What is one effect of increased population density on California's water supply?

Increased population density leads to a higher demand for water resources, making it the correct choice. As the population grows, more water is needed for residential, commercial, and industrial uses. This surge in demand can strain existing water supplies, leading to challenges in management and allocation. For example, urban areas with high population density require extensive water for daily activities such as drinking, sanitation, landscaping, and recreational uses, which can deplete local water sources more rapidly.

While improved groundwater recharge, enhanced conservation practices, and reduction in agricultural land use may occur due to various initiatives or changes in policy, these are not directly a result of increased population density itself. Instead, the immediate impact of more people living in an area is an escalation in water use, emphasizing the importance of effective water resource management to cope with this demand.