Category: Research Blog

Rivers…Streams…and Sediment

Rivers, Streams and Sediment

Written by Carson Pruitt, Intern with Phinizy Center for Water Sciences

Rivers and streams do much more than just transport water downhill. They carry anything in their paths along with the water, many times all the way to the ocean. One of the most important substances that streams carry is sediment. In fact, excess sediment has been identified as the number one pollutant of waters in the United States. There are two main ways that water transports sediment—by rolling sediment along the bottom, called bed load, and by sediment that is suspended in the water column, called suspended load. We also refer to the clarity of water as turbidity. Generally, when you look at a stream that is ‘muddy’ during or following a rain event, we say that it is very ‘turbid’.

As part of The Phinizy Center’s research on rivers and streams in the area, we measure the amount of sediment that travels downstream. Above is a graph showing actual water levels of Rock Creek over time during a particular storm. You can see the water level (black line) go up as the rain (blue line) falls with the red dots highlighting times when we took water samples.

The picture below shows the water samples that were taken during the storm that correspond to the labeled red marks on the graph. The sample labeled ‘Bl.’ is drinking water that is used as a reference. It is easy to see the progression of turbidity in the samples over time; sample 3 is clearly the most turbid. If you look at sample 3 on the graph, you’ll notice that it is the sample where the water level is the highest. This makes sense because, as the water rises during a storm, the velocity and shear stress of the water increases, enabling it to carry more sediment. As the water level comes back down after sample 3, the turbidity also decreases.

South Carolina Water Conference

 A Strong Presence At Water Conference

By Jason Moak, Research Manager

Phinizy Center scientists contributed four poster presentations and six oral presentations at the South Carolina Water Resources Conference in Columbia this week.  This is a biennial conference organized in 2008 by Clemson University for the purpose of sharing important and useful information regarding water research, policy, and management.  This year’s conference had over 300 attendees that included students and professors from multiple universities, state and federal resource agency personnel, consulting firms, utilities, and other non-governmental organizations.

Oscar Flite led off for Phinizy Center Wednesday morning with a presentation on the results our initial river metabolism study which involved continuous dissolved carbon dioxide measurements while floating for five days and 150 down the Savannah River.  That afternoon, Carson Pruitt presented the results of our ongoing effort to describe and predict how rainfall affects water flow in Augusta’s urban streams.  That evening, Oscar, Damon Mullis, Katie Johnson, and Jason Moak presented their posters detailing some preliminary results from our study of Savannah River oxbow lake ecology and hydrology which we recently completed.

Thursday afternoon was a busy one for Phinizy scientiests as we gave four oral presentations.  In the Stormwater session, Katie provided an in-depth look at the methods we are using to assess the geomorphology of streams in Augusta.  Damon presented results illustrating how water temperature from Thurmond Dam effects the communities of aquatic insects downstream in the Savannah River.  Kelsey Laymon explained the experiment we conducted in which we compared differences between aquatic insects collected using three different types of passive sampling devices.  Lastly, Shawn Rosenquist, who is now with Savannah State University, provided an interesting look at the history of nutrient levels in the Savannah River and what implications they may have for future planning.

Phinizy Center’s presence at this conference was impressive and important.  It allowed us to share our research with other scientists and resource managers and further build our reputation for conducting useful basic and applied water science.  It also allowed us to strengthen and build new relationships with other regional scientists and learn about their work .


The Healing Power of Forests

The Healing Power of Forests        img_4674

By: Dr. Oscar Flite

Dr. Dick Dunlop, a retired internist turned plein air painter, flagged me down on the way into the park the other day.  He was excited to share an article that he recently read in Time Magazine, called The Healing Power of Nature (July 25, 2016 issue).  Dr. Dunlap and I have talked a lot about science and about nature over the past few years but this was the first time we were able to really connect the two topics.  While there have been many studies showing the healing power of nature, such as the study in the 1980s that showed surgery patients recovered quicker if given a room with a window view of nature as opposed to a window view of a brick wall (Ulrich, 1984), or another that showed mood and self esteem were more improved by weekly walks through the countryside and urban parks versus weekly trips to a social club swimming pool (Barton et al., 2012), this article pointed to a potential underlying reason why.

It is well known that trees inhale carbon dioxide and exhale oxygen.  Oxygen that trees exhale originates from water molecules that the tree pulls from the ground.  Carbon dioxide that trees inhale from the air is converted to organic molecules like sugars and other carbon-based chemicals.  Some of those carbon-based molecules are gases, like the carbon dioxide that they resulted from originally, are then exhaled by the tree; those carbon-based gases are called volatile organic compounds (VOCs).

