Report and diagrams

The purpose of writing a report is to, in a credible and accessible way, describe an environmental situation.

Credibility
For the sake of credibility, some formal information is necessary such as:

  • Definition of the sampled objects with type, name and location. Lakes should be indicated with coordinates.
  • Who performed the measurement(s) and why.
  • Time of sampling and analysis. If EU norm is used, state it.
  • How and where the sample(s) were taken.
  • Which method of analysis was used and notes of any deviations. Reference is enough if an established standard method was used.
  • The discussion about the importance of source errors is important, especially if it deviates from the standard.

Disposition
The form of the report should of course be adjusted to the type, intention and the content of the report. The writer must from the beginning ask oneself who can be expected to read the report and adjust it to the needs, knowledge and interest of the reader in mind. Thus, the report is designed in different ways if the intention is to publish it in e.g. a popular magazine, trade magazine or as an internal report.

Accessibility

  • The message will be easier to absorb if it is well presented. Remember that a report of this type is not read from cover to cover like a novel.
  • The reader wants to find out: Whether there is an interesting conclusion.
  • Is there a relevant foundation to base the conclusion on?
  • Was the right thing measured at the right place at the right time and often enough?
  • If the results are reliable.

It is good advice to present the results with the help of maps and diagrams. Look through other reports and lend their ideas. Remember that a small, pure, diagram next to the text is more useful than a complicated one in an appendix.

Total concentration of phosphorous in lake Mjörn 2000. Surface water 2 m.

Section diagram
A common tool for illustrating variations in a selected water mass is drawing section lines (isolines) in a section diagram. A correctly drawn isoline diagram provides a quick understanding of how the measured concentrations vary in a water mass where the samples are taken at many different stations, on several depths at each station. At the same time, the diagram shows the bottom profile of the area.

To construct a section diagram:

  • Draw the sampling section on a landscape A4 paper by marking the distance between the stations on the x-axis and the depth at each station on the negative y-axis. Draw by hand!
  • Draw the bottom profile with the help of a map, nautical chart and the measurements taken during sampling.
  • Draw an isoline diagram for the sampling section e.g. for temperature, salinity, oxygen concentration and phosphate. The isolines must be equidistant, i.e. the interval between isolines are always the same within a diagram. For example, draw isolines for each degree, for each 1 promille salinity, for each 0,5 ml/l of oxygen or phosphate each 0,1 μm. Try to adjust the intervals so that there are about 10 lines in a diagram. Observe that ALL lines must be drawn. Do not skip lines because they are too close to each other or add new ones because they seem too few.
  • Write distinct scales and values on axes and isolines.

TS-diagrams
When interpreting oceanographic observations of e.g. salinity, temperature and oxygen, remember that the variables are not independent from each other. The variables do not occur in any combination. Most waters obtain their characteristic properties near the surface in a certain region. Those water properties are determined by the local climate. When the water later descends towards greater depths, or is transported horizontally along density surfaces, it brings these properties with it. As a result, out of all possible combinations of temperature, salinity and oxygen concentrations, only a few specific combinations will be found.

The properties of a TS-diagram make sure that TS-curves can be used to determine the mixture of water masses. The temperature in a TS-diagram is plotted versus the salinity for each depth at each station. All values for temperature and salinity within the oceans falls within a limited section of a TS-diagram with the exception of oceans with deviant salinity such as the Baltic and the Red Sea.


A TS diagram. All possible mixtures between two water masses (I and II) fall along a straight line in a TS diagram. The proportion of respective water mass in the mixture B can be calculated.