Learn about Village Blue Baltimore's water sensors
Village Blue Baltimore uses two water quality sensors to collect real-time data from the Baltimore Harbor. The sensors record water quality data every six minutes, which are displayed live on this website and on USGS National Water Information System.
Village Blue's water quality sensors use multiple probes to measure various characteristics of water in the harbor.
Two sensors are mounted underwater where the Jones Falls River meets the Inner Baltimore Harbor. The water is about eight feet deep in this location and is separated into a top layer, made of fresh water from the river, and a bottom layer, made of salt water from the harbor. One sensor is mounted two feet deep to monitor fresh surface water from the river, while the other is mounted six feet deep, to monitor salt water from the harbor.
NOTE: As of October 8, 2018 the lower water sensor's functionality was reduced to solely measure dissolved oxygen, and nitrate sensor measurements were discontinued. Full historical data (February 15, 2017 - October 8, 2018) for the upper and lower sensors are still available through the USGS National Water Information System.
The division of fresh and salt water in a water body is called a halocline, and occurs when dense salt water sinks below fresh surface water, causing a layered effect.
Jones Falls sensor placement in relation to the halocline.
Village Blue's water quality sensors are mounted underwater in Baltimore's Jones Falls River, shown here. The data collected by the sensors is stored and transmitted by equipment housed in this weatherproof box.
Click below to learn about what the sensors are measuring
Chlorophyll allows plants (including algae) to use sunlight to grow (photosynthesize). Chlorophyll a is the main type of chlorophyll found in green plants and algae.
Although algae are a natural part of freshwater ecosystems, too much algae can result in lower levels of dissolved oxygen and can cause problems such as green scums and bad odors. Some algae also produce toxins that can be of public health concern when they are found in high concentrations.
Gage height (also known as stage) is the height of the water in the stream above or below a reference point. Gage height refers to the elevation of the water surface in the specific pool at the streamgaging station, not along the entire stream. Gage height does not necessarily refer to the depth of the stream. The gage height at the Jones Falls River monitoring site fluctuates periodically due to the influence of ocean tides in the inner harbor.
The stream velocity indicates the speed and direction of the water flow at the location of the sensors. If the velocity is a positive quantity, the water is flowing from the river toward the harbor, whereas a negative direction indicates water flowing from the harbor toward the river. The stream velocity is affected by ocean tides and rainfall.
Turbidity is the measure of how clear a liquid is compared to other liquids. It is an expressed by the amount of light that is scattered by material in the water when a light is shone through the water sample. The higher the intensity of scattered light, the higher the turbidity. Clay, silt, algae, and plankton are examples of materials that cause turbidity.
In this photo, brown colored water, full of sediment from a stream is entering a much clearer Lake Tuscaloosa in Alabama, USA. The sediment-laden water has a high turbidity level compared to the blue-green colored water.
Salinity is a measure of the salt content of water, which affects both the water's density and how the water moves. Water with low salinity, such as freshwater, has a much lower density than ocean water with high salinity. This is why lower salinity (or brackish) river water can flow over the higher salinity water of the inner harbor.
Salinity is typically measured in parts per thousand (ppt). Fresh water contains few salts (less than 0.5 ppt), brackish water is a combination of fresh and salt water with 0.5 ppt but less than 25 ppt, and ocean water averages 25 to 30 ppt. The level of salinity makes a big difference to underwater life.
The oxygen dissolved in lakes, rivers, and oceans is needed by the animals living in these water bodies. As the amount of dissolved oxygen drops below normal levels, the water quality is harmed and creatures may begin to die off.
Normally, a small amount of oxygen is dissolved in water. Oxygen enters the water in several ways: from the atmosphere; in places where water tumbles, such as waves, rapids or waterfalls; through photosynthetic activities of aquatic plants, and from groundwater discharge. Aquatic animals typically absorb this dissolved oxygen through gills.
