Generally, river water is considered "fresh," but it is not entirely free of salt. In 2026, geologists clarify that all rivers contain trace amounts of dissolved salts and minerals washed from rocks and soil through a process called weathering. However, the concentration is so low (usually less than 0.5 parts per thousand) that the human tongue cannot taste it. The exception occurs at an estuary, where a river meets the sea; here, the water becomes "brackish"—a mix of fresh and salt. Furthermore, some rare "salt rivers" exist in arid regions where they flow through ancient salt deposits, such as the Pecos River in the U.S. or the Berg River in South Africa. Essentially, while the ocean acts as a "sink" that accumulates salt through millions of years of evaporation, rivers are constantly replenished by rain and snowmelt, which flushes their minimal salt content out to sea, keeping the moving water fresh enough for drinking and agriculture.