Chapter 3

• Geomorphology


  Aids in understanding lake origins and formative processes
• Morphology


  The study of lake shapes, related to the origins of each system
• Morphometry


  Deals with the quantification of these forms and elements
• Lake


  A body of stationary water in a given basin, not connected to the ocean. Also referred to as lentic systems (from the Latin lentus, meaning lens)
• Principal types of drainage in water basins


  • Parallel Drainage
  • Dendritic Drainage
  • Bayonet Drainage
  • Angular Drainage
  • Radial Drainage
  • Anastomosed Drainage
  • Meandering Drainage
  • Parallel Drainage
  • Dendritic Drainage
  • Bayonet Drainage
  • Rectangular Drainage
  • Annular Drainage
• Types of drainage

  • EXORHEIC - Open drainage/ Perennial and periodic rivers
  • ENDORHEIC - Closed drainage/Periodic rivers
  • DRY - Diffused desert drainage/Sporadic rivers
  • CRYPTOREIC - Karst drainage/ Underground rivers and labyrinths
• Classification of lakes by origin


  • TECTONIC: Formed by Earth's crust movements (faults, rift valleys)
  • VOLCANIC - The formation of depressions, or hollows that do not drain naturally, produces a series of volcanic lakes
  • GLACIATION - Formed by glacial action cause deposits or corrosion of masses of ice and their depositions, with subsequent thawing
  • SOLUTION LAKES - Formed by the dissolution of soluble rock (e.g., CaCO3) by slightly acidic water with CO2
  • LAKES FORMED BY FLUVIAL ACTIVITY - Created by river sediment deposition and erosion
  • LAKES FORMED BY WIND ACTION: Formed in depressions or blocked by dunes; ephemeral and saline due to evaporation
  • LAKES FORMED BY ORGANIC DEPOSITS: Plant growth and detritus obstruct small rivers and depressions, forming shallow lakes
  • LANDSLIDES: Formed by rock or soil movements due to abnormal weather (e.g., excessive rainfall, earthquakes)
  • COASTAL LAGOONS: Formed by coastal deposition in bays or inlets, alternating between fresh and brackish water
  • LAKES OF METEORIC ORIGIN: Created by meteorite impacts forming depressions that accumulate water
  • MULTI-ORIGIN LAKES: Formed by interacting processes (e.g., glaciation, heavy precipitation, tectonic movement)
• Types of lake morphology (Hutchinson 1957)


  • CIRCULAR: volcanic lakes, especially lakes in old craters
  • SUB-CIRCULAR: slightly modified from the circular, due to wind action and transport of material – commonly found in glacial lakes
  • ELLIPTIC: arctic lakes
  • Elongated sub-rectangular: lakes of glacial origin in glacier-carved valleys, approximately rectangular in shape
  • DENDRITIC LAKES: originated from submerged valleys obstructed by sedimentation, with many arms and bays
  • TRIANGULAR FORM
  • IRREGULAR: in regions where basins fused, resulting in irregular shapes
  • CRESCENT SHAPED: some lakes with half-moon shapes in flooded valleys or volcanic regions
• Cryptodepressions


  Maximum depths below sea level
• Well-known cases of tectonic lakes

  • LAKE BAIKAL
  • THE CASPIAN SEA
• Common Structures/ Zonation in Lakes


  • LITTORAL ZONE - Sufficient light penetration allows for aquatic macrophytes growth
  • SUBLITTORAL ZONE - Dimly lit area below the littoral zone. Few macrophyte species survive here due to low light
  • DEEP ZONE - Light does not reach here, and gases like methane and hydrogen sulphide accumulate in stratified lakes
  • PELAGIC (LIMNETIC) ZONE - Found in deep lakes with minimal bottom influence
  • EUPHOTIC ZONE - Extends to the depth where 1% of surface light reaches, allowing for photosynthesis
  • APHOTIC ZONE - Non-illuminated regions, extremely small in clear lakes where the euphotic zone extends to the bottom
• Key Vertical Structure Elements


  • LIGHT ZONATION: Differentiation of the lake's vertical structure based on light penetration
  • THERMAL CHARACTERISTICS: Vary with depth and affect lake processes
• Important Interfaces in Aquatic Ecosystems


  • AIR-WATER INTERFACE
  • SEDIMENT-WATER INTERFACE
  • ORGANISM-WATER INTERFACE
• Shallow Lake


  Irregular sedimentation with erosion periods
• Types of Shallow Lakes


  • SECONDARY SHALLOW LAKES: Formed from siltation in old deep lakes
  • PRIMARY SHALLOW LAKES: Found in marginal areas of tropical rivers, tectonic basins, and arid or semiarid regions, often highly saline
• Unique Limnological Features


  • Thermal stratification and vertical circulation
  • Biological stratification in summer and winter
  • Chemical stratification due to thermal stratification
  • Diurnal fluctuations
• Artificial Reservoirs


  Differ considerably from natural lakes, impacting drainage basins and hydrological cycles
• Hydrodynamics of Reservoirs


  Primarily driven by their operational processes, influencing the vertical and horizontal distribution of plankton populations, as well as the transport of nutrients, carbon, nitrogen, phosphorus, and toxic substances
• Reservoirs often have more dynamic and differentiated horizontal patterns due to variations in retention time, whereas natural lakes exhibit more stable retention times and flow patterns