River investigators
need to take care as conditions can
be unsafe near or in rivers. Select your sampling stations in
localities that are easy to get to and that represent a range
of habitats and conditions. The stations are established by the
preliminary survey and the monitoring plan.
Each measurement must
be taken from a standard site, and using standardised equipment
to be comparable with earlier and later records.
The measuring stations
need to be recorded as word descriptions and as drawn site plans
so that the long term monitoring programmes, that necessarily
employ different samplers, will have useful comparable data.
Example : "Flow rate measured from Green Park footbridge to Main Highway road bridge with flow indicator floats dropped from the centre of the footbridge (beside the 9th handrail support from the northern side)"
There are a great variety
of data that could be collected from any waterway. These are ones
that are meaningful yet easy to collect. In addition to these,
chemical tests of phosphates and nitrates are important, but require
handling chemicals and/or purchase of expensive equipment. The
instructions for taking phosphate and nitrate measurements accompany
the particular kit used. The tests are arranged in order of ease
of conduct and the long-term value of taking them.
Of all the potential
measurements, photographs of the sampling sites have the greatest
long-term value and cover the widest range of information with
the least amount of effort. It is vital, however, that the photographs
be made so they can be shot again in exactly the same way from
the exact same position in the future. This means recording the
location, angle, time, date, and specific landmarks so anyone
can return to the site in later years and snap a comparable shot.
Each particular site
will need at least three views (video can also be used, but be
sure to make a duplicate tape and store it in a dry moisture-proof
container in a cool location). Take an establishing shot that
shows the whole area, including landmarks that are likely to be
visible in later years. Have a member(s) of the team stand at
the site where the next image(s) will be taken. Then take a medium
range shot of the place where the samples will be taken, again
showing team members actually taking measurements, and indicating
where the close shots will be taken. Finally, take a close shot(s)
of habitats of special interest.
Each photograph should
be identified with the river name, station number, date, photographer,
and any relevant comments. They should then be mounted in the
log book and the information giving detailed descriptions and
drawings of how and where they were taken written next to them.
If video is used, the person taking the video or an assistant
should verbally record information on location and other descriptive
information while the images are being taken.
Some groups may be
able to scan or video-capture the images and put on computer for
a database.
The photographs are
especially important because some aspect of the river might change
that was not measured or even thought of during the survey. They
also can capture changes that are extremely difficult to measure
or describe in words.
Against a paint colour
card, or a series of plain colour transparencies, record the colour
of the stream by card name and number. This can be an important
and easily obtained indicator of river health and is suitable
even for primary school children.
Though people do not
have such sensitive powers of smell as some other mammals, like
dogs, we are still good at distinguishing and recognising different
smells. The smell of a water sample can often serve as a useful
record of its cleanliness or pollutants. Have several members
of the group smell the water and secretly write down a description
of the smell before disclosing what each smell sampler's comments.
The human nose can easily distinguish smells which are oily, peaty,
mouldy, or smell of rotten eggs (marsh gas / hydrogen sulphide)
cow shed waste, sewerage, rotting animal flesh or rotting plant
matter.
Smell descriptions can be a useful clue of stream water quality.
Use either a glass
thermometer or electronic probe.
The bulb of a glass thermometer (ideally in a damage protection sleeve) must be in the water while the thermometer is being read. In small streams this can be done from the bank or by standing in the stream at a set distance from the bank. In rivers it is necessary to take a sample of water using a weighted bucket on a rope and measure the water temperature of the water in the bucket
An electronic temperature probe can be suspended in the water if the lead is long enough, and provides instant readings.
On a 14 point pH scale,
water that is neither acid nor alkaline but is neutral, measures
exactly 7. Measurements lower than 7 are acid (vinegar has a pH
of 3) and higher measurements are alkaline (such as bleach which
has a pH of 13).
Unpolluted stream water
may naturally be slightly acid (measuring between pH 7 and 6)
if it has drained from peaty ground or slightly alkaline (measuring
between pH 7 and 8) if it has run off limestone country. Higher
or lower values are generally caused by pollutants in the water.
