Effect of data density on groundwater contouring accuracy.

• Main Author: Davis, Phillip Ray,1946-
• Other Authors: Matlock, William G.
• Language: en
• Published: The University of Arizona. 1972
• Online Access: http://hdl.handle.net/10150/191560

The number of data points required to make a valid contour map is a function of the type of data. Using fewer data points than the maximum available to define a groundwater system has immediate economic benefits. The concept was applied to a 395 square mile section of Avra Valley, a single-aquifer, alluvial groundwater basin near Tucson, Arizona to determine the minimum number of data points necessary to produce a representative contour map. The coefficients of variation of the volume between the groundwater surface and a selected datum and the volumetric change between the groundwater surfaces over a period of time are presented as indicators of the relative accuracy of contour maps. The number of data points ranged from 200, the maximum available, to three. The relationship between the coefficients of variation and the number of data points showed little advantage in using more than thirty data points. The contour maps drawn from the maximum number and the acceptable minimum number (31) of data points showed good correlation for uniform groundwater level contour data and a poorer correlation for non-uniform groundwater level change data. Final acceptance of the minimum density groundwater contour maps depends on the objectives of the study. Using fewer data points than the maximum number available reduces costs, allows better scheduling of the data collection program, and permits faster analysis of the data.