Palmerston North City Council is in the process of substantially upgrading the treated water that is currently discharged to the Manawatū River. One option being considered as part of the upgrade is to shift the discharge location further downstream.

River Lake undertook a series of mixing studies to assess the mixing characteristics of the Manawatū River at multiple locations downstream of Palmerston North. This was done by: 1) releasing a bolus of Rhodamine WT (RWT) dye in to the river and using drone imagery to map its dispersion across the river as it moves downstream; 2) slowly releasing RWT dye into the river to achieve a steady state and using a fluorometer to measure its concentration at along cross-sections downstream.