Heavy winter rains and erosion of the Oroville Dam’s two spillways sparked an evacuation of at least 188,000 people living in the communities of Oroville, Marysville, and surrounding downstream areas.

The events that unfolded over the past eight days can inform a more educated conversation about water management going forward. We address six questions worth thinking about as we move forward.

What’s the Current State of the Crisis?

First, let’s clear up one thing: the Department of Water Resources (DWR), which oversees Oroville Dam, is not worried about the dam itself. Concerns now center on reducing future flood risk while minimizing further damage to the main spillway, and on averting the collapse of the emergency spillway.

A critical question is whether the main spillway will be serviceable for the remainder of the winter. Dam managers must continue to release water down the damaged main spillway to maintain flood space behind the dam for coming storms and spring snowmelt. Bill Croyle, acting director of DWR, told the Sacramento Bee this past Sunday that his agency is not seeing further erosion of the main spillway at current flow levels of 100,000 cubic feet per second (cfs). Managers also shut down the turbines at the base of the dam that normally release up to 15,000 cfs because of downstream obstructions.

If another storm sends water into Oroville Lake faster than it can be released via the turbines and main spillway, then water could again over flow the concrete wall that forms the top of the emergency spillway. If the hillside beneath erodes further, this wall could collapse or be undermined, sending massive amounts of water downstream causing damaging, life-threatening floods.

Sacramento Bee has a concise recap of events here.

How Will California’s Water Supply Be Affected Until the Main Spillway is Repaired?

Lake Oroville is the largest reservoir in the State Water Project, which supplies up to 4.2 million acre-feet of water a year, both to farmers and more than 25 million Californians who depend on it for at least part of their water supply.

California reservoirs keep some empty flood space available during the rainy season to accommodate sudden influxes from big storms. As the dry season approaches in spring, managers allow reservoirs to fill to capacity.

Given the problems with the spillways, managers may opt to keep the reservoir level below capacity until the spillways are repaired. This could mean less water for deliveries to users.

In the long run, non-structural solutions, such as using water more efficiently and capturing and reusing urban runoff, show far more potential for addressing California’s water demands than building more dams.

Can We Prevent These Types of Dam Crises in the Future?

It’s well-documented that the United States has chronically underfunded dams, levees, drinking water and wastewater infrastructure for years. The Association of State Dam Safety Officials estimates the cost of known needed repairs for the country’s 2,000 deficient, high-hazard dams at $21 billion. Drinking water, wastewater, waterways, ports and levees need repairs too. The American Society of Civil Engineers in a 2013 report put the unmet funding needs of our water infrastructure at $187 billion by 2020 (calculated in 2010 dollars).

Had the emergency spillway been lined with concrete, as was recommended in a motion filed by Friends of River, Sierra Club and South Yuba River Citizens League in 2005, it might have prevented the erosion that occurred this past weekend. In hindsight, it’s easy to see that this would have been a worthwhile investment compared to the cost of repairs, mass evacuations, and environmental impacts.

But the Oroville spillway crisis reveals another important question we haven’t been asking about our underfunded infrastructure. That is: How much money do we need to budget for upgrades that are becoming necessary as engineering standards improve and climate change imposes greater pressures on the system? We may be on the hook for even more money than we realize.

Where Are We Going to Get the Money to Repair the Spillways?

Preliminary estimates to repair just the main spillway are in the range of $100m-$200m, according to Bill Croyle at DWR. The State Water Contractors that get their water from the State Water Project will likely have to pay for at least part of the repairs, and they will pass the costs on to their ratepayers. Three more things to note.

First, these expenses are likely to cause increases in costs for ratepayers, some of whom are already struggling to pay their water bill. Second, we should expect a vigorous debate as to who else should help foot the bill. Should residents of the floodplain pay for a portion of the repairs, since they benefit from flood control? Should all California taxpayers chip in via allocations from the General Fund? Third, these types of public works projects cannot be incentivized with tax deductions to private companies looking to build profitable projects, as the Trump administration has proposed.

Are We Going to See More Water Emergencies as the Climate Changes?

Scientific models project, and observational data corroborates, that California’s climate is becoming more variable, with hotter, longer droughts and bigger precipitation events. The state’s water system was designed for a climate we no longer have. More extreme events are going to test the limits of our infrastructure and reveal new weaknesses in the system.

What Does This Mean for the Feather River Ecosystem?

In general, storms are good for rivers. California’s river ecosystems are adapted for big pulses of water in the winter. But the Feather River, where Oroville Dam is located, has been heavily altered by people, so these storms play out differently than they did before the river was dammed and leveed.

Feather River Hatchery spawns about 30 percent of the fall-run Chinook salmon in the state, as well as large numbers of spring-run Chinook and steelhead trout. Spring-run Chinook and Central Valley steelhead trout are listed as threatened under the Endangered Species Act; fall-run Chinook are still an important species for commercial fishing. Hatchery staff relocated five million juvenile salmon to a nearby facility, and have rigged a system to bring in municipal water to support the 1 million steelhead still at the hatchery. If hatchery operations go awry, it could impact populations of these valuable species.

The Feather River itself is still an important spawning ground for natural salmon and steelhead. But levees mean the river is restricted to a narrow channel, where rapid flows scour out the nesting grounds. Meanwhile, influxes of sediment and debris are likely to damage spawning grounds in the short run.

The Oroville Dam and the levees downstream were built for the joint goals of water storage and flood prevention, but floods are healthy for both the river and the floodplain. Long term, California should be thinking about places where it can move levees and allow rivers to reconnect with their floodplains.

Looking Forward

Nobody wants to see people evacuated from their homes because of a potential natural disaster. The silver lining to a crisis is that it can generate political will to deal with unpleasant, chronic problems. The problems at Oroville Dam are linked to unresolved issues we have with funding our infrastructure, adapting to climate change and restoring natural ecosystems. Let’s move forward in ways that address the immediate emergency and the long-term problems.

This article was corrected on February 17 to reflect statements from California Department of Finance spokesman H.D. Palmer, quoted in PolitiFact, that Proposition 1 Bond funds cannot be used to pay for existing State Water Project infrastructure.

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