A Discussion of Watershed-Scale Pollutant Transport and Management

“I’m really concerned about the Neuse River Estuary,” my daughter Sarah announced one evening. “At school today, Norah, Ari, Sienna, and I talked about water pollution and decided that we should do what we can to save the Neuse.”

“Good for you, Sarah,” I said approvingly. “The only difficulty is that we live in Durham and the water quality problems are near the coast, over 100 miles away.”

“Wait a second, Dad. Doesn’t water run downhill?”

“Sure,” I responded, “so what?”

“Well, you once told me that we should be careful with fertilizer and stuff because the pollution from Durham runs into Falls Lake. So, the water that flows out of Falls Lake goes into the Neuse River which, like, carries it to the coast causing algae and dead fish.”

“Okay, it’s basically true that a portion of Durham’s treated wastewater and stormwater runoff ends up in Falls Reservoir, so we do have an impact on Falls Lake.” I agreed. “But, it’s not clear that anything you do in Durham matters very much if you’re concerned about the lower Neuse River and Estuary.”

“Well, does it or doesn’t it?” Sarah demanded. “You’re a water resources professor at Duke University, you should know. Does it matter how much pollution comes from Durham? And what about the people in Raleigh - don’t they pollute the lower Neuse either? What’s the answer?”

“Its not that simple,” I pointed out. “We’re not real certain about the degree of impact from various sources and locations in the Neuse watershed.”

“You’re kidding! You mean to tell me that a Neuse River management plan is being implemented and you don’t really know that it’s going to work?”

“Well, yes and no. We expect water quality to be better in certain regions of the lower Neuse, but the change may not completely satisfy the public’s desire for improvements. It seems likely that refinements to the plan will be necessary.”

Sarah’s dissatisfaction with this response was evident on her face. “How can you approve a plan when you don’t know what it will do?” she asked.

“First of all, I’m a scientist. I don’t approve plans, only elected officials have that right. Second, you’ve got to realize that we always have a plan in operation. We have a plan for the Neuse right now; it just isn’t as stringent as some people might prefer.”

“Okay, that makes sense, but I still want to know about people in Durham and Raleigh - does their pollution affect the lower Neuse?”

“Sarah, that’s a good question. For the Neuse River watershed as well as other large watersheds in the United States, one of the more pressing research priorities is the need to understand pollutant transport and transformation on a watershed scale so that accurate predictions can be made to guide management. Many water pollutants, such as nutrients, synthetic organics, and pathogenic microorganisms may enter a waterbody ten miles to over one hundred miles upstream of a point of concern for possible adverse impact. While it is reasonable to assume that there is some attenuation of these pollutants with distance, the degree of loss or change is currently quite uncertain. The interesting and challenging research task is to develop scientific understanding leading to good predictive models, which are essential for effective and equitable basinwide water quality management.”

“Dad, I’m not one of your students.”  Sarah groaned. “Stop lecturing and tell me what we can do in Durham!”

“Alright, Sarah, it’s reasonable to assume that Durham has some impact on the lower Neuse, even if we can’t quantify it too precisely right now. So, you and your friends might consider a few things that can make a difference, if not in the Neuse, certainly in our nearby Durham streams and in Falls Reservoir.

“One of the most important water pollution factors in residential and urban areas is the stormwater drainage network. Our house is not located near any streams or waterbodies, which at first thought, suggests that we have nothing to be concerned about. However, the storm drains located in the street in front of our house and throughout Durham provide an efficient pathway for fertilizers, lawn chemicals, and general urban debris to be washed from the streets and parking lots directly into our streams.

“This means that in areas with storm drains, location can be a deceiving indicator of impact. Potentially polluting land uses that are located quite remote from a stream or lake may have an impact on surface water quality, because a storm drain efficiently channels the stormwater runoff into the waterbody. So, Sarah, you and your friends can have a positive impact on water quality by urging your classmates and their families to keep polluting substances from washing into storm drains.”

“Thanks, Dad.” Sarah responded, as she dashed off to answer yet another phone call.