Many freshwater creatures
are very sensitive to pH levels.
Acidity / alkalinity
is measured with either a pH meter or pH indicator paper which
changes colour according to the acidity / alkalinity. The electronic
meters are much more sensitive than the paper and are easier to
read. The paper, however, is inexpensive and may be used for preliminary
measurements.
This measure gives
an indication of the amount of suspended solids, natural or artificial
dye substances and / or the density of suspended plant plankton
in the water.
Turbidity is measured
by lowering a weighted marker disc on a graduated line into the
water. The depth at which the disc becomes invisible is recorded.
A standard disc, known
as a "secchi disc", used for these measurements is a
metal plate with alternating quadrants painted black and white.
Secchi disc measurements
give easily comparable measurements of water turbidity for lakes
and the sea where the water is deep but in stream the water is
frequently not deep enough. Where this is the case horizontal
secchi disc measurements can be taken. Fix the disc to a pole
and view it horizontally underwater through a simple, single mirror
periscope. Move the disc away from the observer until it can no
longer be seen and record the exact distance.
In summer when evaporationfrom the land exceeds rainfall there is little run-off and river
levels are low.
In winter when rainfall
is high and the ground is saturated run-off is rapid and river
levels rise quickly after heavy rain.
Well managed water
catchments which retain good amounts of forest cover on the land
have less extreme variation between summer lows and winter highs
and are less subject to sudden large rises in water level because
the bush acts like a sponge to delay run-off. Water catchments
which have land stripped bare of forest for agriculture, horticulture
or industrial and residential development cannot delay run-off
and experience flooding in winter and dry streams in summer.
Water level is a good
measure of catchment stability. It can be measured against a water
level staff fixed to a bridge support in a position where it is
always easily read.
Make it from tanalised 100 mm wide board painted white with black graduations.
Flow rates vary enormously
along a river depending on volume of water running down and the
depth and width of the channel at any particular point.
Flow rate is also variable
across a river. On a straight stretch it is greatest in the deepest
part, usually in the middle and least near the banks on each side.
On a bend it is slowest on the inside of a bend and fastest on
the outside. This often leads to the outer bend being cut away
and to sediment collecting on the inner side of the bend.
Electronic flow meters
can be used to measure flow rate but are expensive, need to be
mounted or held on a boom in a standard manner to give consistent
and useful measurements.
Surface flow measurements
can be made by dropping floats into the river and timing how long
it takes for them to travel over a standard measured distance.
This may be from one bridge to the next or it may involve teamwork
with one person dropping the float from a bridge and another,
down stream recording when it passed between "Ideally these
posts should be natural (eg. two trees) or artificial but permanent
(eg. two fence posts) but it may be necessary to used two marker
poles fixed in each bank specifically for the purpose. Such poles
are more likely to be vandalised, damaged by cattle or washed
away during floods and are therefore less satisfactory.
The floats must be
clearly visible. Ideally they should be recoverable especially
if not made from natural materials.
Oranges, lemons or
grapefruit make very good flow recorder floats. They are very
easily seen and will eventually decay harmlessly if lost downstream.
They also have the advantage of being only slightly less dense
than water so they float up to the water surface and not on top
of it. Floats that are very buoyant (like empty plastic bottles)
can be subject to windage (= being blown along, backwards or across
the river by wind) which reduces the accuracy of the measurements.
If plastic bottles
are used as flow indicators they should be partly filled with
water so that they float in the water like an orange or a cormorant
rather than on it like a boat or a duck.
Tethered floats.
A practical method of using plastic bottle flow measuring floatsis to tie them to fine fishing line that is loosely coiled at
the drop station on the bridge or bank. When a tethered float
has travelled a measured distance it can be hauled back for repeat
runs by different members of the group giving opportunity for
all to drop, watch the finish, time the run and record the results.
Having the float on a line also allows it to be dropped precisely
at the same spot on each trial by lowering it close to the water
and releasing on the timers call. A flag marshal down stream signals
the completion of each run for the timer and float retriever.
