Baini Weirs, including the Shijian Weir and the Yuanbei Weir, are located in Chongyang County, Hubei Province of China. According to the historical records, the Shijian Weir was constructed no later than AD 931, and the Yuanbei Weir was constructed no later than 1226, both with a history of over 1,000 years. Up to now, the two weirs have been playing a role in irritation, flood control, drought relief, water supply, and etc. With an irritated area of over 2,300 ha, they are the representatives of large masonry water conservancy projects in ancient China.

The Shijian Weir is 272 meters long, 2 meters wide at the top, and 5 meters high. It was constructed with large limestone slabs and enhanced with cement paste. In the ancient times, people mixed the glutinous rice paste with the lime to fill the seams of the slabs. There are over 20 holes for installing timber piles at the weir base, the diameter of each hole is 20–30 centimeters, and the distance between every two holes are 1.2–1.6 meters. According to historical records, the earliest Shijian Weir was not a masonry structure, but a simple dam supported by big timbers, so these holes are probably traces of installing timber piles over 1,000 years ago. There is a tunnel at the weir base for the purpose of water discharge and desilting. With a cross section that is 1.5 meters wide and 2 meters high, the tunnel is blocked up with straws and planks in spring, and opened in autumn to release water for repair and dredging. Currently, there are no other historic weirs with such bottom tunnels found in China. The Yuanbei Weir, structurally similar to the Shijian Weir, is 108 meters long and 4–5 meters high.

Thanks to the scientific design and construction as well as the management and annual repair systems, up to now, the two weirs have been used for over 1,000 years. Baini Weirs are located on the bed rock where the waterways are wide to ensure weir base stability. Moreover, crossing the river following an oblique line, the weirs are lengthened to improve overflow capacity, lower the water level at its upstream, and weaken the impact of flood. The construction techniques and materials have also improved gradually. The early wood weirs evolved to stone-slab structures, then the lime paste was used to fill the weir seams, with iron latches and ingots being used for connection and fixing. As a result, the weirs have become more resilient, stable and integral structures. Since ancient times, a set of management and annual repair systems have been applied to Baini Weirs, including appointing weir chiefs and canal chiefs, setting up management rules and project dossiers, and specifying time for opening the desilting tunnel for the convenience of checking and repairing weirs and canals.

Through canal network, the weirs still guarantee the domestic water consumption of the nearly 30,000 residents of the Baini Town, which has been a remarkable achievement. Shijian Weir has a bottom tunnel for water discharge and desilting, which is on the main line of the waterway. Historically, in late autumn when irrigation was not needed, the tunnel was opened to release water for annual repair and dredging. This practice ensured the adequate storage capacity and safe operation for over 1,000 years, nowadays the weir still plays an important role in multiple aspects.
The weirs were constructed on the base rock of the riverbed and connected to it by thick timber piles. The stone slabs of the weir are crisscrossed with each other and fixed by iron latches, similar to the mortise and tenon joint structure in traditional Chinese architecture. In this way, the integrity and stability of the weir are enhanced. The weirs have been in use for about 1,000 years despite the adverse effect of the bottom tunnel on the structure.

The weirs not only brought a huge benefit of irrigation, but also played an important role in water transport. According to historical records, it was in the Ming Dynasty (1368–1644) that the water transport in Baini Town began to develop with the help of the weirs. The construction of the weirs promoted the rise and prosperity of Baini Town as well as the social and economic development of the region. Baini Town was therefore formed. At first, the town’s market was located at Bainizhen. With the development of water transport, it gradually extended to Dashi River, forming the Baini Port, which was an important trade port in southeast Chongyang County in the Ming and Qing Dynasties. In modern times, the prosperous Baini Town even crossed over Dashi River and continued to expand.

Baini Weirs are located on the bed rock where the waterways are wide. Crossing the river following an oblique line, the weirs are much longer than the width of the river. Similar to that of long-crested weir in contemporary hydraulic projects, this kind of structure can improve overflow capacity, reduce the obstruction to water discharge, minimize intervention in the natural river and the impact of water currents on the weirs.