• Leaching Requirement (LR) in Salinity Management:
• The Leaching Requirement ($LR$) is the fraction of applied irrigation water that must pass through the crop root zone to prevent soil salinity from exceeding a specified threshold:

where:

• $D_d$ = depth of drainage water percolating below root zone
• $D_i$ = depth of applied irrigation water
• $EC_{iw}$ = electrical conductivity of the irrigation water
• $EC_{dw}$ = electrical conductivity of drainage water at bottom of root zone
• Conclusion: Option 1.

Correct option: (1) Option 1

• Classification of Irrigation Efficiencies:
• Water Conveyance Efficiency ($\eta_c$): Ratio of water delivered to the farm fields to water diverted from the source canal network: $\eta_c = (W_f / W_d) \times 100$. (True)
• Water Application Efficiency ($\eta_a$): Ratio of water stored in the crop root zone during irrigation to water delivered to the field, directly governed by the irrigation method (surface, sprinkler, drip). (True)
• Economic Efficiency: Evaluates overall economic returns generated per unit cost/volume of irrigation water across the system. (True)
• Conclusion: (A), (B) and (C) are all correct (Option 4).

Correct option: (4) (A), (B) and (C).

• Mechanisms of Sediment Transport in Streams:
• Bed load consists of coarse particles moving in contact with or near the channel bed by rolling, sliding, and saltation (bouncing). (True)
• In natural alluvial rivers, bed load typically constitutes less than 10% to 25% of the total sediment load, while suspended load constitutes 75% to 90%. (True)
• Suspended load is measured directly in streams using depth-integrating (e.g., US DH-48) or point-integrating samplers. The statement says it is not measured, which is False.
• Conclusion: Statements (A) and (B) only are correct (Option 1).

Correct option: (1) (A) and (B) only.