In considering the impacts of groundwater development, we make a number of basic assumptions that simplify the discussion; they are:
- All water molecules under consideration have the same composition – in other words we are not considering groundwater transport of differing quality water.
- The groundwater flow equation describes the material (mass) balance – and Darcy’s Law can be applied to obtain the direction and rate of groundwater flow at any point within the system. The dependent variable within the groundwater system being considered is hydraulic head.
- Groundwater systems exist over long periods of time prior to development. Before development they are in a kind of steady state or long-term dynamic equilibrium in which short-term and seasonal fluctuations in precipitation and recharge average out over the longer-term period.
- Conservation of the mass of water within the system is preserved.
All of these assumptions can be relaxed; needless to say, one must take care in relaxing these ideas.