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MAGNET allows for simulating reactive decay of a pollutant (1 -order) by checking the radio box next to
‘First Decay:’. The rate of reaction can be controlled by assigning a first order decay coefficient (units of
-1
days ) or a known half-life (days). For the former, select the radio button next to ‘Coefficient ‘ and enter a
non-zero value in the provided text box. For the latter, select ‘Half Life’ and enter a non-zero value in the
provided text box.

Figure 4-12: Biochemical sub-menu (for Zone conceptual features).

4.2.5 Sources and Sinks (Head Dependent)

Click on the ‘Sources and Sinks Head Dependent’ tab title to access the Head Dependent Flux sub-menu
(see Figure 4-13). This sub-menu is used to assign the zone as a two-way or one-way source or sink of
water, or as a “general head-dependent flux” (see more below in this subsection).

Two-way head-dependent flux. To assign the zone as a two-way source (e.g., a lake or pond), check the
radio box next to ‘Two-way’. The drop-down menu next to ‘Name’ provides different naming options for
the zone feature that will be used in displaying results, e.g., when performing water balance analyses (see
Section 6.2). The stage of the water source/sink can be assigned as:

• a constant value that does not change with time – select the radio button next to ‘Const:’ and enter
the desired value)
• a constant value that is time-varying – after selecting the radio button next to ‘Const:’, check the
radio box next to the ‘Transient’ button
• the aquifer top elevation minus some prescribed value; by default, the stage is set to the aquifer
top elevation, as indicated by the value of zero in the text box next to ‘Top E – ’ shown in Figure
4-13.

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