Researcher: Timing key in river water withdrawal

Timing is very important when it comes to withdrawing water from the Shenandoah River, according to Jennifer Krstolic, a geographer with the U.S. Geological Survey.

Krstolic was the lead researcher in a study that looked at projected water use and its possible impact to habitats and fish species within the South Fork, North Fork and Main stems of the river.

On Tuesday night, Krstolic presented the results of the study and its implications to the Warren County Board of Supervisors.

Krstolic said the study looked at a “worst-case scenario” for the “most water withdrawal” that the area is projected to see between now and 2040.

For this research, Krstolic said she looked at projected increases in population and water use from the Virginia Department of Environmental Quality as well as the Northern Shenandoah Valley Regional Commission.

Based on this data, Krstolic said, “We’re looking at a 46-56 percent increase in water withdrawal and water use in the Shenandoah Valley” and a population spike to 649,000 within the Shenandoah watershed.

With this projected consumption, Krstolic explained that most area localities such as Warren County could be at their “permitted water withdrawal limit” — or the most water they can use — by 2040.

Researchers then applied similar withdrawal increases of 10, 20 and 50 percent to simulated models for normal flow years and low-flow drought years to gauge “what effect they have on habitat during drought years and during normal years.”

More specifically, the study looked at the data’s possible effects on habitat availability for local fish species such as smallmouth bass, sunfish and river chub.

“The game fish seem to be more at-risk than some of the native species on the Shenandoah River,” Krstolic noted, citing the smallmouth bass as an example.

In the models for drought years, the habitat strain for adult and sub-adult smallmouth bass was greater than it was normal flow years.

On the same token, Krstolic added that, during normal-flow seasons, habitat availability “did not seem to be affected” by increased water use.

Researchers also found that, even in simulated drought conditions, the habitats for other species, such as the redbreast sunfish and river chub, were “not very stressed” by the increases in withdrawal.

“As long as habitat and stream flow are pretty much in the normal range, increase in water withdrawal during that time doesn’t really result in a great loss in habitat,” Krstolic said.

“If the river flows are already normal, if the habitat is already normal,” Krstolic said any increased water withdrawal “doesn’t equate to a great loss in habitat.”

The big takeaway from all of this, Krstolic noted, is that localities can use data like this for the timing of their water withdrawal.

“Good planning and good management could include just paying attention to the timing of water withdrawals,” Krstolic added.

While this study was looking at water availability, Krstolic also indicated that she would like to test flow reduction on fish populations moving forward.

She said other studies found that reduced water flow during the month of August has correlated with decreased fish abundance.

“I’d really like to be doing more work to see if that … is a true statement for the Shenandoah River,” Krstolic added.

Moving forward, Krstolic and other researchers have set up shop along the river to test different river contaminants on the health of fish.

Krstolic will be working on the project with USGS Geochemist Larry Barber and Alan Vajda, a professor at the University of Colorado in Denver and adjunct USGS researcher.

She said the data collection for this next project is expected to take 21 days.

Contact staff writer Kevin Green at 540-465-5137 ext. 155, or kgreen@nvdaily.com