Due to huge amount exploitation of karstic water in Tai′an-Jiuxian water source area, scope of karstic funnels and unwatering areas of Quaternary pore water enlarged quickly from 1989. Large square of collapes and cracks were produced at the same time, and karstic water quality got worsen. In 1993, after major karstic water mining wells were closed, karstic water level got higher, water quality became better and hazards of collapses and crack weaker. It showed that reasonable exploitation of underground wa...