2.1.5.1.1 Stream–aquifer interactions

As stream discharge volume is inherently related to stream water quality, relating stream discharge to EC can potentially provide an insight into baseflow contribution to streams and help with the identification of gaining or losing reaches.

There are two observed datasets on river and stream water quality in the Clarence-Moreton bioregion. These are datasets from the NSW Office of Water (Dataset 1) and the Queensland Department of Natural Resources and Mines (Dataset 2).

The NSW Office of Water dataset contains surface water quality data provided by the NSW Office of Water from 122 sampling sites within the Richmond and Clarence river basins (Table 28). Samples were collected at irregular intervals for a wide range of parameters including major ions, selected trace elements, turbidity and field parameters (e.g. EC and dissolved oxygen). EC is typically a good indicator of groundwater discharge to streams, as groundwater is often more saline than surface water due to processes such as evapotranspiration, which results in an increase in groundwater salinity during groundwater recharge. The NSW Office of Water dataset contains more than 7000 sampling records with EC readings for the Clarence-Moreton bioregion. The monitoring duration is highly variable with some sites having records of up to 40 years or more. The spatial distribution of sampling points is shown in Figure 63 and Figure 64.

The Queensland Department of Natural Resources and Mines (DNRM) dataset contains 75 sampling sites in Queensland for the Clarence-Moreton bioregion (Table 28) where water quality field parameters such as EC and dissolved oxygen were recorded during irregular sampling campaigns and where water chemistry was analysed in the laboratory. The total number of EC recordings (corresponding to individual sampling events) in this surface water dataset is more than 2800, but the number of measurements and their periods vary significantly among different sites. For example, a gauging station at the Logan River in Yarrahappini has 206 records collected from 1970 to 2013, whereas only few measurements were recorded at some other sites. The distribution of river and stream water quality sampling sites within the Clarence-Moreton bioregion in Queensland is shown in Figure 63 and Figure 64.

Streamflow data for the bioregion are readily available from DNRM (2014) and NSW Government (2014), and an overview on the active stream water monitoring sites and basic statistics are in companion product 1.1 for the Clarence-Moreton bioregion (Rassam et al., 2014). A comprehensive discussion of this relationship is outside the scope of this product and will be covered in more detail in companion products 2.3 (Raiber et al., 2016) and 2.6.1 (Gilfedder et al., 2016) for the Clarence-Moreton bioregion.

Table 28 Summary of stream water quality and chemistry sampling sites in the Clarence-Moreton bioregion

EC=electrical conductivity

^aAn unusually high electrical conductivity (38,000 µS/cm) was recorded at Teviot Brook in the Logan-Albert river basin at the ‘Overflow’ in 1974. However, as both previous and the following measurements as well as all other 97 measurements recorded at this site show maximum electrical conductivities of 5,200 µS/cm, it is assumed that this high reading was incorrect or that it is a spelling mistake.

^bThe very high electrical conductivity measurements in the Richmond river basin and Clarence river basin are limited to coastal areas (Figure 63 and Figure 64), and are likely to be linked to tidal influence or estuarine mixing.

Data: NSW Office of Water (Dataset 1), Queensland Department of Natural Resources and Mines (Dataset 2), Bioregional Assessment Programme (Dataset 3)