial Uses of Water: 

6.  Expanded Urban use and Waste: 

7.  Unequal Distribution of Freshwater: 

8.  Water Pollution:

 

TO INCREASE FRESHWATER SUPPLY

 

1. Build dams and reservoirs

2. Bring in surface water from another area

3. Withdraw groundwater

4. Convert saltwater to freshwater (desalination)

5. Improve the efficiency of water use

6. Conserve water:

        a) On the Farm - 

        b) In industry - use of treated sewage water for heating

        c) On College Campuses and Homes: Bathroom showers, In the

             Kitchen, On the lawns

7.  Reclaim Sewage Water from urban areas for reuse.

8.  Rain-making through cloud seeding

9.  Harvesting icebergs.

 

SURFACE WATER POLLUTION

 

Surface water pollution can be defined as any contamination of surface water that lessens its value to humans and nature. There are two broad sources of water pollution:

1.   Point pollution: a source from where contaminates are continuously released into water

2.   Non-Point Solution: has its source over large areas such as

                i)    Farmlands:  (pesticides, fertilizer, manure, sediment)

                ii)   Grazing Lands:  (animal wastes, sediment)

                iii)  Stream banks: (sediment)

                iv)  Abandoned Mines: (acid drainage from coal mines)

                v)   Roadside (deicing salts, sediment, lead)

 

Types of Surface Water Pollution:

 

a)  Sediment pollution: By rivers, from mining and construction sites, farmlands etc.

b)  Nutrient pollution:  The nutrient enrichment of an aquatic ecosystem is known as

     Eutrophication.  Human activities speed up the release of excessive amounts of nutrients into

     aquatic ecosystems in a process is known as Cultural eutrophication.

c)  Thermal pollution:  An increase in temperature of water that adversely affects organisms that

      live there.

d)  Toxic Chemicals pollution:  Chemical wastes from factories may be poured into lakes and

      rivers

e)   Disposal of waste from Sewage

 

HYDROLOGICAL CYCLE.

 

The hydrologic cycle is a model of earth’s water system that operates within the lower atmosphere to several kilometers beneath earth’s surface. Water soaks into the subsurface through infiltration, or percolation into the soil to form groundwater.

 

Evaporation is the net movement of free water molecules away from a wet surface into air. Transpiration is the movement of water through plants and back into the atmosphere. Evaporation and transpiration are combined into one term—evapotranspiration. Evaporation and condensation entail a natural process of water purification called Distillation.

 

The amount of water vapor in the air at any particular place and time is termed as Humidity. Relative humidity is the amount of water vapor in the air compared to the total amount that the column of air can hold.

 

Precipitation

The moisture supply to earth’s surface is precipitation, arriving as rain, sleet, snow, and hail.

a) Solar heating causes air to rise, cool and condense.

b) Moisture-laden air encountering a mountain range.

c) When a warm dry air mass meets a cool heavy air mass, the point of

    contact is called a Front. At the frontal zone, the cool air mass

    undercuts the warm air and deflects it upward. The warm air then

    rises, cools and condenses and then fall as rain.

 

GROUNDWATER

 

Water from precipitation may follow 2 pathways:

(a) soak into the ground (infiltration) or …

(b) run over the surface through channels (streams & rivers and ultimately into the sea from where the water may evaporate into the sky.

 

Groundwater is a part of the hydrologic cycle, but it lies beneath the surface beyond the soil-moisture root zone. Groundwater replenishment is tied to surface water surpluses. Excess surface water moves through the zone of aeration, where soil and rock are less than saturated. Eventually, the water reaches the zone of saturation, where the pores of the soil are completely filled with water.

 

The texture and the structure of the soil dictate available pore spaces, or porosity. The soil’s permeability is the degree to which water can flow through soil; impermeability describes the condition where flow is restricted. Permeability depends on particle sizes and the shape and packing of soil grains. An aquifer is a rock layer that is permeable to groundwater flow in usable amounts. An aquiclude is a body of rock that does not conduct water in usable amounts.

 

The upper limit of the water that collects in the zone of saturation is called the water table; it is the contact surface between the zones of saturation and aeration. The aquifer recharge area extends over an entire unconfined area

 

As water is pumped from a well, the surrounding water table within an unconfined aquifer will experience drawdown, or become lower, if the rate of pumping exceeds the horizontal flow of water into the aquifer around the well. Aquifers frequently are pumped beyond their flow and recharge capacities, a condition known as groundwater mining. Groundwater may reach the surface as a cool continuously flowing water called Spring, or as a continuously flowing warm water called Hot Spring or intermittently gush out some warm water as a Geyser.

 

Sources of Groundwater Pollution

 

a)  Seepage from Industrial Landfills:

b)  Septic Tanks: 

c)  Leaks from underground Gasoline Storage Tanks:

d)  Dissolved chemicals from Farms

e)  Run off from industrial wastes sites.

 

Human activities interrupt the hydrological cycle at one or more of the following points:

        a)  The evaporation-transpiration loop

        b)  The surface run off loop, or

        c)  The groundwater loop.

 

WATER SUPPLY PROBLEMS

 

1.  Drought:   

2.  Floods:

Ÿ          Flood control measures include:

        a)  Protecting the Watershed through reforestation

        b)  Measuring snow pack to predict floods

        c)  Constructing levees at varying distances from the river bank

        d)  Dredging to clear a river's channel of silt deposits

        e)  Building dams to control the flow of the river.

        f)  Zoning of flood plains

3.  Overdraft of Surface Water

Can cause serious Ecological Effects on downstream of rivers and Estuaries may be deprived of their species of fish.

4.  Overdraft of Groundwater

The decrease in the level of a water table has several impacts including:

        a) Diminishing surface water:

        b) Land subsidence:

        c) Sinkholes

        d) Saltwater intrusion (encroachment)