Pollutants and Water Management. Группа авторов

and the socio‐economy of the inhabiting population. However, this wetland still only has a limited number of scientific studies, which is an indication that it has not been given much attention by the scientific community for its proper monitoring and conservation. Therefore, this work was conducted to identify the key factors that adversely affect the wetland, as well as human health and the societal status of this area. This study is also aimed to find solutions for the identified factors.

2.2 Materials and Method

      2.2.1 Study Area

The study was carried out in Kanwar wetland (Figure 2.4), one of the largest inland freshwater lakes in the Indo‐Gangetic biogeographic zone. It was formed naturally by the meandering of the Burhi Gandak River in the geologic past (Rodger and Panwar 1988a, b). It was declared as a Wildlife Sanctuary in 1989 by the Ministry of Environment and Forest, Government of India. Geographically, it is located between (25°35^′00″ – 25°40^′00″ N and 86°05^′00^″ – 86°10^′00″ E) and covering an area of 6311 ha. It is classified as wetland type 19, because of the type of wetland habitat present, i.e. paddies (Scott 1989). It is a flat terrain with an average elevation of 44 m above mean sea level. This area is found in the tropical wet zone of India (Sarthi and Singh 2013), and temperature varies in a range of 7–38 °C. It mainly experiences four distinct seasons of winter (December–February), summer (March–May), monsoon (June–August), and post‐monsoon (September–November). The average annual rainfall is 1100 mm mainly received from the southwest monsoon between July to September. It often gets recharged either from rainwater or excess water from the river Burhi Gandak during the monsoon period. It was identified as a lake of national importance and included in the National Wetland Conservation Programme by the Ministry of Environment and Forest, Government of India in 2009.

Figure 2.4 A map of (a) India, (b) Bihar, and (c) study area with sampling locations.

      The wetland supports a large variety of micro‐ and macro‐flora and fauna in and around its boundary. The vegetation around the wetland area is characterized by tropical dry mixed forest, tropical seasonal swamp forests, and wooded grasslands (Champion and Seth 1968). The major tree species Peepal (Ficus religiosa), Indian Banyan (Ficus benghalensis), Cluster fig (Ficus racemosa), White fig (Ficus infectoria), Babool (Acacia nilotica), Sissoo (Dalbergia sissoo), Arjuna (Terminalia arjuna), and so on support the shoreline and raised mounds or rahies. Common reed (Phragmites karka), water hyacinth (Eichhornia crassipes), lotus (Nelumbo nucifera), Hydrilla (Hydrilla verticillata), and Sesbania species are the most prominent aquatic species of this wetland (Rakshi and Sanghi 1996).

      The wetland is an important waterfowl habitat of different residential (107 species) and migratory (59 species) birds (Ramakrishna et al. 2002). The white‐rumped vulture (Gyps bengalensis), the Indian vulture (Gyps indicus), the greater spotted eagle (Aquila clanga), and the Sarus crane (Grus antigone) are the most threatened bird species in this lake (Collar 2005). Different wild animals like blue bulls (Boselaphus tragocamelus), bats (Chiroptera), squirrels (Sciuridae), and jackals are often visible in the late monsoon seasons (Rakshi and Sanghi 1996).

      More than 16 hamlets are situated around the wetland. These hamlets were less populated and mainly dominated by the local community during the late 1980s. They were completely dependent on the lake for fishing, bird capture, fuelwood, livestock grazing, and wetland paddy cultivation for their livelihoods (Rodger and Panwar 1988a; Rakshi and Sanghi 1996). Nowadays, the population has drastically increased because of the movement of other communities. During the late monsoon season, when the water recedes, the people cultivate different crops on the open areas of the wetland. The four crop seasons are Kharif (August–November), Rabi (November–February), Aghani, and Garma (March–May). Major crops such as paddy, sugarcane, wheat, maize, pulses, and different vegetables are commonly cultivated. In addition, a practice of double cropping pattern is also common.

      2.2.2 Data Collection

First, secondary data including toposheets from the Survey of India (SOI), Patna branch, population data of 2001 and 2011 from the census report, the Government of India website, and rainfall and temperature data from the European Centre for Medium‐Range Weather Forecasts were collected for this area.

      The LULC change dynamics were estimated by using Landsat imageries and geographic information system (GIS) software. The samples of water and soil/sediments were collected from 14 different locations (Figure 2.4). The samples of aquatic species of flora and fauna, and the cultivated vegetation species, especially crops, were also collected and estimated for the general parameters and the content of specific contaminants, i.e. heavy metals, by following APHA procedures (APHA 2005). Further, the water quality index (WQI) and the health risk index (HRI) was calculated by adopting standard procedures. For WQI, the modified weighted arithmetic mean procedures were used (Shah and Joshi 2017; Singh et al. 2020). The HRI was calculated by using the formula given by Khan et al. (2010).

      Where,

      Further, with the help of toposheets, ten villages were identified in close vicinity of the wetland, which were also documented in the Gazette of Bihar, while this wetland was declared as a wildlife sanctuary. These villages are Manjhaul, Jaimangalpur, Jaimangalgarh, Ekamba, Parora, Narayanpiper, Sakra, Rajaur, Kanausi, and Manikpur. A rapid survey was conducted among these villages from June 2013 to August 2013 to understand the overall wetland resource use pattern and its dynamics, to identify different resource user groups (RUGs) and their dependency and socio‐economic status, and the attitude for the conservation of this wetland. The objective‐oriented questionnaire was prepared after the rapid survey, with a total of 47 key questions, which were open‐ended (with options), closed‐ended (yes/no), and suggestive types. Later, an intensive survey was conducted through a specific questionnaire among the identified RUGs in these villages from July 2015 to July 2017. A total of 147 households were interviewed to gather information on various aspects. In addition, the local representatives of government agencies, leaders, social workers, and regular visitors were also interviewed.

2.3 Results

      2.3.1 Climatic Variation

The monthly average rainfall and temperature over the study area are shown in Figures 2.5 and 2.6, respectively. The average monthly rainfall was 107.25 mm in 2012, 128.44 mm in 2013, 92.61 mm in 2014, 102.16 mm in 2015, and 101.24 mm in 2016, while the average monthly temperatures for the years 2013, 2014, 2015, and 2016 were 20.1, 20, 20.1, 20.6, and 20.94 °C, respectively.

Figure 2.5 Monthly rainfall (mm) variations.

Figure