Final answer:
The drying up of a river vital to a civilization would necessitate drastic measures such as finding new water sources, altering agricultural practices, and possibly migrating. Historical civilizations faced similar challenges and needed to adapt technologically and socially to survive.
Step-by-step explanation:
If the river by which a new civilization settled went completely dry, it would profoundly affect the civilization's ability to sustain itself. Ancient civilizations often settled near water sources such as rivers, relying on them for drinking water, irrigation, and transportation. A dry riverbed would require significant adjustments, including finding alternative water sources or relocating the settlement. To survive, community leaders would need to make critical decisions about water conservation, food production, and potential migration. Decisions that would need to be made include developing new agricultural techniques appropriate for drier conditions, establishing trade relationships with water-rich regions, and exploring technological solutions like deep drilling for groundwater or desalination for coastal civilizations. Additionally, social systems and governance might need adaptation to manage these resources fairly and effectively.
Historical examples like the decline of the Indus Valley Civilization due to climate change and the environmental adjustments in Mesopotamia highlight the importance of water management in sustaining a civilization. These societies had to make complex decisions without centralized states and adapt to environmental changes, often resulting in drastic societal and cultural shifts.