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Horizontal Anisotropy of the Principal Ground‐Water Flow Zone in the Salinas Alluvial Fan, Puerto Rico
Author(s) -
QuiñonesAponte Vicente
Publication year - 1989
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1989.tb01969.x
Subject(s) - anisotropy , ellipse , geology , minor (academic) , aquifer , square (algebra) , geometry , alluvium , least squares function approximation , tensor (intrinsic definition) , thermal diffusivity , aquifer test , cube root , mathematics , mineralogy , geotechnical engineering , geomorphology , statistics , groundwater , optics , physics , law , thermodynamics , estimator , groundwater recharge , political science
Well drawdown data from an anisotropic aquifer in the Salinas alluvial fan were collected and analyzed with a computer program called TENSOR2D. The program uses ordinary and weighted least‐squares optimization procedures to solve the system of simultaneous equations needed to define the theoretical transmissivity ellipse. Results from the alluvial fan aquifer at Salinas, Puerto Rico indicated that when applying the ordinary least‐squares method: (1) the major and minor transmissivity tensors are 52, 339 and 17,800 feet squared per day (ft 2 /d) respectively; (2) the square root of the major and minor diffusivity tensors are 12,066 and 7,036 ft 2 /d, (3) the ratio of horizontal anisotropy is 2·94 to 1·00, and (4) the direction of major anisotropy tensor is along a line 31 degrees west from the true north. From the application of the weighted least‐squares method: (1) the major and minor transmissivity tensors are 38,840 and 23,987 ft 2 /d, (2) the square root of the major and minor diffusivity tensors are 11,282 and 8,866 ft 2 /d, (3) the ratio of horizontal anisotropy is 1·62 to 1·00, and (4) the direction of major anisotropy tensor is along a line 28 degrees west of the true north. Prediction of drawdown data was made by coupling the anisotropy ellipse with the Hantush modified leaky‐confined or Theis model. Drawdown data predicted by using the theoretical directional diffusivity obtained with the weighted least‐squared fit gave a more accurate representation of the actual drawdown data than when using the test‐data directional diffusivity.