In early river valley farming, which factor most significantly contributed to enabling stable harvests and urban growth?

• A. Sole reliance on rainfall
• B. Limited storage
• C. Trade networks
• D. Irrigation and farming efficiency

Answer: (D)

Water control through irrigation is what makes harvests stable in river valley farming. By channeling floodwaters and managing moisture, farmers could lessen the risks of unpredictable rainfall and floods, extend the growing season, and push yields higher. When irrigation is paired with efficient farming practices—better tools, planning, and methods—surplus food becomes reliable year after year. That steady supply supports larger populations, enables storage for lean times, and frees people to specialize in crafts and governance, which are the seeds of urban life. Trade networks naturally grow from this surplus, but without irrigation and efficient farming, harvests would remain too variable to sustain cities. Rain-fed farming alone is too risky, and merely having storage capacity isn’t enough without the means to produce a reliable surplus.