June 18, 2024

The Israeli military said Tuesday that it had begun pumping water into the vast network of tunnels beneath Gaza, which Hamas has used to launch attacks, store weapons and imprison Israeli hostages.

The military “has implemented new capabilities to neutralize underground terrorist infrastructure in the Gaza Strip by channeling large volumes of water into the tunnels,” the Israeli military said in a statement.

The statement was the military’s first public acknowledgment that its engineers were flooding tunnels, a contentious strategy that some military officials have said is ineffective and that the U.N. has warned could damage Gaza’s drinking water and sewage systems.

Even before the war started in October, Israeli military officials had warned that Hamas’s tunnels presented a major threat. In the months since Israel launched its ground offensive and started uncovering the underground network, military spokesmen have expressed surprise at the length, depth and quality of the tunnels. Some sections of the network are large enough to drive a truck through.

Elsewhere, the military has discovered underground chambers in which, they say, some of the 240 hostages taken to Gaza after the Hamas-led assault on Oct. 7 have been held.

Senior Israeli defense officials, who spoke on the condition of anonymity to discuss intelligence matters, estimated this month that the underground network is between 350 and 450 miles — extraordinary figures for a territory that at its longest point is only 25 miles. Two of the officials said there are close to 5,700 separate shafts leading down to the tunnels.

In December, after reports that the military had begun experimenting with flooding some tunnels in northern Gaza, a U.N. official in Gaza warned against it.

“It will cause severe damage to the already fragile water and sewage infrastructure that’s in Gaza,” said Lynn Hastings, then the U.N.’s humanitarian coordinator for the Palestinian territories.

In its statement Tuesday the military said it had selected tunnels to flood after an “analysis of the soil characteristics and the water systems in the area to ensure that damage is not done to the area’s groundwater.”

The military began experimenting with flooding tunnels only after the war began, according to three military officials with knowledge of the effort, which was code-named Atlantis. The purpose was never to drown Hamas fighters taking refuge in the subterranean network, but rather to flush them out, the officials said.

On the whole, however, the project has had limited success, the officials added. Despite large volumes of water being pumped, many of the tunnels are porous, resulting in seepage into the surrounding soil rather than a deluge through the passageways.