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Approximate analytical solution to the Boussinesq equation with a sloping water‐land boundary
Author(s) -
Tang Yuehao,
Jiang Qinghui,
Zhou Chuangbing
Publication year - 2016
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 - 10.1002/2015wr017794
Subject(s) - hydraulic head , flow (mathematics) , nonlinear system , head (geology) , aquifer , mathematics , mathematical analysis , boundary value problem , algebraic equation , laplace transform , groundwater , geotechnical engineering , geology , physics , geometry , quantum mechanics , geomorphology
An approximate solution is presented to the 1‐D Boussinesq equation (BEQ) characterizing transient groundwater flow in an unconfined aquifer subject to a constant water variation at the sloping water‐land boundary. The flow equation is decomposed to a linearized BEQ and a head correction equation. The linearized BEQ is solved using a Laplace transform. By means of the frozen‐coefficient technique and Gauss function method, the approximate solution for the head correction equation can be obtained, which is further simplified to a closed‐form expression under the condition of local energy equilibrium. The solutions of the linearized and head correction equations are discussed from physical concepts. Especially for the head correction equation, the well posedness of the approximate solution obtained by the frozen‐coefficient method is verified to demonstrate its boundedness, which can be further embodied as the upper and lower error bounds to the exact solution of the head correction by statistical analysis. The advantage of this approximate solution is in its simplicity while preserving the inherent nonlinearity of the physical phenomenon. Comparisons between the analytical and numerical solutions of the BEQ validate that the approximation method can achieve desirable precisions, even in the cases with strong nonlinearity. The proposed approximate solution is applied to various hydrological problems, in which the algebraic expressions that quantify the water flow processes are derived from its basic solutions. The results are useful for the quantification of stream‐aquifer exchange flow rates, aquifer response due to the sudden reservoir release, bank storage and depletion, and front position and propagation speed.