Reading the Dashboard: the 2017 Oroville Spillway Crisis

Every reservoir here reports four things — inflow (water coming in), storage / elevation (how full it is), and outflow (water released). Watching how those move together tells you the story. Here's how they captured one of the most dramatic weeks in California water history — day by day, from the same data on the reservoir pages.

Lake Oroville — Feb 2017 (inflow & outflow, left · elevation, right) source: CA DWR / CDEC

Blue = inflow, orange = outflow/release, yellow = lake elevation. The red line is the emergency spillway crest (901 ft); dashed markers are key events. Hover the chart to read any day's values.

Step by step
1 Feb 1–6 · The setup

A wet winter; the lake fills. Inflow climbs from ~9,000 to ~49,000 cfs and elevation rises from 850 ft. Normal, so far.

Reading it: inflow and elevation rising together is a filling reservoir — watch how much headroom is left below the spillway.

2 Feb 7–8 · The spillway breaks

An atmospheric river drives inflow to 106,000 cfs. Operators spot a crater in the main spillway and cut releases to ~11,700 cfs to inspect it.

Reading it: the danger sign — outflow dropping while inflow spikes. With the exit throttled, the lake now rises fast.

3 Feb 9–11 · Over the emergency spillway

Inflow peaks at 155,000 cfs. Elevation crosses 901 ft and hits 902.6 ft on Feb 11 — water pours over the emergency spillway for the first time in the dam's history.

Reading it: the elevation line crossing the red 901-ft crest is the whole crisis in one number.

4 Feb 12 · The evacuation

The emergency spillway's hillside erodes alarmingly, threatening the weir. ~188,000 people are evacuated. Operators reopen the damaged main spillway hard to drop the lake below 901 ft.

Reading it: outflow turns sharply upward — the operators accepting more spillway damage to buy safety.

5 Feb 13–15 · The drawdown

Release ramps to ~100,000 cfs — the largest in Oroville's history — while inflow subsides. Elevation falls steeply, back under the crest.

Reading it: outflow far above inflow = a falling reservoir. This is the lake being deliberately drained to create a buffer.

6 Feb 16–20 · Back to balance

Inflow and outflow re-converge near ~60,000 cfs; elevation stabilizes ~30 ft below the crest. The immediate crisis is over (the main spillway was later rebuilt, 2017–2019).

Reading it: when inflow ≈ outflow, storage holds steady — a reservoir back under control.

Now try it yourself. Open Lake Oroville, zoom any chart back to Feb 2017, and you'll see these exact lines. The same reading — inflow vs. outflow vs. level — works for every reservoir on the site, from Shasta to Lake Mead.

Provisional data subject to revision. Public agency observations only — no causal or policy interpretation.