In the face of drought and a dwindling Colorado River, the job of balancing the needs of people, hydropower, and agriculture is more challenging than ever. In this interview, David Arend, Reclamation’s new deputy regional director for the Lower Colorado Basin Region, talks with Hydro Leader about the effects the basin’s increasingly unpredictable hydrology have on the hydropower the region depends on. 

[siteorigin_widget class=”SiteOrigin_Widget_Headline_Widget”][/siteorigin_widget]

Hydro Leader: Please tell us about your background and how you came to be in your current position. 

David Arend: Right out of high school, I joined the navy and went into the Navy Nuclear Power Program, which started my background in power generation. I served 20 years as a navy nuke. Most of that time was spent on nuclear submarines, but I also did a couple of tours working with the naval reactors at Idaho National Laboratories. After retiring from the navy in 1996, I worked in the private sector for about 6 years before returning to federal service. I was hired at Hoover Dam as a power systems electrician and electrical foreman. After about a year and a half, I transferred downriver to become the facility manager at Davis Dam. Then, I served as Reclamation’s power compliance manager for about 6 years. After that, I became the Power Office chief for the Lower Colorado Basin Region. That position involves oversight of the operation and maintenance of all our federal power plants. We handle all the power contracts for generation, ensure our facilities maintain compliance with the reliability standards of the North American Electric Reliability Corporation and its Western Electricity Coordinating Council, and coordinate the renewable energy that is requested to come on to federal facilities and lands. In December 2021, I was selected to be the deputy regional director for the Lower Colorado Basin Region. 

Hydro Leader: Please tell us about the hydropower facilities that you oversee. 

David Arend: I oversee 14 facilities. Three of them—Hoover, Parker, and Davis Dams—are owned, operated, and maintained by Reclamation. We also have 11 facilities that are owned by Reclamation but are maintained and operated by other entities, most of them by the Salt River Project. In addition, there is one operated by the Central Arizona Project, one by the Imperial Irrigation District, and one by the Yuma County Water Users Association. The Western Area Power Administration (WAPA) is our power marketing agent; it schedules and distributes the power generated, assists with the contracts, and invoices the customers. 

Hydro Leader: What effect is the Colorado basin drought having on Reclamation’s hydropower fleet? 

David Arend: The drought has caused us to lose some capacity, especially because of the lower water levels in Lake Mead and Lake Powell and the resulting loss of head pressure. The higher the head pressure, the more efficiently our turbines operate and the more we can generate per cubic foot per second of water going through the units. Additionally, as we conserve more water, we put less water through the units, which means lower generation capacity as well.

Hydro Leader: To what degree is the drought already affecting the amount of power that you’re generating, and how might it continue drought affect generation? 

David Arend: We did several studies and compared total generation from 1988 to 1991 as well as the average over the last 21 years, beginning when the drought started. We’ve seen a reduction in power generation in the lower Colorado basin of about 10.8 percent over that period. The costs of the operation and maintenance continue, so we saw an increase in the rates paid by our power customers. Hoover, Parker, and Davis Dams do not have appropriated funding, so our power customers, not the taxpayers, pay the bills. We try to keep our costs as low as we can. We’ve shifted some projects out to a later date. Working with our power customers, we do everything we can to make our power an economically feasible product. Going forward, we may see some additional increases in power customer rates. The size of those increases is difficult to predict, because Colorado basin hydrology is extremely unpredictable. We’ve made significant efforts to mitigate rate increases through efficiency gains, cost cutting, the pursuit of other sources of funding, and increasing our non-power-related revenues. 

Hydro Leader: How does the situation of the lower basin differ from that of the upper? 

David Arend: The two basins have different hydrologies and sometimes different customers, but overall, we look at the Colorado River basin as one basin. We’re working with the Upper Colorado Basin Region to tackle the situation together, because in the long run, whatever affects one region affects the other. If Glen Canyon Dam in the upper basin were to reach a minimum power pool, that would further reduce the amount of water coming into Lake Mead. 

Hydro Leader: What water levels would most seriously affect hydropower generation in the lower basin? 

David Arend: As the levels go down in the lake, there are fewer efficiencies and more cavitation, and we get less generation per unit. But the real red line for Lake Mead would be our minimum power pool elevation of 950 feet. At that point, Hoover Dam would not be able to generate any more power. That’s not to say that we couldn’t still move water through Hoover Dam and downstream, because we could bypass the units and allow water to go down the stream a different way. The hydrology studies that we’ve done show little, if any, chance of us reaching that point in the next several years, but again, we’ve seen the hydrology change very quickly. 

Hydro Leader: Aside from potential rate increases, what other effects might a reduction in hydropower generation have on your power customers? 

David Arend: For every megawatt (MW) that we don’t produce, customers have to get power from somewhere else. WAPA, our marketing agent, goes out and gets the power for them on the market 

We’ve also changed when we generate power. With all the solar and wind coming online, there is a lot of energy available during the day, so we’ve actually shifted our generation back into the hours when energy costs are higher. It doesn’t matter whether we generate at 10:00 a.m. or 10:00 p.m.—our costs are the same. 

