1.   Purpose and objectives

     Pumping test evaluation based on analytical solution. The package calculates optimal values of geohydrological parameters from observed changes in ground water heads due to pumpage from one or more wells. The subsequent analysis of variance yields information on the reliability of  the optimised parameter values.

2.   Description

     The flow is described by Darcy's law and the mass continuity equation. Existing analytical solutions are used to calculate the head drawdown.

     The parameter values (transmissivity and storage coefficients for aquifers, and resistance of aquifers) are calculated by an automatic inverse procedure using least-squares optimisation. The minimum and maximum allowable parameter values or prescribed fixed values can be specified. Following the optimisation, an analysis of variance yields information on the reliability of the parameter estimates.

     Both steady-state and transient systems can be modelled. The well rates can vary either step-wise or piece-wise linear in time.

     AQ-AT can handle the two following cases:

     - Multi-layered aquifer-aquitard system with up to 10 aquifers, 
       assuming horizontal flow in the aquifers and vertical flow through 
       the aquitards. The wells fully penetrate the relevant aquifers.  
       The layers are laterally homogeneous and isotropic. This case 
       includes the classical Hantush (single aquifer-aquitard) and Theis 
       (single confined aquifer) systems.

     - Fully three-dimensional flow in a single aquifer overlain by an 
       aquitard. The wells can partially penetrate the aquifer. The 
       aquifer and aquitard are laterally homogeneous. The aquifer can be 
       anisotropic in depth.

     In both cases, a laterally infinite system is assumed and storage in the aquitards is neglected, which implies that the flux is constant over the aquitard thickness.

3.   Input

     Data for pumping wells (location and abstraction rate), groundwater head drawdowns in observation wells, and initial estimates of the value of hydrogeologic parameters to be estimated.

4.   Output

     - Plot of observed and calculated head values per well, linear and logarithmic time axis;

     - Plot of confidence contours for a pair of parameters;

     - Various (printable) tables.

5.   Operational requirements and restrictions

     The AQ-software packages run on Personal Computers under DOS, OS2 and WINDOWS95 operating systems. A pen plotter is required, unless other plot viewing systems are used. Two types of plotters are supported: HP7475A (or HP-compatible) and Calcomp MODEL84/81

     AQ-AT consists of a number of computer programs communicating through data files. The programs are controlled interactively through screen menus in English, and feature a unit versatility and full error checking procedures.

     The model can be handled by persons familiar with general hydrogeological principles and groundwater modelling concepts. A basic knowledge of statistics is required.

     Easy installation following the manual. The model package takes a short time to acquire proficiency in handling. As the source code is not supplied, no FORTRAN compiler is needed.

6.   Form of presentation

     Run version of the computer program package on several diskettes with comprehensive user manual in English.

7.   Operational experience

     The model has been widely used since 1987, mainly in The Netherlands, especially for operationally orientated groundwater investigations, e.g. by water supply companies and consulting engineers.

8.   Originator and technical support

     The program is developed at IWACO B.V., Consultants for Water and Environment, Rotterdam, The Netherlands. Technical support will be provided by IWACO B.V.

9.   Availability

     From the HOMS National Reference Centre for The Netherlands.

10.  Conditions on use

     A charge is made for the model, but updates of new run versions will be forwarded to users automatically for a certain period of time.