In response to water deficiency in Northern China. a scheme called the Middle Route Project was devised under the South-to-North Water Transfer Division to divert water from the Han River. the biggest tributary of the Yangtze River. to supply two provinces (Henan and Hebei) and two municipalities (Beijing and Tianjin) in the north. https://www.roneverhart.com/1-4-20-HD-Galvanized-Spring-Nuts-for-Unistrut-Channel-4118G-P1006-1420/