Conjunctive use of water refers to the planned and coordinated utilization of surface water (canals, reservoirs, rivers) and groundwater resources to optimize irrigation efficiency, minimize environmental hazards, and ensure sustainable water supply.

Rationale:
Surface water is often inadequate or seasonal, while groundwater may have high salinity, alkalinity, or sodicity. By combining both, the limitations of each source are balanced.

Management practices for poor-quality water (salinity hazards):

Blending: Mixing saline groundwater with fresh canal water to bring salinity within permissible limits.

Cyclic use: Alternating irrigation between saline and fresh water in successive applications.

Leaching requirement: Applying excess water periodically to flush soluble salts below the root zone.

Proper crop selection: Growing salt-tolerant crops like barley, cotton, mustard, and sorghum.

Fertilizer management: Applying gypsum or organic matter to improve soil structure and counter sodium effects.

Improved irrigation methods: Drip and sprinkler systems minimize salt accumulation compared to flood irrigation.

Drainage management: Installing surface and subsurface drainage reduces waterlogging and salt buildup.

Mulching and green manures: Enhance soil microbial activity and reduce salt concentration near roots.

Thus, conjunctive water use with proper management safeguards crop productivity in saline-prone areas.