1. Introduction

The monitoring of chemical and/or biological parameters is required by a range of environmental legislation to assess the state of different compartments (e.g. water, soil, air), the risks associated with different pressures (e.g. diffuse or point-source pollution), to track the effectiveness of action programs (control or restoration), and/or to study trends. In this context, monitoring programs are an indispensable element of any water management system (figure 1 ).