North China's Hebei Province, the major water supplier to Beijing, has overused 120 billion cubic meters of groundwater in 30 years, causing serious problems such as subsidence and seawater contamination, says an expert with the provincial water conservancy department.

With diminishing supplies, Hebei has 331 cubic meters of water per person, one seventh the national average, said the expert who declined to be named.

As well as meeting its own needs, Hebei must also supply water to neighboring Beijing and Tianjin, where the three big reservoirs of Miyun, Guanting and Panjiakou are backed by water from Hebei Province.

The province consumes 23 billion cubic meters water annually, but it has only 17 billion cubic meters of surface water, leaving groundwater to supply the difference.

The expert noted that groundwater overuse began in 1976, and with about four billion cubic meters of groundwater taken annually, the total volume in the past three decades equaled 200 Baiyangdian lakes, referring to the largest freshwater lake in north China.

Environmental problems such as subsidence and seawater contamination had affected the Cangzhou city area, which had subsided more than two meters, and groundwater in Qinhuangdao city was unpotable due to seawater inflow.

The plain areas in southern Hebei, the main water source for Beijing and Tianjin, had seen subsidence of 70 cm across almost 621 square km, and the area would expand to 18,836 square km in 2030.

The expert urged the government to invest more money in environment protection, and to take water efficiency measures to reduce consumption.