**4. Water quality monitoring and management**

Water quality monitoring is a basic tool for managing freshwater resources. Monitoring water quality in a river and its status gives clues for the health of the river and also the health of the river basin. River basin approach has been introduced to monitor and manage water quality in all most all countries in the world [13]. Therefore, this book introduces the section on water quality monitoring and management under the river basin.

There are many ways to monitor water quality. The conventional method of assessing water quality is evaluating the physical, chemical, esthetic, and biological properties of water. However, biological measurements of the abundance of animal life and aquatic plant and the use of bioanalytics, use of remote sensing, and IoT are becoming popular. Biomonitoring is considered more efficient and effective than traditional methods. It is widely used worldwide to monitor river pollution as bioindicators are sensitive enough to detect environmental change [14]. Biomonitoring is of two types active and passive. Active biomonitoring uses organisms under controlled conditions into the site to be monitored, whereas passive biomonitoring uses organisms, organism associations, and parts of organisms that are a natural component of the ecosystem and appear there spontaneously [15]. Aquatic insects can be used as bioindicators in aquatic ecosystems. Each aquatic insect has a different tolerance value to environmental conditions in which only a few species can survive in polluted ecosystems. One chapter discusses the use of aquatic insects to assess water quality along with some physical and chemical parameters. In addition to aquatic insects, algal communities are robust indicators of the physical, chemical, and biological changes of water induced by environmental flows which alter

nutrient concentration, salinity, and alkalinity. One chapter in the book offers a comprehensive review of the monitoring conditions of rivers and streams using biological indices with an emphasis on algae. However, monitoring the point source pollution, such as effluent disposal from the industry to a waterbody, can be done efficiently using the conventional evaluation technique for the chemical, physical, and biological status of the water. One another chapter in this section deals with the pollution evaluation of industrial effluents from consolidated breweries using conventional approaches.

Improving access to clean water for drinking, bathing, and irrigation as per the standard is a top priority in all countries. The nature-based solution that leverages ecosystem functions is gaining more attention and is widely used to manage water quality [16]. The watershed management approach considers the nature-based concepts where forests, wetlands, and grasslands, as well as soils and crops, are managed properly. These well-managed watersheds provide high-value green infrastructure for enhancing source water protection.