A group of those tree-derived volatile organic compounds, generally known as phytoncides, have been shown to have anti-bacterial, anti-fungal, and anti-viral properties and help trees protect themselves against bacterial, fungal, and viral threats ( Li, 2008).  In essence, a tree protects itself by making its own “insect repellent” which it “sprays” throughout the forest.  As we walk through the forest, we inhale those chemicals too.  Over the past two decades, there has been an increase in scientific evidence that phytoncides have considerable health benefits to humans as well.

Phytoncides have been shown to decrease the amount of stress hormones in humans giving people an overall calming effect after walking through a forest.  Furthermore, protective cells within the human body, that are important for our own defense against viruses, bacteria and tumor cells, have been shown to increase in numbers and activity within the body as a result of phytoncides (Li, 2009).  It was found that the effects on protective cells lasted up to 30 days after a walk through the forest.  When compared to an equivalent walk through the city, they found there was no response on the numbers or activity of the same protective cells, in fact, the city air was found to be completely devoid of phytoncides!!

As a result of over nearly 4 decades of research showing the positive health  effects of walking through the woods, Japanese researchers have coined the term “forest bathing”, or shinrin-yoku, for the therapeutic practice of spending time in the woods.  What is really going on is that the trees are breathing life back into us, literally.

Given the positive benefits of phytoncides on human health and that a stroll through the woods at Phinizy Swamp Nature Park is free, our new saying at the park is, “A stroll a day will keep the doctor away”.  Please take the challenge of trying it out for yourself for the next month; let us know if you feel better as a result.

Oxbow Lake Study – Bluegill Abundance

131d30de-0151-4db9-92e0-350e0846395a-thumbnailOxbow Lake Study – Bluegill Abundance  

By Jason Moak, Phinizy Research Manager

Our study of four oxbow lakes along the Savannah River has ended and we are in the process of analyzing the results and drafting a study report.  During this investigation, we collected a total of 3,287 fish representing 15 families, 25 genera, and 38 species.  Numerically, bluegill were the most abundant species, representing 39% of all fish captured.  As such, it is worth taking a closer look at this common species.

The scientific (genus and species) name for bluegill is Lepomis macrochirus (Greek, lepis = scaled, pomis = gill cover (operculum); macrochirus = large hand).  Bluegill belong to the Centrarchidae fish family, native to the freshwaters of North America and commonly referred to as “sunfishes,” which include other common species such as largemouth bass and crappie.  The genus Lepomis includes 13 individual species, most of which are commonly referred to as “bream” (pronounced brim).

Bluegill are characterized by a dark-colored (blue or black) opercular (ear) flap, and have a dark blotch at the rear base of their dorsal fin.  They can have rows of dark vertical bars along their body, and breeding males often have brightly-colored orange “throats.”

Bluegill are widely distributed in north American freshwaters, especially in lentic (slow-moving water) environments such as lakes and ponds.  They are usually found in our near cover, such as aquatic vegetation, snags, docks, etc. Bluegill feed on a variety of invertebrates, incluing zooplankton, mollusks, terrestrial and aquatic insects, worms, and even small fish.

Bluegill spawn during the spring and summer, and individual fish may spawn several times during these warmer months.  Males construct nests consisting of shallow circular depressions excavated in shallow margins.  Males guard the nest until fertilized eggs hatch (2-3 days) and larvae are able to swim.

Olympic Swimming Pools

Olympic Swimming Pools

By Jason Moak, Research Manager

Photo Credit: Flicker / Atos

Photo Credit: Flicker / Atos

Many of us have marveled at the swimming dominance of Team USA’s Katie Ledecky and Michael Phelps during the 2016 Olympics in Rio this Summer. They’re combined nine gold and two silver medals between them is a monumental feat. While watching, though, I realized that I didn’t know that much about the pools that they compete in.

It turns out that Olympic swimming pools have some pretty specific dimensions. They are 50 meters long, 25 meters wide, and 2 meters deep. In terms of volume, when full, these pools hold 2.5 million liters of water or about 660,000 gallons. If you used a normal garden hose to fill one of these pools, it would take roughly 19 days to get it full.

Since we do a lot of research on rivers and their flow rates, I got curious about how the amount of water flowing down the Savannah River compares. At the time I am writing this, the current flow rate in the Savannah River is 4,130 cubic feet per second, which equals roughly 31,000 gallons per second. That’s enough water to fill an Olympic swimming pool in just 21 seconds! In fact, at this flow rate, the Savannah River could fill 172 of these pools in just one day! That many pools would occupy the same surface area as 40 football fields and, when put end to end, would span a distance of over five miles.

