Water Resources and Water Pollution Notes
The Earth’s Water Budget
About 97% of Earth's water is saltwater, while 3% is freshwater.
Approximately 2.59% of freshwater is stored in ice caps, glaciers, and deep groundwater, which are hard to access.
Less than 0.5% of freshwater is readily available as soil moisture, surface water (lakes and streams), water vapor, and easily extractable groundwater.
The water cycle, also known as the hydrologic cycle, continuously replenishes this essential resource.
Breakdown of Earth's Water Budget:
Oceans: 97.2%
Glaciers: 2.15%
Groundwater: 0.62%
Freshwater lakes: 0.009%
Saline lakes and inland seas: 0.008%
Soil moisture: 0.005%
Stream channels: 0.0001%
Atmosphere: 0.001%
Importance of Water
Water is essential for life; humans can only survive a week without it.
The human body is about 60% water, blood is at least 50% water, and the brain is approximately 77% water.
Water is used in sports and recreation and significantly affects the weather.
Properties of Water
1. Hydrogen Bonds
A water molecule () consists of two hydrogen atoms and one oxygen atom joined by covalent bonds.
Water molecules are linked by intermolecular forces of attraction, enhanced by hydrogen bonds.
2. Boiling and Freezing Points
At sea level (1 atmosphere or 101,325 pascals), water boils at 100°C and freezes at 0°C.
At about 300 m above sea level, the boiling point is lower, around 99°C.
Water remains liquid over a wide temperature range, crucial for our needs.
Water can exist as liquid, solid, or gas within readily attainable temperatures.
3. High Heat Capacity
The specific heat capacity of water is 4.184 J/g°C, meaning 4.184 J of energy (1 calorie) is needed to raise the temperature of 1 g of water by 1°C.
Water has a high heat of vaporization, requiring significant energy to evaporate bodies of water.
Perspiration cools the body as sweat evaporates and removes heat.
4. Polarity
Water is a universal solvent, easily dissolving many substances.
Ionic compounds like table salt and polar substances like table sugar dissolve in water.
This property also makes water easily polluted.
5. Transparency
Water is clear and allows light to pass through, which is crucial for underwater photosynthesis by green plants.
6. Density of Ice
Ice is less dense than liquid water, allowing it to float.
When liquid water solidifies, its density decreases slightly below 1g/ml.
This keeps aquatic life alive under ice surfaces in cold regions during winter.
The Water Cycle
Water is a major renewable resource with a relatively fast cycle.
Atmospheric moisture can be renewed in 7 days, while other water cycles can be slower.
Water in lakes renews in about two decades, and groundwater takes over a thousand years.
Water evaporates from bodies of water like oceans, seas, and lakes. It also evaporates from plants and drying clothes.
Evaporation of perspiration has a cooling effect.
Water vapor condenses to form steam, fog, or clouds.
Evaporation, Transpiration, Condensation, Precipitation
Water evaporates from oceans, land, and plants through evaporation and transpiration.
This water accumulates in the atmosphere and condenses to form clouds.
Nimbus clouds, heavy with water, deliver rainwater to the Earth's surface through precipitation.
Infiltration, Percolation, Absorption, Runoff
Rainwater is distributed via infiltration, percolation, absorption, and runoff.
Infiltration: water enters the soil.
Percolation: water moves down into the soil and permeable rocks to reach aquifers or groundwater storage.
Plants absorb rainwater from their roots and distribute it to stems and leaves through capillary action, then transpire.
Runoff: water flows in downslopes, returning to rivers, lakes, or seas.
Water Cycle Variations
Water evaporates faster during long, hot summer days, leading to parched soil and critical water levels.
Water rationing may be implemented to limit consumption.
During the rainy season, abundant rainfall can lead to water reservoirs filling to capacity, requiring the release of excess water to prevent floods.
Water as a Renewable Resource
Water is renewable but potentially non-renewable if polluted, wasted, or depleted.
Freshwater can become non-renewable if its use exceeds its sustainable yield.
Sources of Water
Water is available as surface water or groundwater.
Surface Water: Water in rivers, lakes, seas, and reservoirs, replenished through precipitation and runoff.
The oceans are interconnected, with water circulating vertically and horizontally, although restricted by land barriers.
Groundwater: Rainwater that seeps into the ground through voids and permeable rocks.
Groundwater flows through permeable rock materials known as aquifers.
