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Difficulty: MediumEnvironmental Hazards and Resource Management in Nigeria

In large-scale irrigation schemes across northern Nigeria's river basins, such as the Hadejia-Jama'are floodplain, inadequate drainage combined with intense evaporation during dry seasons often leads to land degradation. Which specific environmental hazard is directly caused by the capillary rise and accumulation of dissolved salts on the surface layer of these farmland soils?

  1. Soil salinization, which increases surface toxicity and reduces crop yieldAnswer
  2. B
    Gully erosion, caused by vertical headward incision of surface runoff
  3. C
    Podzolization, resulting from intense leaching under dense rainforest vegetation
  4. D
    Marine coastal inundation, driven by tidal surges and ocean thermal expansion

Answer

Soil salinization, which increases surface toxicity and reduces crop yield
In the semi-arid northern belts of Nigeria, continuous irrigation without adequate drainage channels leads to a rising water table. Under high ambient temperatures, water rises to the surface by capillary action and evaporates, leaving behind a crust of dissolved salts. This process, known as soil salinization, degrades farmland soil fertility.

Step-by-Step Solution

1
Identify the geographical setting and environmental conditions described.
The setting is an irrigated river basin in the semi-arid northern region of Nigeria with high evaporation rates and poor drainage.
Environmental hazards depend heavily on regional climate and human management practices.
2
Analyze the physical process of water movement in dryland soils.
Water carrying dissolved salts moves upward through soil pores via capillary action toward the surface.
High ambient temperatures cause rapid evaporation of water at the surface, leaving salt minerals behind.
3
Select the hazard corresponding to salt accumulation on topsoil.
Soil salinization is the direct outcome, deteriorating soil structure and stunting crop growth.
Salinization is a major land degradation hazard in northern Nigerian irrigation schemes like Hadejia-Jama'are and Bakolori.

Key Concept

Soil Salinization in Nigerian Irrigated River Basins
Estimated Time:1m 0s
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Topics

Environmental Hazards and Resource Management in Nigeria

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