In water management, the most dangerous scenario isn’t a drought or a flood. It’s the violent, unpredictable pendulum swing between the two.

France’s February 2026 crisis illustrates this perfectly — and provides a data-rich warning for Australian dam operators and water resource planners.

A Case Study: Lac de Serre-Ponçon

Lac de Serre-Ponçon in the French Alps is one of France’s most historically reliable reservoirs, managed by EDF for hydropower and water supply. It has a long operational record and sophisticated management protocols.

Between 2022 and 2025, repeated severe droughts drew the reservoir down to critical levels. By Summer 2025, EDF had deployed aggressive management protocols just to hold storage near 771m — well below the optimal 780m operating target.

As of February 20, 2026, live SMADESEP data showed the lake at 761.93m NGF — 18 metres below its maximum operating level.

Then the whiplash hit.

France was struck by a 37-day extreme rainfall sequence. But instead of gradual winter recharge, the drought-depleted catchments couldn’t absorb the shock. Baked, drought-stressed soils converted rainfall almost immediately to surface runoff.

France went from managing a structural, multi-year water deficit to battling a generalised nationwide flood emergency almost overnight. Major catchments flooded catastrophically while the reservoirs within them were still in the early stages of recovery.

The reliable seasonal wet-dry cycle simply vanished.

The Lesson for Australia

Australia is familiar with hydroclimatic extremes — arguably more so than most countries. But what’s shifting is the amplitude and speed of the oscillation between states.

Our seasonal forecasting tools and dam operation manuals are calibrated to historical inflow patterns. When the rain does eventually return after a prolonged dry, our models assume a gradual recovery track. The European data suggests we need to stress-test that assumption.

When catchments are deeply depleted and drought-baked, returning rainfall may not gently refill storages — it may bypass soil infiltration entirely and immediately challenge spillways.

This has three practical implications for Australian practitioners:

  1. Seasonal inflow forecasting needs to account for soil moisture state, not just rainfall climatology
  2. Spillway adequacy assessments for reservoirs currently running at low levels need to consider worst-case rapid inflow scenarios, not just gradual recovery
  3. Operating rules built around historical seasonal curves need explicit review against non-stationary forcing

Australia has the expertise to contribute to global practice on this. We’ve been living with hydroclimatic volatility longer than most. The question is whether we’re applying that knowledge proactively.

Data source: SMADESEP (real-time reservoir monitoring), EDF operational records. Originally shared on LinkedIn — 2,006 impressions.