Impermeable rock materials called aquitards prevent the flow of water.
Only water filling the saturated area underground is called groundwater.
The upper limit of this saturated area is the water table.
Above the water table is the unsaturated area, or vadose zone, containing vadose water.
The depth of the water table varies by location.
Spring: Groundwater that naturally surfaces from fissures in an aquifer's base.
Groundwater can be extracted via artesian wells or motorized pumping systems.
The ability to use underground water depends on the water table depth.
Depleted groundwater is replaced slowly, over hundreds to thousands of years, and such depletion contributes to land subsidence.
Water Consumption
Water consumption includes domestic, public, commercial, and industrial uses.
Domestic demand: water for drinking, cooking, washing, and laundering.
Public demand: water for fire protection, street cleaning, and use in public buildings.
Commercial and industrial demands: water for stores, offices, hotels, laundries, restaurants, and manufacturing plants.
Total water demand varies among communities based on population, location, climate, commercial/industrial activity, and water cost.
Water use is expressed as average daily consumption per capita.
Water consumption in developing countries can be as low as 15 liters (4 gallons) per capita per day.
The world average is estimated at approximately 60 liters (16 gallons) per person per day.
Water demand varies seasonally, daily, and hourly.
Peak demands in residential areas usually occur in the morning and early evening.
Commercial and industrial districts have uniform water demands during the workday.
Minimum water demands typically occur in the early morning hours.
Civil and environmental engineers study water use patterns to design efficient pumping and distribution systems.
El Niño – La Niña Phenomena
Droughts and rainy days are often associated with El Niño and La Niña.
El Niño in the Philippines extends the summer months and causes decreased precipitation, leading to critical water levels and parched farmlands.
These events have significant economic and environmental consequences.
El Niño
Along the west coast of South America (Peru), strong winds cause upwelling, bringing cold, nutrient-rich water and supporting a large fish population.
Sea birds feed on the fish, creating guano deposits, a natural phosphate-rich fertilizer.
During El Niño, a warm, nutrient-poor current moves towards the South American coast, reducing fish harvests.
The Peruvians named this El Niño (the Child Jesus) because it often occurs in December.
La Niña
In meteorology, this condition is known as El Niño Southern Oscillation (ENSO).
While ENSO occurs in Southern America, the Philippines experiences long rainy days, known as La Niña, which contrasts with ENSO.
ENSO events can last from weeks to months, with longer events having adverse economic and environmental impacts.
El Nino vs La Nina
El Niño Conditions
Warmer surface waters along the coasts
Sharp decline in fish harvest
Long dry season resulting in critical water levels
Drying up of farmlands, resulting in poor crop harvests
Serious economic consequences
La Niña Conditions
Frequent and stronger typhoons; longer rainy season in Southeast Asia
Colder and longer winter season in the northern hemisphere
Flooding in coastal regions and floodplains
Vulnerability of Water Resources
Many places in the Philippines lack access to clean water for household use.
Many areas are not serviced by waterworks facilities like MWSS.
One in five Filipinos in 24 provinces get water from shallow and easily polluted springs.
Heavy freshwater consumption can cause depletion of water tables, seawater intrusion, and land subsidence.
Seawater intrusion: contamination of freshwater with saltwater.
Land subsidence: Depression of land due to massive water extraction leaving underground voids.
Water scarcity occurs in places surrounded by seas due to the high cost of desalination.
In the Middle East, water scarcity is addressed through cooperation for just and equitable sharing of water resources from the Tigris-Euphrates, Nile, and Jordan rivers.
Water scarcity is a problem in countries with drought or little precipitation, leading to food shortages and starvation.
A floodplain is a flat land beside rivers that submerges during floods. The soil is fertile due to sediments and minerals.
Floodplains are often used for agriculture but face high flood risks.
Several Asian countries face heavy rains and massive flooding due to their location in low-lying areas and floodplains.
Bangladesh loses many lives yearly due to flooding.
Other places below sea level suffer from too much surface water, aggravated by dense population and poor drainage, like Malabon, Metro Manila.
Venice, Italy, has transformed its submerged city into a tourist attraction.
Water Pollution
Water pollution occurs when water becomes unfit for its intended use.
Early humans used water for drinking, washing, and cooking. Their wastes enriched the land, and self-purification cleaned the water through natural processes.
As agriculture developed, irrigation became common. Population increased, leading to more waste and water contamination.
