Complex sentence: The Central Valley is the most productive agricultural region in the United States with a estimated value of 17 billion for the 250 crops grown in the region, and irrigation is the largest withdrawal of groundwater from the aquifer.
Split into simpler sentences: The Central Valley is the most productive agricultural region in the United States with a estimated value of 17 billion for the 250 crops grown in the region. Irrigation is the largest withdrawal of groundwater from the aquifer.