Ponds and weirs are important facilities for storing water for irrigation of farmland in hilly and mountainous areas

Ponds and weirs are small water-storage works commonly found in rural areas of hilly and mountainous regions. They generally refer to ponds and weirs built by excavating pits and constructing dams according to the terrain to intercept and store rainwater, spring water or stream water, and their main function is water storage for irrigation. They are modest in scale and widely distributed, and have always been an important part of the farmland water-conservancy system; especially in areas lacking large and medium-sized reservoirs, ponds and weirs play a key role in supplying water nearby.

In terms of structure, a pond and weir usually consists of the pond body, the dam embankment, the spillway and the outlet. The dam embankment is mostly built by taking local soil and tamping it, and the pond bottom and dam slope need proper seepage prevention treatment to reduce water-storage loss. The spillway is used to discharge excess inflow and ensure that the water level does not exceed the safety limit during the rainy season, while the outlet makes it convenient to deliver water to the fields according to irrigation needs.

The uses of ponds and weirs are relatively diverse. In addition to irrigating rice paddies and dry land, after water is stored they can also be used to raise fish and grow aquatic crops, and fruit trees or green-manure crops can often be planted on the pond embankments as well. At the same time, ponds and weirs can intercept slope runoff and reduce mountain floods, and they also help to some extent in regulating the local microclimate and improving the rural water environment.

Management and maintenance are the key to whether ponds and weirs deliver benefits. After long-term use, sediment easily accumulates at the bottom of the pond, reducing water-storage capacity, so regular desilting is needed; if the dam body shows signs of seepage, cracks or landslides, it should be reinforced and treated in a timely manner. Before the flood season, it is necessary to check whether the spillway is unobstructed to prevent floodwater from overtopping the dam, and ordinarily the storage and release of water should also be reasonably arranged according to farmland water use.