Diatom Assemblages in Four Oxbows

Diatom Assemblages in Oxbows: What Diatom Diversity is Like at our Four Savannah River Study Sites and What these Baseline Data Tell Us

By Katherine Johnson, Research Scientist

Ecology & Systematics of Algae Iowa Lakeside Laboratory Summer Class 2016 From left to right: Annie Drahos, Merry Zohn, Derek Struder, Dr. Kalina Manoylov, Maggie Blackledge, Katie Johnson, Shelly Wu, and Alyssa Thomson

Ecology & Systematics of Algae Iowa Lakeside Laboratory Summer Class 2016
From left to right: Annie Drahos, Merry Zohn, Derek Struder, Dr. Kalina Manoylov, Maggie Blackledge, Katie Johnson, Shelly Wu, and Alyssa Thomson

This summer during algae systematics training at the Lakeside Laboratory, we were able to analyze preliminary data from our pilot study on diatom assemblages in four oxbows (Whirligig, Conyers Lake, Possum Eddy, Miller Lake) along the Savannah River. In collaboration with and under the advisement of Dr. Kalina Manoylov from Georgia College & State University, Alyssa Thomson (Manoylov’s research assistant) and I were able to count and identify up to 200 diatom valves on permanent slides for each of the oxbows. Analyses of these baseline data conducted on one of the Phinizy Center’s sampling events last Fall revealed some interesting findings that will help shape the design of the Center’s future monitoring. Contrary to previous hypotheses, diatom diversity was not found to be the most similar among oxbows with similar regimes, or in other words, oxbows that were connected or disconnected from the Savannah River*. This may be due to the methodology of using only diatometers to sample sites as they would inherently select for those species, which could attach themselves to substrates. After looking at the histograms however, we see that sites vary in species that specialize in distinct habitats (e.g., planktic vs. benthic). For example, Aulacoseira is a genus of centric diatoms found in plankton, whereas, Diadesmis is a genus of biraphid aerophilic diatoms usually found on mosses. Although these data were taken from only one sampling event and only 200 valves were counted, results have yielded insights to changes in future methodologies to get a more representative idea of diatom communities in each oxbow. Mainly, we will include mud samples as well as assess colonization times of diatometers to monitor succession in future studies. Depth measurements should also be included in statistical models. Below are the histograms of the species and abundances found at each site.

Slide 1

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Slide 3

Slide 4

* Standard EPA protocol calls for counts of 600 valves ( Because this study was first piloted with the objective of acquiring baseline data, reporting of statistics is not included here but will be for future studies.

Benefits of an Increasing Beaver Population

Benefits of an Increasing Beaver Population

By: Damon Mullis, Research Scientist


Photo by Jennifer Holcomb

Freshwater ecosystems are under constant pressure from a growing global human population and an ever-increasing demand for water resources. Because of these factors decision makers, stakeholders, and resource managers have resorted to techniques and strategies that have altered natural systems to better suit the needs and demands of a growing society. Such alterations include construction of dams, channelization of rivers and streams, and transformation of wetlands to dry land. These changes can eliminate the ecological services that freshwater ecosystems provide. In doing so, not only have we changed the potential ecological benefits that we receive from these systems, but we often decrease biodiversity by eliminating organisms that depend on these systems for habitat and resources. While some organisms have been inadvertently lost due to habitat losses, pollution, or other anthropogenic causes, others are purposely removed because they are considered to be a nuisance. One example of such an animal is the North American beaver. Beaver were common throughout North America before European contact, but by 1900, exploitation for the fur trade brought them to the brink of extinction. Over the past century beaver populations have rebounded, and beavers now inhabit most of their former range. This increase in beaver range and population size has raised interest as to their influence on aquatic ecosystems.

Beavers are considered ecosystem engineers because they convert free flowing streams into areas of standing water. Their activities also increase habitat heterogeneity and thus increase biodiversity through the creation of wetlands and the increased connectivity with adjacent floodplain habitats. This increase in riparian area allows for the colonization of new aquatic habitats by plants, insects, birds, and mammals, resulting in increased biological diversity.

