It’s hard to know why, but the Nansemond River is sick. Just this week, following a lingering storm that brought more than eight inches of rain to parts of Suffolk, a portion of the river near Sleepy Hole Park was closed to shellfishing because of the potential for contamination by floodwaters and sewage overflows. The closure is set to expire Oct. 14, but the Virginia Department of Health could extend it if another big storm passes through in the next week or so.

Such closures are common after major storms, but the Nansemond’s problems are more persistent than the isolated events would suggest.

In fact, the area that was closed was already set for a conditional closure by the health department prior to this week’s storm. High levels of bacteria in the river during the previous dry period had caused state officials to issue the previous conditional condemnation order.

It seems the river cannot get a break — both wet and dry weather conditions contribute to its pollution problem. The result is that oysters and clams from the Nansemond cannot be consumed, and the river’s utility as a recreational resource is curtailed, as well.

The Nansemond River Preservation Alliance, the city’s public works department and the Virginia Department of Health Division of Shellfish Sanitation are working together to try to understand the problem, but they have yet to identify a single point that is the source of the river’s pollution.

Each of those organizations and agencies has increased monitoring and water sampling along the river in recent years in an attempt to gauge the extent of the problem and identify what’s causing it. While the answer to that question remains elusive, the problem seems more apparent with every sample that’s taken.

Fixing the Nansemond could well turn out to be a generational task, but that doesn’t mean it’s impossible. Norfolk’s Lafayette River was closed to shellfishing in 1934, but oysters — nature’s little water filters — made a comeback there, and it was recently reopened for recreational uses.

It may be too much to hope the Nansemond River will soon be known again for its delectable oysters, but the hard work of the Nansemond River Preservation Alliance, in concert with city and state officials, could well provide the boost oysters need to begin to turn the tide on pollution.