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A helicopter‐borne electromagnetic survey to delineate groundwater recharge rates
Author(s) -
Cook P. G.,
Kilty S.
Publication year - 1992
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/92wr01560
Subject(s) - groundwater recharge , geology , groundwater , vadose zone , hydrology (agriculture) , electromagnetics , soil science , environmental science , aquifer , geotechnical engineering , physics , engineering physics
Groundwater recharge is one of the most difficult components of the water balance to measure. For this reason, electromagnetic methods have been used to infer its variability from measurements of apparent electrical conductivity. In this study, groundwater recharge was estimated at 20 sites using unsaturated zone chloride methods. Interpolation between drill sites was accomplished with the aid of a helicopter‐borne electromagnetic survey (DIGHEM IV ). Correlations between recharge and apparent electrical conductivity were only significant ( R 2 = 65%) at the highest frequency (56,000 Hz). Using these single‐frequency data, variations in recharge were mapped over an area of 32 km 2 . Recharge, as inferred from the electromagnetic data, appears to be lognormally distributed, and varies from less than 1 to more than 50 mm yr −1 . Within the study region, spatially averaged recharge can be estimated from the electromagnetic data, with an accuracy of approximately −60%, +140% (90% probability). This is comparable to the estimation accuracy when surface electromagnetic methods are used. Aerial electromagnetic methods appear very useful for identifying areas of high and low recharge over large regions.