Contaminated water became undrinkable, and self-purification could not keep up with human and animal wastes.
Rivers have been important resources and often used as sewers, becoming polluted with organic wastes containing pathogens.
Pathogens transmit infectious diseases like typhoid, dysentery, cholera, and diarrhea.
Microbes produced from oxygen-demanding wastes deplete dissolved oxygen, killing aquatic organisms.
Industrial wastes are now the most common and hazardous water pollutants.
Industries are often situated along rivers for water-cooling and transport.
Industrial wastes include dangerous organic chemicals, heavy metals, nitrates, grease, oil, and radioactive chemicals.
Sources of Water Pollution
Residential buildings, abandoned mines, septic tanks, oil spills, mariculture, sludge, atmospheric deposition, factories, industrial runoff, combustion (cars), urban runoff, livestock, sewage treatment facilities, plants, algae, farms, agriculture fertilizer, landfills, aquifer.
More Water Pollutants
1. Lead and Mercury
Lead (Pb) is a neurotoxin that damages the central nervous system, causing hyperactivity and low attention spans in children.
It is linked to low IQ and poor school performance.
Lead concentrations are higher in areas with lead water pipes, preventing corrosion.
Other lead sources include paint products and leaded gasoline.
Many alternatives to leaded products are now used in developed countries.
The Philippines still has old plumbing systems with leaded materials.
Studies have shown high concentrations of lead in fish and shrimp species in some rivers.
Oil spills prevent oxygen entry into the water, essential for aquatic species respiration, and coat the gills of fish, leading to suffocation.
Oil can also affect birds, making their feathers sticky and heavy.
Cleaning up oil-covered surfaces is a major challenge.
2. Nitrates and Phosphates
Too much nitrates () and phosphates () in water lead to eutrophication.
Nitrates and phosphates are used in fertilizers and become part of agricultural runoff.
Phosphates are found in household detergents.
Abundance of these chemicals causes excessive algae growth (algae bloom), oversupplying nutrients for fish.
As fish populations increase, they consume more dissolved oxygen.
Algal blooms reduce oxygen penetration, resulting in large fish populations competing for less oxygen and causing massive fish kills.
3. Acids
High acid concentrations in water, from acid rain or industrial wastewater, lead to massive fish kills.
Many aquatic species have low tolerance for acidic water.
Acid dissolves necessary nutrients for algal growth, disrupting the food chain.
4. Persistent Organic Pollutants (POP)
POP are stable compounds that persist in the environment for a long time, found in water, soil, and air.
The "dirty dozen" POPs: Aldrin, Dieldrin, Endrin, Chlordane, Heptachlor, Toxaphene, Mirex, DDT (dichlorodiphenyltrichloroethane), HCB (hexachlorobenzene), PCBs (polychlorinated biphenyls), Dioxins, and Furans.
These are groups of organic pesticides, with Dioxins and Furans having as many as 17 to 210 kinds.
Dioxins, Furans, and HCBs are synthesized through anthropogenic activities like burning chlorinated organic substances.
POPs are very toxic to humans and animals.
Dioxins are considered the most carcinogenic compounds.
DDT was developed in the 1940s as a "magic bullet" against malaria, but later found to be carcinogenic and persistent, biomagnifying in the food chain.
Insects develop resistance to DDT after years of exposure.
The United States banned its use in 1971, followed by other developed countries, but developing countries still illegally import DDT.
5. Dead Rivers
Rivers and lakes are important water sources.
The Philippines has over 400 rivers and 50 natural lakes.
Five major river basins: Cagayan (Region II), Mindanao (Region XII), Agusan (Region X), Pampanga and Agno (Region III), supply water for various uses.
The Angat River in Bulacan (Region III) supplies Metro Manila with water through MWSS, Maynilad Water, and Manila Water Corporations.
Many rivers have been identified as dead rivers.
The Philippine Environmental Quality Report of 1990 – 1995 defines a dead river as "one which is not suitable for any beneficial purpose".
Rivers can be physically lost due to sedimentation or chemically/biologically polluted.
A biologically dead river no longer supports aquatic species due to oxygen depletion and deteriorated conditions.
Many river sub-basins in Metro Manila, like the Tullahan River, have become garbage dumpsites.
The Pasig River has been declared biologically dead, serving as a conduit for Metro Manila's sewage towards Manila Bay, but rehabilitation efforts are showing improvement.
