North Side Canal Company (NSCC), located in southern Idaho, supplies irrigation water to 160,000 acres of agricultural land and generates hydropower. Recently, its system has also become the site of recharge activities funded by the State of Idaho that seek to rehabilitate the Eastern Snake Plain aquifer (ESPA). In this interview, NSCC General Manager Alan Hansten tells Irrigation Leader about the hydrological and economic situation of the area and the importance of the recharge activities that are going on in the company.
Irrigation Leader: Please tell us about your background and how you came to be in your current position.
Alan Hansten: I came to work for NSCC in 2009 as the assistant manager. Prior to that, I worked in engineering consulting. In 2013, I took over as the general manager of NSCC. NSCC supplies irrigation water to approximately 160,000 acres of farmland on the north side of the Snake River in southern Idaho. The company also generates electricity through five hydroelectric power plants and sells it to Idaho Power Company. In addition, the company partners with the State of Idaho on groundwater recharge activities in an effort to sustain the ESPA. The company first diverted water from the Snake River for irrigation in 1908.
Irrigation Leader: Where does NSCC draw its water from?
Alan Hansten: All of NSCC’s supply is classified as surface water from the Snake River. The headwaters of the Snake River are on the eastern side of the Teton Mountains, in Yellowstone and Grand Teton National Parks, and the company is a joint spaceholder in Jackson Reservoir. The company has natural flow rights on the Snake River and storage rights in Palisades Reservoir and American Falls Reservoir. There are spring flows from the ESPA in the American Falls area that flow into the reservoir there and make up a portion of the natural flow water rights that NSCC has on the Snake River.
Irrigation Leader: Please tell us about the groundwater situation in your area, especially as it relates to the ESPA.
Alan Hansten: When irrigation was first developed on the Eastern Snake Plain in the early 1900s, the irrigators began diverting water out onto desert lands, and the percolation of this water through the soil began to raise the water table in the underlying aquifer. The water level and storage amount of the aquifer continued to increase until the early 1950s, when the development of deep well pumping technologies made it feasible to begin extracting water from the aquifer to irrigate farmland. The State of Idaho began issuing groundwater rights on the ESPA, and irrigation expanded. This caused the aquifer to begin to decline, and since the early 1950s, the water table elevation has been going down and the stored volume has been decreasing. In an effort to stop their declining water supply, senior water users have made water calls against junior water users. If those water calls were to result in groundwater pumping curtailment, it would have serious effects on the livelihood and economy of southern Idaho. Now, NSCC, the State of Idaho, the groundwater pumping community, and others are trying to stabilize the aquifer at the level at which it stood in the early 1990s.
Irrigation Leader: Does the aquifer level affect your supplies of surface water?
Alan Hansten: It does. The Snake River and the ESPA influence each other. There are areas where water from the river feeds the aquifer through percolation and areas where water comes out of the aquifer through springs and enters the river. A decline in those spring flows reduces NSCC’s water supply and requires the company to use more of the water stored in the reservoirs to make up the difference. Our surface water supplies are significantly lower in years with low snowpack and low spring flows.
Irrigation Leader: Would you tell us about some of the programs that have been put in place to manage and sustain the aquifer?
Alan Hansten: In 2015, an agreement was reached between the Surface Water Coalition (SWC), which includes NSCC, Twin Falls Canal Company, and other surface water user entities below the American Falls Reservoir, and Idaho Groundwater Appropriators, Inc. (IGWA). The agreement laid out mitigation actions to be undertaken by IGWA to obtain a net positive change in aquifer volume of 240,000 acre-feet per year. Aquifer levels that need to be reached by certain dates were also established in the agreement. In exchange for IGWA’s efforts, the SWC agreed to not pursue further water calls through the Idaho Department of Water Resources against junior groundwater users that signed onto the agreement as long as the aquifer level milestones were being met. SWC consultants and IGWA consultants got together and identified a number of wells on the plain to be used as sentinel wells in the administration of the agreement. The State of Idaho also stepped up to the plate and started constructing recharge facilities on NSCC’s systems and other systems on the ESPA. The recharge facilities on NSCC’s system are all funded by the state. The state aims for an average annual recharge volume of 250,000 acre-feet a year. Combined, the groundwater users and the state are aiming to return at least 490,000 acre-feet of water to the aquifer on average each year in order to stabilize it and bring it back to the levels of the early 1990s.
