Live data – Saltwater Creek

Live data from Saltwater Creek gauging station.

What we're monitoring	Its part in a healthy waterway	What is healthy?
Dissolved inorganic nitrogen (DIN) levels - Load and concentration	Nitrogen is a gas that makes up almost 80% of the earth’s atmosphere. Nitrogen is essential to all life on earth but too much can be harmful. Dissolved inorganic nitrogen (DIN) is a dissolved component of total nitrogen (TN) in water. Load is a measurement of concentration x flow. Flow is a measurement of volume of water flowing in the river per unit of time (e.g. litres flowing per second or m³ per second).	Nitrogen is measured in milligrams per litre (mg/L). Natural levels of nitrogen are usually less than 1 mg/L. Concentrations in healthy estuaries for the Cairns area for TN are at or below 0.25 mg/L and for DIN are at or below 0.045 mg/L (dry season) and 0.668 mg/L DIN and 0.114mg/L (high flows - wet season). Concentrations over 10 mg/L will have an effect on the freshwater aquatic environment. As per the Barron River Basin Environmental Values and Water Quality Objectives for protection of aquatic ecosystems.
Water Clarity (Turbidity)	Turbidity is a measure of how particles suspended in water affect water clarity. The effects of these suspended solids on fish and aquatic life are an extremely important cause of water quality deterioration. Increased turbidity will also increase water temperature, lower dissolved oxygen and prevent light from reaching aquatic plants.	Turbidity is measured in Nephelometric Turbidity Units (NTU). A high turbidity (low clarity) reading means that there are suspended solids in the water, likely resulting from erosion and sediment possibly after heavy rainfall. The Barron Water Quality Objectives for estuaries is 10 or less. This is for dry season conditions. During high flow events the NTU in a healthy estuary is likely to be considerably higher than 10 for periods during the event.
Temperature	Water temperature is affected by air temperature, stormwater runoff, groundwater inflow, turbidity and exposure to sunlight. The maximum temperature is the highest water temperature the organism can live for a few hours. The optimum (normal) temperature is the temperature at which it will thrive. Water temperatures outside the “normal” range for a river or creek can cause harm to the aquatic organisms that live there and add to rising ocean temperatures that can lead to coral bleaching.	With so many factors affecting water temperature it is difficult to asses what is 'normal'. Depth, shade, clarity, season, cloud cover, flow are all major factors in monitoring temperature.
Dissolved Oxygen	Aquatic plants and animals rely on oxygen that is dissolved in the water for survival. This 'Dissolved Oxygen' is the most important indicator of the health of a body of water. Levels of dissolved oxygen vary depending on factors including water temperature, time of day, season, depth, altitude, and rate of flow. Consistently high levels of dissolved oxygen are best for a healthy ecosystem and when it drops too low can be devastating for the environment. A major cause of low dissolved oxygen is the decomposition of organic material (palm fronds, grass cuttings, leaves etc), as the organic material breaks down oxygen in the water is consumed. If the dissolved oxygen levels drop too low, there is not enough for animal survival and it can lead to ‘fish kill events’, where large numbers of fish die within a short period.	Dissolved oxygen can be measured in milligram per litre (mg/L) or parts per million (ppm). 0-2 mg/L: not enough oxygen to support life. 2-4 mg/L: only a few fish and aquatic insects can survive. 4-7 mg/L: good for many aquatic animals, low for cold water fish 7-11 mg/L: very good for most stream fish Dissolved oxygen can also be measured in percent saturation.
pH	pH is a scale in chemistry used to measure the acidity or alkalinity of a solution. If the pH level of water is too high or too low, the aquatic organisms living in it will die. Changing levels of pH in a creek or river can be an indicator of increasing pollution or some other environmental factor.	A pH value is a number from 1 to 14, with 7 as the middle (neutral) point. 1 is the most acidic. The optimum pH levels for fish are from 6.5 to 9.0.
Chlorophyll - a	Chlorophyll-a is a green pigment found in plants. It absorbs sunlight and converts it to sugar during photosynthesis. Monitoring Chlorophyll-a is a commonly used measure of water quality and concentrations are an indicator of algae abundance and productivity in aquatic environments. Higher concentrations typically indicate poor water quality, usually when high algal production is maintained due to high nutrient concentrations. It is natural for chlorophyll-a concentrations to fluctuate over time and they are often highest after rain, particularly if the rain has flushed nutrients into the water during the warmer, sunnier months of the year.	Chlorophyll-a is measured in micrograms per litres.(ug/L). Healthy waterways generally have less than 3 ug/L.
Salinity	Salinity is a measure of the content of salts in soil or water (mainly sodium chloride (common table salt)).The water in rivers and creeks is usually fresh, oceans are salty. Excessive amounts of dissolved salt in freshwater can affect ecosystem health, including native vegetation, to die. Salinity can occur with land clearing and altered land use. Saltwater Creek is tidal and has both freshwater and saltwater areas.	Because the water in estuaries is a mix of fresh water and ocean water, the salinity in most estuaries is less than the open ocean. Bottom water almost always contains more salt than surface waters.
Depth and flow	The overall size, depth and flow of a waterway can affect its water quality. For example contaminants entering deep and fast moving rivers will have less effect on the river than the same amount of contaminants entering a slow moving, shallow creek. However tides, weather, the landscape and obstructions such as rocks, fallen trees and bends in the waterway, will further influence depth and flow. Measuring flow allows us to observe any change in the load of contaminants and sediment that may be in the water. Load is a measurement of concentration x flow. How deep a creek is can also affect other ‘parameters’ of water quality, such as temperature and light which both decrease with depth. Depth will also affect how stormwater is discharged from the catchment.	Flow is the volume of water flowing in the river per unit of time (e.g. litres flowing per second or m³ per second). Tropical estuaries are generally shallow, less that 5m deep which can mean they flow relatively slowly. Saltwater Creek is tidal. Flow velocity is lower nearer its mouth because of incoming tides. Faster freshwater flow is expected in the upper catchment. In the tidal zone where freshwater and saltwater mix at the mouth of a river or creek (the estuary) there may be limited and minimal flow. A major storm event may cause a sudden increase in flow coming out of the Saltwater Creek catchment.