Wednesday, June 1, 2016

Water Starts Flowing Through Egin Bench Irrigation Canal [otd 06/01]

On June 1, 1883, water flowed from a pioneer canal onto Egin Bench farmland. The Bench bends for about 12-14 miles along the west side of Henry’s Fork, some 25 to 35 miles north of today’s Idaho Falls.
Egin Bench farmland near Henry’s Fork.

The first settlers arrived on the bench during the summer of 1879, shortly after Utah & Northern Railway tracks reached Eagle Rock (today’s Idaho Falls). While they saw potential there, they had to be content at first with cutting hay and raising stock. The river level lies 30 to 40 feet below the plain along much of the Bench's expanse. Farming had to wait until a ditch could be dug to take water from the river above today’s St. Anthony.

Still, the area proved attractive to homesteaders and a post office was established at Egin within a year. Locals thought “Garden Grove” would be a suitable name. The U. S. Postal Service said no … that name was already taken within Idaho Territory. As the story goes, the settlers met to pick another name on a nasty, cold day. They then chose “Egin,” an Anglicized version of the Shoshone word for “cold.”

The settlers began digging a canal during the fall after they arrived. However, they lacked the capital to hire more men and equipment, so it took four long years to complete the channel. Still, by all indications, that first water delivery in 1883 was a success. Perhaps enough water came through to mask what they would learn later.

Soon, more settlers began to break out land and dig irrigation ditches. The results were a shock to farmers used to normal flood irrigation: The coarse, sandy soil absorbed the water almost faster than they could deliver it.

Reports indicate that this phenomenon discouraged some settlers, who left. In reality, Egin Bench is one of the few places in the world that provides natural sub-irrigation. Although the ground absorbs a tremendous amount of water initially, a layer of basalt stops the seepage not too far down (the depth varies). After that, the underground flow can only go sideways.
St. Anthony Sand Dunes,
a popular recreational spot west of the bench.

Once the soil is “charged,” crops receive moisture directly to their root systems, and evaporation losses are minimal. With such a structure, the depth of the water table can actually be regulated by raising or lowering the water level in a network of strategically-spaced canals.

Egin Bench subirrigation also has a notable side effect. Water began to “escape” west by percolating underground over the impermeable rock layer. When it had charged all that area, the flow resurfaced to form today’s Mud Lake, 25-30 miles away. Before that, the low area had water only during periods of very heavy run-off.

Today, large greenhouses often use sub-irrigation to water their indoor crops. Sub-irrigation of field crops using man-made structures is very costly and is generally done only in special situations. (The trade-offs involved are far beyond the scope of this brief article.)
                                                                                 
References: [French]
Mark Fiege, Irrigated Eden: The Making of an Agricultural Landscape in the American West, University of Washington Press, Seattle (1999).
“Golden Jubilee Edition, 1884 1934,” Idaho Falls Post-Register (September 10, 1934).
Andrew Jenson, “The Bannock Stake of Zion: Parker Ward,” The Deseret Weekly, Vol. XLII, No. 9, The Deseret News Co., Salt Lake City, Utah (1891).
L. A. Zucker, L.C. Brown (eds.), “Agricultural Drainage: Water Quality Impacts and Subsurface Drainage Studies in the Midwest,” Ohio State University Extension Bulletin 871, The Ohio State University, Columbus (1998).

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