High School Earth Science: Human Actions and Earth’s Water - Humans and the Water Supply — Flashcards

Ways to motivate farmers to use more water-efficient irrigation systems might include subsidizing installation of the systems, requiring them to pay for all the water they use, and fining them if they waste water.

Using Water for Irrigation    
Agriculture is the single greatest use of water worldwide, and most of the water used in agriculture is used to irrigate fields of crops. Common irrigation methods include:    
- sprinkler irrigation, in which water is sprayed onto the fields from overhead.    
- trench irrigation, in which canals carry water from a water source to the fields and through the fields along rows of crops.    
- flood irrigation, in which water is allowed to flow over the fields, like flood water of a river overflowing its floodplain.    

All three of these irrigation methods waste water. More than a third of the water may never reach the crops because it evaporates or runs off the fields. Water that runs off a field often carries valuable soil with it.    
A much more efficient way to water crops is by drip irrigation. With drip irrigation, pipes and tubes deliver small amounts of water directly to the soil at the roots of each plant. The water is not sprayed into the air or allowed to run over the ground so nearly all of it goes directly into the soil near plant roots. Very little water is lost to evaporation or runoff. However, drip irrigation systems are relatively expensive to install and maintain, so they are  not used as widely as they could be. Where farmers do not have to pay the full cost of their water use, they may lack financial incentives to use less water. In these situations, farmers may not be motivated to install more expensive drip irrigation systems.