The missions of Central Texas relied on farming to feed the people in the missions and the surrounding countryside. Central Texas only gets 20 to 30 inches of rain a year, not enough to ensure successful crops. How did the missions water their crops? A. They used windmills to pump groundwater. B. They built irrigation ditches called acequias. C. They relied on runoff from area mountains. D. They built a dam on the San Antonio River.