AREA OF IRRIGABLE LAND SOMETIMES NOT LIMITED BY WATER SUPPLY. While, as a general fact, the area of arable land is greater than the area of irrigable land, by reason of the insufficient supply of water, yet in considering limited tracts it may often be found that the supply of water is so great that only a part of it can be used thereon. In such cases the area of irrigable land is limited by the extent to which the water can be used by proper engineering skill. This is true in considering some portions of Utah, where the waters of the Green and Colorado cannot all be used within that territory. Eventually these surplus waters will be used in southern California. METHOD OF DETERMINING THE SUPPLY OF WATER. To determine the amount of irrigable land in Utah, it was necessary to consider the supply; that is, to determine the amount of water flowing in the several streams. Again, this quantity is variable in each stream from season to season and from year to year. The irrigable season is but a small portion of the year. To utilize the entire annual discharge of the water, it would be necessary to hold the surplus flowing in the non-growing season in reservoirs, and even by this method the whole amount could not be utilized, as a great quantity would be lost by evaporation. As the utilization of the water by reservoirs will be to a great extent postponed for many years, the question of immediate practical importance is resolved into a consideration of the amount of water that the streams will afford during the irrigating season. But in the earlier part of the season the flow in most of the streams in this western region is great, and it steadily diminishes to the end of the summer. Earlier in the season there is more water, while for the average of crops the greater amount is needed later.