Definition: An increase in the nutrients in water, particularly nitrogen (N) and phosphorus (P).
Possible Sources of Eutrophication:
Agricultural Fertilizers: Used in farming practices, contributing excess nutrients to water bodies.
Manure and Human Sewage: Runoff containing organic waste increases nutrient levels.
Certain Industrial Wastewater: Industrial processes may release nutrient-rich wastewater into water bodies.
Algal Blooms and Dead Zones
Algal Bloom: A rapid increase in the population of algae in aquatic systems due to nutrient enrichment.
Dead Zones: Areas in water bodies where oxygen levels are too low to support marine life, often resulting from high nutrient inputs.
Biological Oxygen Demand (BOD)
Definition: The amount of oxygen required by aquatic organisms to decompose organic matter in water.
Oxygen Sag Curve
Definition: A graph representing the changes in oxygen levels in a water body over distance, showing the relationship between BOD and the availability of oxygen.
Direction of River Flow: The oxygen sag curve often declines downstream, indicating areas of higher BOD.
Risks to Human Health
Certain algal species can produce toxins harmful to both aquatic life and humans, posing health risks when contaminated water is consumed.
Sedimentation
Definition: The process by which sediment settles at the bottom of a body of water.
Mechanism: Rivers carry sediment as a result of erosion.
Types of Sediment:
Clay-sized particles
Sand grains
Gravel-sized sediments
Effects of Sedimentation:
Clay-sized particles tend to settle farthest fromshore in calm waters, whereas larger particles settle closer.
Human Impact on Sedimentation:
Natural Origin vs. Human Activity: 30% of sediment is from natural sources, while 70% is attributable to human activities such as construction, farming, and mining.
Consequences of Excess Sedimentation:
Turbidity (cloudy water)
Reduced sunlight penetration
Decreased oxygen levels
Increased nutrient levels
Clogged gills of aquatic organisms
Reduction in water depth as sediment accumulates on the bottom.
Thermal Pollution
Definition: The degradation of water quality due to a change in water temperature, most often caused by water discharged from industrial facilities.
Mechanism: Power plants and factories often use water as a coolant and release it back at temperatures 10 to 15°C hotter than the source.
Impacts on Ecosystems:
Many aquatic organisms may struggle to survive in altered temperatures.
Warmer water holds less dissolved oxygen.
Increased metabolic rates in ectothermic animals lead to higher oxygen demands.
Potential for species migration to cooler environments.
Possible Solutions:
Cooling towers for dissipating heat into the atmosphere
Recycling cooling water within power plants to minimize environmental discharge.
Noise Pollution
Definition: Underwater noise pollution primarily results from human activities, affecting marine animal communication and behavior.
Mechanism of Sound Travel: Sound travels 4 times better underwater than through air, making it crucial for the navigation and hunting of aquatic species.
Sources of Noise Pollution:
Ships
Submarines
Offshore drilling platforms
Sonar operations
Consequences of Noise Pollution:
Disruption of animal communication
Interference with echolocation for navigation and hunting
Potential forced migration of species to unfamiliar areas
Increased instances of beaching among whales and dolphins.
Possible Solutions:
Redesigning ships for quieter operation
Using alternate shipping routes to avoid critical habitats
Reducing sonar usage where possible.
Controlling Water
Overview: Humans depend on water but face dangers from flooding and other natural disasters. Strategies to manage these risks include:
Levees: Earth embankments to prevent flooding from rivers.
Dikes: Embankments to protect against sea flooding.
Dams: Barriers to control river flow and create reservoirs.
Aqueducts: Systems transporting water from one location to another.
Levees
Purpose: To keep riverbanks from overflowing during floods.
Construction: Usually made from earth, designed to protect land on the dry side.
Disadvantages:
Reduced fertility of floodplains
Increased development near rivers, posing risks if levees fail.
Dikes
Purpose: To control flooding by seas and oceans, creating protection for lands typically underwater.
Function: They can also reclaim land from aquatic areas, as seen in the Netherlands, where a significant area lies below sea level.
Dams
Definition: Structures designed to restrict and control water flow in streams and rivers, creating reservoirs.
Purposes of Dams:
Water supply
Recreation
Electricity generation
Flood prevention
Advantages and Disadvantages:
Advantages:
Provides water supply
Enables recreational activities
Generates renewable energy
Controls flooding risks downstream.
Disadvantages:
Alters nearby ecosystems
Hinders natural fish migrations
Displacement of local communities during construction.
Aqueducts
Definition: Systems of canals and ditches to transport water from one location to another.
Advantages:
Efficient distribution of water to needed areas.
Disadvantages:
Redistribution may change the hydrology of originating rivers or lakes.
Notable Example: The environmental crisis of the Aral Sea, due to water diversion for irrigation.
Access to Safe Drinking Water
Global Statistics:
1 in 6 people lacks access to safe drinking water.
Annually, approximately 3,400,000 deaths are attributable to water-related diseases.
Cholera Death Rates by Region (Notable Statistics):
Papua New Guinea: 330,000
Chad: 160,000
Guinea: 140,000
Mozambique: 60,000
Desalination of Water
Overview: Desalination is the process of removing salt from seawater to produce potable (drinkable) fresh water.
Methods of Desalination:
Distillation:
Involves boiling seawater to create vapor, leaving salt behind (brine).
Disadvantage: Requires a significant amount of energy; disposal of brine can be problematic.
Reverse Osmosis:
Forces saltwater through a semi-permeable membrane, allowing water to pass while blocking salt.
Disadvantage: More cost-effective than distillation, but still expensive to implement; brine disposal remains a challenge.