The amount of light
passing down into a stream greatly affects the wildlife found
there. Animal life flourishes where the water is overhung by leafy
trees and becomes scarce where riverside vegetation has been removed
and the banks "cleaned up".
This partly because
in small streams or in slow moving shallow water at the edges
of large rivers, the water can become much hotter on sunny days.
Warm water can hold much less dissolved oxygen than cold water.
The amount of oxygen that can be dissolved in water is halved
when the water is warmed by 10 C.
Some cold blooded animals
become more active as temperature rises and therefore need more
oxygen. In slow moving water oxygen replacement through the surface
may be insufficient on warm days and the aquatic wild life may
suffocate.
High light levels also
make small invertebrate animals much more visible for predators
like wading birds and certain fish.
Baseline light levels
should be measured right across a river from bank to bank and
plotted against distance from the banks. A simple photographic
light meter can be used, held just above water level as it is
carried across the stream. For fast flowing streams the measurer
should, for safety, be loose shackled to a rope stretched tightly
across the river. The rope should be boldly marked off at one
metre intervals with permanent pen or paint marks and light readings
called out to a recorder on the bank.
If bank vegetation
changes from one year to another - due to bank bush being removed
or to a bare bank being planted with trees - changes should be
expected to the river's wildlife.
Biological Indicators
Freshwater plants and animals are an excellent indication of the health of a waterway. They are a more reliable index of water health than physical parameters because while physical parameters can change rapidly the animal population must remain there for some time, thus indicating the long term physical conditions.
Macrophytes - Large
plantsTo appreciate the diversity and learn some of the names of pond and river plants, it is useful to make a class collection. This can be stored and presented as a herbarium collection or ideally for younger scientists as a large wall poster in which the specimens are arranged in appropriate sites, depths and relationships on a sectional background drawing of a stream or pond.
Water plants make excellent
biological indicators. The New Zealand Ministry for the Environment
has published water quality quidelines with colour photographs
of algal conditions that indicate various stages of waterway pollution.
Copies of these quidelines are available from the ministry at
a small cost.
Mounting water plants
for reference and display. As most water plants are soft and
flexible they are easy to layout, dry and display.
Microscopic plants.
Rivers, streams, and
lakes are filled with microscopic plants. When rivers receive
too many nutrients, these tiny plants bloom in tremendous numbers
and colour the water a vivid green or brown with their small bodies.
Using them as an index of water quality is difficult without a
quality microscope and some specialised equipment. There are two
ways to collect and measure microscopic water plants.
Diatometers are simply
microscope slides placed in the water for a day or two and then
removed and examined under a microscope to see what has settled
on them. A diatometer is easy to build.
Cut a short piece of
plastic pipe (18 to 25-mm in diameter, about 300-mm long) about
half-way through in a series of six horizontal notches. This is
quite easy to do with a small saw. Bend the pipe back, away from
the cuts, to open the slots and put the microscope slides into
the notches. (The slides should be numbered with a felt tipped
pen so you can identify them later). When the pipe is released,
the plastic grips the slides, providing a horizontal rack. Carry
the pipe and numbered slides to the waterway to be investigated
and assemble the diatometer just before placing it in the water.
Push one end of the pipe into the sediment of the stream so the
rack of slides is below the water but above the sediment. Record
the exact time and location of placement, along with the numbers
on the microscope slides. You might want to have three or four
diatometers to place in different habitats of the waterway. After
two to three days, the slides will have a thin settlement of plankton
that can be looked at under a microscope.
Diatometers are highly
quantitative and it is easy to repeat the measurements to compare
conditions at different times of the year or under different circumstances.
You can do two different measurements from this collection. Identification
of the diatoms or other algae is one measurement. This requires
having an identification manual.
Secondly, and perhaps
easier, is to count the number of cells within a specified area.
