For many irrigation districts throughout the United States, groundwater recharge has become an increasingly important element of water management. Such is the case with the Central Nebraska Public Power and Irrigation District (CNPPID), which is partnering with the Platte River Recovery Implementation Program (PRRIP), the U.S. Fish and Wildlife Service, the Tri-Basin Natural Resources District, and the Nebraska Department of Natural Resources to mitigate the negative effects of low water levels in the Platte River. In this interview, Joshua Dill, the managing editor of Irrigation Leader, speaks with Tyler Thulin, a civil engineer at CNPPID, about his district and its groundwater recharge program.
Joshua Dill: Please tell us about your background and how you ended up in your current position.
Tyler Thulin: I studied civil engineering at the University of Nebraska–Lincoln. The summer before I graduated, I was offered an internship with the Central Nebraska Public Power and Irrigation District. A couple months after the summer internship ended, the district offered me a full-time job. Water was something I was always interested in college, so I took the job. Seven years later, I am still there. Joshua Dill: Please tell us about CNPPID. Tyler Thulin: CNPPID delivers surface water through three irrigation canals (the Phelps Canal, E65, and E67) and a supply canal to just under 108,000 acres across Nebraska’s Gosper, Phelps, and Kearney Counties. Our main storage reservoir is Lake McConaughy, which is located in the western part of the state and is the largest reservoir in Nebraska. Water is released from Lake McConaughy and diverted into our supply canal from the North Platte River at North Platte, Nebraska. From there, the water flows through three hydropower plants before either being diverted into the irrigation canals toward the tail end of the supply canal or being returned to the Platte River near Lexington, Nebraska. Water that is diverted into our irrigation canals is either delivered to fields for irrigation or to recharge the groundwater. Our irrigation canals consist of approximately 350 miles of open laterals and 140 miles of pipelines.
Joshua Dill: Would you tell our readers about the pipeline you are currently installing?
Tyler Thulin: It is a 42-inch PVC pipeline that runs a little over 1½ mile from the Phelps Canal to the water retention area at the Cottonwood Ranch Complex, where it is used
for groundwater recharge and for habitat creation for the endangered whooping crane and other migrating waterfowl. When the Platte River flow exceeds the target flows set by the U.S. Fish and Wildlife Service, water can be diverted for groundwater recharge. The target flows are set based on current hydrologic conditions. Those targets vary by time of year but are set the lowest during the winter months, meaning that that is when there is the best chance that they will be exceeded and that water can be diverted for groundwater recharge.
Joshua Dill: Would you describe the groundwater recharge process?
Tyler Thulin: When flows in the Platte River exceed target levels, we are able to divert water into our irrigation canals for groundwater recharge. Once in our canals, the water is either diverted to an off-canal site, such as the Cottonwood Ranch Complex, or allowed to seep through our canals and recharge the local groundwater. Water that is recharged will eventually flow back to the river and increase the river’s flow. The hope is that the water flows back to the river during times when flows are below target levels and reduce the shortage.
Joshua Dill: Who are the other parties involved in the project?
Tyler Thulin: The Platte River Recovery Implementation Program is the other entity involved. It manages the Cottonwood Ranch Complex property and has hired a contractor to install the pipeline and do the earthwork on the property itself. The portion of the pipeline that we are in charge of installing runs from our Phelps Canal to the Cottonwood Ranch Complex, a distance of about 1½ miles. The PRRIP has hired a contractor that will hook onto our pipeline at the edge of the property and extend the pipeline another ½ mile. That pipeline will include two outlets that will go into the separate recharge cells.
Joshua Dill: How does the scale of this project compare to other projects that CNPPID has done?
Tyler Thulin: This is the largest-diameter pipeline we have installed for the purpose of groundwater recharge. This year, we are also installing five other pipelines from our irrigation canals to U.S. Fish and Wildlife Service Waterfowl Production Areas around the region for similar purposes. They contribute to groundwater recharge as well as to habitat creation, which improves recreation opportunities and benefits waterfowl hunters.Joshua Dill: How do these projects affect irrigation?Tyler Thulin: They will not affect irrigation at all. Most of the water deliveries we envision will occur during the nonirrigation season. We may also deliver water to the property during the irrigation season if river flows exceed target levels, which is not common for that time of year. However, our Phelps Canal has enough capacity to deliver irrigation water and serve the Cottonwood Ranch Complex at the same time.
Joshua Dill: Has this project faced any special challenges?
Tyler Thulin: The only special challenge we have had to face is installing the pipeline down a county road ditch. That means we have to deal with existing utilities, including buried power lines, pipelines, and phone lines, that either parallel or cross the ditch. In addition, we usually shoot for about 3 feet of cover on top of our pipes, so when you factor in the depth of the ditch and diameter of the pipe, the pipeline trench will be quite deep.
Joshua Dill: What are the advantages of using PVC pipe for this project?
Tyler Thulin: The biggest advantage is that the pipe friction loss is lower than with other pipe materials, which means you can get more water through PVC pipe than through a pipe of the same diameter made of a different material. It is also cheaper and easier to handle and install. You do not have to weld joints or deal with heavy, short sections of concrete pipe.
Joshua Dill: As an engineer, what other kinds of projects do you work on?
Tyler Thulin: I primarily work on projects related to the irrigation side of the operation. We have a lot of pipelines to install during the nonirrigation season. Our structures are aging, so there are a lot of rehabilitation and replacement projects as well. What we do is evolving. We used to focus only on irrigation, but in the last 6 or 7 years, we have started to do a lot of recharge projects during the winter. It is a lot of work to ensure that our pipelines are watertight and that our gates and structures can handle the ice.
Joshua Dill: Do you remember when the need for recharge started to become a priority? Tyler Thulin: That began with the Platte River Recovery Implementation Program about 6 or 7 years ago. One of the goals of the PRRIP is to retime water in the Platte River to reduce the shortages to target flows by
130,000–150,000 acre-feet per year. A lot of the groundwater recharge projects in our system serve to help them meet their goals.
The pipelines to the Waterfowl Production Areas are being built in partnership with the U.S. Fish and Wildlife Service and our local Tri-Basin Natural Resources District. The Tri-Basin Natural Resources District’s goal is to maintain or increase groundwater levels in the area. The U.S Fish and Wildlife Service's goal is to fill the Waterfowl Production Areas to create habitat for migrating waterfowl and provide recreation opportunities.
Joshua Dill: What kind of plans does CNPPID have for next year?
Tyler Thulin: We are always looking for more recharge opportunities. We have discussed putting water in reuse pits and sending it farther down our canal system to increase recharge to other areas of our irrigation system.