A LAKE that formed after the Sichuan earthquake was almost certain to burst its banks in Beichuan County and threaten tens of thousands of people, chief engineer of the Ministry of Water Resources said last night.

Liu Ning, the ministry's chief of quake relief, said there was a "93 percent probability" that the Tangjiashan quake lake will burst because of heavy rainfall or aftershocks.

The May 12 earthquake caused a landslide that formed a 124-meter-high dam at the barrier lake. If the water level rises to 40 meters of the top of the dam, it could burst at any time, Liu said.

The water level has increased an average of 1 meter per day. Water levels increase 1 meter for every 2 millimeters of rain that falls in upper river areas, Liu added.

The area's average rainfall is 140 millimeters in June, 360 millimeters in July and 330 millimeters in August, Liu said.

Frequent aftershocks are also a threat to the barrier lake, Liu added.

The engineer said that because the lake was formed by a landslide that cut off a river, its structure was unclear.

Up to 1.3 million people in the province have been told to be prepared for evacuation orders. More than 200,000 have already been relocated to safer areas, previous reports said.

唐家山堰塞湖抢险指挥部昨天深夜举行新闻发布会，水利部总工程师、唐家山堰塞湖抗震抢险指挥部专家组组长刘宁，详细分析了唐家山堰塞湖目前面临的确定与不确定的危险性。刘宁说唐家山堰塞湖因其堰塞体巨大、余震威胁、气象条件恶劣，在采取了多种措施后，仍处于极危险状态。

刘宁表示，目前已采取的工程除险措施正在发生较好的效果。据统计，地震形成的堰塞湖由于遭受较大洪水引起溃决的概率达到了93%。唐家山堰塞体高程达到82－124米，形成的水头在60－80米，可以给下游造成巨大威胁。同时，唐家山堰塞湖上游来水面积达到3550平方公里。据测算，流域内每降2毫米的雨量，堰塞湖坝前水位将提高１米。而据历史资料，6、7、8月的降雨量分别为140毫米、360毫米、330毫米，也为唐家山堰塞湖带来巨大的风险。 刘宁和武警水电部队的官兵在现场坚持了7天6夜，这使他对唐家山的险情有更深的感触和认识。

刘宁认为，唐家山堰塞湖除险减灾方案立足早动而不是晚动、主动而不是被动，工程除险与撤离群众避险相结合，是一个系统、周全的方案，体现以人民群众生命至上的指导思想。目前，有关部门对唐家山堰塞湖正进行全天候、全自动的监测，以便提供及时的预警。 负责群众疏散工作的绵阳市副市长林新通报了群众撤离避险的最新进展。从5月31日开始，唐家山下游的绵阳市已转移25万多名群众，共设置252个安置点，安置群众的基本生活都能得到保障。

抢险官兵已于5月31日抢修完成了导流槽，预计今天将开始进行导流泄洪。