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Understanding and quantifying focused, indirect groundwater recharge from ephemeral streams using water table fluctuations

Cuthbert, MO; Acworth, RI; Andersen, MS; Larsen, JR; McCallum, AM; Rau, GC; Tellam, JH; (2016) Understanding and quantifying focused, indirect groundwater recharge from ephemeral streams using water table fluctuations. Water Resources Research , 52 (2) pp. 827-840. 10.1002/2015WR017503. Green open access

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Abstract

Understanding and managing groundwater resources in drylands is a challenging task, but one that is globally important. The dominant process for dryland groundwater recharge is thought to be as focused, indirect recharge from ephemeral stream losses. However, there is a global paucity of data for understanding and quantifying this process and transferable techniques for quantifying groundwater recharge in such contexts are lacking. Here we develop a generalized conceptual model for understanding water table and groundwater head fluctuations due to recharge from episodic events within ephemeral streams. By accounting for the recession characteristics of a groundwater hydrograph, we present a simple but powerful new water table fluctuation approach to quantify focused, indirect recharge over both long term and event time scales. The technique is demonstrated using a new, and globally unparalleled, set of groundwater observations from an ephemeral stream catchment located in NSW, Australia. We find that, following episodic streamflow events down a predominantly dry channel system, groundwater head fluctuations are controlled by pressure redistribution operating at three time scales from vertical flow (days to weeks), transverse flow perpendicular to the stream (weeks to months), and longitudinal flow parallel to the stream (years to decades). In relative terms, indirect recharge decreases almost linearly away from the mountain front, both in discrete monitored events as well as in the long-term average. In absolute terms, the estimated indirect recharge varies from 80 to 30 mm/a with the main uncertainty in these values stemming from uncertainty in the catchment-scale hydraulic properties.

Type: Article
Title: Understanding and quantifying focused, indirect groundwater recharge from ephemeral streams using water table fluctuations
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/2015WR017503
Publisher version: http://doi.org/10.1002/2015WR017503
Language: English
Additional information: © 2016. American Geophysical Union. All Rights Reserved.
Keywords: Groundwater recharge; ephemeral stream; water table fluctuation; semiarid hydrology; indirect recharge; focused recharge; dryland hydrology; mountain front
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
URI: https://discovery.ucl.ac.uk/id/eprint/1527576
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