A method for estimating subdaily evapotranspiration of shallow groundwater using diurnal water table fluctuations

Loheide, Steven P.

doi:10.1002/eco.7

Cited by 113 publications

(169 citation statements)

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“…No model outperformed the others in each of these error benchmarks, thus illustrating that errors in the estimation of S y are compensated by errors in the estimation of recovery (Fahle and Dietrich, 2014). The methods that provided the best estimates for recovery of the groundwater used approaches to estimate sub-daily rates of ET g and recovery (Gribovszki et al, 2008;Loheide, 2008). In both methods, recovery was estimated from the previous and following nights, although application to other methods might require site-specific parameterisation of the time period that is most representative for their study conditions (e.g.…”

Section: Sub-daily Fluctuation In Groundwater Depthmentioning

confidence: 99%

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Eamus

Zolfaghar

Villalobos‐Vega

et al. 2015

Hydrol. Earth Syst. Sci.

121

112

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Abstract. Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs.We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream.We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources.Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and then provide an ecosystem-scale, multiple trait, integrated metric of the impact of differences in groundwater depth on the structure and function of eucalypt forests growing along a natural gradient in depth-to-groundwater. We conclude with a discussion of a depth-to-groundwater threshold in this mesic GDE. Beyond this threshold, significant changes occur in ecosystem structure and function.

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Section: Sub-daily Fluctuation In Groundwater Depthmentioning

confidence: 99%

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Eamus

Zolfaghar

Villalobos‐Vega

et al. 2015

Hydrol. Earth Syst. Sci.

121

112

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“…The White method, which was originally developed to estimate the magnitude of groundwater consumption by phreatophytes (Loheide, 2008;Loheide et al, 2005), has since been used to estimate ET and groundwater exchange in small, surface water systems (Carlson Mazur et al, 2014;Hill and Durchholz, 2015;McLaughlin and Cohen, 2013). In these systems, diurnal variations in high-resolution surface water level data are used to decouple ET dynamics from groundwater exchange.…”

Section: Introductionmentioning

confidence: 99%

The socioecohydrology of rainwater harvesting in India: understanding water storage and release dynamics across spatial scales

Meter

Steiff

McLaughlin

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. Rainwater harvesting (RWH), the small-scale collection and storage of runoff for irrigated agriculture, is recognized as a sustainable strategy for ensuring food security, especially in monsoonal landscapes in the developing world. In south India, these strategies have been used for millennia to mitigate problems of water scarcity. However, in the past 100 years many traditional RWH systems have fallen into disrepair due to increasing dependence on groundwater. This dependence has contributed to accelerated decline in groundwater resources, which has in turn led to increased efforts at the state and national levels to revive older RWH systems. Critical to the success of such efforts is an improved understanding of how these ancient systems function in contemporary landscapes with extensive groundwater pumping and shifted climatic regimes. Knowledge is especially lacking regarding the water-exchange dynamics of these RWH tanks at tank and catchment scales, and how these exchanges regulate tank performance and catchment water balances. Here, we use fine-scale, water-level variation to quantify daily fluxes of groundwater, evapotranspiration (ET), and sluice outflows in four tanks over the 2013 northeast monsoon season in a tank cascade that covers a catchment area of 28 km 2 . At the tank scale, our results indicate that groundwater recharge and irrigation outflows comprise the largest fractions of the tank water budget, with ET accounting for only 13-22 % of the outflows. At the scale of the cascade, we observe a distinct spatial pattern in groundwater-exchange dynamics, with the frequency and magnitude of groundwater inflows increasing down the cascade of tanks. The significant magnitude of return flows along the tank cascade leads to the most downgradient tank in the cascade having an outflow-to-capacity ratio greater than 2. At the catchment scale, the presence of tanks in the landscape dramatically alters the catchment water balance, with runoff decreasing by nearly 75 %, and recharge increasing by more than 40 %. Finally, while water from the tanks directly satisfies ∼ 40 % of the crop water requirement across the northeast monsoon season via surface water irrigation, a large fraction of the tank water is "wasted", and more efficient management of sluice outflows could lead to tanks meeting a higher fraction of crop water requirements.

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“…Several studies have analyzed groundwater well hydrographs in an attempt to estimate water consumption from phreatophytic vegetation whose roots directly access groundwater [e.g., White, 1932;Troxell, 1936;Meyboom, 1964;Gerla, 1992;Loheide et al, 2005;Butler et al, 2007;Lautz, 2008;Loheide, 2008]. Direct consumption of groundwater by phreatophytes (ET g ) represents an explicit link between ecosystem processes and subsurface hydrological dynamics.…”

Section: Introductionmentioning

confidence: 99%

On groundwater fluctuations, evapotranspiration, and understory removal in riparian corridors

Martinet

Vivoni

Cleverly

et al. 2009

Water Resources Research

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[1] This study utilizes 7 years of continuously monitored groundwater-level data from four sites along the Río Grande riparian corridor in central New Mexico to calculate evapotranspiration from groundwater and assess impacts of understory vegetation removal during a restoration project. Diurnal groundwater fluctuation measurements were used to compare the well-known White method for estimating evapotranspiration from groundwater (ET g ) to colocated measurements of total riparian evapotranspiration (ET) measured using the eddy covariance method. On average, the two methods were linearly correlated and had similar variability, but groundwater hydrograph estimates of ET g tended to be larger than tower ET estimates. Average ET g estimates for two wells at one site ranged from 91.45% to 164.77% of measured tower ET estimates, but were also shown to range from 57.35% to 254.34% at another site. Comparisons between the methods improved with deeper water tables, reduced groundwater and river connectivity, and where soil profiles were dominated by coarse-sized particles. Using a range of texturebased estimates of specific yield (S y ) with water table position improves the field application of the White method. River-induced fluctuations in groundwater increased the variability of ET g measurements. Removal of understory vegetation at one site resulted in a small but significant reduction in diel groundwater fluctuation amplitude of 19-21%. Caution is required when understory vegetation removal is used as a means to decrease overall riparian ET. Diel groundwater fluctuation amplitudes can be useful in gauging the hydrological effects of vegetation removal. Riparian groundwater hydrographs are critical to investigating the hydrologic connectivity between river and shallow groundwater, the temporal patterns of vegetative consumption, and monitoring changes to the vegetation community.

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A method for estimating subdaily evapotranspiration of shallow groundwater using diurnal water table fluctuations

Cited by 113 publications

References 20 publications

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

The socioecohydrology of rainwater harvesting in India: understanding water storage and release dynamics across spatial scales

On groundwater fluctuations, evapotranspiration, and understory removal in riparian corridors

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