Water
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St Jude's Junior School "Water Show" text

Program: St Jude's 24th of March, 9.45 to 10.15am (Junior school).

Background knowledge: Fresh water is our most valued and sought-after renewable resource. Clearing and subsequent land uses, urban developments and changes to the natural flow of our rivers have affected the physical, biological and chemical characteristics of fresh water and contributed considerable quantities of sediment, salts, nutrients and toxic chemicals to our waterways and wetlands.

Good-quality water is important, since poor-quality water can affect human health, harm wildlife and limit food production. Most monitoring programs involve surveys of stream habitat, macro-invertebrates and algae as well as tests to monitor the physical and chemical conditions of the water. The entire area from which a stream or river receives its water, from both surface and sub-surface or groundwater run-off, is called a catchment.

When it rains, the water drains naturally to the lowest point on the land, forming into small creeks that feed into larger streams and rivers as they run downhill.

To monitor water quality:

Aquatic environment:
Food: Riparian vegetation provides a range of food for animals living in the water. This food mainly comes in the form of falling leaves, branches and logs. Branches and logs also hold decomposing vegetation long enough for it to be used by animals in the stream. Insects attracted to the riparian zone become part of the food supply by either falling in the water or laying eggs.

Protection: Within the stream, many animals depend upon the logs and branches that fall as a source of shelter. These larger forms of debris also affect the flow of the water and thus provide better living conditions for some of the animals. Shade from the overhanging trees lowers water temperatures, improving conditions for plants and animals. By reducing the light entering the water body there is less chance for imbalance to occur with respect to the amount of plant growth in the water.

Experiments:

1. `The pole technique': To collect water from wide or deep streams, use a plastic bottle taped securely to a long pole such as a broomstick. Use this pole to collect your sample from a point as far from the bank as you can safely reach. Alternatively, attach a small container such as a plastic yoghurt container to a fishing rod and lower it into the stream from the bank.

2. Use Distilled water or deionised water: You can use either distilled water or deionised water for these chemical tests, although the instructions use the term distilled water. Both distilled and deionised water are available from chemical suppliers and supermarkets; deionised water is the cheaper of the two.

3. Dissolved Oxygen: What is it?

Dissolved oxygen (DO) is the small amount of oxygen that is dissolved in the water. This oxygen is vital to fish, other aquatic animals, micro-organisms and plants which depend upon it for the process of respiration, i.e. to 'breathe'. Maintenance of healthy and diverse aquatic ecosystems depends on oxygen levels being maintained at consistently high levels. Reductions in DO levels result in loss of the more sensitive species. At very low DO levels, only very few species may be present.

The DO level is also a useful indicator of water quality. It can tell us how a water body is behaving and it can indicate the presence of certain pollutants, particularly organic matter (matter that has come from plants and animals e.g. fallen leaves, animal manure, sewage effluent). One accurate test for dissolved oxygen is to use a wet chemical preparation called the Modified Winkler Titration Method.

Should be about 70% in the wetlands.

4. Temperature: What is it?

We all know what temperature is, but its significance with regard to water quality is not quite so straight forward since temperature influences many other characteristics of water. Temperature is measured in degrees Celsius (°C).

Many of the physical, biological, and chemical characteristics of a river are directly affected by temperature.

· The temperature of the water influences the amount of oxygen that can be dissolved in the water.
· Riparian vegetation keeps waters cool.
· Temperature influences the rate of photosynthesis by algae and large water plants.
· Temperature influences the sensitivity of organisms to toxic wastes, parasites and diseases.
· The temperature of water varies depending on the water body.

Maximum recommended increase in the natural temperature of any inland or marine waters is 2°C.

5. Turbidity (Suspended solids)

As erosion occurs within a catchment tiny particles of clays, silts or small organic particles are washed into water bodies. Industrial wastes and sewage also can contribute particles. These tiny particles can be held by the water and are termed suspended solids. The faster the water is moving the more suspended solids it can carry.

Suspended solids can be measured in milligrams per litre (mg/L) by filtering the water and weighing the dried residue.

Turbidity is the result of suspended solids and is a relative measure of the clarity of water: the greater the turbidity, the murkier the water. Increases in turbidity reduce the transmission of light.

· Increased turbidity silts up stream habitats.
· The fine particles settle in downstream areas and make the bottom habitat unsuitable for many animals.
· Increased turbidity reduces light penetration through the water
· This reduces the amount of light for plant growth and thus limits growth of beneficial aquatic plants.
· Increased turbidity affects pollutants.

The most effective method of testing for turbidity is by using a turbidity tube. For this test you simply collect water and pour into the tube until you cannot see the markings on the bottom. Record the reading from the side of the tube. If possible, stand the tube on a white tile. These tubes are handy because they are cheap and simple to use. A seechi disc can also be used. For greater accuracy use a nephelometer. This instrument determines the scattering of light and is measured in standard Nephelometric Turbidity Units (NTU).

