FOCL conducts regular water quality testing monthly from May through August. Testing is in conjunction with the Virginia Tech lab and classroom resources in the Biological Systems Engineering Department and includes testing for the following parameters:

• Seechi Depth Readings (m)

• DO Meter Readings:

  • Dissolved Oxygen (mg/L)

  • Temperature (deg C)

  • Specific Conductance (uS/Cm)

  • Total Dissolved Solids (mg/L)

• E.coli and Total Coliform (MPN/100 ml)

• Total Phosphorus

• Total NitrogenChlorophyll-a 

If you’d like to be trained and volunteer with water quality sampling, please contact us and let us know!

Test Sites

FOCL Water Quality Sampling Program

FOCL coordinates a long-term water quality monitoring program. Currently, there are 12 water sampling locations monitored throughout Claytor Lake. FOCL volunteers collect  monthly samples in June, July, and August. Over the course of 8-hours, volunteers and students from Virginia Tech travel on the water from the dam to Allisonia, and up Peak Creek above Conrad Brothers. Samples are collected at the water surface at a depth of approximately 0.5 - 1.0 meters. Direct measurements of water temperature, dissolved oxygen, specific conductance, and sechii depth are made. At Virginia Tech in the department of Biological Systems Engineering, water samples analysis includes bacteria, nutrients, and chlorophyll-a.

The following factsheet provides an update on the current water quality status as of June 2024, the basic hydrology of Claytor Lake, some things you can do, and basic water quality definitions.

Current Status

Samples were last collected in mid-June 2024, and the initial results suggest descent water quality. We can look at spatial patterns from upstream to downstream, and compare this year’s June samples to the previous May/June samples from all of the previous years using percentiles. You can think of this as a gradient from 0-100%, where a low percentile indicates the current value is low relative to all other May/June values at that site. Spatially, water temperature increases from upstream (Allisonia) into the main reservoir. For example, this June the water temperature at Allisonia was 71F (38th percentile) and increased to 78F at the State Park (70th percentile). Surface water was less salty (lower SPC, 96 to 87 uS/cm respectively) and had lower bacteria counts (9th percentile at Allisonia) which are signs of better water quality. The Secchi depth was a ¼ meter lower at the State Park (57th percentile) compared to Allisonia (73rd percentile)  likely due to higher phytoplankton activity. We can also look at Peak Creek, one of the tributaries of the New River. At this location above Conrad Brothers, conditions were the following:  water temperature 72F (39th percentile), SPC (285 uS/cm, 38th percentile), and bacteria (9th percentile). Results from the first summer sampling are impacted by both cooler temperatures and streamflow conditions. The forecasted warmer air temperatures will impact water quality, as well as delivery of nutrients from both the upstream watershed and areas around the lake. Future analysis will examine longer term water quality patterns throughout the larger system.

Hydrology and the Watershed of Claytor Lake

Claytor Lake’s water quality is a function of our upstream watershed, environmental conditions, and the amount of streamwater flowing from the New River and other tributaries coming into the lake. The New River’s headwaters are in the mountains of North Carolina near Boone. While we all intuitively have an understanding that streamflow will increase when it rains, the amount of increase is dependent on how dry the soil is and the intensity of the rain event (see here for a primer on the hydrologic cycle). A simple analogy used in hydrology relates to a checking account. At the beginning of the month, your paycheck is deposited into your account. Payments for electricity, housing, food, and entertainment reduce your account balance until you receive the next paycheck. Water resources is similar – in the fall, water availability is typically at it’s lowest due the water demands of vegetation and higher amounts of evaporation with summer’s higher temperatures and longer days. As the fall progresses, leaves begin to fall, the days get shorter, and evaporation and vegetation water demands decrease. At some point, we stop watering our tomato plants and gardens. This provides an opportunity for rainfall to being to replenish our soils – our watershed’s checking account. Over the course of the winter, more and more water is stored in our soil and groundwater, which ultimately sustains our summertime streamflow when it’s not raining. As the water table increases, less rain is needed to generate an increase in streamflow within the New River. Furthermore, if a rain event is intense (raining like cats and dogs), we will observe the majority of that water flowing downhill over the ground surface and ultimately into a nearby stream. These types of rain events will pick bring with it material that’s on the surface – from tree branches and soil to bacteria and nutrients that are less visible to us. Below we’ll look at what this means for water quality within Claytor Lake, and some resources that you can consider that will help our local waterways.

