Analysis of Aquifer Test Data: A Handbook Prepared for a Short Course Offered December 29, 2001 Through January 9, 2002
Shabbir A.S. Sayed
This handbook was prepared to serve as a training aid and background material for a short course on ‘Analysis of Aquifer Test Data-Advanced Level’ organized by the Makkah Project of the Saudi Geological Survey (SGS) in December 2001-January 2002. The course was a continuation of earlier course held December 1998.
In this course more advanced methods of aquifer test analysis were addressed.
In preparation of this handbook the author has drawn on a lot of literature which may not be normally available to groundwater professionals.
The handbook, unlike a textbook, shall guides the reader, step-by-step, to understand the boundary conditions for various complex solutions for radial flow to wells and selects and uses the methods of aquifer test analysis under these conditions.
Because of its practical value, this handbook is being produced as technical report of SGS. The handbook is divided into ten sections.
The first four sections are of more general nature and the remaining sections deal specifically with different methods of analysis of aquifer test data not covered in the previous course.
Section One introduces various types of water-bearing formations and definitions of their hydraulic characteristics, types flow, aquifer test terminology, brief history of aquifer test methods, etc.
Section Two is devoted to various steps of aquifer test design which include identification of site constraints, listing the required aquifer properties so as to select the appropriate analysis method, preliminary estimation of aquifer properties which shall help specification of test conditions such as geometry of water entry section of production and observation wells, number and location of observation wells or piezometers, selection of appropriate well discharge and pump size, and hence casing diameter, estimating expected drawdown in the production and observation well, etc.
Section Three describes the conditions which require correction of drawdown before using it for analysis.
Methods of drawdown correction have been described for water level trends, atmospheric pressure changes, tidal, river stage and loading changes, and decrease in aquifer thickness. Section Four provides an overview of the commonly used methods of aquifer test analysis.
It actually summarizes the topics covered in the first course so as to provide the reader with a base for understanding the more complex methods covered in the succeeding sections.
Theory of superposition has also been introduced here. Section Five describes flow to wells partially penetrating confined nonleaky and leaky aquifers, solutions under various conditions such as short time, long time, steady state etc. and methods of aquifer-test analysis.
Section Six deals with flow to partially penetrating wells in unconfined aquifers.
Aquifers of finite and semi-infinite thickness have been considered.
Methods of aquifer test analysis with abstraction wells of both infinitesimal diameter and large diameter have been described.
Section Seven covers mutually leaky aquifers.
This is a new concept that has not yet found its way into textbooks. Unlike the earlier solutions for leaky aquifers the head in the source bed does not remain constant but declines with time as pumping of the leaky aquifer proceeds.
There fore determination of hydraulic parameters of both the pumped aquifer and unpumped source bed is possible.
Some of the special case solutions presented in the original reference have been further simplified and the use of the straight line method has become possible in addition to the conventional type-curve matching method.
Section Eight deals with fractured rock aquifer and describes flow in a fissure-block system and determination of hydraulic characteristics in both the fissure and the block.
Automated analysis of aquifer test data is becoming increasingly common and quite a few software packages with graphics capability have been marketed.
Section Nine provides a basic insight in the method of automated analysis explaining the concept of least squares and its use in linear and nonlinear equations. Examples of aquifer test analysis in fully and partially penetrated confined and unconfined aquifers has been provided.
Section Ten considers groundwater flow in the presence of aquifer discontinuities such as barrier and recharge boundaries, use of theory of superposition for location and number of image wells and their influence on drawdown, and methods of aquifer test analysis.
Both type curve matching and straight-line methods have described.
A large number of tables for type curves for various solutions are included in the appendix. Some of them have been taken from the literature and the remainder were computed for this course using FORTRAN programs.
Sayed, S.A.S., 2002, Analysis of aquifer test data: A Handbook prepared for a short course offered December 29, 2001 through January 9, 2002: Kingdom of Saudi Arabia, Saudi Geological Survey Technical Report SGS-TR-2002-2, 167 p., 71 figs., 23 Tables, 1 app.