Powering Strong Communities

Planning for Less: Adapting Power Planning Amid Drought

Wide swaths of the U.S. faced drought conditions in 2022, with western states facing years-long drought that saw key reservoirs that feed hydroelectric dams reach historic low levels. In order for public power to adapt to widespread drought conditions, many utilities are changing the models they use to calculate future resources and are joining with their neighbors to help craft plans to help adapt to changing conditions.

Relying on New Trends

Public utilities can no longer rely on long-term historical records to help model future resource needs. The Bonneville Power Administration, a federal power marketing agency that sells electricity generated from 31 federal dams on the Columbia and Snake Rivers to 149 public power utilities and business customers in the Pacific Northwest, has changed a key variable used in its hydrogeneration forecast. This year, BPA started using 30 years of streamflow records (1989-2018), rather than its 90-year historical record (1929-2018) to calculate long-term hydropower generation planning.

“We just don’t see the same types of flows coming onto the system like we did 80 to 90 years ago,” said Ryan Egerdahl, manager of the long-term power planning group at BPA. “All of this is for the sake of climate change preparedness and resiliency. We have seen the climate changing, more and more, and we’re confident in making this change.”

BPA’s analysis showed that over the last several decades, increasing temperatures throughout the Columbia River Basin have contributed to increased average winter and early spring stream flows, with average peak spring runoff now appearing several days earlier, along with decreased summer flows. Bonneville’s climate change study, known as River Management Joint Operating Committee, indicates that in the coming decades these trends will likely continue.

Temperatures in the Columbia River Basin are expected to increase, as the region experiences wetter winters, along with longer summer dry periods, declining snowpack, higher average fall and winter flows, earlier peak spring runoff, and longer periods of low summer flows.

By the 2030s, BPA expects the Snake River Basin will have higher average fall and winter flows, earlier peak spring runoff, and longer periods of low summer flows. The earliest and greatest streamflow changes are likely to occur in the Snake River Basin, although that is also the basin with the greatest modeling and forecast uncertainty, BPA said.

BPA’s study found that using generation from fiscal year 1937, which had very low winter and very high summer flows, was inconsistent with emerging climate change signals and future projections and was unlikely to reoccur.

Because of the lingering drought in Washington, Oregon, Idaho, and Montana, BPA has also increased its budget for managing vegetation along its 15,000-mile transmission network to help prevent wildfires. And for the first time in its history, BPA instituted a policy to shutdown transmission lines when forecasts call for high winds and hot temperatures.

“The last few decades the climate has absolutely been changing, and we are trying to change with it, so our forecasts don’t misrepresent what’s happening,” Egerdahl said.

Par for the Course

In the Platte River Valley of Central Nebraska, the “wetter periods are wetter, and the drier periods drier,” said Devin Brundage, general manager of the Central Nebraska Public Power and Irrigation District.

The district has been managing water for both hydroelectric generation and irrigation since it was launched in 1941. “It’s been dry on the plains,” Brundage said. “But given our history, this is just par for the course. We’ve gotten very good at drought planning.”

According to a recent report from U.S. Drought Monitor, over 98% of Nebraska is experiencing at least moderate drought conditions. Central’s main storage reservoir is Lake McConaughy, Nebraska’s largest reservoir that can store almost 2 million-acre feet of water. But two years of drought have left the reservoir about 42% full, and inflows into the 22-mile-long lake are some of the lowest levels in the reservoir’s history. Water year 2021-22 was the fifth driest since 1940-41, the first year water records were kept, and nine of the 10 lowest inflow years have occurred in the last 20 years.

“There’s just been a dry trend that has become the norm over last couple of decades,” Brundage said. The district operates four hydroelectric plants that generate 113 MW, and its network of canals and pipelines irrigate around 110,000 acres of mostly corn and soybeans.

Finding ways to use water more efficiently has been Central’s goal since it was founded nearly 80 years ago. For years, the district helped irrigators facilitate new center pivot irrigation systems, where equipment rotates around a pivot and waters crops. Center pivots have now become one of the cornerstones of water conservation in the district.

“Center pivots have been a huge component to how we efficiently deliver water,” Brundage said. “Irrigators are able to optimize their yields with not nearly as much water as they used in the past. Our irrigations customers treat water like any other input.”

The district has also lined its canals and built a pipeline system to help conserve surface water as it is delivered to the area. And is also at the forefront of helping create region-wide water plan for the Platte River Valley, for the benefit of both surface and ground water users. The objective is to make sure there’s plenty of surface water for irrigation, but during drought conditions, some irrigators can turn on wells and tap into the aquifer. Most irrigation customers in the region can tap into both surface and groundwater, if necessary, but many irrigators in the Valley don’t have that dual connection.

“We are always planning and looking ahead, and really reevaluating where we are today versus 20 years ago” Brundage said. “Our management technologies have improved, so our ability to model and hold the line has really improved. Irrigators are always concerned about water and we want to make sure we are working together to sustainably manage the water supply.”

Bringing Down Consumption

In the Southwest, the Salt River Project is managing through a 27-year drought that is threatening to curtail hydroelectric generation from a pair of dams on the mighty Colorado River. SRP provides water and power to more than 2 million people in central Arizona. It is made up of two separate organizations: the “Association,” a private water corporation founded in 1903, and the “District,” an electricity provider formed as an agricultural improvement district and a political subdivision of the State of Arizona in 1937.

The utility has a diverse generating portfolio that’s anchored by coal, natural gas, and nuclear power plants, and augmented by hydroelectric, wind, solar, geothermal energy. The utility’s fossil fuel and nuclear plants require huge amounts of water, and SRP has secured long-term water rights for the plants, some of which is being supplied by reclaimed water from the Phoenix area.

Michael Reynolds, manager of resource analysis and planning at SRP, said he doesn’t “foresee any reliability concerns for a lack of water for the thermal plants.” SRP’s water conservation programs have been in place for decades. The utility uses less water today than it did 50 years ago, Reynolds said, and has set a goal of reducing water consumption at its energy facilities by 20% on an intensity basis by 2035.

“We have been blessed by the long-term planning of previous decades.” Reynolds said. “Think about all the water storage in the region that has enabled us to live in the desert through decades of extreme drought. But that water storage is not infinite. Water storage is low in the region. We need to figure it out as a region, and change the balance of not drawing on water storage resources that have been taxed for so long.”

SRP is working with neighboring utilities on a water management plan to help reduce water consumption in the Southwest. And is participating, along with BPA, in the development of a Western resource adequacy program, where utilities around the West could more easily share power during extreme weather events. Recently, the federal government announced it was preparing to rewrite rules on Colorado River water use, after states failed to file a plan in August to cut water use by 15% to 30%. The goal is to keep water levels at Lake Powell as high as needed to generate electricity at Glen Canyon Dam and Hoover Dam.

“So far,” Reynolds said, “power from Hoover and Glen Canyon dams on the Colorado River has been there. But there’s less water behind the dams, which is reducing power production.” SRP manages seven reservoirs, and thanks to an active monsoon season, the utility said it’s in “pretty good shape” heading into the winter.

“The tale of long-term planning is ... we don’t know what will happen,” Egerdahl of BPA said. “But we have to try to model what is likely possible. And looking at data from the past 30 years lines up much more closely with what we can expect from climate change.”