Seasonal mean turbidity and suspended solids levels must not change by more than 10%.

6. Salinity:

Salinity is simply a measure of the amount of salt dissolved in the water. Salts are substances such as common table salt (sodium chloride, NaCl), limestone (calcium carbonate, CaCO3) and many others. They are picked up by the water as it runs over and through the rocks and soils of the catchment. Low levels of these salts are vital to the growth of aquatic plants and animals but high levels can cause problems for aquatic life and for human uses such as crop irrigation.

There are two ways to measure salinity: using total dissolved solids (TDS) or electrical conductivity (EC).

· Salinity is determined by the geology and soils of the catchment.
· Salinity varies with flow.
· Aquatic plants and animals need the natural salts contained in waters for growth.
· Human induced changes to catchments can affect the salinity of runoff water.

Fresh waters should not exceed 1,000 mg/L. Typical sea water is 35,000 mg/L. Drinking water should be less than 1,000 mg/L.

7. pH testing:

pH is a measure of how acid or alkaline the water is, on a scale of 1-14. It is a measure of the hydrogen ion (H+) concentration. Water (H2O) contains both H+ and OH- ions. Pure distilled water contains equal numbers of H+ and OH- ions and is considered neutral (pH 7). Because pH is a logarithmic scale, every unit change (for example from 5 to 4) represents a ten-fold increase in acidity.

The pH of fresh water usually lies in the range 6.5 to 8.2, although wide variations can occur because of catchment geology. It can also be affected by a range of factors including industrial run-off and sewage.

Animals and plants in streams are adapted to certain ranges of pH. Even under natural conditions, the animal and plant communities of acid streams contain many different species to those in alkaline streams. An increase or decrease in pH outside the normal range of a water body will cause sequential loss of the species depending on their sensitivity. Extremely high or low pH values will lead to the death of all aquatic life, so to retain a healthy diversity of life, pH must be kept within the range of natural variation for the water in question.

· The pH of natural waters is largely determined by the geology and soils of the catchment.
· Increasing salinity causes increase in pH.
· The photosynthetic activities of plants and algae can cause significant variations in pH.

Freshwaters pH values of more than 0.5 units outside the natural range should be investigated. Less than 6.5 may be corrosive. More than 8 progressively decreases efficiency of chlorination. More than 8.5 may cause scale and taste problems.

Litmus paper: Test for pH of water.

8. Nutrients:

Phosphorus and nitrogen are both nutrients that occur naturally in water. They appear to be the most important nutrients in the eutrophication of water bodies.

Nutrients are also contained in stream sediments. If these are suspended they can maintain eutrophic (increased plant growth) conditions for many years. Many factors influence how much nutrient in waterways is dissolved (soluble) or attached to particles (particulate). Some of these factors are listed.

· Environmental factors
· Catchment characteristics
· Management practices

9. Phosphorus:

Phosphorus is a mineral nutrient which is essential for all forms of life. It plays a major role in energy transfer processes in the cells of living organisms. Phosphorus has the chemical symbol, P. Phosphorus occurs naturally at low concentrations in surface waters and is an essential part of the food chain. Under these conditions it is derived from processes such as the weathering of rocks and the decom-position of leaf litter or other organic matter.

Phosphorus concentrations very considerably under natural conditions, depending on factors such as local geology, soil types and seasonal conditions. Concentrations can be expected to be much higher when wet weather conditions generate runoff and stream flows are high. It is important to consider stream flow rates and recent weather conditions when interpreting phosphorus results. In natural waters, phosphorus occurs in several different forms. These can be broadly categorised as dissolved forms and particulate forms. In the dissolved form phosphorus occurs as phosphates (phosphates are phosphorus bound to oxygen, e.g. PO4). These may be present as simple `reactive phosphate' or as more complex forms of phosphate. Particulate forms include phosphorus bound to clay minerals suspended in the water (for example, from eroded soil) and biological forms such as algae.

The delicate balance of an ecosystem can be upset when phosphorus concentrations become too high. Resulting problems can include algal blooms, excessive growth of aquatic weeds and loss of species diversity. High concentrations of phosphorus in water bodies are often the result of human activities. Rural and urban runoff, sewage effluent and industrial discharges can all contain large amounts of phosphorus from fertilisers, eroded soil, detergents and plant and animal wastes. Under certain conditions, high phosphorus concentrations in water may come from bottom sediments, where they may have accumulated over many years.

Total P (mg/L) in rivers & streams must be between 0.01 - 0.100. In lakes & reservoirs between 0.005 - 0.050.