Groundwater-surface water interactions manifested on stream network geometry across United States

The branching angles of stream network are the fingerprint of the processes that shape our landscape. However, the mechanisms that give rise to stream network patterns on Earth are not fully understood. Recent studies have shown controls of climate, tectonics, and lithology on channel incision and the planform geometry of stream networks. Our analysis of one million river junctions and over 4.2 million groundwater well observations across the contiguous United States shows for the first time that stream network branching angle vary systematically with the degree to which streams and groundwater interact.  Streams that are losing their water to groundwater exhibit narrow branching angles while streams that are gaining water from groundwater exhibit wide branching angles on average. We show that the correlation between branching angle and fraction of losing streams is stronger than branching angle and other controls of stream network planform geometry. The systematic relationship between branching angle and losing fraction persist across a range of topographic gradient and across several stream orders. Our findings brings forward a mechanistic linkage between previously shown correlation between branching angles and climate.