The amount of dissolved oxygen is reduced in water through animal respiration, organic matter decomposition, and chemical/biological reactions. Dissolved oxygen levels below 2 mg/L are considered "poor," while oxygen levels above 5 mg/L are considered "good". Monitoring dissolved oxygen is important to assess the health of the aquatic ecosystem.
Nutrients such as nitrate and phosphorous in water serve the same basic functions as fertilizers for a lawn or garden. In a river or lake, nutrients may make a large amount of algae grow - leading to the development of Harmful Algal Blooms (HABs) with toxic algae species.
Nitrate sources include stormwater runoff, which may carry fertilizers from lawns and cropland as well as organic matter such as leaves and grass; waste products from farm animals and domestic pets; and from industrial and municipal wastewater treatment plants.
Temperature has a major influence on the biological activity and growth of aquatic plants and animals. Temperature also determines the kinds of organisms that can live in particular areas. Fish, insects, zooplankton, phytoplankton, and other aquatic species all have a preferred temperature range. As temperatures get too far above or below this range, the number of individuals of that species may decrease. If the temperature remains unsuitable, all of that species may leave the area or die off.
Warm water holds less dissolved oxygen than cool water, and may not contain enough dissolved oxygen for the survival of different species of aquatic life. Some chemical compounds are also more toxic to aquatic life at higher temperatures.
pH is a measure of how acidic/basic water is. The range goes from 0 - 14, with 7 being neutral. A pH of less than 7 is acidic, whereas a pH of greater than 7 indicates a base (sometimes called alkalinity).
The pH of water partly determines how much specific nutrients, such as nitrogen and carbon, and heavy metals can be dissolved in water. This in turn affects how much of these quantities are available for plants and animals to absorb. When the pH is too high or too low it can impact the health of animals and plants that live in the water.
Phycocyanin / Phycoerythrin
Phycocyanin and Phycoerythrin are components of blue-green and red algae respectively. Algae are a natural part of aquatic ecosystems; however, when present in large quantities as "blooms", they can pose a significant potential threat to human and ecological health. These harmful algal blooms (HABs) are often made of microorganisms known as cyanobacteria, some of which have the potential to produce toxins that can cause adverse health effects in humans and animals through the contamination of waterways used for recreational purposes and as drinking water supplies.
Explore Village Blue Baltimore data
Village Blue's water quality sensors record and transmit data in real-time. Real-time water quality data helps communities stay informed about local water conditions and make decisions to protect public health.
Explore Village Blue Baltimore's water quality data over time:
The visualization of provisional data is updated every five minutes. These data can be downloaded using the USGS National Water Information System.
- Use the +/- controls to expand or shrink the plots.
- Use the checkboxes to choose which data to display.
- Hovering the mouse over the plots will show the precise data values.
- Upper data (in blue) is above the halocline, and lower data (in red) is below the halocline.
- Zoom into the plots by left clicking and dragging to define an area of interest. Click the reset button to return to the default zoom level.
Village Blue Baltimore partners
EPA is partnering with federal, state, and local organizations to implement the Village Blue project and raise public awareness about the importance of monitoring and protecting local waters.
Federal and State Partnership:
EPA is providing water quality sensors, and is responsible for data integration, website design, data visualization, and modeling.
The Maryland Department of Natural Resources (DNR) has an extensive network of real-time and non real-time water quality monitors and is contributing to the data visualization. Maryland water quality data and related information can found through DNR's Eyes on the Bay website
The U.S. Geological Survey (USGS) provides operation and maintenance of the water sensors, data quality assurance, and access to water quality data through its water services infrastructure
. USGS will also be contributing to the data visualization and sensor evaluation.
- Blue Water Baltimore
- City of Baltimore
- Maryland Science Center
- National Aquarium
- Waterfront Partnership of Baltimore
Learn more about Village Blue Partners and their roles in the project.
The National Aquarium, a Village Blue Baltimore partner, meets with community members for an education / outreach event about biodiversity and water quality in Baltimore Harbor.