Premium
Approximate Solution of a Non‐Steady‐State Drainage Problem
Author(s) -
Gardner W. R.
Publication year - 1962
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1962.03615995002600020011x
Subject(s) - outflow , drainage , thermal diffusivity , hydraulic head , mechanics , water table , steady state (chemistry) , water flow , flow (mathematics) , hydrology (agriculture) , position (finance) , mathematics , geology , geotechnical engineering , thermodynamics , physics , chemistry , groundwater , ecology , oceanography , biology , finance , economics
Flow in the unsaturated zone during one‐dimensional drainage is taken into account approximately by assuming the water content to be a linear function of the hydraulic head. The problem is then treated as one in unsaturated flow. After a brief initial period, the rate of outflow should decrease exponentially with time, with the outflow rate proportional to the soil‐water diffusivity. Agreement with experimentally determined outflow rates is reasonable; however, the exact water content distribution cannot be calculated. The treatment is extended to two dimensions by the equivalent of the Dupuit‐Forchheimer assumption. The total amount of water in the profile at any horizontal distance from a drain is calculated rather than the position of the water table. The theoretical outflow is in good agreement with results of sand tank and field measurements.