Beaver dams also affect stream flow and hydrologic regimes, which lead to changes in nutrient cycling, organic matter retention and downstream export of particulates. Streams of the southeast are generally heterotrophic and dissolved organic carbon generated as leachates from allochthonous inputs of detritus represents an important energy source for aquatic communities.  These inputs of organic material must be retained in a stream and processed into fine particulates and dissolved forms to contribute to the local food web.  In addition, due to the low gradient of local streams and rivers and high retentive capacity of fine mineral substrates, woody debris (snags) can be an important coarse substrate providing stable habitat. Other effects of beaver impoundments include modification of bank erosion and altered stormwater water runoff and flooding patterns. A result of modern urban development and agricultural schemes is the transformation of perennial flow regimes to “flashy” ephemeral flow that can scourer or flush aquatic organism. Beaver activity can return a measure of stability to stream flow. It is because of these habit alterations that beavers have been viewed as agents of stream restoration.

The Low Down on the Cool River

The Low Down on the Cool River

By Jason Moak, Research Manager

Summer temperatures have arrived, and with them, many people’s sweat-drenched search for a way to cool off.  While a large number of CSRA folks head up to “the lake” to enjoy the water, a growing number are turning to the closer, cooler alternative of the Savannah River below Thurmond Dam.  Even at the peak of summer, the water in the stretch of river that passes through the metro Augusta area remains relatively cool, with daily average temperatures around 22 degrees Celsius (72 F) and maximum daily water temperatures of around 26 degrees Celsius (79 F).  But how can this be?

If you’ve been swimming at Thurmond Lake during the summer, you know that its temperature can get pretty warm, almost like bath water.  Thurmond is a big lake, with over 70,000 acres of surface area and water depths up to 180 feet.  Because of this, the lake actually experiences a process called stratification, where colder water is found in the lower depths, and warmer water is found near the surface.  This happens because cold water is more dense, or heavier than warm water.

In scientific or limnological terms, the warmer, upper layer of the lake is called the Epilimnion, and the colder bottom layer is called the Hypolimnion.  In between these is an area where temperature drops sharply, called the thermocline, located in the middle layer known as the Metalimnion.  You may have noticed this if you ever dove into the lake and felt the water get colder the deeper you plunged.  Sometimes, you can even feel the temperature difference between your chest and feet.

LakeStratificationThurmond Dam generates electricity by allowing lake water to flow through giant (20-ft diameter) pipes called penstocks through turbines and out into the Savannah River below.  These penstocks are located near the mid to lower depths of the lake, where the water is much cooler than the surface during the summer, which is why the Savannah River is so cool as it flows through the CSRA.  Eventually, as we move into fall and air temperatures grow cooler, the surface waters of the lake also cool.  At some point, usually in October, the surface water becomes roughly the same temperature as the deeper water, and mixes – a process sometimes referred to as lake turnover.  From that point until spring the next year, water temperatures in the lake are mostly uniform from surface to bottom.

Effects of Seasonal Flooding on Fish

Effects of Seasonal Flooding on Fish

By Damon Mullis, Research Scientist

Katie with Carp

Research Scientist Katie Johnson processes a large carp collected during a fish sampling event in April 2016 after flood waters recede.

This past fall and winter, the Savannah River experienced unusually high water levels. Although flooding can have negative impacts in the form of property and infrastructure damage, it can have many benefits. Floods are normal occurrences that fill natural depressions, reservoirs, irrigation canals, and help recharge ground water supplies, which all are important sources of drinking water or essential for agriculture.  This periodic inundation of the floodplain is critical for the maintenance of the river’s ecological, geomorphological, and hydrological integrity. This interaction between the river and its floodplain is believed to be a major driving force for the maintenance of biotic diversity and the production of plant and animal biomass, including fish. This suggests that the floodplain provides an abundance of food for riverine fish and increases overall production. Many fishermen have observed this relationship, catching larger fish after flooding events.

Flooded Boat Landing at Oxbow

December 29th 2015- Flooded boat landing and parking area at Savannah River Oxbow (Miller Lake, Tuckahoe WMA)

In addition, high flows allow fish access to floodplain environments which are believed to be ideal spawning habitats for some species. It seems the timing of periodic flooding is also important for successful fish recruitment, with good recruitment occurring in situations when the rise in water level and temperature are coupled, and conversely, poor recruitment occurring if seasonal flooding does not occur or retreats too quickly during the spring.  This relationship suggest that flooding enhances recruitment by directly stimulating spawning and/or providing adequate spawning habitat, and indirectly by enhancing larval and juvenile survival by providing abundant food and habitats on the inundated floodplain. Since this recent flooding event occurred during our ongoing Savannah River Oxbow research project (, we will be able to explore the effects of flooding on the fish in these lakes as well as many other communities and ecological processes.