Ideally, you might be able to get a measuring grid reticule from
a hospital of the type used to count blood cells under a microscope
(this might be difficult as these days blood counts are usually
done electronically). Otherwise you could simple pick a suitable
magnification and count the cells within one field of view, then
shift the position of the slide and count again. Count at least
10 views on each slide and average the results to obtain an average
number of cells per view. Be sure to record the exact magnification
of the objective and eyepiece used. If possible, directly measure
the size of the field of view using a standard grid and record
the data as number of cells per square millimeter.
Freshwater animals
are numerous but secretive. Most are difficult to see in their
natural environment and many are equally difficult to catch. Some
can be found clinging to boulders - usually the undersides and
some are fairly easy to trap in nets if they can be disturbed.
Many stretches of swiftly flowing streams have rather small amounts
of wildlife that is easily trapped. Some animals (birds and fish)
are only seen but not caught but still need to be recorded.
Wildlife go to rivers
and creeks to drink. There are many other animals that make their
homes on river banks or in rivers. You will never see the larger
creatures unless you make a special effort. From the resident's
point of view, human beings are the most dangerous, wanton killers
imaginable. Almost every wild creature on the planet - even tiny
birds - flee at the first sight or sound of human beings. But
they can get to know individual people and eventually learn to
trust them.
Just as a pet dog or
cat will let you approach, wild birds and other creatures will
gain confidence and trust around individual people who don't make
loud noises or act aggressively. Sometimes, if one or two people
sit quietly - without talking - and observe, the creatures will
begin to go back to their own affairs.
People who do wildlife
photography, especially of birds, often build a "blind"
where they can sit out of sight of the wildlife. Sometimes they
will have a friend or two enter the blind with them. The friend(s)
then leave the photographer alone in the blind, so the birds -
which are watching very closely - will think the people have left.
They are not good at counting.
Bacterial counts, especially
of fecal Coliform, are an important measurement of the health
of a waterway. Sampling for fecal Coliform bacteria requires special
equipment and sampling techniques. Details of taking these measurements
are available from the manufacturer of kits for measuring and
culturing bacteria. There is a new system for measuring sewage
pollution using an enzyme reaction test that makes the process
much simpler.
In shallow slow flowing
creeks where it is safe to stand in gumboots in calf deep water,
animals can usually be disturbed from the bottom by gently shuffling
about in the gravel and mud.
Hold a trap net about
half a metre to a metre down stream from where the bottom is being
disturbed to trap small creatures carried away by the current.
The net of tough nylon
should have a fine 2 mm mesh size and be fixed to a sturdy frame
of aluminium strip. This can be bent easily to shape and if required
can be reshaped in the field so the opening is flat at the bottom
or rounded to suit the shape of the bottom.
Items trapped and washed
down into the end of the net are released by turning the end inside
out in a white plastic tray containing a little water. Shake the
net gently in the water to release the animals.
(An ice cream carton can be used for a tray but a larger, shallower
tray is better).
Using fingers or tweezers
small animals can be picked off stones and submerged or bankside
logs or along clean firm stony stream beds. These are such creatures
as small snails (especially Potamopyrgus antipodarum ) the fresh
water limpet Latia neritoides and caddis fly larvae in their various
cases.
A variety of trapscan be used to catch elusive river critters. A small collection
of river rocks, placed in a chicken-wire basket will become a
home for lots of small insects and worms if left in the water
for a few weeks. Tie the basket to a length of fishing line so
you can retrieve it. The most difficult part of this method is
to be sure where you left it so you can find it again. The second
most difficult part is hiding it well enough that someone else
will not come along and disturb it out of curiosity.
Koura,
or freshwater crayfish, are easy to trap and can be a useful biological
indicator.
From a standard identification
sheet or book sort and count the different animals collected.
It is important that all members of the class or group are given
plenty of opportunity to inspect the animals caught and to relate
them to drawings on ID sheets. They are then more likely to be
familiar with what was in the stream when the exercise is discussed
later.
Establishing a reliable
database is dependent on accurate identification. A method may
be needed to verify that participants are correctly identifying
and counting their catches. Small insect larvae are frequently
difficult for experienced students to separate and identify. It
may be necessary to limit the observed creatures to general categories
in the first stages of the investigation.
