明代吴淞江中下游的旱情敏感

The Drought Sensitive in Middle and Lower Reaches of Wusong River in the Ming Dynasty

宋代吴江长桥修建使吴淞江水流流速缓慢,河道淤积加强。到明代,随着山区开发,水流更加浑浊。为了防治淤塞,明初治水者将吴淞江中下游主干河道转移到黄浦江。黄浦江水深流急,排水速度提高,吴淞江溢流排水的丰水环境被改变。昆山与嘉定的原吴淞江两岸地区由此产生旱情。由于海潮顺各河快速上溯,泥沙沉积格外严重,沿岸高地的形势日益强化。因清水经常断流,潮水灌溉也大为减少,整个地区对旱涝的敏感程度明显提升。旱情在嘉靖年间日益严重,江南水乡出现了旱情敏感。水乡中出现了旱地化景观,也出现了一些次生的变化。旱灾导致高地难以再持续种植水稻,不得不以种植棉花替代。水稻种植比重下降,棉花种植比重上升。

The building of Wujiang Longbridge in the Song Dynasty made the flow of Wusong River water slow strengthened the watercourse's deposition. In the Ming Dynasty, with the development of mountain areas, the water was more turbid. For prevention and control of silting, the administer of water conservancy in early Ming Dynasty transferred main water flow of Wusong River in middle and lower reach trunk into the Huangpu River. In the Huangpu River, the water was fast and drainage speed was also increased,and the wet environment produced by overflow drainage was also changed. The drought was taken place in this environment in the high land in Kunshan and Jiading on both sides of the original Wusong River bank. Because the tidal was fast back along the river, and the sediment deposition was particularly serious, coastal highlands situation was increasingly strengthened. The clear water reduced increasingly, and the tide irrigation is greatly reduced. An increased sensitivity to drought and flood across the region was taken place. In Jiajing period of the Ming Dynasty, there were increased droughts in Jiangnan water area,and there appeared drought sensitive. The dry land landscape appeared in the wet country, and there were also some secondary changes. The drought was is in such a serious state, that parts of the highlands were hard to continue to grow rice, and the peasants had to plant cotton to replace it. So the rice planting proportion declined while the cotton planting proportion rose.