Rain, Streamflow, and Nitrogen Loading

If you read this blog regularly, you probably see me write about precipitation a lot! (You can check out some old posts here!)

And for good reason! Precipitation is something everyone living in the Chesapeake Bay near-shore region pays attention too!

For example, when I wake up in the morning, this first thing I do is look out the window: is it raining? Is it sunny? Should I wear a raincoat?

Rainy or Sunny?…..these are two weather types that your mind immediately recognizes. Who has ever felt the need to go outside just because it was sunny, even if it was cold? Or stay inside with a book because it’s drizzling, even if the temperature is perfect?

Precipitation has the ability to affect other things besides your mood and what you wear. In today’s post, we will show you that precipitation also affects streamflow into Chesapeake Bay as well as nitrogen loading.

And in Chesapeake Bay, the amount of precipitation we get each year is increasing (Figure 1)!


Figure 1: Total Annual Precipitation has increased over the past century in the near-shore Chesapeake Bay area.

Figure 2:

Figure 2: Streamflow into Chesapeake Bay versus the Total Annual Precipitation.

It makes perfect sense that river discharge is affected by precipitation! Have you ever noticed a creek seem to trickle during a summertime dry spell or rage after a huge thunderstorm? Precipitation as it falls on land tends to flow downhill (gravity!) and some can end up in a flowing river.

Figure 2 shows that I am telling the truth! Annual average discharge is significantly correlated to the total annual precipitation in the Susquehanna, Potomac, and James River (three of the largest tributaries in Chesapeake Bay). So years with a lot of annual precipitation likely are also years with more streamflow!

Again, this makes sense, but it is still important to demonstrate this connection! There is still a lot of other factors which affect streamflow (evaporation, for example) and precipitation (taken up by plants, for example); this is why it is not a perfect fit.

Figure 3:

Figure 3: Relationship between total annual precipitation with streamflow and nitrogen load in Mattaponi River.

Now let’s take a look at how total annual precipitation affects one of our study areas! The Mattaponi River is a tributary to the York River, which is where the Chesapeake Bay National Estuarine Research Reserves in Virginia are located.

Figure 3 shows that Mattaponi River is also significantly correlated to precipitation. But is it also significantly correlated with the mean total annual nitrogen load. In other words, years with a lot of precipitation bring more streamflow which brings more nitrogen!

In future posts and products, we will take a look at how precipitation increases may affect nitrogen loading at the CBNERRs, and other sites, throughout Chesapeake Bay!

Kari Pohl

About Kari Pohl

I am a post-doctoral researcher at NOAA and the University of Maryland (Center for Environmental Science at Horn Point Laboratory). My work investigates how climate variability and extremes affect the diverse ecosystems in Chesapeake Bay. I received a Ph.D. in oceanography from the University of Rhode Island (2014) and received a B.S. in Environmental Science and a B.A. in Chemistry from Roger Williams University (2009). When I am not busy being a scientist, my hobbies include running, watching (and often yelling at) the Boston Bruins, and taking photos of my cat.
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