Reclaiming land around lakes should be based on the principle of not destroying water system safety and environmental ecology. If the sea is reclaimed indiscriminately, it will bring serious harm. In this regard, the experience and lessons left by the reclamation of lakes in the Song Dynasty are very profound. First of all, it aggravated the flood and drought disasters. Taihu Lake is surrounded, which leads to "drought" ... People's land is not profitable, floods are far and near, people are not allowed to enter the lake, but people's land is gone. Therefore, The History of the Song Dynasty says, "Suzhou, Huguang, Changzhou and Xiu Xiu were flooded in the past, but now they are dry, which is the reason." Jianhu Lake is surrounded. "When the spring water overflows, there is no water in the fields of civilians ... Between summer and autumn, there is more rain or less rain, and there is no water irrigation. (Yin Shan and Huiji) There are floods and droughts everywhere." "History of the Song Dynasty Food Record" said: "There are vicious lakes in Ming and Vietnam, which are generally higher than fields, and fields are higher than rivers and seas. When there is drought, the lake will be used to irrigate the fields, and when there is flood, the fields will be flooded into the sea, so there is no flood and drought disaster. ..... Since the political reform, the lake has been turned into a field, which is the people of two states. It was affected by floods and droughts at the age of 18. " At that time, Shaoxing magistrate Shi Hao said: "However, water is harmless, and people can't turn a lake into a field." Hit the nail on the head and tell the crux. Secondly, it caused the loss of cultivated land. In the ninth year of Shao (1 139), Zhou Gang went to Mingzhou to investigate the situation of Guangde Lake after it was abandoned, and said, "I have inquired about the old farmers in many ways, thinking that when the lake was not abandoned, the people in the seven townships produced six or seven kilograms of crops per mu, but now the harvest is less than half of the previous day, and the benefits of lake water irrigation have been lost. Counting the fields of seven townships, it is no less than 2,000 hectares, and there is no worry about losing the valley. " Cai Xiang said in "Claiming Back Five Ponds" that after Baoyuan (1038- 1040) abolished five ponds, "more than 100 hectares of ponds were expropriated to support more than 30 official households". From then on, it only rained in the coastal saline-alkali land (1000 hectares). The economic loss is too great to be calculated. Third, it leads to the loss of the country. Chen Yun said in "On the Lower Cover of the Lake": "In the first year of Jianyan (1 127), more than 5,400 stones were collected in two years, and the people's fields lost the benefits of the vicious lake, and there was no drought in all places. In two years, Qiumi inspected and released more than 22,500 stones. Only one county in Shangyu is like this. From this perspective, its gains and losses are not entirely so. "Jianhu, too. Xu Ciduo said in "On the Mirror Lake": "The husband lake field is only more than 50,000 stones, and the one-year-old two counties are flooded, and the loss is almost no less than 100,000 stones. Its gains and losses have been eliminated. After the completion of "Yongfengwei", the annual income was only 20,000 meters. At the age of four, there was a flood, and the rent for the lost people was ten times. "It can be seen that the land tax has not increased, but it has increased the financial difficulties of the government. Fourth, it has intensified social contradictions. After the lake was surrounded, the conflict between land and water continued and civil disputes continued. Guangde Lake is surrounded. " Without tenants, the lawsuit will never stop. ""Litigation about occupation and fighting is getting more and more troublesome. "My hall is surrounded, and the land watered in the past is scorched and withered, and the people are arguing for litigation" (Cai Zhonghui's Collection). Mulan was besieged in the north, and "the villagers died fighting for water. "This has added new turbulent factors to the society. Coupled with the destruction of aquatic resources and traffic, it can be seen that the reclamation of land around lakes in the Song Dynasty has more advantages than disadvantages. This historical lesson is still worth learning.