Effects of Intraborehole Flows
Two new research papers published in 2019, by an Australian research group led by David Poulsen, build on earlier work by McMillan et al (2014) and others in improving our understanding of the depth origin of water samples collected from long-screened and open boreholes.
When sampling groundwater wells and open boreholes, many practitioners think no further than using sampling guidance, which is generally only suitable for use in short-screened monitoring wells (i.e., three times well volumes, low flow and passive/no purge sampling methodologies). There are dangers in doing this, which I have explored in earlier blogs (see links below) and are a theme constantly evolving through my training courses and workshops.
Given the vast legacy of long-screened wells and open boreholes (practically, think of anything more than three to six metres in length, depending on which guidance you follow), we cannot ignore the use of long-screened wells for characterizing the water quality of groundwater. However, when we use these boreholes…