Irrigation Leader: Are groundwater and surface water managed and regulated conjunctively in Idaho?
Alan Hansten: Yes, in the case of the Snake River and the ESPA.
Irrigation Leader: What recharge facilities have been built on NSCC’s system so far?
Alan Hansten: One recharge facility has been constructed at what we call the Wilson Canyon site. We have four hydroelectric power plants above the site, and the State of Idaho came in and installed deicing equipment and bulkheads on the power plants. This will allow us to run water around the plants and keep ice from building up and forming ice loads against the structures during the winter. We are now able to begin recharge activities on the main canal system and at the Wilson Canyon site every year as soon as we finish the irrigation season. We started recharging at the Wilson Canyon site for the first time on October 25, 2019, and continued through May 2020.
Irrigation Leader: How does the water infiltrate from the Wilson Canyon facility into the ground?
Alan Hansten: Wilson Canyon is a large basin surrounded by lava rock, about 20 acres in size, located off to the side of the company’s main canal. There is significant fracturing in the basalt rock in that area, which gives it high permeability. When we put water out there, it infiltrates well. We were able to run 500–600 cubic feet per second (cfs) into the basin nonstop from October to May.
Irrigation Leader: How many other recharge structures do you anticipate constructing?
Alan Hansten: Right now, we’re waiting for the state to decide if it wants to build another one. There is a potential site below the Wilson Canyon site that it may want to develop. The state is still studying whether it’s feasible and makes sense to add another site to its recharge portfolio.
Irrigation Leader: What effects do you expect to see from this project and others like it?
Alan Hansten: We’re expecting to see the aquifer begin to cease declining and then begin to recover so that it gets back to early-1990s levels. The State of Idaho is tracking that for us. The state monitors the groundwater level via the sentinel wells. Over the last 5 years, we’ve seen an increase in the level and the amount of water stored in the aquifer. We are currently on a positive trend and have actually been exceeding the goals that were set out in the original agreement. As long as that trend continues, we will be in good shape. We don’t attribute the rise in the aquifer solely to recharge—we’ve had a couple of unusually wet winters on the Snake Plain, which we’re sure had an effect as well. On the whole, we’re cautiously optimistic.
Irrigation Leader: The recharge program is being paid for by the state and implies no extra cost for NSCC’s customers, correct?
Alan Hansten: Right. It’s a financial benefit to the company. NSCC gets paid by the State of Idaho to run the recharge water.
Irrigation Leader: Would you tell us about the recharge activities going on in neighboring areas?
Alan Hansten: The Twin Falls Canal Company and American Falls Reservoir District #2 also participate in the recharge efforts. Twin Falls can recharge up to 40 cfs into Murtaugh Lake, and American Falls Reservoir District #2 has three sites along its canal that allowed it to recharge up to 1,400 cfs this past spring. Several other irrigation districts and canal companies in eastern Idaho also divert water from the Snake River to help with recharge efforts.
The state is also monitoring levels in wells that were installed around the recharge basins. Idaho Department of Water Resources staff also place rhodamine dye in the recharge basins to study the flow direction and velocity of the water within the aquifer, which can be determined based on when and where the dye shows up in surrounding wells. The dye tracing helps us all gain more knowledge and understanding of the aquifer and how the water flows within it, which will ultimately help the state understand which recharge sites are best for continued recharge development.
Irrigation Leader: What is your vision for the future of groundwater recharge at NSCC?
Alan Hansten: The COVID‑19 pandemic is having a short-term effect on the state’s budget and abilities, and I suspect that we’ll all be seeing some economic fallout from it and that recharge may be affected. We may have to reduce the amount that we recharge in a year because of the state’s funding constraints, but I think that recharge activities will continue. Recharge is an important part of a long-term effort to maintain a sustainable economy in southern Idaho. Agriculture makes up a big portion of southern Idaho’s economy, and without irrigation water, there would be no crops and consequently no economy. I think the state will be looking to develop further recharge sites, because not all the sites can be used all the time due to winter maintenance activities. When water is available, the state needs to have other places to send it to keep the program going.