This document provides an overview of water and irrigation. It discusses the molecular structure of water, its physical states, solvent properties, and interactions like cohesion, adhesion, surface tension, and capillary action. It also covers diffusion, osmosis, pH, plant water relations, evapotranspiration, and important irrigation principles like applying the proper amount of water based on soil type. Common irrigation methods like drip, spray, bubblers, and automatic timers are also summarized.