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<br />l\.) <br />to <br />Uf <br />r.)) <br /> <br />smaller, creating a condition of uniform depth of wetting across <br />the field. The automatic reduction of time during soak cycle <br />prevents excessive runoff. As a result, vastly improved irrigation <br />efficiencies have been realized by many irrigators and the results <br />are being continuously published. <br /> <br />Lower Gunnison Basin <br />salinity Control project units 1, 2 & 3 <br /> <br />The Lower Gunnison Salinity Control Project is situated in west <br />central colorado and the irrigated cropland area stretches into two <br />counties, Delta and Montrose. The project Unit 1 and part of Unit <br />2 fall within Delta and are serviced out of Delta County. units 2 <br />and 3 within Montrose county are serviced out of Montrose County. <br />About 169,000 acres are irrigated by gravity flow; water diverted <br />either from the creeks coming down from Grand Mesa, or the Gunnison <br />and Uncompahgre River system. The water is delivered to the fields <br />by unlined canals and ditches. The entire area is underlaid by a <br />saline marine formation known as Mancos shale. Since the <br />irrigation water is quite plentiful and inexpensive, considerable <br />over-irrigation occurs. This over-irrigation coupled with leakage <br />from the unlined canals contributes about 840,000 tons of salt form <br />the shale through the return flow to the Colorado River system. <br />The croplands lie on both valley and high mesa. The crops are <br />diverse, ranging from orchard fruits to hay, and these include corn <br />for both grain and silage; hay--alfalfa, grass or mixed grass and <br />alfalfa; small grains, several varieties of orchard fruits; onions, <br />dry beans, sweet corn and other produce crops. Production on a <br />per-acre basis is good and the quality of the fruits is unique. <br /> <br />. <br /> <br />The surge project <br /> <br />Forty one cooperators were invited to participate in the USBR <br />sponsored surge irrigation and demonstration project. The <br />participating cooperators were given a surge controller with either <br />a T-valve, in-line valve for gated pipes or a ported ditch surge <br />gate. A short workshop on the use of the surge valves was <br />organized for the cooperators at the time of distribution of units. <br />Thirty five cooperators installed the units in their fields and <br />started using them. six would-be cooperators could not obtain <br />necessary appurtenances like gated pipe, proper water structure for <br />ported ditch, etc. and were kept on hold. <br /> <br />The Delta-Montrose Cooperative Extension team was able to monitor <br />78 irrigation events, both surge and conventional, of which 32 <br />produced usable data. Inflow and outflow of a furrow were measured <br />using V-notch furrow flumes fitted with automated data gathering <br />devices (potentiometers, datapods and computer chips). Generally <br />a non-wheel furrow was selected to place the furrow flume for the <br />evaluation. This presented conditions conducive to the greatest <br />amount of deep percolation and least run-off of the applied water <br />(a worst case scenario). Thirty-two such irrigations gave usable <br />data; the remainder were rendered unusable due to furrow washouts <br />cross-overs, and occasional malfunctions of the data-gatherin~ <br />equipment, or simply not used because both surge and conventional <br /> <br />3 <br />