<Li> Rain water harvesting </Li> <Li> Water to Water heat exchangers . </Li> <P> For crop irrigation, optimal water efficiency means minimizing losses due to evaporation, runoff or subsurface drainage while maximizing production . An evaporation pan in combination with specific crop correction factors can be used to determine how much water is needed to satisfy plant requirements . Flood irrigation, the oldest and most common type, is often very uneven in distribution, as parts of a field may receive excess water in order to deliver sufficient quantities to other parts . Overhead irrigation, using center - pivot or lateral - moving sprinklers, has the potential for a much more equal and controlled distribution pattern . Drip irrigation is the most expensive and least - used type, but offers the ability to deliver water to plant roots with minimal losses . However, drip irrigation is increasingly affordable, especially for the home gardener and in light of rising water rates . Using drip irrigation methods can save up to 30,000 gallons of water per year when replacing irrigation systems that spray in all directions . There are also cheap effective methods similar to drip irrigation such as the use of soaking hoses that can even be submerged in the growing medium to eliminate evaporation . </P> <P> As changing irrigation systems can be a costly undertaking, conservation efforts often concentrate on maximizing the efficiency of the existing system . This may include chiseling compacted soils, creating furrow dikes to prevent runoff, and using soil moisture and rainfall sensors to optimize irrigation schedules . Usually large gains in efficiency are possible through measurement and more effective management of the existing irrigation system . The 2011 UNEP Green Economy Report notes that "(i) mproved soil organic matter from the use of green manures, mulching, and recycling of crop residues and animal manure increases the water holding capacity of soils and their ability to absorb water during torrential rains", which is a way to optimize the use of rainfall and irrigation during dry periods in the season . </P>

Importance of water and the methods of its storage and conservation