Executive summary
Sinclair Knight Merz (SKM) was commissioned by the Ministry for the Environment in October 2004 to provide a preliminary hydrogeological assessment of groundwater quantity in the Waitaki River Catchment. The information obtained from this study, while preliminary in nature, will assist the Waitaki Catchment Water Allocation Board to understand groundwater resources and the groundwater interactions with surface water.
The specific objectives of the study were to provide assessments of:
- groundwater flow directions and quantity
- groundwater interaction with surface water bodies and its significance
- the level of confidence in the interpretations made
In general terms, the main considerations for groundwater in the Waitaki Catchment are:
- Groundwater flow generally occurs towards major surface water sinks (ie rivers, streams and lakes). However, some aquifer areas are recharged by stream flow where suitable hydraulic conditions permit (eg Irishman Creek and Tekapo River).
- There are larger groundwater storage areas located in the upper catchment (eg Tekapo and Twizel Basins), and also in the lower catchment (eg Glenavy and Lower Waitaki Plains).
- The impact on surface water from spring outflow depletions requires specific consideration when allocating groundwater in some basins that have existing surface water allocations (eg Omarama Basin, Hakataramea Valley, Maerewhenua Basin and Papakaio Formation).
- Currently, the Glenavy and Waitaki Plains areas receive a major component of recharge from the Waitaki River irrigation schemes.
Overall, a reasonable understanding of the aquifer flow regime has been established and should provide the Water Allocation Board with information appropriate for catchment-scale planning. However, it is important to note that the information contained in the report is not an appropriate basis for site-specific water allocation decisions.
