University of Oulu

Marttila H, Dudley BD, Graham S, Srinivasan MS. Does transpiration from invasive stream side willows dominate low‐flow conditions? An investigation using hydrometric and isotopic methods in a headwater catchment. Ecohydrology. 2018;11:e1930. https://doi.org/10.1002/eco.1930

Does transpiration from invasive stream side willows dominate low‐flow conditions? : an investigation using hydrometric and isotopic methods in a headwater catchment

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Author: Marttila, Hannu1; Dudley, B. D.2; Graham, S.3;
Organizations: 1Water Resources and Environmental Engineering Research Unit, Faculty of Technology, PO Box 4300, 90014 University of Oulu, Finland
2National Institute of Water and Atmospheric Research Limited, P.O. Box 8602, Christchurch, New Zealand
3Landcare Research, PO Box 69040, Lincoln 7640, New Zealand
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe201803286230
Language: English
Published: John Wiley & Sons, 2018
Publish Date: 2018-12-19
Description:

Abstract

Understanding seasonal partitioning of water in riparian areas is important for assessing how vegetation affects water resources. A combined hydrological‐isotopic field study was conducted within a headwater catchment to explore the dynamics of stream discharge and the effect of riparian evapotranspiration on summer low‐flow conditions. In addition to collection of meteorological data and depth to unconfined groundwater, streamflows were measured at three locations along the length of the river. Isotope ratios of local precipitation, stream water, groundwater, and willow xylem water were used to estimate pathways and sources of water used by vegetation. Using meteorological variables, leaf area index and stand area measurements, willow transpiration was estimated using the Penman–Monteith method. Combining the data from hydrometric, isotope, and vegetation evapotranspiration analysis revealed that water abstraction by stream‐side willows peaked to 5.6 mm/day and had a distinct impact on summer low‐flow conditions and patterns of stream discharge at the daily time scale. Average annual willow transpiration was 270 mm, whereas average annual precipitation during the study period was 1067 mm. However, willow transpiration reduced streamflow and altered water budgets most strongly during critical summer low‐flow periods. Our analysis of transit times, young water fraction, and depth to groundwater water data showed Waipara headwater areas have limited water storage capacity, making them vulnerable to annual variations in precipitation and any other changes in water usage. Removal of streamside willows could potentially influence water balance during summer months when flows tend to be the lowest.

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Series: Ecohydrology
ISSN: 1936-0584
ISSN-E: 1936-0592
ISSN-L: 1936-0584
Volume: 11
Issue: 2
Article number: e1930
DOI: 10.1002/eco.1930
OADOI: https://oadoi.org/10.1002/eco.1930
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Funding: This research was funded by the NZ Ministry of Business, Innovation and Employment (Contract C01X1006: “Waterscape”). Dr. Marttila's work was supported by the Academy of Finland (AKVA Grant 263597) and by Maa‐ ja vesitekniikan tuki ry.
Academy of Finland Grant Number: 263597
Detailed Information: 263597 (Academy of Finland Funding decision)
Copyright information: This is the peer reviewed version of the following article: Marttila H, Dudley BD, Graham S, Srinivasan MS. Does transpiration from invasive stream side willows dominate low‐flow conditions? An investigation using hydrometric and isotopic methods in a headwater catchment. Ecohydrology. 2018;11:e1930. , which has been published in final form at [Link to final article using the https://doi.org/10.1002/eco.1930. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.