Which of the following statements about headwaters is true?

Headwaters are indeed a critical component of river systems and are often described as the sources of streams and rivers where water flow originates. The statement that headwaters comprise half of the stream network is true because headwaters account for a significant portion of the total length of all streams and rivers within a watershed or drainage basin. They are essential for the overall health of aquatic ecosystems and play a vital role in the hydrological cycle. Headwaters are typically characterized by their small size, steep gradients, and often, this region features higher water quality and biodiversity compared to larger downstream water bodies.

The other statements do not accurately reflect the characteristics of headwaters. They can be found in both humid and arid climates, across various elevations, and in both urban and rural areas. Their presence is not limited to high elevations, nor are they restricted to urban environments, highlighting the diversity in environments where headwaters can be situated.