Category: Phinizy Blog Feed

How Much Water is Flowing Down That River?

How Much Water is Flowing Down That River?

By Oscar Flite, Ph.D.

Riverwalk Ampitheater The Savannah River has been at the highest level over the past year than it has been in many years.  But can you visualize how much water is flowing down the river at a time?  Our CEO / Senior Scientist, Dr. Oscar Flite, explains just how much water flows down the river at a time using our own homes and a view from a boat dock. Measurements of how much water is flowing in a river, or river discharge, is quantified in units of cubic feet per second. Well, what is that?  To answer that, we have to think about two things, a volume component (cubic feet) and a time component (seconds). For the volume component, we can visualize a standard floor tile which is often 12 inches on each side, or 1 foot x 1 foot, or one square foot (1ft2).  If you built a box around that floor tile using the same sized floor tiles, you would have four sides of the box that were each 1ft high x 1 ft wide (1ft2), and a lid that was the same as the first floor tile, 1ft2.  The box would then be 1ft long x 1ft wide x 1 ft tall and would have a volume of 1 cubic foot (1ft3).  The amount (volume) of water in streams and rivers is measured relative to the size of that box, a cubic foot. For the time component, we can visualize ourselves sitting on a dock on the river.  The time component of the discharge measurement is how much water passes a stationary location each second – in this case, the dock.  That stationary point is actually an imaginary thin pane of glass that crosses the entire river along the water surface and extends to the bottom from the water surface, straight down to the bottom of the river at each point along the glass pane. The discharge in a river is then equivalent to how many of those 1 cubic foot boxes pass through the glass pane each second, or cubic feet per second (cfs or ft3/s). If we extend the floor tile concept, the ceiling height in most homes is 8 feet high.  If a particular room is 10 feet long x 10 feet wide x 8 feet high, the room is then 800 cubic feet (ft3).  The average square footage of a home in the US in 2010 was just under 2400 ft2.  If the entire house had 8ft ceilings, then the total volume of that 2400 ft2 house would be 19,200 ft3. The daily average flow for the Savannah River at the Augusta USGS gauge since 1956 is approximately 7000 ft3/s. That is equivalent to a home with 875 ft2 of living space and 8ft ceilings floating past the dock each second. The river is currently flowing at 30,000 ft3/s.  That is equivalent to a home with 3,750 ft2 of living space.  Last year’s flood event had a maximum flow of 40,000 ft3/s, or a home equal to 5,000 ft2.  Since Thurmond Dam was constructed, the highest daily average flow was nearly 85,000 ft3/s, which is equivalent to a home with 10,625 ft2 of living space.  Some of the highest measured flows for the river, prior to Thurmond Dam installation, exceeded 100,000 ft3/s, which is equivalent to a 12,500 ft2 home floating down the river every second.  For interest, the daily average flow of the largest river in the world, the Amazon River, is over 6,000,000 ft3/s, or a building with 8 ft high walls and a square footage of 750,000 or 17.2 acres!

Why Don’t Ducks Freeze?

Why Don’t Ducks Freeze?

By Chalisa Nestell, Research Scientist

Between the high water levels and this bitter cold snap, there are thin sheets of ice across the shallower areas of Butler Creek.  The mallards and other dabbling ducks are completely unfazed. How are the ducks able to withstand such chilly temperatures?  Why don’t the ducks get hypothermia?

Those bright orange legs are equipped with an amazing counter current exchange system.

The counter current exchange system is a unique alignment of blood vessels, with veins and arteries lying next to each other, that allows for the exchange of materials.  In this case, the system allows for the exchange of heat. In a nutshell, warm blood from the body, in the arteries, going into the duck’s feet is used to warm the blood coming from the feet and back into the body, in the veins. This has two advantages. First, it ensures blood going back into the body is warm. Second and more importantly, it conserves body heat by minimizing heat loss.

Physics tells us that the greater the difference in temperature between two things, such as duck feet and cold creek water, the greater the potential for heat loss. This is the beauty of the counter current exchange system. As the veins absorb heat and warmth, the temperature in the arteries decreases and the blood temperature in the feet becomes closer to the temperature outside.  The reduced temperature difference results in reduced heat loss.  Hence the duck isn’t continually losing large amounts of body heat while its dabbling bottoms-up for food in the water.

So the ducks’ toes do indeed get cold, several degrees colder than the body.  But thanks to the counter current exchange system, the body stays nice and warm.

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Betty’s Branch Fish Kill

Betty’s Branch Fish Kill

By: Oscar Flite, Ph.D.

