One characteristic of all environmental observations is that the phenomena under consideration are variable in space and time, so that without base-lines, their interpretation is very difficult or even impossible. A base-line comprises observations and records made over long time intervals which permit extraction of reliable design conditions and a meaningful assessment of environmental impacts. Only by reference to base-lines is it possible to decide whether records or observations in hand are typical. A month's record of hourly sea levels at a station provides, at least in theory, a basis for the computation of tidal constants and the prediction of times and heights of tides. Seasonal sea level variations can only be assessed after the period of observation has been extended to one year or, better still, far beyond.

For example, experience with dyke construction in Europe over hundreds of years has shown that the criteria for the determination of their required heights demands regular revision. Modern shipping developments impose ever-increasing demands on draught availability in Australian waters. Gradually, the number of ports which can accommodate tankers, bulk carriers and container ships is decreasing and expensive dredging programmes have to be undertaken. Tide-programmed port operations is at many locations the only solution to this problem.

One of the major access routes to the ports of Eastern Australia passes through Torres Strait, where limited water depths severely restrict the passage of larger ships. Scheduling of shipping after intensive study of the local tides and currents has begun. Variations in the temperature and salinity of sea water determine its specific gravity, and hence the buoyancy of ships, their carrying capacity and draught. In the case of valuable mineral cargo, large sums of money may be involved. When draught margins become very tight, calculations based on monthly average temperature and salinity data may provide welcome checks.

The need to dispose of ever-growing quantities of waste of all kinds points towards the use of the ocean as depository. Beyond the continental shelf lie the abyssal depths where, by present-day knowledge, carefully-packaged materials may be deposited safely. Hence the distances from Australia's major ports to different depths of water are of interest, information which will also become useful if the temperature differential between the deep ocean and its surface is to be exploited as an energy source. Many power stations and chemical factories around Australia's coast employ sea water for cooling. At the design stage for such projects, monthly average temperatures of air and water provide base-lines for calculations.

Tidal energy and its exploitation are associated with large tidal ranges and currents. Tidal ranges and types give a first lead to possible areas where tidal power plants might be constructed. Areas with major inshore current systems can be isolated by harmonic analysis of tidal data. One day, Torres Strait between New Guinea, Bass Strait between Australia and Tasmania, Backstairs Passage and Investigator Strait between South Australia and Kangaroo Island may well become sites for electric generators, operated by tidal currents.

Future planning of townships must include extensive studies of meteorological parameters. New factories, power stations, abattoirs and railway stations will be built in locations, where their emissions and noise will not affect housing.

Australians now travel more frequently and explore further away from familiar areas, as modern means of transport improve. .Different landforms along Australia's coast and popular surf beaches as well as distributions of fish species are of interest.

Solar radiation, air temperature and humidity data are basic to planning of energy saving and efficient means of air conditioning.