In this portion of Utah irrigation is essential to agriculture. If all the single acres it is possible to cultivate without artificial irrigation were aggregated, I do not believe the sum would reach one-fourth of one square mile, and every foot of this meager amount is irrigated naturally. Springs are of infrequent occurrence. The great source of the water supply is the streams fed by the rains and snows of the high table lands and mountains. All these streams have a rapid fall in their upper courses, and are here often of considerable size; but upon reaching the lower and more level country their waters are rapidly absorbed by the porous soil and evaporated by the higher temperature. So great is the loss from these causes that some streams fail to reach the main drainage channel during the warmer months, and all are greatly shrunken in volume. All the arable lands--or lands where altitude, slope of surface, and quality of soil permit successful cultivation, if a supply of water can be obtained, and from which lands to irrigate, or irrigable lands, may be selected--are in the valleys adjacent to the streams. Usually this area in many valleys is in excess of that which the water in the streams can irrigate, and choice in the location of lands to cultivate is often practicable. In this report I have considered irrigable lands to be such only as possess all the necessary qualifications of altitude, slope of surface, and fertility of soil, and have, in addition, an available supply of one cubic foot of water per second for each hundred acres. The great dissimilarity between the valleys makes it desirable to consider the drainage basin of each separately, in respect to arable lands, irrigable lands, volume of water, and practicability of increasing this supply during the irrigating season. THE VIRGIN RIVER.