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Applying satellite‐derived evapotranspiration rates to estimate the impact of vegetation on regional groundwater flux
Author(s) -
Swaffer Brooke A.,
Habner Nardine L.,
Holland Kate L.,
Crosbie Russell S.
Publication year - 2020
Publication title -
ecohydrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.982
H-Index - 54
eISSN - 1936-0592
pISSN - 1936-0584
DOI - 10.1002/eco.2172
Subject(s) - groundwater recharge , evapotranspiration , groundwater , hydrology (agriculture) , environmental science , water balance , water table , depression focused recharge , vegetation (pathology) , groundwater discharge , aquifer , geology , ecology , medicine , geotechnical engineering , pathology , biology
Freshwater resources are at a premium across the world, including many water‐limited areas across Australia. Ongoing water level decline in some groundwater systems suggests that the rate of loss may have reached unsustainable levels . However, identifying which factors are primarily responsible for the trend (lack of rainfall–recharge, presence of vegetation, and groundwater pumping) remains challenging using groundwater observations alone. We applied satellite‐derived estimates of evapotranspiration ( ET a ), which, when combined with local rainfall data and field‐based groundwater level observations, established a regional water balance spanning 1,500 km 2 and seven groundwater lenses over a 10‐year period (2000 – 2010). Assuming that the extent of the freshwater isohaline represents the recharge area for a lens, the water balance suggests that the median annual groundwater recharge rate varied between 226 ± 92 mm year −1 (Mikkira) and −162 ± 194 mm year −1 (Uley East). Uley South is the most regionally significant lens in the system and recorded a median annual recharge rate of 91 ± 182 mm year −1 . Overlaying vegetation highlighted the impact of woodland areas on groundwater recharge, where the trees were accessing groundwater to support ET a , provided the water table was <10 m. Areas of grassland demonstrated the highest median groundwater recharge rates of 151 mm year −1 , followed by cropping (133 mm year −1 ) and pasture (95 mm year −1 ). Exploring the resilience of the groundwater system to variations in extraction (pumping) and woodland coverage suggests that resource managers must consider both systematic losses in order to maintain groundwater equilibrium.