Analytical modeling (AMWELLS)

AMWELLS is an analytical tool that can be applied for:

- optimisation of water supply and dewatering pumping rates;

- design of well fields for water supply, dewatering and depressurisation;

- planning of aquifer tests;

-estimates of dewatering requirements;

-assessment of well field impact on environment.

The module can also be used for groundwater resources determination, delineation of well catchments and wellhead protection areas (WHPA).

Various hydrogeological conditions and borefield layouts can be modelled.

For operational borefield design, AMWELLS will help to optimize:

•the number of pumping and monitoring wells,

•pumping rates, and

•well locations.

AMWELLS can predict piezometric head drawdowns during the planning stage of an aquifer test. The results will assist in selecting:

•optimal distances between pumping and observation wells, and

•test production rates.

Borefield layouts can be assigned either manually or automatically. Automatic set up of a borefield is based on layouts of various geometry (i.e. linear, rectangular, polygon) or their combination.

Modelled production and monitoring wells may penetrate one or several horizons (including partial penetration of some horizons).

Modelling results are presented in tabular and graphical formats with 2D and 3D animation of transient aquifer piezometry if required.

Production well catchments and wellhead protection areas (WHPA) are calculated using a particle tracking method for most of the hydrogeological conditions and borefield layouts.

AMWELLS applies the following solutions for typical aquifer types and boundary conditions:

1) Confined aquifer, fully penetrating production well:

•Infinite extent aquifer;

•One straight areal boundary with assigned prescribed head or prescribed flux;

•Bounded (strip) aquifer with assigned prescribed head or/and prescribed flux (superposition principle); and

•Anisotropic aquifer of infinite areal extent

2) Confined aquifer, partially penetrating production well, profile anisotropy:

•Infinite extent aquifer;

•One straight areal boundary with assigned prescribed head or prescribed flux; and

•Bounded (strip) aquifer with assigned prescribed head or/and prescribed flux.

3) Unconfined aquifer, partially penetrating production well, profile anisotropy:

•Infinite extent aquifer;

•One straight areal boundary with assigned prescribed head or prescribed flux; and

•Bounded (strip) aquifer with assigned prescribed head or/and prescribed flux.

4) Leaky aquifer with constant hydraulic head in an adjacent aquifer (no aquitard storage):

•Infinite extent aquifer;

•One straight areal boundary with assigned prescribed head or prescribed flux;

•Bounded (strip) aquifer with assigned prescribed head or/and prescribed flux; and

•Anisotropic aquifer of infinite areal extent

5) Leaky aquifer, partially penetrating production well, profile anisotropy;

6) Leaky aquifer with variable hydraulic head in adjacent aquifer (no aquitard storage, for drawdown in the main aquifer and for drawdown in the adjacent aquifer)

7) Leaky aquifer with constant hydraulic head in adjacent aquifer and with aquitard storage (drawdown in the main aquifer and drawdown in the adjacent aquifer);

8) Leaky aquifer with variable hydraulic head in adjacent aquifer and with aquitard storage (drawdown in the main aquifer and drawdown in the adjacent aquifer);

9) Three-layer aquifer system:

•aquifer system is over- or underlain by aquifer with constant water levels;

•aquifer system is over- and underlain by aquifer with constant water levels;

•aquifer system is over- and underlain by aquicludes;

10) Two-layer aquifer system:

•aquifer system is over- or underlain by aquifer with constant water levels;

•aquifer system is over- and underlain by aquicludes;

11) Two-layer unconfined aquifer;

12) Aquifer with areal heterogeneity;

13) Limited aquifer -pumping near river.

In solutions (2) and (3), drawdown is determined for a piezometer at a specified depth. AMWELLS applies the same solutions for depth-averaged drawdown in observation wells.