干旱区生态环境知识资源中心

Groundwater pumping schemes in semi-arid south-eastern Australia intercept saline groundwater flowing into the River Murray and divert it to natural or man-made basins where super-concentrated brines (> 350g/L) form. These brines infiltrate through the sediments of the basins, potentially mixing with the underlying groundwater (similar to 50g/L). This study uses environmental tracers to provide field evidence to support the hypothesis of mixing of such brines with regional groundwater. A system of natural salt lakes is studied, as a long time-scale analogue to man-made evaporation ponds. Significant downward movement, and mixing with regional groundwater is observed in the geochemical signatures of the brines and an evaporation-leakage model suggests large amounts of groundwater through-flow for the salt lakes. Regional groundwater compositions at depths > 40m also indicate mixing with the brines. Geochemical mass transfer processes inferred from PHRQPITZ mixing model calculations suggest a substantial influence of re-mixing on brine compositions.