Another factor that affects water quality within Claytor Lake is it’s residence time. And now it’s time for another analogy. Imagine you’re replacing the water in a bathtub, where you simultaneously remove 1-cup and add 1-cup of water. The amount of time it would take to remove all of the existing water is a measure of the simple residence time. For Claytor Lake, we have a known volume (V in units of L3) of water the reservoir holds (like a bathtub). We also have a measure of the amount of water that flows into the reservoir (largely from the streamflow gage at Allisonia) over time – streamflow (Q – L3/T). We can then estimate the average annual residence time by dividing the reservoirs volume by average annual streamflow. For Claytor lake, this results in an average residence time of ~30 days. While this makes assumptions on the hydrology and water mixing of Claytor Lake, it provides some understanding of how the watershed operates. Higher streamflow will decrease the residence time, whereas prolonged low flow during droughts will increase the residence time. Why is this important? Well, while high streamflow will “flush” existing water, it can also replenish the reservoir with nutrients, sediment, and bacteria.

To put this residence time in perspective, let’s compare Claytor Lake to Smith Mountain Lake. The average annual streamflow into Claytor Lake is 2,767cubic feet per second, in contrast to the primary input into Smith Mountain Lake from the Roanoke River (1,017 cubic feet per second). However, Claytor Lake’s surface area is less than ¼ of Smith Mountain Lake. Thus, the smaller size of Claytor Lake combined with streamflow that’s almost 3xgreater results in lower average residence time in Claytor Lake compared to Smith Mountain Lake. While the low water residence time contributes to generally good water quality, secluded sections off the main channel are likely to have longer residence times.

What can you do?

There are some simple things we can all do to contribute to the health of Claytor Lake. Fundamentally, we want to minimize nutrients and bacteria that enter the lake or adjacent stream. We call these practices Best Management Practices, or BMPs. Some of these BMPs serve to slow water down, and others to reduce the use of nutrients on lawns and gardens. Below are some suggested VCE extension factsheets that provide guidance:

o   First, we all want to ensure that our septic tanks are maintained. This factsheet explains your role as a homeowner. If you are on a well, you may also consider having your well-water tested regularly. Virginia Cooperative Extension provides an extension service for drinking water.

o   Landscape practices (factsheet) are one approach to reduce nutrient delivery to waterbodies.

o   Rainbarrels and rooftop redirection are other approaches that help slow water down.

o   Redirecting water from your roof or driveway into Rain Gardens is an integrated approach. Check with your local nursery on suitable plants or refer to this factsheet.

o   Throughout watersheds, riparian buffers are another approach that have been shown to positively impact water quality.

o   To learn more about the larger New River watershed, check out the New River Valley Watershed Roundtable, FOCL, and the New River Conservancy.

Definitions

Secchi depth = A measurement of how deep one can see into a stream or lake. A disk is lowered into the water and observed until no longer visible – this is considered the Secchi depth. This measurement of a water’s clarity relates is impacted by sediment and algae. During a high-water, a stream is generally brown and turbid; in contrast, the rocks, cobbles, and fish can be often be seen in a healthy stream when water levels are low.

pH = pH is a measure of the amount of hydrogen ions in water on a log-scale, where values less than 7 indicate acidic conditions and greater than 7 basic conditions. The pH of streams, lakes and reservoirs generally ranges from 4.5 – 8.5. Local geology and rainwater can contribute to lower pH values, in addition to natural waters with high biological activity.

