Book excerpt: The main purpose of water quality monitoring may be seen as evaluating water quality conformity against water quality standards, especially for administrative purposes. Moreover, water quality monitoring data can be applied to estimate and evaluate pollutant loads in rivers. Chronological water quality fluctuations and vertical water quality profiles in water bodies are also important when taking into account the effects of land-based pollutants on coastal sea and estuary water quality. This book discusses the relationships between pollutant discharge and water quality, taking into account urban development and indicators like the pollutant load per capita flowing into the water body (PLCwb), an index used to evaluate the contribution of municipal wastewater pollutant discharge to pollutant loads flowing into ambient water bodies such as coastal zones, bays and lakes.