I use my most distilled explanation of the water cycle for my four-year old son, it goes like this:

The rain falls on the creek, the creek flows to the river, the river flows to the ocean, the ocean makes the clouds, the clouds make the rain, the rain falls on the creek…

The surface of the ocean is the lowest surface-water level on earth (sea level).  Since water flows downhill, it makes sense that all freshwater flows toward the ocean.  Freshwater primarily flows toward the ocean in channels we call rivers and streams. While the ocean is the lowest water elevation on the surface of the earth, rivers are the second lowest water elevation on the surface of the earth; rivers flow toward the ocean.  If the elevation of a river increases (because of higher river flows), it can have a dramatic impact on the land surrounding the river, especially if the land is the same elevation as the rising river; this we know as flooding. When the river elevation rises, it has an immediate effect on the smaller creeks that flow toward the river.  Since water flows downhill and the river elevation is rising, the creek water can no longer flow toward the river and the creek water starts to rise too.  Water that gets backed up in creeks starts to flood into land areas that do not normally undergo such wet conditions.  Those areas are often highly vegetated and range from wetlands to nicely manicured backyards.  If the river and creeks remain elevated for a few days, bacteria in the water and soil will start to decompose the newly wetted vegetation and within several days (depending upon the season) the bacteria will start using the newly flooded vegetation for food.  That bacterial consumption has a direct impact on the amount of oxygen in water.  Much like when you and I eat vegetables, our bodies convert that plant material into carbohydrates and water, but it is done at the expense of oxygen in in our blood; our bodies need oxygen to convert the plant material to carbohydrates for energy.  So too do the bacteria in the water.  However, unlike the large and nearly limitless amount of oxygen in the atmosphere, the water has a more limited amount of oxygen.  If the oxygen in the water is used up at a rate higher than it can be produced by algae or replaced by wind mixing, then the dissolved oxygen concentration in the water will decrease which can ultimately lead to suffocation of animals that require dissolved oxygen to be above a certain concentration.

A fisherman observed a large fish kill in Betty’s Branch, a creek that flows to the Savannah River, on July 27, 2013. Preceding the fish kill, flows within the Savannah River were unusually high as a result of a nearly month-long rain event starting in late June 2013 (see Figure 1).  Under “normal” flows throughout the year, the river gauge near the Fury’s Ferry bridge reads an average of 14 feet.  However, during the flood event the water increased over 5 feet according to the gauge and remained at that level for nearly 2 weeks.  On July 19, 2013, flows in the river were rapidly reduced by nearly 2 feet to an average gauge height of nearly 18 feet; flows remained there for nearly 1 week. On the morning of July 27, 2013, the morning of the fish kill, the river flows were rapidly reduced by nearly 3 feet to a gauge height of 15 feet.  The extended flooding condition within the vegetated areas of Betty’s Branch was long enough for the bacteria to decay vegetation and use up all the dissolved oxygen in the stagnant water.  The rapid decrease of river elevation caused a release of low dissolved oxygen water from the stagnant pools within the wetlands and backyards to flow toward the creek, ultimately suffocating fish within the creek.  After the fish kill, GADNR contacted SNSA to discuss the fish kill.  During that time, one of the biologists said they measured high concentrations of iron in the water.  This piece of data was strong evidence that the rapid decrease of river level caused low dissolved oxygen water to rapidly flow to the creek because once bacteria use all of the available dissolved oxygen within the water, other bacteria will use nitrate, then iron and manganese, then sulfate, and finally carbon dioxide for energy.  This series of energy producing substances for bacteria is called the “respiration cascade” and is a well-known series of chemical reactions that allow bacteria to inhabit almost every environment known.  In essence, the measured iron played an important role in allowing us to understand the complex scenario of this particular fish kill; the iron severed as an indicator of the water quality and water flow conditions.

While many fish were killed during this event, the positive aspect of this event is that it easily allows us to recommend operational strategies to avoid killing fish under similar circumstances in the future.  Since the USACE regulates flows within the Savannah River, the rapid decreases in river flow were caused by decreased water discharge from Thurmond Dam.  In the future, flows after extended flooding could be slowly ramped down over several days to allow for slow release of low dissolved oxygen water from flooded areas.  This would slowly introduce smaller amounts of low dissolved oxygen water to the creek, which will either give fish an opportunity to seek higher dissolved oxygen water or dilute the low dissolved oxygen water with more oxygenated water in the creek.   Over the next few years, the USACE will be seeking information and data on how to better operate flows within the river with one of the main goals of protecting the river ecosystem.  Lowering the flows after flooding will be one easy operational recommendation for ecosystem protection.