.jpg) By monitoring water quality and biological indicators (living creatures that tell us how healthy the water is) such as water bugs, local communities can observe and learn about the health of their rivers and can identify problems and take action.
Waterwatch data can also provide an historical record of how river systems have changed over time. The data can help to identify problems and show if activities to fix the problems are working.
The quality of water in our rivers and creeks is affected by a range of factors such as the level of salinity (the amount of salt in the water), sediment (the amount of soil and rubbish washed into our waterways) and nutrients and algal blooms (the increased growth of algae that can cause plants, fish and insects to die).
Monitoring Water Quality
To monitor water quality, Waterwatch measures:
Water Temperature
Temperature affects the amount of oxygen that can be dissolved in water. Warmer water holds less oxygen. If the temperature changes too rapidly plants and animals do not function as effectively and become more vulnerable to toxic waste and diseases. If temperature changes more than two degrees Celsius (2°C) in a 24 hour period most aquatic organisms can experience stress, and with extreme temperature change, many will die. Photosynthesis and bacteria decomposition happens faster in warmer waters, which can result in a build up of nutrients and algal blooms. Photosynthesis is a process where plants convert carbon dioxide and water into glucose and oxygen, using energy from light in the presence of chlorophyll (a compound found in plants). Temperature can also affect salinity as salt is more soluble in warmer water. Water temperature can be affected by factors such as air temperature, exposure to sunlight and shade, turbidity of water, the inflow of groundwater into the waterway, and discharge of warmed water from industries and power plants.
Dissolved Oxygen (DO)
Dissolved Oxygen (DO), is the amount of oxygen found in the water. All creatures, including those that live in the water, need oxygen to survive. Waterways gain oxygen from the atmosphere and from plants as a result of photosynthesis. Oxygen also enters the water when the water moves. Agitated waters therefore contain more oxygen as the mixing process dissolves more oxygen than still water. When water flows over riffles (rocks in water) the water becomes oxygenated, meaning oxygen enters the water. Stagnant water, or water which is not moving, has very little oxygen in it which makes it hard for animals to survive. Oxygen levels are measured in milligrams per litre (mg/L) or as percentage saturation (%sat).
pH
The pH of water is a measure of hydrogen ion concentration. It shows the acidity or alkalinity of water. Measurement of pH is important for water quality as all aquatic animals and plants are adapted to specific pH ranges. The pH scale ranges from 0-14 with freshwater usually falling between 6.5 to 8.2 on the scale. The pH of water increases in warmer temperatures, so pH levels can be affected by the time of day a sample is taken or if it's a sunny day. If salinity is high, this can also increase the pH. The geology of the waterway can also affect the pH.
Electrical Conductivity (EC)
Electrical conductivity (EC) is generally used to measure the salinity of water as salty water conducts electricity more readily than pure water. Salinity is the amount of salt in the water. The types of salts causing the salinity are sodium, magnesium, calcium, potassium, chlorides, sulphates and carbonates. Electrical conductivity is measured in microSiemens per centimetre (µЅ/cm). Waterwatch takes EC measurements using EC meters (by inserting the EC probe into the water sample). The ideal salinity level for most water life is around 200. EC levels can be affected by geology and soils, rainfall, surface run-off, groundwater inflows, temperature, evaporation, dilution and the flow of the waterway. Contamination discharge into stormwater can change the water’s electrical conductivity. A waterway's salinity levels can also rise naturally due to the closeness of groundwater, tidal influences and tree clearing.
Turbidity
Turbidity is the measure of how clear the water is. The more suspended solids in the water, the greater the turbidity. High turbidity reduces the amount of light passing through the water. Plants grow and produce oxygen when they photosynthesise. To do this they need light. While there are some plant species that can photosynthesise in low light, this is a limited number of species. If just these aquatic plants are surviving in a highly turbid waterway the biodiversity of that waterway is reduced. As erosion occurs within a catchment, tiny particles of clay, silt or small organic particles (sediment) are washed into waterways. Industrial waste, litter, algae and sewage can also contribute particles. In highly turbid waterways the fine particles settle in the spaces in between rocks, where many water bugs live, breed and hide from strong flows and predators. This can also reduce the biodiversity of aquatic animal life in a waterway.
Turbidity meters measure the intensity of a light beam when it has been scattered by particles in the water. Turbidity can be expressed by a range of units, including the preferred Nephelometric Turbidity Units (NTU).
Phosphorus
Phosphorus is a form of nutrient that is found in both surface water and groundwater at low concentrations. It comes naturally from the weathering of rocks and the decomposition (rotting) of organic material, but it can also enter waterways in runoff or discharges. Soil and fertiliser particles can carry phosphorus and sewage is also rich in phosphorus. High concentrations of phosphorus in water bodies is often the result of human activities. High levels of phosphorus concentrations in water result in problems such as algal blooms, excessive growth of aquatic weeds and loss of species diversity. Phosphorus concentration varies considerably under natural conditions, depending on factors such as local geology, soil types and seasonal conditions.
Nitrates/Ammonia
Nitrogen is essential for all forms of life but few living things can use nitrogen when it is in gas form. Nitrogen is used by plants and animals all the time and can be found in both surface and groundwater. High levels of nitrogen in salt water can cause algal blooms, excessive growth of aquatic weeds and some species to die. The most common nitrogen compounds come from animal and human waste, such as sewerage, decomposing (rotting) plants and animals, nitrogen-containing fertilisers and industrial discharges (waste). The cadmium reduction (colour comparator) method can be used to test for Nitrate (NO3), however Waterwatch Melbourne recommends that groups monitor ammonium instead. Ammonium is a safer and cheaper option. Ammonia (NH3) is a product of the decomposition of organic waste and can be used as an indicator of the amount of organic matter in the waterway.
Water Bugs (Macroinvertebrates)
Water bugs (macroinvertebrates), are creatures such as snails, mites, bugs, beetles, dragonflies, freshwater crayfish and worms that live in rivers and streams. Water bugs are very sensitive to pollution which means they can tell us how healthy our waterways are. Waterways with good quality water have many different kinds of water bugs (also known as having a high level of species diversity).
Find out more about monitoring water bugs. |