both subspecies of south asian river dolphins have been very adversely affected by human use of the river systems in the subcontinent. irrigation has lowered water levels throughout both subspecies' ranges. poisoning of the water supply from industrial and agricultural chemicals may have also contributed to population decline. perhaps the most significant issue is the building of more than 50 dams along many rivers, causing the segregation of populations and a narrowed gene pool in which the dolphins can breed. currently, three subpopulations of indus river dolphins are considered capable of long-term survival if protected.