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hydraulically connected to the surface stream, and transpiration by non-agricultural vegetation along ditches and on the perimeter of cropped areas. These types of losses will be called "incidental" or "nonproductive" consumptive use in this analysis because they are unintended results which produce no economic gain for the irrigator, While these losses are not intentional, neither are they completely avoidable under practical irrigation techniques, Since part of this consumption of water occurs during the necessary process .of moving water from the stream to the point of use, it probably can not be considered a non-beneficial use, The user receives benefit from these losses because they allow for a practical method of delivering his crop water needs. A second category of losses illustrated in the water budget results in return flows, water returning to the stream from which it was diverted. These losses include deep percolation from ditches and fields into tributary aquifers, necessary or accidental water spills from the distribution system, and tailwater or unused irrigation water which runs off of the irrigated acreage, Since these losses can frequently be observed and can be as high as 50% of the amount diverted they are cited as indicating the waste and inefficiency of irrigated agriculture, However, by definition this water returns to the stream and is available for use by downstream appropriators, thus the pejorative term "waste" should not be automatically applied, To decide if water is "wasted" the observer must determine whether any other use (decreed or not) is deprived of water due to the losses resulting from the irrigator's actions, and whether or not those losses are reasonable and necessary., Often return flows help meet the late season water supply needs of other users, In the South Platte basin return flows get re-diverted as they move downstream and used some three times before reaching Julesburg, The remainder of the water diverted for irrigation is available for consumptive use by the crop, This use involves root uptake of soil water delivered to the crop's root zone, and subsequent evapo-transpiration by the plant and incorporation into the plant tissues. - This consumptive use is the ultimate beneficial use for which the diversion was made and represents the bulk of the depletions caused by irrigation, When certain irrigation techniques are employed more water is delivered to the root zone than can be used by the plant or stored in the soil. Deep percolation occurs whenever gravity moves water from soil that is too wet, to a level below which a crop's roots can no longer reach it. This water continues moving downward until it reaches the water table, signifying the presence of an aquifer, Once in an aquifer (either seasonal or permanent) deep percolation water normally begins moving toward the stream from which it was diverted, unless an intervening geologic barrier creates an isolated basin of non-tributary water, In regions where the soil and/or the irrigation water supply contains salts some deep percolation is necessary to maintain a salt balance in the soil. Extra water is intentionally applied to the field to leach out salts deposited in the soil from previous irrigations. Leaching carries the salt below the root zone where it will not hinder plant growth, Much of this saline deep percolation water eventually drains back to the surface water system as return flow, 4