Preface

The current knowledge about the water cycle at the river basin level is relatively incomplete due to random and complex processes that are difficult to measure or estimate in their integrity. Moreover, hydrological and water quality data for all rivers that make up a river network are scattered, discontinuous, or incomplete, which makes it difficult to assess river flow information for water resources management, flood risk, or pollutants' load assessment. Water quality is influenced by the characteristics of the river basin, such as land use and its geology, seasonal influence, river discharge, and chemical properties of tributary waters. Important factors in the quantitative balance of surface waters are precipitations and snowmelt with quantitative and qualitative influences, mainly due to the surface transport of germs, suspensions, pesticides, and fertilizers. Water quality parameters include a broad range of physicochemical and biological properties. Overall, there are six main indicators widely monitored to characterize the status of waters: water temperature, dissolved oxygen, pH, turbidity, nitrate chemicals, and bioindicators.

Consequently, despite the numerous approaches existing in the literature regarding water quality issues, there is a need to continuously monitor and assess the evolution of water resources and to find and implement new solutions for proper water management and protection. Thus, this book offers a wide image of the factors and impacts influencing water quality worldwide. It discusses the use of new analytical and monitoring methods and novel technologies for decontamination and protection of polluted waters.

The book is organized into three sections containing ten chapters.

The first section, "Monitoring and Assessment of Water Quality," contains four chapters that underline the need for monitoring water quality based on a series of relevant parameters and proper data analysis to avoid water shortages and food insecurity in the analyzed basins and areas by reducing the presence of contaminants.

The second section, "Factors of Water Quality Degradation," discusses the significant pressures and the impact of human activities on the state of surface waters and groundwater. The three chapters in this section discuss interesting aspects regarding the degradation and improvement of urban rivers, the effects of illegal artisanal gold mining operations, and the mobility of heavy metals in aquatic environments. Thus, a milestone is defined to start new research on excessive sediment and erosion mixed with microplastics, pathogens, toxic elements and compounds, and nutrients discharged in waters.

The third section, "Methods for Water Quality Improvement," contains three chapters that point out the implications of proper decontamination methods for various polluted waters based on bio-polyelectrolytes, natural products including agricultural waste, and other waste materials.

Water quality is a key environmental concern at the global level, having a significant role in promoting socioeconomic development but with the need of maintaining

viable and functional ecosystems. The protection of water quality requires improved monitoring and assessment methods included in reliable watershed management plans.

I would like to thank Dr. Petre Bretcan for the useful discussions and recommendations regarding various aspects related to water quality presented in this book. I am also grateful to Sara Debeuc and Anja Filipovic at IntechOpen for their professional support throughout the publication process.

> **Daniel Dunea** Department of Environmental Engineering, Valahia University of Târgoviște, Târgoviște, Romania

Section 1
