China once again appears to be turning to American know-how is an attempt to make the great economic leap onto the 20th Century.

Thus, while the governments of the United States and the People's Republic of China deal delicately with one another at the highest diplomatic levels, the two nations are rapidly building ties at the technical levels.

As they did in the 1930, the Chinese are exploring the potential of U.S technical assistance it developing their vast system of inland waterways both for transportation purposes and to harness hydroelectric power.

Within the last two months, representatives from China have visited the United States to look at its rivers and harbors, while business and government representatives from the United States have visited peking to discuss inland waterways.

According to one administration source, it all began when presidential science adviser Frank press visited China last June. "We learned of their interest in talking to the Army Corps (U.S. Army Corps of Engineers) about development of their rivers" he said.

China subsequently invited Corps officials to come to Peking to talk about river mavigation and harbors.

Sending a psendo-military delegation to China posed some problems for both governments. Not only is China not classified as a friendly country (the Army Corps has projects in 11 friendly countries such as Saudi Arabia), but the U.S. does not maintain formal diplomatic relations with Peking.

Whatever reservations the State Department had about sending Pentagon employes to China were resolved, and Corps representatives have gone there three times in the last several months to discuss mavigation and hydroelectric power. Most of the Corps' delegates have been civilians.

And then, late last month, a top-level delegation of Chinese civil engineers began a two-month tour of U.S. water and harbor projects. The delegation whose hosts are Dravo Corp. of Pittsburgh and the American Society of Civil Engineers, it headed by Kuo Tsien, China's vice minister of communications.

Dravo is one of the first large American engineering and construction firms to sense the potential business in the People's Republic. So far, Dravo's relationship has been more of a diplomatic than commercial nature - the company is reticent about saying too much - but a spokesman said, "Obviously we're interested in the commercial potential."

A Danish affilite alerted Dravo to the potential for an American role in river and harbor development in China. About the same time that Dravo made overtures to the Chinese liaison mission here last spring, the Chinese were taking up a two-year-old American Society of Civil Engineers invitation to visit the United States.

When we learned of Dravo's interest, we asked them to co-host the visit," said the ASCE's executive director, Eugene Zwoyer.

While they are here, until mid-December, the Chinese civil engineers will spend much of their time at Army Corps projects - 26 of them, according to a Corps spokesman.

They will visit flood control projects, the terminals in New Orleans, locks and dams in the Ohio River basin and the St. Louis area, as well as spend several days at the Corps' massive Mississippi River experimental facilities in Vicksburg.

Dravo, along with representatives of the Corps, sent delegates to a Peking conference on waterway problems early last month. Little more than a technical exchange of information has occurred so far, according to spokesman for both Dravo and the Corps.

And, according to officials close to China, little more probably will happen until more formal diplomatic links are forged between the U.S. and the People's Republic. China's ability to hire American firms is further limited by that nation's lack of foreign exchange.

While foreigners control 600 billion or more U.S. dollars, China has little of it. At the same time, however, China has not tapped the international credit markets and has natural resources it could barter to finance its development plans.

But serious diplomatic obstacles remain to pentagon participation in Chinese construction, even though the work is not military in nature and presumably would attract mostly civilian employes of the Corps.

These obstacles can be overcome, however, notes one Chinese expert. The links between the U.S. and China, especially in hydraulic engineering, once were very strong. American engineers plays a major role in Chinese river projects in the 1930.

China has relied for thousands of years on its inland waterways for internal long-distance transportation and, according to Chinese experts, their rivers are already well developed. But the country must undertake many important projects before it can reach the level of economic sophistication it desires.

China wants to exploit Western Know-how (Chinese delegations also have visited Europe) about barge facilities, lock-building, linking facilities and dredging.

The vast Yangtze River, China's Mississippi, has a massive flow, but one that varies considerably with the season. During the light flow of winter, the water level can be 40 to 50 feet lower than during the summer. That makes building docking facilities extremely difficult.

Furthermore, the river drops precipitously as it flows from the Sze-chuan basin in the west. While the gorges that mark the drop are considered among the most magnificent in the world, they make navigation almost impossible at points. China wants to build its large hydroelectric dam in the Yantze Gorge. The project not only nearly would double the country's ability to produce electricity, it also would make navigation easier at points.