*5.2. Brownfield Developments*

There has been some discussion in the Australian context, that brownfield developments should respond more quickly due to antecedent moisture. The results here show that while this partially occurs for high values for *B*, there are no lateral impacts (i) for *B* = 0.1 or 1, or (ii) for separations of 250 m or more; and that (iii) for no separation, there are delays in recharge that outweigh the early breakthroughs. The lack of lateral impacts, especially for *B* = 0.1, 1, appears to be due to limited wetted extent outside irrigated fields. The later time delays for *B* = 10 are probably due to the inability of water to move laterally on one side. The e ffect would be similar to a larger irrigation field, with higher perched water table and relatively smaller wetted extent.

The small interaction between irrigated fields means that a complex irrigation area with new developments occurring at di fferent times could be modelled as a superposition of impacts for individual fields. This would greatly simplify the calculation of recharge under the irrigation district. Should the circumstances be such that there are interactions (high *B*, small gaps between irrigation fields, the results here indicate that there may be simple approximations, but this would require more work.
