1. The problem asks why water is not used as a hydraulic fluid. 2. Hydraulic fluids must have certain properties: incompressibility, lubrication, corrosion resistance, and stability under pressure and temperature. 3. Water is compressible compared to typical hydraulic oils, which reduces efficiency and responsiveness in hydraulic systems. 4. Water has poor lubrication properties, leading to increased wear and damage to hydraulic components. 5. Water causes corrosion in metal parts, which shortens the lifespan of the system. 6. Water can freeze or evaporate easily, making it unstable under varying temperature conditions. 7. Therefore, water is unsuitable as a hydraulic fluid because it does not meet the essential requirements for effective and durable hydraulic system operation.