China still has weaknesses in its water conservation efforts, a senior water official said.

Flood prevention and control is up to standard in only 17 percent of the river area, said Jiao Yong, deputy minister of water resources.

Meanwhile, China has more than 93,000 reservoirs across the country for water supply and irrigation. But the total usable storage of those reservoirs now is only about 170 billion cubic meters, meaning the current water supply capacity is quite limited, he said.

Jiao's conclusion was based on the latest results from China's first-ever national water census, jointly released by the Ministry of Water Resources and National Bureau of Statistics on March 26.

The three-year census, starting from 2010, covers rivers, lakes, water conservation projects and institutions as well as domestic water use.

The census shows China now has 45,203 rivers with individual catchment areas of 50 square km or above, with a combined length of 1.51 million km.

There are 2,865 lakes with individual perennial water surface area of 1 sq km or above, with the total water surface area of 78,000 sq km, excluding the parts of transboundary lakes outside the border of China, according to the census results.

Irrigated area in China now is at 66.8 million hectares, of which 61.5 million hectares are cultivated land, it said.

Total water consumption in China is about 621.3 billion cu m, of which 47.4 billion cu m is for domestic water use, 416.8 billion cu m for agricultural use, and 120.4 billion cu m for industrial use, it said.

"China has made remarkable achievements on its construction of water conservation projects, which basically cover both rural and urban areas," Jiao said.

For instance, nearly 59 million water supply projects are in rural areas across the country now, benefiting 812 million local residents, according to the census.

"By conducting the national water census, we have made clear what the country has in the sector of water conservation for the first time. The census data filled in information gaps in China in the sector," he said.

Nearly 900,000 surveyors across the country participated in data collection and processing, the ministry said.