Tri-County Lakes Administrative Commission
(Bobby Whitescarver)

The degradation of insects has vast consequences for the water’

BY:  – DECEMBER 4, 2023 12:02 AM

The State Water Control Board last week approved new limits on how much sediment, or loose dirt, can enter into waterways in the counties of Rockbridge, Augusta, Bedford, Franklin and Pittsylvania because of the impact such pollution has on aquatic life.

The new limits, called waste load allocations, are being imposed by the Virginia Department of Environmental Quality, which found that aquatic or semi-aquatic insects like mayflies, stoneflies and caddisflies are less prevalent on waterways in those counties than in waters elsewhere. 

Scientists are concerned about the low number of insects because of the ripple effect that decreases in those species can have on other aquatic life, like fish, who feed on them. Mayflies, for example, “not only move nutrients within aquatic ecosystems, but they also move nutrients between them,” found one 2019 study published in Insects journal.

“The degradation of insects has vast consequences for the water,” said Joe Wood, a scientist with the Chesapeake Bay Foundation.

The agency found that a roughly 20-mile total stretch of segments of Moores and Mill creeks in Rockbridge and Augusta counties, as well as segments of Beaverdam Creek, Fryingpan Creek, Pigg River and Poplar Branch in Bedford, Franklin and Pittsylvania counties, “do not support a healthy and diverse community of aquatic life.” 

“Without this valuable habitat, the diversity of aquatic life in a stream may be severely limited,” DEQ concluded.  

The waterways were previously identified as impaired in Virginia’s 2020 Water Quality Assessment Integrated Report, which found they weren’t meeting standards for healthy populations of benthic animals, or those that dwell at the bottom of waterways. 

In 2021, a DEQ analysis found that the primary stressor to insects in the impaired waterways was sediment. While sediment can be washed into waterways from many sources, including construction sites, the agency’s research points to farming as a main culprit. Fields that don’t have a cover crop with deep roots to hold dirt in place are more susceptible to releasing sediment than acreage that is forested or blanketed with no-till plantings that minimize soil disturbance. 

According to DEQ, the largest amounts of sediment flowing into the Moores and Mill creek watersheds — about 55% and 54%, respectively — come from hay and pastureland, with the rest coming from forested, urban/suburban and other sources. Beaverdam Creek, Fryingpan Creek, Pigg River and Poplar Branch also traced the majority of their sediment to hay and pastureland, with loads ranging between 36% and 61%.

If sediment loads flowing into these waterways can be reduced, “healthy aquatic life is expected to be restored in these streams,” DEQ found. 

DEQ will now craft a plan to meet the new limits, which will require approval by the U.S. Environmental Protection Agency. While the agency will be calling for reductions across multiple sectors, the agricultural decreases it’s seeking will be significant, ranging from 23% for some watersheds to 76% for others. 

Some of the strategies DEQ will likely be including in its plan are planting riparian buffers — bands of trees along streams whose roots filter out sediment — fencing cattle out of streams, encouraging farmers to adopt conservation tillage practices and restoring eroded stream banks. Expanding street sweeping programs in urban areas can help too, DEQ states.

The department says it won’t require local pollution sources that already have a stormwater permit, such as Devils Backbone Brewing Company in the Mill Creek watershed, to change their operations to meet the new load reductions.

Virginia operates cost-share programs to help farmers adopt such practices, generally called best management practices, or BMPs. The General Assembly put $116 million toward the programs last year, and $286 million was allocated this year as a result of a state revenue surplus. 

Legislation this past session extended the deadline for farmers to voluntarily install BMPs before state officials require them as part of broader goals to clean up the Chesapeake Bay. A workgroup is now gathering data to understand the current rates of BMP adoption in Virginia.

Only some of the waterways that will be subject to DEQ’s new sediment limits fall within the Chesapeake Bay watershed. Others, such as the waterways in Bedford, Franklin and Pittsylvania counties, are part of the Roanoke River Basin that flows down into North Carolina. Officials’ efforts to clean up those bodies are aimed at addressing water quality issues more locally, explained Wood. 

“It’s an early step,” Wood said. “We need to do something.”