What causes the alkalinity to rise?

Alkalinity in water typically rises due to the presence of bicarbonate (HCO3-) and carbonate (CO3 2-) ions, which are often derived from the dissolution of limestone or other calcium and magnesium-containing minerals. Additionally, biological processes, such as photosynthesis by aquatic plants, can increase alkalinity by consuming carbon dioxide, which shifts the balance of carbon species in the water. Human activities, such as agricultural runoff or wastewater discharge, can also contribute to elevated alkalinity levels.