Which of the following irrigation methods leads to the least wastage of water?

The correct option is Drip irrigation.

To understand why drip irrigation leads to the least wastage of water, let us examine how the different irrigation methods operate:
1. Flood Irrigation: In this traditional method, water is pumped or routed to a field and allowed to flow freely over the entire soil surface. This leads to massive water loss due to surface evaporation, runoff, and deep percolation below the root zone.
2. Furrow Irrigation: This method involves creating narrow channels (furrows) along the crop rows and filling them with water. While more controlled than general flooding, it still results in substantial evaporation and uneven water distribution.
3. Sprinkler Irrigation: Water is sprayed into the air through pressurized nozzles, mimicking natural rainfall. Although it is more efficient than flooding, a significant amount of water evaporates in the air or is blown away by the wind before reaching the ground.
4. Drip Irrigation: This micro-irrigation system delivers water directly to the soil near the roots of individual plants, drop by drop, using a network of pipes, tubing, valves, and emitters. By targeting only the root zone, evaporation is minimized, runoff is virtually eliminated, and deep percolation is controlled.

Therefore, drip irrigation is highly efficient (often exceeding 90% water-use efficiency) and leads to the least wastage of water.