This is fen country – the mills drive pumps that drain the land.
这是一个沼泽国 - 这些工厂启动水泵排干地面积水。
《柯林斯英汉双解大词典》
2
Areas that are naturally at exactly sea-level are always coloured blue regardless, that's why this map of England's fen-land is peppered with blue, even at + 0m: fenland at + 0m.