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# 2:4.3 Deep Aquifer

The water balance for the deep aquifer is:

$$aq\_{dp,i}=aq\_{dp,i-1}+w\_{deep}-Q\_{gw}-w\_{pump,dp}$$                                                                                               2:4.3.1

where $$aq\_{dp,i}$$ is the amount of water stored in the deep aquifer on day $$i$$ (mm H$$*2$$O), $$aq*{dp,i-1}$$ is the amount of water stored in the deep aquifer on day $$i-1$$(mm H$$*2$$O), $$w*{deep}$$ is the amount of water percolating from the shallow aquifer into the deep aquifer on day $$i$$ (mm H$$*2$$O), $$Q*{gw}$$ is the groundwater flow, or base flow, into the main channel on day $$i$$ (mm H$$*2$$O) and $$w*{pump,dp}$$ is the amount of water removed from the deep aquifer by pumping on day $$i$$ (mm H$$\_2$$O). The amount of water percolating into the deep aquifer is calculated with the equations reviewed in section 2:4.2.4. If the deep aquifer is specified as the source of irrigation water or water removed for use outside the watershed, the model will allow an amount of water up to the total volume of the deep aquifer to be removed on any given day.

Water entering the deep aquifer is not considered in future water budget calculations and can be considered to be lost from the system.


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