Consuming brackish water is unsafe for human health and is not a sustainable source of hydration. This water represents a transitional state between freshwater and seawater, carrying a salt content high enough to actively dehydrate the body. The danger lies in the high salt concentration and the severe physiological response required to process it once ingested.
What Defines Brackish Water
Brackish water is defined by its intermediate level of salinity, making it distinctly saltier than freshwater but less salty than the ocean. Fresh drinking water typically contains less than 500 parts per million (ppm) of total dissolved solids (TDS). Brackish water generally falls within the range of 1,000 ppm to 10,000 ppm of dissolved salts, compared to seawater’s average of 35,000 ppm.
This salinity profile is commonly found where two different water types meet and mix. Estuaries, where a river’s flow meets and dilutes the ocean’s tides, are the most recognizable examples. Brackish water can also be found in coastal aquifers infiltrated by seawater or in certain inland deep groundwater reservoirs. The dissolved salts include sodium chloride, calcium, magnesium, and sulfates, all contributing to the high TDS count.
The Dehydration Cycle: Why Brackish Water Harms the Body
The primary danger in consuming brackish water is the severe stress it places on the body’s osmoregulation system. This biological process maintains the correct balance of water and electrolytes across cell membranes. Drinking brackish water introduces a large influx of dissolved salt, increasing the concentration of solutes in the bloodstream and surrounding body fluids.
The kidneys are immediately tasked with filtering this excess salt load. However, the human kidney can only produce urine that is less concentrated than the brackish water ingested. To excrete the salt, the kidneys must draw water from the body’s cells and existing fluid reserves to dilute the urine.
This process results in a paradox where drinking water leads to a net loss of hydration. The volume of fresh water required to flush the high salt content is greater than the volume of brackish water consumed. Although the body attempts to compensate by increasing thirst and releasing antidiuretic hormone (ADH), the salt burden actively overrides these mechanisms.
Continued consumption accelerates this cycle, leading to rapid dehydration. The physiological strain manifests as increased urination, nausea, vomiting, and diarrhea as the body attempts to expel the excess salt. Over time, the inability of the kidneys to manage the salt concentration can lead to acute kidney injury and a potentially fatal electrolyte imbalance.
Methods for Making Brackish Water Drinkable
Brackish water can be made safe for consumption, but it requires specialized processes that remove dissolved salts. Standard methods like boiling or simple filtration only eliminate biological contaminants, such as bacteria and viruses, leaving the harmful salt and minerals behind.
The most reliable technique for removing salt is distillation, which mimics the natural water cycle. This process involves boiling the brackish water and capturing the pure steam as it condenses, leaving all dissolved solids in the original vessel. Distillation is highly effective and can be performed with simple materials in a survival situation, though the resulting yield is low.
For large-scale purification, reverse osmosis (RO) is the most widespread method for treating brackish water. The RO process forces the water through a semi-permeable membrane under high pressure. The membrane’s microscopic pores allow water molecules to pass through while blocking the larger dissolved salt ions. Treating brackish water with RO is significantly more energy-efficient and cost-effective than treating seawater due to its lower initial salt concentration.