Aquatic Ecosystems and Freshwater Resources

Aquatic Ecosystems and Freshwater Resources

Freshwater Distribution

• Total Water on Earth: 100%

  • Oceans: 97.5% (salt water)

  • Freshwater: 2.5%

  • Groundwater: 20% of freshwater

  • Ice caps and glaciers: 79% of freshwater

  • Lakes: 52% of surface freshwater

  • Rivers: 1% of surface freshwater

  • Soil moisture: 38% of terrestrial fresh water

  • Atmospheric water vapor: 1%

Hydrologic Cycle

• Precipitation: Transfer of water from atmosphere to the surface.

• Interception: Capture of water by vegetation before it reaches the ground.

• Evaporation: Water vapor released back into the atmosphere.

• Transpiration: Evaporation of water from plant surfaces.

• Infiltration: Movement of water into the soil.

• Runoff: Water flowing from land into rivers and streams.

Groundwater

• Aquifers: Critical water supplies, crucial for many regions.

  • Recharge zones: Areas where water enters the aquifer.

  • Notable Aquifers:

  • Central Florida: Home to the largest collection of freshwater springs.

  • Ogallala Aquifer: Largest groundwater reservoir in the world.

• Withdrawals: Excessive groundwater withdrawal can turn springs into sinks.

Rivers and Streams

• Lotic Systems: Flowing water ecosystems, e.g., rivers and streams.

• Watershed/Drainage Basin: Area drained by a river system and its tributaries.

• Geographical Impact:

  • Rivers through rugged terrain cut deep valleys.

  • Rivers in flat areas meander and create oxbows.

  • Depositional features include braided channels in flat regions.

• Floodplain: Low lying areas alongside rivers enriched by silt deposition.

Lakes and Ponds

• Lentic Systems: Stagnant water bodies like lakes and ponds.

• Zones of Lakes:

  • Littoral Zone: Shallow waters near the shore.

  • Benthic Zone: Bottom of the lake.

  • Limnetic Zone: Sunlit surface waters.

  • Profoundal Zone: Deep waters where sunlight cannot reach.

• Oligotrophic Lakes: Clear, nutrient-poor lakes with high oxygen levels.

• Eutrophic Lakes: Nutrient-rich, often leading to low oxygen levels and high organic matter.

Wetlands and Their Types

• Wetlands: Areas of shallow standing water.

  • Marshes: Dominated by herbaceous plants.

  • Swamps: Forested wetlands.

  • Bogs: Ponds covered with vegetation.

  • Vernal Pools: Seasonal water holding pools.

Water Availability and Use

• Global Water Distribution: Not evenly distributed globally, with significant variations in available freshwater per capita.

• Water Use:

  • Irrigation: Largest consumer of water, particularly from aquifers.

  • Hydroelectric Dams: Non-consumptive use of water for electricity generation.

Recent Changes in Water Bodies

• Lake Powell: Affected by excessive usage and drought, reaching record low levels in 2010.

• Lake Mead: Has seen significant drops, threatening water supply for Las Vegas and electricity generation.

• Colorado River: Runs dry before it reaches its sea, demonstrating the impact of water consumption.

• Aral Sea: Devastated by damming and irrigation, now drastically reduced.

Pollution Sources and Treatment

• Surface Water Pollution: From organic wastes, sediments, mine drainage, urban runoff, etc.

• Point vs Non-Point Sources: Specific vs diffuse sources of pollution.

• Treatment Processes:

  • Primary Treatment: Settling out solids from wastewater.

  • Secondary Treatment: Biological treatment for oxygen-demanding wastes.

  • Tertiary Treatment: Utilization of wetlands for nutrient absorption.

Desalinization

• Desalination: A process used to convert salt water to fresh water, increasingly utilized worldwide to address freshwater scarcity.