Dissolved oxygen =  Dissolved oxygen, or DO, is measured in mg of oxygen per liter of water (mg/L) or as percent saturation. In natural streams, DO will generally vary over 24-hours in response to photosynthesis during the day. The amount of DO in streamwater is a function of the amount of photosynthesis that makes oxygen, the amount of biological respiration that consumes oxygen, the temperature of the water, and the amount of oxygen exchange between air and water. When there is incoming sunlight, oxygen production from algae is greater than oxygen consumption resulting in higher DO levels. At night, DO generally decreases within streams and lakes. DO will also vary as a function of depth, where deeper waters will generally be light limited and have lower DO especially when a lake is thermally stratified during the summer months.

Specific conductance =  Specific conductance, or SPC, is a measure of the ability of water to transmit electrical currents. In streams and lakes, units for SPC are typically in microsiemens per centimeter, uS/cm. Local rain and snow will have values below 40 uS/cm, streams may range from 200 – 500 uS/cm, and ocean water above 50,000 uS/cm. Specific conductance arises from the presence of inorganic dissolved solids within water, including chloride, nitrate, sulfate, sodium, magnesium, iron, calcium, and iron. The amounts of dissolved solids is largely controlled by the underlying geology. For example, some rocks will more easily dissolve and contribute dissolved solids to groundwater. In southwest Virginia, limestone is a large contributor of calcium and bicarbonate which in turn increases the specific conductance. Other non-natural factors include runoff from our activities across the landscape, whether from lawn and agricultural runoff or point-source discharge from permitted industrial facilties. Monitoring specific conductance is an inexpensive approach that provides an opportunity to detect changes in a freshwater’s water quality.

Bacteria =  Bacteria are small organisms that naturally inhabit lakes and streams. They come from various sources including animal waste, sewage, failing septic tanks, livestock, wildlife, and pets. We are likely to get sick by drinking lake water, and recreating in water with high levels of bacteria may also impact human health. We measure bacteria in the laboratory using the IDEXX method which quantifies bacteria levels in unites of the Most Probable Number (MPN). Low MPN values indicate cleaner water, while high values suggest potential contamination and health risks. Monitoring MPN at different locations within a lake allows comparisons. Scientists can identify areas with higher contamination and track changes over time.       

Nutrients = Phosphorus and nitrogen are critical for assessing water quality in lakes. These nutrients are essential for aquatic plant growth, but excessive levels can harm the ecosystem. Excess nutrients cause rapid algae growth, leading to reduced water clarity, impacts on recreation, and harm to aquatic life. Some cyanobacteria produce toxins. Additionally, low dissolved oxygen due to algal respiration can stress or kill sensitive organisms.

Streamflow =  Streamflow is a measure of the amount of water (as a volume) moving past a location over a given period of time. The U.S.G.S. typically reports streamflow in units of cubic feet per second, or CFS. Within Claytor Lake, we have several gages upstream (e.g. New River @ Allisonia), Peak Creek, and downstream (New River @ Radford) available for current streamflow and forecasted streamflow. The National Water Prediction Service maintains a data portal that is useful to gage current and future conditions.

Agriculture cost sharing program and best management practices for fencing off livestock to protect waterways.

CDC reminders and recommendations on safe swimming in oceans, lakes and rivers.

“Germs found in the water and sand (swim area) often come from human or animal feces (poop). One way germs can be carried into swim areas is by heavy rain. Water from heavy rain picks up anything it comes in contact with (for example, poop from where animals live) and can drain into swim areas. These germs can also come from humans or animals pooping in or near the water.

Water contaminated with these germs can make you sick if you swallow it. It can also cause an infection if you get into the water with an open cut or wound (especially from a surgery or piercing).

Taking a few simple steps when you visit oceans, lakes, rivers, and other natural bodies of water can help protect everyone from these germs."