6. Thermal Pollution
Thermal pollution, or heat pollution, happens when hot wastewater from industries or power plants is released into rivers or lakes.
It does not make the water dirty but has harmful effects.
High temperatures reduce dissolved gases like oxygen.
Fish and other organisms suffocate due to lack of oxygen.
Heating the river or lake disrupts the ecosystem and causes massive fish kills as fishes are cold-blooded.
7. Mine Spills
Spills from mine tailings pollute bodies of water.
Tailings are wastewater from mineral ore processing, collected in catchment basins.
Basin spills pollute rivers with toxic chemicals like mercury and cyanide.
High concentrations have been found in rivers near mine sites in Boac (Marinduque), Mt. Diwalwal (Compostela Valley), and Rapu-rapu (Albay), affecting people's health and damaging aquatic ecosystems.
Strategies of Water Management
Protecting Watersheds
A watershed is a region from which every drop of surface runoff drains towards a common stream, river, or body of water.
It is considered a protected area and should be kept free from encroachment and pollution.
Components include trees, and humus from forest litter makes the soil fertile, enabling it to absorb more water.
The La Mesa Watershed in Metro Manila has 2,700 hectares of forest land and a lake used as a reservoir.
According to the National Water Quality Status Report 2001 – 2005, the La Mesa watershed supplies 12 million residents of Metro Manila with 1.5 million liters of water daily.
Many watersheds' forests are denuded, including the La Mesa watershed.
ABS-CBN Foundation’s Bantay Kalikasan helped save the area through its “Save the La Mesa Watershed Project”.
Rehabilitation efforts include encouraging tourists and eco-watchers to protect and conserve the area.
Reforestation programs stop the degradation of the watershed and ensure the continuous supply of water.
Despite watershed protection efforts, many forests are still denuded.
Massive tree cutting has increased soil erosion, promoted sedimentation, and caused flash floods and landslides, resulting in deaths.
A nationwide management program must be strictly implemented to ensure watershed protection and conservation.
Water Treatment
Public drinking water systems use different treatment methods to provide safe drinking water for their communities.
Public water systems often use a series of steps, including coagulation, flocculation, sedimentation, filtration, and disinfection.
Coagulation
Coagulation is often the first step, where chemicals with a positive charge are added to neutralize the negative charge of dirt and particles.
Particles bind with the chemicals to form larger particles.
Common chemicals include specific types of salts, aluminum, or iron.
Flocculation
Flocculation follows coagulation, involving the gentle mixing of water to form larger, heavier particles called flocs.
Additional chemicals may be added to help flocs form.
Sedimentation
Sedimentation is used to separate solids from water.
Flocs settle to the bottom because they are heavier than water.
Filtration
After sedimentation, clear water is filtered to separate additional solids.
The clear water passes through filters with different pore sizes made of sand, gravel, and charcoal.
These filters remove dissolved particles and germs, such as dust, chemicals, parasites, bacteria, and viruses.
Activated carbon filters remove bad odors.
Ultrafiltration can be used instead of traditional filtration, where water goes through a filter membrane with very small pores.
This filter only lets through water and small molecules like salts.
Disinfection
After filtration, water treatment plants add one or more chemical disinfectants (chlorine, chloramine, chlorine dioxide) to kill remaining parasites, bacteria, or viruses.
To keep water safe as it travels, water treatment plants ensure the water has low levels of the chemical disinfectant, killing germs in the pipes between the treatment plant and houses.
Wastewater Treatment
Sewage is wastewater produced from bathrooms and toilets.
A sewerage system connects a house to a sewage and wastewater treatment plant through pipelines.
Only about 1% of the country has access to a sewerage system (ADB report).
In places with no sewerage system, a septic tank, a large concrete tank built underground, is used to receive household sewage.
The solid component (sludge) collects at the bottom, while the liquid component (effluent) goes to the drainage system and ends up in a body of water.
In the absence of a septic tank, sewage goes directly underground through a pit latrine, or is discharged directly into a body of water.
In Metro Manila, MWSS, through Maynilad Water and Manila Water, collects sludge from household septic tanks.
These companies provide this service for free or for a minimum fee.
Through a sewerage system, sewage is separated into sludge and liquid wastes.
Sludge is transformed into organic fertilizer or other useful inorganic material through bioremediation, using bacteria.
Liquid wastes are treated separately.
Aeration may be used to allow aerobic bacteria to decompose the wastes, or chemical treatment may be applied.