Brackish water is best described as water with what salinity range?

• A. Freshwater with low salinity
• B. Water with high salinity
• C. Water with variable salinity between freshwater and marine
• D. Pure seawater

Answer: (C)

Salinity levels determine whether water is freshwater, brackish, or seawater. Brackish water arises from a mix of fresh and seawater, so its salinity sits between freshwater and marine water and can change with tides, rainfall, or evaporation. In practice, brackish water is often in the range roughly from about 0.5 to 30 practical salinity units (psu/ppt), unlike freshwater (very low salinity) or seawater (high salinity, near 35 ppt). Therefore it is best described as water with variable salinity between freshwater and marine. The other descriptions imply consistently freshwater, consistently high salinity, or pure seawater, which do not match the mixed, fluctuating nature of brackish water.