Serbs fail to destroy dam their fathers built: Thanks to Croats and their enemies the threat of a deluge is receding, reports Robert Fisk

PERUCA - Tito's men knew how to build dams. The concrete on top is cracked six inches wide and the tarmacadam has rippled as if an earthquake moved through the walls of concrete; which is more or less what happened last week when the Serbs set off their mines.

The cement floor by the sluice gate moves beneath your feet, vibrating as the waters of the man- made Peruca lake force their way over the pine trees into the Cetina river, the spray drenching the guard rails in stalactites of ice.

Trust war to honour warriors with shame. For even the Croats who captured the dam admit that it was the Serbs who built it. Between 1958 and 1961, in the heyday of Yugoslav socialist construction, the Serbs from Krajina - the men who constructed the great dams of Kurdistan - hauled the machinery down from the largely Serb-manned factories of Karlovac and trapped 1,550 million cubic metres of water above the meadows of Sinjsko Polje to bring light to the people of Knin and Zadar and Split. Serbian fathers built the place; their sons could not destroy it.

They tried hard. The Croatian frogmen who dived deep behind the cracked concrete rampart yesterday emerged from the green waters to reveal that the Serbs had placed their largest mine at the base of the hydro-electric dam, deep in the foundations, in a sluice tunnel that flung hunks of concrete half a mile when the explosives were detonated.

The statistics were quite simple, according to the Croatian engineers. The lake's depth must be lowered by 9 metres to ensure that the dam will not crack. Of the 1,550 million cubic metre capacity, between 150 and 180 million cubic metres were being let loose into the Cetina every day, lowering the lake's depth by 80 centimetres every 24 hours. Already, the waters had fallen by 3 metres. Another 6 metres and the dam was safe.

Of course, this equation was in no way reflected on the dam wall yesterday afternoon. Victorious Croatian militiamen, television camera crews and understandably silent United Nations observers - their Kenyan troops had, after all, abandoned their posts at each end of the dam when the Croatians commenced their assault last week - wandered the cracked concrete between truckloads of earth and broken masonry. 'We cried when we first saw this,' a Croatian major announced with an emotional, slivovic-laden sigh as he stood high above the drowning generators. 'But when we realised we had driven the Serbs back 10 kilometres - a third of the way to Knin - we laughed.'

What possesses armies to wreak such destruction upon themselves as well as on their enemies? The Peruca dam helped power the Serbs' self-styled Krajina capital of Knin as well as the Croatian villages of Sinjsko Polje. Electricity will be needed by both communities long after this war is over.

Perhaps environmental catastrophe is now a legitimate weapon; the Iraqi army and the US air force spread oil over the Gulf, while Saddam Hussein set the Kuwaiti wells on fire and stained the Himalayan snow. The roar of water punching through the walls above the Peruca yesterday sounded almost identical to the subterranean thunder of Kuwait's burning oil shafts.

Standing at the southern foot of the dam, it was not difficult to imagine how swiftly disaster could pour down upon the meadows of the little, unheard-of villages in the lower valley. Their names - Bitelic, Rumin, Bajagic, Gala, Glavice, Orok, hitherto marked only by long-dishonoured, bullet-scarred Partisan memorials - would be obliterated in the flood which followed.

But thanks to pre-stressed concrete and its Serbian manufacturers, the potential Armageddon which drew the camera crews to this anonymous valley is unlikely to be fulfilled. The three British engineers sent to Croatia, trucked up to the dam in a vehicle emblazoned with a Union flag, happily concurred with this assessment.

Spectators were thus left to gaze upon the usual detritus of war: a mined ambulance, four shelled lorries, hundreds of roofless, gutted homes and fields of Serbian artillery bunkers, the earth around them splashed with ammunition boxes and used shell- cases.

Down the valley, the waters of the Cetina had risen several feet, creeping up the pastures of square farm houses, brushing the underneath of the road bridge at Obrovac Sinjski, edging the dirt road with ice beneath the Dinara mountains; but leaving the 22,000 Croatian villagers unmoved by predictions of disaster. They were relying on the skill of Croats and Serbs alike to save them.