With the need for sustainable, long-term water resource management in much of the world, managed aquifer recharge (MAR) is increasingly being viewed as suitable to balancing environmental benefits and economic needs.
MAR can be a successful means of providing replenishment to depleted groundwater systems. Supplementing the recharge that naturally occurs can help offset groundwater use, while maintaining ecologically dependent levels.
In New Zealand, regional water planning efforts on South Island are looking at MAR. Overuse of groundwater in this area has resulted in declining springs, rivers, and groundwater levels. This has limited the full storage potential of the underlying aquifers.
The MAR assessment process is designed to help identify the use of natural geologic features for potential groundwater storage. For this particular project, a MAR recharge trial infiltrated surface water through an existing gravel river bed. The watershed area consists of sloping plains, underlain by gravel-rich sediment, which contain groundwater fed from rainfall and from seepage from the rivers and irrigation systems that cross them.
An existing spillway structure was used to divert the recharge water from one of the major rivers that flows from a higher elevation, allowing the water to be recharged to the target aquifer via natural infiltration.
We led the development of this project, and monitored and reported on the flow of the diverted water and the levels of groundwater in wells around and downstream of the discharge point. A pre-trial risk analysis and post-trial assessment of the results were done. We took into consideration water quality and quantity and, at the same time, have maintained a strong community involvement focus.
As an ongoing project, we will seek to continue dialogue with the Ngāi Tahu peoples of the Maori culture who live in the area, and establish collaborative partnerships with the regional andlocal stakeholders who are very interested in how and where MAR might be best suited.