Question

how does the flow of acid rain water into a river make the survival of aquatic life in the river difficult ​

Answer 1

Acid rain water, if mixed with river water, lowers its pH below 5.6, i.e., makes river water acidic. But the living body works normally within a pH range of 7-7.8. That's why flow of acid rain water to river makes the survival of aquatic life in the river difficult.