Over-tree irrigation is a classic application, and is very efficient against frost. However, the technique requires a high allotment of water, both at the level of the irrigation district for the simultaneous requirement for irrigation by many farms in the district, and at farm level (rainfall of about 4-5 mm per hour is estimated as necessary, and an average event of 10 hours means consumption of 40-50 mm of water). Significant water savings are possible with a localised over-tree irrigation system that does not wet the inter row areas, but only targets the rows of fruit, which usually, with modern trellis orchards, cover only 1/4 of the surface; this system uses specific sprinklers called flippers that only have to sprinkle a surface strip, the one under the row, allowing savings of 50-55% compared to the classic method. By exploiting the principle of freeing of calories through continued freezing of the water distributed on the fruit-farm/vineyard, below zero temperatures can be counteracted, even by 7-8 °C. However, the water quantity should not be reduced too much, as the plants must be irrigated on a uniform basis (continuously), with a sprinkler rotation velocity of 30-40 seconds when normal over-tree sprinklers are used. There is also the option to use mini sprinklers mounted on pipes for each row that only wet the plants. In both the over-tree systems and under-tree systems, there can be no wind in order to avoid lack of uniformity of the irrigation (over-tree systems) and evaporation of the water instead of freezing, or movement of the cushion of warm air formed by freezing the water releasing heat (under-tree system).