It's difficult to say definitively which freshwater source is *most* important to people, as the importance of different sources varies depending on location, population density, and needs. However, rivers are often considered to be the most important source of freshwater for a few reasons:

* Accessibility: Rivers are generally easily accessible for drinking, irrigation, and transportation.

* Abundance: Rivers carry large volumes of water, making them a reliable source.

* Renewable: River water is constantly replenished through precipitation and runoff.

* Multiple uses: Rivers are not only used for drinking water, but also for irrigation, hydropower, recreation, and transportation.

Other important freshwater sources include:

* Lakes: Large bodies of water that can provide drinking water, irrigation, and recreation opportunities.

* Groundwater: Water stored underground, accessed through wells. A vital source in many areas, especially during dry periods.

* Glaciers and ice sheets: Large stores of freshwater, but access is often difficult and they are increasingly threatened by climate change.

It's important to note that:

* The importance of each source can vary greatly depending on the region. For example, groundwater may be more important in arid regions than in areas with abundant rivers.

* Sustainable management of all freshwater sources is critical to ensure their availability for future generations.

Overall, while rivers are often considered the most important freshwater source, all sources are vital for human life and require careful management.