Water Monitoring - How To

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Where to sample:

Try to get a sample from the main flow of water and not the edges or where water is held in pools, where there is likely to be more variation from the main body of the river. Unless there is a specific reason to sample water from a different location, the running water in the centre of the river gives the best overall sample.

It is important not to disturb the area that you are going to sample. Stand downstream of where you will take the sample.

How to sample:

The pole is extendable to approx. 2.5 metres. The sample bottle clips into place at the end of the pole. Having more than one bottle available will be helpful, if samples have to be taken away.

Rinse the bottle a few times from water in the river before taking the sample and avoid touching the rim of the bottle to avoid contamination of the sample from anything on the hands.

 

Place the bottle inverted in the body of water and turn it to the horizontal, facing into the flow of water.

 

 

 

 

It is recommended that the bottle be 10-20cm below the surface of the water (depending upon the depth of water at the sampling point).

 

 

 

 

 

 

 

 

 

For badly polluted water, it is a good idea to use rubber/disposable gloves (from a health and safety point of view) if there is any concern over the water quality.

Measuring Water Temperature

To measure temperature, place the probe directly in the main flow of water - only the metal probe (and not the plastic handle) should be submerged. It is also possible to take the temperature measurement from the sample bottle of water instead. However, it is important to do this as soon as the water sample has been obtained.

20 deg C is considered to be the upper desirable limit for water temperature, however the temperature range will vary according to a number of factors - shading, time of day, season, locality, etc.

One of the reasons for monitoring water temperature is because of the sensitivity of living creatures in the river system to changing temperature. Generally, they have adapted to a particular range and if the temperature varies greatly from this, such as several days at higher than normal temperatures, then it puts additional stress on them and their eco-system. For example, willow removal has the potential to increase the water temperature dramatically in an area and thus monitoring is important to assess impact on that locality's eco-system.

Measuring Water Turbidity

This is a measure of the amount of sediment in the water. This may be a problem at certain times of the year, such as after heavy rainfalls or during flooding, where soil is washed into the river system. Fine layers of sediment are deposited as a result which may affect macro-invertebrates living on the bottom of the river. As these are towards the bottom of the food chain, whatever affects them can also have an affect on those creatures that live off of them.

Turbidity Tube

This is in 2 pieces which slot together - make sure that all the figures on the side are in line before starting - and at the bottom of the tube are a series of wiggly lines.

To measure the turbidity of a particular sample of water, pour in water from the sample until the wiggly lines are only just visible when viewed from the top of the tube, looking down through the volume of water.

The measure on the side represents nephelometric turbidity units or NTU's, with a scale from 400 at the bottom of the tube to 7 at the very top. 25 NTU's is considered a reasonable standard - anything greater than that indicates a problem. The relationship between NTU and the depth of tube is an exponential curve (not linear) and this needs to be considered when estimating readings in between the marked scale.

In situations where the water is extremely murky (in the 200-400 NTU range) then the sample can be diluted to help in reading the gauge (the reading would have to be adjusted for the dilution afterwards).

Generally, any staining of the water such as due to tannins, does not affect the turbidity measurement.

It is important to keep the tube clean (can use a bottle brush) as it relies on light entering the tube through the sides to enable correct readings to be taken.

Measuring Conductivity

The conductivity meter measures electrical current between 2 electrodes and is therefore a measure of the salinity of the water. This measure can be useful for indicating if a problem exists upstream, by monitoring for any change.

Conductivity is variable with temperature and the meter therefore has an in-built calibration to adjust the reading for a temperature of 25 deg C. Conductivity is also usually higher with lower water flows.

Conductivity is measured in micro Siemens per centimetre ( S/cm) - 350 S/cm is considered to be an upper limit for acceptability. For the rivers in our catchment (ie Dasher, Minnow and Upper Don) an expected normal range would be 80-130 S/cm.

How to measure Conductivity

The meter can be placed directly into the main flow of the creek or river if it can be easily accessed, otherwise it can be used in the sample bottle.

The meter automatically takes the temperature of the water at the same time in order to compensate for and adjust to 25 deg C. It is important therefore to allow sufficient time for the meter to adjust to the temperature of the river (can be a minute or more especially if it has previously been in the sun or a warm car). Press the HOLD button when you are ready to take a reading, then the meter can then be removed from the water and read.

The bottom of the probe should be kept clean and rinsed with distilled water. Do not touch, wipe clean on clothing or anything similar as this can contaminate and therefore invalidate the reading.

The meter should be checked and re-calibrated at periodic intervals (3 to 6 months) from a solution of known conductivity. Calibration is via 2 buttons inside the top cover.

pH

Ph can vary according to the geology and catchment. Typically a PH between 6.5 and 7.5 is considered a normal range, however in Tasmania in upper catchment areas this may often be higher.

PH can be an indicator of higher nutrient levels (possibly caused by excessive fertiliser use or leaking septic tanks).

PH is often at the lowest during the morning and increases during the day. The daily cycle of vegetation, in particular of photosynthesis is one reason for this.

How to measure pH

A syringe may be helpful to aid in filling the testing tube from water in the sample bottle, both of which should be rinsed out a few times before the reading is taken.

A length of the test paper is inserted in the tube, sufficiently long to fill the length of the tube, leaving the portion touched by the hand outside of the tube. It is important not to handle the paper that is being used for testing PH as contamination of the sample can occur. Nor should the finger be used as a stopper for the same reason.

Pour in the water after the paper is in place and replace the stopper. Place the test tube on the PH chart along the black line and wait for 1 to 5 minutes before reading the nearest PH value. If the colour appears to be within 2 values, then take the higher value (comparisons done by NW Water Watch have indicated that the readings on this scale are slightly on the low side).

General Considerations On Water Monitoring

Standards for water quality within Australia have been set but are very general and can vary according to many factors such as geology and the location. It is very difficult to identify what is considered to be "right" for one particular water system. To set a standard, would need a minimum of 24 readings over a minimum period of 2 years.

The locations chosen for water monitoring need careful consideration as geology and land use play a large part in this equation. For example, while there is ongoing river care work being done - such as willow removal - this will effect change on the water quality and therefore introduce variability in measurements taken to establish a "standard". One option would be to include water monitoring of a near pristine stretch of river to establish a consistent benchmark against which other monitoring could be measured.

A standard recording sheet will assist in proper record keeping and ensure that all relevant data is collected together in a consistent format.

Time of day is important to the water monitoring - measurements should be taken at the same time of day. If temperature was a particular priority for a series of measurements, then sampling at the hottest part of the day would give the best indication of temperature related problems.

When taking measurements, if any reading is well outside of the expected range, then the sampling should be repeated again and even with different equipment, to ensure that there is no error in either the procedure or the equipment.

As well as a regular schedule of monitoring, it would be beneficial to take readings after occasional events such as heavy rainfall, particularly for turbidity checks.

Finally, in order to substantiate the water monitoring done and that the data recorded is viewed as accurate, it is important to keep records of the calibration of all instruments.