Stream daylighting can increase watershed-scale nitrogen retention. Nitrate travels on average 18 times farther downstream in buried streams than in open ones before being removed from the water column. Burial substantially reduces nitrogen uptake in streams.
Beaulieu, Jake J., Heather E. Golden, Christopher D. Knightes, Paul M. Mayer, Sujay S. Kaushal, Michael J. Pennino, Clay P. Arango et al. (2015). Urban Stream Burial Increases Watershed-Scale Nitrate Export. PLOS ONE, 10(7), e0132256.