For thousands of years,
early agriculturists depended on the rain to ensure a good harvest.
But this puts agricultural communities in danger when there is no
rain or too much rain. If the rainy season is too heavy, floodwaters
can destroy a season's harvest. If the rainy season is too light, the
rice plants can be destroyed as well.
Early Southeast Asian farmers tried to limit this problem by building tanks and dams to control and direct water into the fields. However by using irrigation techniques, they were able to grow even more surplus rice and feed even more people.