Introduction to water investigations

Arrangement of a water examination

This text describes general considerations for water investigations, not specifically for VIRTUE. 

First, decide what needs to be investigated. E.g., is it an urgent investigation to find out what has killed the fish? Is it an inventory of the current condition in the acidified area? A study of the causes of bottom death in a fjord? Or, is the purpose to see if the actions that have been taken in agriculture to decrease the nutrition leakage have any effects on the water? Furthermore, decide the optimal selection of variables. The amount of sampling points that are necessary and how often the samples need to be taken. Figure out what kind of equipment will be needed and how much time and money are available, and thereafter adjusting the method after what can be afforded.

One important balance is that between the number of sampling occasions and the number of sampling points. If e.g. the variables vary greatly over the seasons, such as nutrients, more sampling occasions will be needed in order to do a budget calculation with statistic precision. Many times, it is possible to combine so that a few smaller sampling points are sampled several times a year and an inventory of bigger sampling points is performed yearly. Many liming surveillance programs are arranged this way.

If the goal for a measurement program mainly is to determine the transport and spread of a contaminant or the areas lead the capacity, time and money are better spent on determining the water turnover as accurately as possible rather than making intense efforts to measure the water quality.

The properties of a specific water area are often determined by one or a few special factor(s), such as depth conditions, tributaries or stratification. Start with figuring out which/what factor(s) that are crucial for the area. Salinity and oxygen often characterise coastal sea and tells us how the area is coping.

Before conducting an investigation program, there are a couple of points to think over so that the results will be as useful as possible. 

Which variables?

  • What will the results be used for?
  • Official requirements (control programs etc.)
  • Economics
  • What samples have been taken previously?
  • What support variables exists?
  • What factors characterises the area?


  • What will the results be used for?
  • What variables will be measured?
  • Who will use the results?
  • Where have samples been taken previously?

How often?

  • What will the results be used for? (statistical evaluation etc.)
  • Official requirements (control programs etc.)
  • Economics
  • How often were previous samples taken?
  • Demands of quick results?
  • Will the measurements be followed up in the future?