The influence of riparian evapotranspiration on stream hydrology and nitrogen retention in a subhumid Mediterranean catchment
Riparian evapotranspiration (ET) can influence stream hydrology at catchment scale by promoting the net loss of water from the stream towards the riparian zone (i.e., stream hydrological retention). However, the consequences of stream hydrological retention on nitrogen dynamics are not well understo...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-09-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | http://www.hydrol-earth-syst-sci.net/20/3831/2016/hess-20-3831-2016.pdf |
| Summary: | Riparian evapotranspiration (ET) can influence stream hydrology at catchment
scale by promoting the net loss of water from the stream towards the riparian
zone (i.e., stream hydrological retention). However, the consequences of
stream hydrological retention on nitrogen dynamics are not well understood.
To fill this gap of knowledge, we investigated changes in riparian ET, stream
discharge, and nutrient chemistry in two contiguous reaches (headwater and
valley) with contrasted riparian forest size in a small forested
Mediterranean catchment. Additionally, riparian groundwater level (<i>h</i><sub>gw</sub>)
was measured at the valley reach. The temporal pattern of
riparian ET was similar between reaches, and was positively correlated with
<i>h</i><sub>gw</sub> (<i>ρ</i> = 0.60) and negatively correlated with net
riparian groundwater inputs (<i>ρ</i> < −0.55). During the vegetative
period, stream hydrological retention occurred mostly at the valley reach
(59 % of the time), and was accompanied by in-stream nitrate release and
ammonium uptake. During the dormant period, when the stream gained water from
riparian groundwater, results showed small influences of riparian ET on
stream hydrology and nitrogen concentrations. Despite being a small component
of annual water budgets (4.5 %), our results highlight that riparian ET
drives stream and groundwater hydrology in this Mediterranean catchment and,
furthermore, question the potential of the riparian zone as a natural filter
of nitrogen loads. |
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| ISSN: | 1027-5606 1607-7938 |