Finally, after 130-165 days the rice is ready. The field transitions from a
green color (top left), to a golden color (top right) because of the mature
rice and the plant entering senescence. At the beginning of
this process the grower uses his experience, soil knowledge and skill to
determine when he should "drain" the field.
Remember, water has been in the field during the whole time the rice has been growing. The rice will reach a point where the plant's job is done and the plant will begin to die. Removing the water too soon will prevent the kernels from reaching their proper weight. The other side of the decision is that the grower wants the field dry enough to support the harvest equipment and not create deep ruts in a muddy field. So it is very important that the grower make good decisions about managing their water.
You can see by the center picture that the kernels are held on a slender stalk and they are bent over essentially pointing at the ground. The plant is heavily loaded at this point. Sometimes, a dry, hot "north wind" will start blowing at this time of the year. The rice plant can hardly hold itself up at this point and a strong wind will often knock it down (bottom picture) so that the plant is lying parallel to the ground. This makes harvest slower and more difficult, but California growers are prepared for this situation.