1.   Purpose and objectives

     Calculation of head drawdowns in aquifers and fluxes across aquitards, based on analytical solutions.

2.   Description

     The relevant physical processes are described by Darcy's law for groundwater flow and the mass continuity equation. Existing analytical solutions are implemented to calculate the head drawdown in aquifers and, as a derived variable, changes in the vertical flux across the aquitards. Both steady-state and transient systems can be modelled. The well rates can vary either step-wise or piece-wise linear in time.

     The following two principal systems are available:

     -  Multi-layered aquifer-aquitard system, assuming horizontal flow in 
        aquifers and vertical flow over separating and/or overlaying
        aquitards. Up to 10 aquifers are permitted. The wells fully
        penetrate the relevant aquifers. The layers are laterally
        homogeneous and isotropic. This 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. The latter implies that the vertical velocity is constant over the whole aquitard thickness.

3.   Input

     Well data (location and abstraction rate), hydrogeologic parameters pertaining to aquifers (transmissivity, hydraulic conductivity, storage coefficient) and aquitards (hydraulic resistance).

4.   Output

     - Graphs: variation in time in selected points, linear and logarithmic time axis;

     - Maps: contours over an area;

     - Profiles: variation over a line section across a model area;

     - Selected points: values at discrete points, and at specific time instants.

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-AP 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 a number of diskettes. A comprehensive users' manual in English.

7.   Operational experience

     The model has been widely used primarily The Netherlands since 1988, especially in the operationally orientated areas of 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 will be made for supplying the model. Updates of the new run versions will be forwarded to users automatically during a certain period of time.