Lacustrine zone in a reservoir

(i) is broad deep lake-like basin

(ii) is autochthonous

(iii) has P > R

(iv) has turbid water

Choose the correct answer from the code given below :

The correct answer is 2) Only (i), (ii), (iii).

Key PointsUnderstanding the statements in relation to Lacustrine Zone

• Broad Deep Lake-like Basin
  • The lacustrine zone in a reservoir typically describes the part that resembles a deep lake, characterized by a broad and deep basin.
  • This area is generally found near the dam where water is the deepest. Hence statement (i) is correct.
• Autochthonous Nature
  • Autochthonous refers to materials such as organic matter that originate within the lake itself rather than being transported from outside.
  • The lacustrine zone, being deep and inactive, often supports autochthonous production due to the presence of internally generated nutrients. Hence statement (ii) is correct.
• P > R (Production greater than Respiration)
  • P > R indicates that the primary production (P) of organic material via photosynthesis exceeds respiration (R).
  • This condition can occur in the lacustrine zone where nutrient inputs can lead to high productivity. Hence statement (iii) is correct.
• Turbid Water
  • Turbid water usually contains high levels of suspended particles, making it less clear.
  • The lacustrine zone in a reservoir typically has clearer, less turbid water compared to other zones such as the riverine zone. Hence statement (iv) is incorrect.

Additional Information

• Characteristics of Lacustrine Zones
  • Lacustrine zones are key areas in large artificial reservoirs where water resides for long periods, allowing sedimentation to occur.
  • The water in these zones is generally more stable and clearer due to reduced sediment inflow and higher settling rates of suspended particles.
• Comparison with Riverine and Transitional Zones
  • Unlike the riverine (inflow) and transitional (middle) zones of a reservoir, the lacustrine zone is characterized by its depth and clearer water.
  • The riverine zone is more turbulent with high levels of suspended sediments and nutrients, leading to turbid conditions.