Forata discharges into Magro, not Poyo: two basins and a map

Forata discharges into Magro and Poyo originates in another basin: no transfer

Can water released from the Forata dam appear in the Poyo stream? No. And there is no need for a hydraulic model to verify this: simply open a map. Forata is on the Magro river, which flows into the Júcar and the sea at Cullera. The Poyo stream runs through a different network, one that empties into l'Horta Sud between Aldaia, Catarroja, and Quart de Poblet. The Turia reservoirs discharge into the Turia. Three systems that do not communicate, no matter if they coincided in time. Confusion set in from day one —articles mixing data from Forata and Poyo as if they were the same channel— and eventually spawned the most imaginative theory of the October 29 flood: that all Spanish reservoirs emptied simultaneously into the same stream. Quantum aquatic entanglement, they call it.

Why Forata water cannot reach the Poyo stream

The argument is topographic and allows no interpretation. Forata releases into the Magro, and the associated relief and irrigation channel is concreted: it does not connect to streams or dry riverbeds. Poyo belongs to another network. Between them lies the Turia. Some argue that a simultaneous discharge episode could connect channels through overflow in flat convergence zones; the arithmetic does not add up, because for that to happen, water would have to flow uphill. It is the same error seen in the Buseo case: its spillway is on the side, with two discharge outlets, and when the dam was overtopped, water jumped down the gorge. Never upwards.

What peine at Forata: 900 m³/s and warning at 19:30

The official timeline for Forata is different and should be separated from the noise. The reservoir entered scenario 2 at 18:00, and at 19:30 the Júcar Hydrographic Confederation verbally communicated in the meeting with Emergencies that it was moving to scenario 3. At that moment, it was already discharging 900.046 m³/s, with predictions of reaching 1,500 m³/s in the Magro. This water flooded the Cullera area and sections of the Magro itself, which also suffered damage and casualties. What is debatable there is the protocol and the timeliness of the warning, not the destination of the flow. That someone in a hurry mixes the two basins does not turn the Magro into the Poyo.

Buseo, the dam that took its own crown with it

In Buseo, the problem was internal. The side spillway and the two discharge outlets were not enough: the dam was overtopped, the crown failed, and water exited through the Hoz stream. The altimetry explains this without literary flourish. The crown is at 460 meters; the Hoz stream originates around 850 meters, in La Lobera and the Vallera pass, and descends to feed into the reservoir. As with almost all streams on the planet, it goes downhill. This is compounded by an uncomfortable precedent: the dam had caused problems years before, and the repair was assumed to be complete without anyone having yet shown the full file.

Why Poyo behaved like a tsunami

The most weighty hypothesis requires no dams: obstruction. The Poyo crosses a highly urbanized corridor with columned bridges that act as plugs. When the channel clogs, water backs up, and when the plug bursts, a wave goes down. It is the Biescas pattern. The basin also received extreme rainfall, and some recall that Utiel-Requena saw only 150-200 mm: the difference between one episode and another is abysmal. This channel has been built upon for decades, and it is not new: in 1957, Poyo flooded alongside the Turia, and at the crossing of the current A-3 with the stream, the first rains swept away a car with four occupants; two bodies were found, and the other two were never located.

Works that have been unexecuted for fifteen years

The other thread of the matter is budgetary. There are prevention plans for Poyo that involve diverting flows into the Turia channel, which in some points runs just meters away. Nothing has been executed in over fifteen years. There is talk of 150 million denied due to lack of budget in an organization that spent 42 million on advertising. And a comparison that hovers over the entire discussion: in the Tous disaster, 2,000 Hm³ fell in its basin for a reservoir with a capacity of about 300 Hm³. With those volumes, no small infrastructure saves anything on its own.

In the end, the map question has an answer, and it has had one from the beginning. What has no answer is why, after 1957, no one moved a stone in Poyo. There, effectively, quantum mystery remains.