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Analytical expressions for transient specific yield and shallow water table drainage
Author(s) -
Nachabe Mahmood H.
Publication year - 2002
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 - 10.1029/2001wr001071
Subject(s) - water table , aquifer , yield (engineering) , groundwater , well drainage , drainage , table (database) , soil science , hydrology (agriculture) , waves and shallow water , geology , transient (computer programming) , environmental science , geotechnical engineering , computer science , materials science , ecology , oceanography , data mining , metallurgy , biology , operating system
New closed‐form expressions are introduced to capture the dependence of specific yield on time and depth to water table. The expressions allow the user to convert observations of water table fluctuations to volumes of water released from storage in a shallow water table aquifer. Whereas a linear relationship between water table fluctuations and released volumes holds for a deep water table aquifer, this relationship is nonlinear for shallow water table aquifers. The dependence of specific yield on time stems from the slow drainage of soil water from pores above the water table. The new expressions allow determination of transient specific yield and time to drain the soil water profile for a given water table fluctuation. If the time step in a numerical groundwater model is longer than the time for limiting specific yield, then a constant (time independent) specific yield can be justifiably adopted. The new expressions are easy to use and require knowledge of soil hydraulic properties which are readily available from soil water retention data and surveys.