A technical report has indicated that groundwater is likely to have a significant impact on surface water in the Waituna catchment.
The report has been compiled by Environment Southland groundwater scientist Karen Wilson in response to concerns over the health of the Waituna Lagoon.
The catchment has highly complex geology making it difficult to interpret the data, however Ms Wilson estimates that between 20 and 50 percent of annual stream flow is coming from groundwater discharging into the Moffat and Waituna Creeks.
This may have an influence on nitrate concentrations in the lagoon, although just how much groundwater drains directly into the lagoon is unknown.
To find out more about the interaction between groundwater and surface water in the catchment, scientists are working to address the information gaps. Several measures are already in place, including installing temporary piezometers around the edge of the lagoon so the rate and nutrient input of groundwater flowing into the lagoon can be quantified. Landowners are being asked about springs on their properties to help gain a clearer picture and automated groundwater level monitoring sites are being installed. Landowners in the catchment are also being asked to advice Environment Southland about any shallow monitoring bores which can be sampled.
More information on the Waituna Lagoon and what is happening there is available at www.es.govt.nz .