A proactive approach to replace irrigation canal siphons will help preserve uninterrupted irrigation, regional economic vitality, groundwater recharge and water-based recreation.

Many of Nebraska’s surface water irrigation projects — of which there are dozens — face the problem of aging infrastructure and limited funds to maintain and repair irrigation structures. The importance of irrigation infrastructure to agricultural productivity and effective management of water resources is often overlooked when the topic of irrigated agriculture is discussed in the state. The Central Nebraska Public Power and Irrigation District (known as Central) is working to address its aging infrastructure.

Central is the largest surface water irrigation project in the state. It provides irrigation deliveries, hydroelectric generation, groundwater recharge, recreation and wildlife habitat. Headquartered in Holdrege, Nebraska, Central owns and operates Kingsley Dam and Lake McConaughy, Nebraska’s largest storage reservoir and the linchpin of its irrigation and hydropower project which began operation in 1941.

Central delivers water to more than 110,000 acres under contracts with its irrigation customers, most of whom take water from three main irrigation canals. An additional 100,000 acres are served by other irrigation projects receiving water from Lake McConaughy. Central’s system of reservoirs and canals also provides documented groundwater recharge benefits to another 310,000 acres.

Repairs for E-65

The E-65 Canal is one of the main canals. Its head gate is located adjacent to the Johnson Lake inlet southwest of Lexington, Nebraska. The canal extends south six miles before reaching the Carl Curtis Pump Station. The facility’s three 350-horsepower pumps can pump 245 cubic feet per second of water into Elwood Reservoir, which was added to the irrigation project in 1977.  Elwood Reservoir covers 1,100 surface acres, has an operational capacity of 24,715 acre-feet and total storage capacity of 40,000 acre-feet.  It also is well known for its fishery stocked with a variety of game fish.

The E-65 siphons were part of the original project construction in the late 1930s and have been in service since 1941. The siphons are essential to conveying water to 150 irrigation customers at 414 separate turn-out points serving more than 42,000 acres.

After 80 years of service, the existing siphons are in a deteriorating condition. The longest section has required numerous repairs over time.  Because the siphon’s cathodic protection failed many years ago, a temporary synthetic coating was used to extend the pipe’s operational life, but the repairs were not intended to be a permanent solution.

A new siphon alignment has been designed to replace this essential infrastructure at an estimated cost of $15 million. Central recently sought funding assistance of $8.9 million from the state’s Water Sustainability Fund, a source of financial support to help local project sponsors achieve goals set out in state statute. The Nebraska Natural Resources Commission oversees the fund, including application review, scoring and ranking, and awarding funding to successful applicants. The Department of Natural Resources administers the fund by initially reviewing applications and forwarding those that meet minimum statutory requirements to the NRC.

Current irrigation releases would continue through the existing system during construction of the new canal/siphon project.  The new siphon system would be approximately 5,400 feet long and would consist of high-density polyethylene (HDPE) pipe and approximately 5,300 feet of open canal sections protected by a combination of riprap and synthetic lining. Installation of the new siphon would secure uninterrupted long-term delivery of water in the E-65 system and ensure that irrigation, recharge, recreation and wildlife benefits are sustained into the future. Maximum flows through the siphon would be approximately 450 cubic feet per second.

A failure of the existing siphon(s) would result in the loss of irrigation deliveries to the area, with significant coinciding economic impacts. In addition to the regional economic effect of lost agricultural income, multiple secondary benefits also would be lost, such as groundwater recharge and recreation.  The inability to convey water through the siphons would ultimately result in a dry Elwood Reservoir.  In turn, the absence of water in the reservoir would result in the loss of water-based recreation, the fishery, and important groundwater recharge to both the Platte and Republican Basins.

The groundwater recharge provided by Elwood Reservoir and the E-65 Canal benefits both river basins — in addition to area groundwater users — by enabling the state and other entities with water management responsibilities in the region to meet state and federal obligations. This includes the Republican River Interstate Compact and efforts related to Endangered Species Act compliance through the Platte River Recovery Implementation Program.

The groundwater recharge provided to the Republican Basin is counted as an “Imported Water Supply Credit” by the interstate (Colorado, Kansas and Nebraska) compact.  It is estimated that the E-65 system provides about 10,000 acre-feet annually to the Republican Basin, which would not occur without functioning siphons. In addition, other management actions would be required to replace lost recharge such as utilizing water from the Nebraska Cooperative Republican Platte Enhancement project, which pumps groundwater to offset streamflow depletions in the Republican and Platte basins, or shutting down or allocating irrigation usage.

Learning from experience

Central officials cite a tunnel collapse that occurred along the Gering-Fort Laramie Canal in Wyoming in July 2019 as a lesson on the consequences of not addressing aging critical infrastructure. According to a report prepared by Nebraska Extension, Wyoming Extension and the University of Wyoming Department of Agricultural and Applied Economics, the tunnel collapse interrupted irrigation deliveries to 107,000 acres in eastern Wyoming and western Nebraska and resulted in total economic losses of $89 million.

The siphon project illustrates the critical nature of irrigation canal works in an agricultural economy dependent upon irrigation.  A proactive approach to replace the siphons will preserve the regional economic vitality supported by the 42,000 irrigated acres within the E-65 Canal area as well as the significant benefits of groundwater recharge and water-based recreation associated with the system.

Scott Dicke is the irrigation and water services manager for the Central Nebraska Public Power and Irrigation District.