Hydro Leader: How many hours per day do you generally generate power? 

David Arend: We’re always generating some amount, because we have to continue flow down the river and maintain certain minimum flows. How much we generate at any given time varies from day to day and from season to season. It also depends on water orders. When there’s less water demand, there’s less generation. Especially in the wintertime, we take advantage of that to take units offline for maintenance and upgrades. 

Hydro Leader: What is the best way to balance power generation and water supply for agricultural, residential, and industrial use? 

David Arend: That is a tough question, because there is no one best way. We’re working our stakeholders—the states, Native American tribes, agricultural communities, and irrigation districts—to find solutions. In December, we launched the 500+ Plan, a partnership that will invest $200 million in conservation efforts to add another 500,000 acre-feet to Lake Mead each year for the next 2 years. The Drought Contingency Plan that’s been in place for several years has allowed us to create what is called intentionally created surplus to help maintain water in Lake Mead. The Infrastructure Investment and Jobs Act will create additional opportunities to invest in infrastructure improvements and conservation. While residential and industrial uses are important, agricultural use is also important to the entire country. In addition to growing our food, agriculture creates jobs and supports communities. 

Hydro Leader: How is Reclamation working to ensure continued power generation at the lower Colorado basin dams? 

David Arend: The Drought Contingency Plan, the 500+ Plan, and the intentionally created surplus all help to bank water in Lake Mead, which helps ensure that we can still generate later on. We’ve also completed several modifications or upgrades to Hoover Dam that have increased our efficiency by 83–87 percent since 2007. We’ve reclaimed approximately 120 MW of capacity and approximately 1,600–1,700 megawatt-hours per year in energy. 

For example, we installed what are called wide-head turbines at five of the units at Hoover Dam from 2012 to 2017, increasing our efficiency by 3 percent per turbine. We also have what are called over-stroke wicket gates. About half of the 17 units have already been modified to allow the wicket gates to open past their historical 100 percent opening. That allows more water to pass through the gates and enter the turbine, allowing us to reclaim about 5 percent of lost capacity for each unit. I know these sound like small numbers, but when you add them up, it starts making a real difference in the value and cost of our power. We also installed thinner stainless-steel wicket gates. This reduces leakage past the gates and allows more water to enter and pass through the turbine, reclaiming an additional 5 percent of lost capacity for each unit. Also, as our units age, we overhaul and rewind them, replacing the old copper windings and steel. We’ve actually been able to increase the efficiency of our units by several percent by replumbing, changing out facing plates, and tightening clearances on the seals. At Davis Dam, one of the units is going to be rewound in the next fiscal year. That’s going to increase the unit’s capacity from 48 MW to at least 52 MW, so with the same water, we’ll get another 4–5 MW to use—about a 10 percent increase. 

Finally, one of the last things was unit control modernizations. All the units at Hoover, Davis, and Parker Dams went through controls upgrades. That consisted of new protection systems, pilot excitations, digital governors, and digital unit controls. That increased our efficiency by another 2 percent and allowed us to use a new operational algorithm to dispatch the units more efficiently. The new algorithm makes use of better responsiveness and performance ramping. We can ramp up faster, we have less overshoot, and it improves our transitions in and out of motoring. Motoring refers to the fact that when we’re not generating, we’re actually running the unit as a motor. The unit is online, but it’s not generating power. That allows us to immediately start opening wicket gates and to bring that unit up more quickly to respond to any changes or issues that might be on the grid. It also allows us to provide some reactive energy to help stabilize the grid with voltage stabilization. One good thing about hydropower facilities, which is also true of large steam plants, is that their large generators have a lot of spinning inertia, which helps to stabilize the frequency control or speed control of the grid itself. 

Hydro Leader: What can you tell us about recent snowfall and its likely effect on the year’s water supplies? 

David Arend: Snowfall in Colorado actually has two parts: what falls on the western slope and what falls on the eastern slope. We need the snow to fall on the western slope to affect our area, because when the snowpack melts, that’s what flows into the Colorado River. Earlier this winter, we had some good snowstorms, but they were followed by one of the driest Januarys in a long time. Fortunately, it remained cold, so the snowpack is not melting into the ground as quickly as we expected. As a result, the snowpack is still slightly above average. We did see some snow coming into Utah, which also helps feed into the river. While we saw some early positive signs, the last month or so has counteracted them. This shows you the volatility of the weather patterns. It makes it that much harder to predict where we’re going to be moving forward and how this will affect us. We are hoping for as much snow as we can get, especially on the western slope. 

Hydro Leader: What is your outlook on the future? 

David Arend: Right now, the hydrology modeling presents a bleak picture, but it’s hard to predict going forward, especially past the next few years. I can say for certain that we are hard at work looking at every possible solution and collaborating with the states, the tribes, and the agricultural community. We’re continuing to look at every option we have. We do modeling on a continual basis now, looking for every option for the worst-case, best-case, and most probable scenarios. By working together, we’re going to develop the best possible plans. Much has been done already, but there’s still a lot more to do. 

David Arend is the deputy regional director for the Bureau of Reclamation’s Lower Colorado Basin Region. He can be contacted at