Final answer:
The primary factor in the modern freshwater crisis is the uneven distribution of precipitation combined with human-induced overuse and pollution, affecting water availability and quality.
Step-by-step explanation:
The predominant underlying factor contributing to our modern freshwater crisis is a combination of physical and human factors.
Precipitation, which is a major control of freshwater availability, is unevenly distributed globally, with more precipitation falling near the equator and less near the latitudes where the world's largest deserts are located.
Additionally, human activities such as overuse and water pollution exacerbate water scarcity and degrade water quality, while climate change alters precipitation patterns and exacerbates water stress in some regions.
Over-use and pollution of freshwater by pathogens, heavy metals, plant nutrients, and oxygen-demanding waste threaten the limited supply people depend on, leading to waterborne diseases and causing nearly two million deaths annually, primarily in children under five.
This issue is compounded by the rapidly growing human population and is identified as a top environmental concern by Gallup public polls, along with issues like air pollution and global warming.
Furthermore, the cost of obtaining clean water interferes with survival and social mobility, as water hauling, often done by children and pregnant women, negatively affects education and physical health.
The sustainability of fresh water supply is a major global challenge, with traditional approaches like dams and aqueducts being reconsidered in favor of holistic, resilient solutions to address the water supply crisis.