The value of water to particular users depends crucially on its location, quality and timing. Its location determines its accessibility and cost. Its quality affects whether it can be used at all, and at what treatment cost. The time when it is available governs its reliability and its relative value for power, irrigation, environmental or potable uses. In addition, the value of water, especially in agriculture, is inseparable from the type of land to which it is applied, the nature of the soil, its drainage possibilities, etc.
Saline water is, for instance, unusable on some soils, but viable on others.
The value per unit weight tends to be low. Transporting and storing water is costly relative to its economic value at the point of use. Water is also difficult to identify and measure because it is a fugitive resource - it flows, evaporates, seeps and transpires. This evasive nature means that exclusive property rights, which are the basis of a market economy, are hard to establish and enforce. Water projects that attempt to compensate for extreme seasonal variations such as floods and droughts frequently require enormous investments.