ABSTRACT
The selection of variables for any water quality assessment programme depends upon the objectives of the programme. Appropriate selection of variables will help the objectives to be met, efficiently and in the most cost effective way. This chapter provides information which helps the appropriate selection of variables. It discusses each variable with respect to its origins, sources, behaviour and transformations in the aquatic system, the observed ranges in natural and polluted freshwaters, the role of the variable in assessment programmes, and any special handling or treatment of samples that is required. The chapter suggests some combinations of variables which might be used for different water quality assessment purposes. These can be used as a basis for developing individual programmes. The chapter presents a summary of the principal analytical methods for major variables. It also presents a summary of pre-treatment and storage of samples for different analyses.
