Pollutants and Water Management. Группа авторов

36 202 0 NA 20 Minor river basins draining into Myanmar and Bangladesh 31 NA Total 1869.35 690

India is the largest and fastest consumer of groundwater, which fulfills the demands of nearly 80 and 50% of the rural and urban population, respectively (Shankar et al. 2011). The groundwater resources of the country are estimated to be 433 BCM, which is 39% of the total water resources of India (CGWB 2017). The net groundwater availability is 396 BCM, while the available for potential use is 245 BCM. The stage of groundwater development is 61% (CGWB 2017). The Indian state Uttar Pradesh has the highest net annual groundwater availability (~72 BCM) and Delhi has the least (0.29 BCM) (CGWB 2014). Around 85% of the rural population uses groundwater for drinking purposes. The volume of groundwater is inadequate to fulfill the demand of the large population, agricultural practices, rampant industrialization, and urbanization. The overall account of groundwater resources assessment 2004–2017 is presented in Table 1.3.

The per capita average water availability in India is continuously decreasing. India has a huge potential in river and precipitation water (rainfall+snowfall), but currently, not even 50% of the potential is being used. Due to the lack of use of the water potential of river and precipitation, groundwater resources are under tremendous pressure and the water table is continuously increasing in most parts of the country over time.

Table 1.3 Groundwater resources assessment from 2004–2017.

      Source: CGWB (2017).

Year	Annual replenishable groundwater resources (BCM)	Net annual groundwater availability (BCM)	Annual groundwater draft for irrigation, domestic, and industrial uses (BCM)	Stage of groundwater development
2004	433	399	231	58%
2009	431	396	243	61%
2011	433	398	245	62%
2013	447	411	253	62%
2017	432	393	249	63%

1.3 Quality of Available Water Resources in India

Water quality of both available surface and groundwater resources does not satisfy the criteria for potable water in most parts of the country. The Ministry of Jal Shakti report revealed that 70% of water resources in India are polluted by untreated sewage and industrial effluents. The monitoring report of the Central Pollution Control Board (CPCB 2011), based on biological oxygen demand (BOD) and coliform bacteria count, indicated that organic pollution is predominant in aquatic bodies. The groundwater of around 600 districts (i.e. almost one‐third of India) is nonpotable. On the other hand, the Central Groundwater Water Board (CGWB) has reported the presence of contaminants like fluoride, nitrate, arsenic, iron, and other heavy metals in the groundwater of many regions (Table 1.4). As and F⁻ contamination of groundwater is a significant public health risk concern for Indian people. As and F⁻ contamination of groundwater is a health threat for approximately 100 and 66 million Indian people, respectively (Bindal and Singh 2019; Kadam et al. 2020). Other major groundwater contaminants like U, NO₃⁻, Fe, HCO₃⁻, etc. have also been reported in several parts of India. High nitrate content in water is another grave concern in many states (Ministry of Water Resources 2014; Kaur et al. 2019). Apart from governmental organizations, various studies/reports on groundwater and surface water quality have confirmed the presence of other contaminants like uranium, cadmium, lead, copper, sulfate, pesticides, and organic pollutant in the water resources of India (Bacquart et al. 2012; Mittal et al. 2014; Chowdhury et al. 2016; Kumar et al. 2016; Bajwa et al. 2017).

      Both the groundwater and surface water quality are not qualifying criteria for potable water in most parts of the country. Surface water is continuously facing quality issues due to the discharge of sewage and industrial and agricultural wastes. Groundwater in India is affected by heavy metals (As, Fe, Pb, U) and anions (F⁻, NO₃⁻, SO₄²⁻) in different parts of the country.

Table 1.4 Number of states and districts affected by geogenic contamination in groundwater.

      Source: CGWB (2019).

Contaminants	No of affected states	No of affected districts
Arsenic (As)	10	68
Fluoride (F−)	20	276
Nitrate (NO3−)	21	387
Iron (Fe)	24	297

1.4 The Impact of Climate Change on the Quantity of Water Resources

Climate change affects water resources through warming of the atmosphere, alterations in the hydrologic cycle, glacier melting, rising sea levels, and changes in precipitation patterns (amount, timing, and intensity). In the Indian scenario, due to the alteration of monsoon patterns, rainfall becomes more intense and cumbersome, and it is concentrated on fewer rainy days. Climate change influences the quantity of water resources of India through the impact on glaciers, groundwater, and flood events. The probable climate change impacts on water resources of India are depicted through the flow diagram in Figure 1.1.

      1.4.1 Rainfall

Using decade‐wise average rainfall annual data of 116 years of data (1901–2019), no significant trend was observed for annual rainfall on a national basis (Figure 1.2). However, a decreasing trend in annual rainfall was observed across India since the year 2000. This data set is based on more than 2000 rain gauge data spread over the country.

      Climate