In the event of a sodium hydroxide leak into water, appropriate measures should be taken based on the estimated amount of leakage and the characteristics of the water body. Depending on the water body's environment and the pH level, determine whether to add acid for neutralization and, if so, how much. Also, determine how much water should be added for dilution.
Analytical methods
The concentration of sodium hydroxide is typically determined using an acid-base neutralization titration method, with methyl orange as the indicator. The endpoint is reached when the solution changes from yellow to orange upon titration with a standard hydrochloric acid solution. 
Neutralization of sulfate in water bodies.
Concentrated sulfuric acid should be diluted before being added. The minimum amount of sulfuric acid required to neutralize sodium hydroxide can be calculated using the formula y = 125.07x, where y represents the mass of concentrated sulfuric acid (98% concentration) to be added, and x represents the mass of sodium hydroxide leakage. Specifically, x = ωm, where ω is the mass fraction of the leaked sodium hydroxide, and m is the mass of the leaked sodium hydroxide. 
Hydrochloric acid contamination in water bodies.
Concentrated hydrochloric acid should be diluted before being added. The minimum amount of hydrochloric acid required to neutralize sodium hydroxide can be calculated using the formula y = 303.77x, where y represents the mass of concentrated hydrochloric acid (30% concentration) to be added, and x represents the actual mass of sodium hydroxide leaked. In this formula, x = ωm, where ω is the mass fraction of the leaked sodium hydroxide, and m is the mass of the leaked sodium hydroxide.