Figure 7: Drainage sump replacing old drainage shaft at Bumbang (Photo courtesy RMCG).
The Nyah to Border Plan also reinforced the need for every new development to have adequate drainage disposal plans in place prior to approval for new development. This includes a requirement to set aside a minimum of 10%-15%11 of the land developed for future inland drainage disposal areas. All new development also requires a soil survey - the information gleaned from these surveys assists developers to avoid planting areas prone to high water tables. (Figure 8)
Figure 8: Aerial shot showing unplanted areas (Photo courtesy RMCG).
Careful selection of planted areas combined with the use of drip irrigation provided the ability to control root zone drainage from irrigation and absorb rainfall in the non-wetted zone (refer Mallee Salinity Workshop Chapter 5: The Irrigation Footprint Sunraysia). This decreased the amount of pressure on perched water tables developing and there are large areas now without artificial subsurface drainage that rely on natural drainage to discharge zones on non-planted areas on the property. The sustainability of this will be site specific, because rainfall cannot be easily managed and some form of artificial subsurface drainage is likely to be needed after extreme rainstorms, especially summer storms when crops are most sensitive to water logging. It is worth noting that in wet years even dry land produces perched water tables. It is where those perched water tables form that is the issue.
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10% if more than half of the catchment area is drip otherwise a minimum of 15% was required. 14