Stormwater Problems and Solutions

Stormwater Problems and Solutions

By Aaliyah Ross, Environmental Educator

Stormwater fees are currently a topic of debate in many cities and towns. Why does stormwater cause so many problems in urban areas? Read on to find out more about this issue and possible solutions.

The Water Cycle

USGS water cycle

The Water Cycle. Source: United States Geological Survey

You’re probably already familiar with the water cycle—rain falls to the Earth, where it either is intercepted by plants, flows downhill over the land surface (runoff), or is absorbed into the soil. Water in the soil can either be taken up by plant roots or can move downward and become groundwater. Groundwater provides a steady, consistent flow of water to streams, which is especially important during droughts.

The Water Cycle in an Urban Landscape

A comparison of the water cycle in a forested and an urban landscape. Rainfall can reach the stream in one of three ways: overland flow (i.e., surface runoff (O)), subsurface flow through topsoil (S), or percolation (P) into groundwater (G).

A comparison of the water cycle in a forested and an urban landscape. Rainfall can reach the stream in one of three ways: overland flow (i.e., surface runoff (O)), subsurface flow through topsoil (S), or percolation (P) into groundwater (G). Walsh et al., 2004

As areas become urbanized and more developed, natural land cover is replaced by impervious surfaces. Impervious surfaces do not allow water to soak into the ground; these include roads, sidewalks, parking lots, and roofs. This means that less rainfall is absorbed into the soil to become groundwater, and more rainfall becomes surface runoff.

impervious surface

Depending on the amount of impervious surface in a watershed, the annual volume of storm water runoff can increase by up to 16 times that of natural areas. Source: Schueler, Thomas (1995) Site Planning for Urban Stream Protection.









Flashy Streams

A flashy stream in Oregon’s Tualatin River watershed. Flashy streams have dramatic differences in streamflow between wet and dry weather, resulting in high, steep banks as seen in the picture on the left.

A flashy stream in Oregon’s Tualatin River watershed. Flashy streams have dramatic differences in streamflow between wet and dry weather, resulting in high, steep banks as seen in the picture on the left. Photo by Tualatin Riverkeepers

In an urban area with lots of impervious surfaces, a large amount of rainfall flows into streams as surface runoff. This increases the frequency and severity of flooding, because a large amount of water enters the stream in a short period of time. Increased surface runoff results in higher levels of nonpoint source pollution in the stream.

Less rainfall soaking into the soil means that more water reaches the stream via runoff instead of through groundwater flow. This results in “flashy” streams with low flow during dry weather and dramatically higher flow during wet weather.  Flashy streams typically have high, undercut banks that can erode during heavy rain, have warmer water (which holds less oxygen than colder water), and support less biodiversity.


As our population continues to grow both regionally and globally, engineers and hydrologists have developed several innovative solutions to minimize negative impacts caused by impervious surfaces. Some examples include:

  • Bioswales—ditches lined with plants, compost, and rocks that are designed to receive runoff from a paved area. The natural materials lining the ditch allow some runoff to infiltrate the soil, and also help to trap pollutants before the water is discharged to a stream.
The plants in bioswales can filter pollutants out of runoff and allow more water to infiltrate into the soil. Source: City of Salem Public Works Operations Division, Salem, OR

The plants in bioswales can filter pollutants out of runoff and allow more water to infiltrate into the soil. Source: City of Salem Public Works Operations Division, Salem, OR

  • Retention ponds—manmade ponds used to collect and store runoff from areas such as parking lots, shopping malls, dog parks, pastures, and stockyards. Storm drains are sometimes re-routed to feed into retention ponds instead of streams. They help trap pollutants and also control flooding after heavy rains.
  • Rain Gardens—usually much smaller than retention ponds and often include attractive landscaping and wetland plants designed to make the area more aesthetically pleasing. Rain gardens are often built in residential yards and in community parks. They generally perform the same functions as retention ponds, but on a smaller scale.
rain garden

A residential rain garden in Athens, GA. Homeowners Gwyneth Moody and Daniel Peiken were awarded the 2016 Citizen Stormwater Steward Award by Athens-Clarke County Stormwater Management.

Many municipalities now collect fees from property owners to fund the development of stormwater infrastructure. Citizens can often reduce their fees by taking measures to decrease the amount of runoff generated on their property. Effectively managing stormwater protects water quality in our rivers and streams, reduces the risk of flooding, and helps maintain habitat for aquatic organisms. If you live in either Richmond, Columbia, or Aiken County, you can find out more about local efforts to reduce the impacts of stormwater by visiting the links below.

Richmond County Stormwater Utility:

Columbia County Stormwater Utility:

Aiken County Stormwater Management: