Natural contaminants-arsenic: Found in groundwater in parts of West Bengal, Bihar, Uttar Pradesh, and Assam, arsenic poses severe health risks like skin lesions and cancer. Endemic in Rajasthan, Gujarat, and Andhra Pradesh, fluoride contamination can lead to skeletal fluorosis. High iron content in water is common in northeastern states like Assam and parts of Bihar and West Bengal, which affects water taste and causes staining 11.

Human-induced contaminants- industrial pollution: In areas like Delhi, Gujarat, and Tamil Nadu, industrial effluents cause severe water pollution, with heavy metals like lead, mercury, and cadmium posing health hazards. Fertilizers and pesticides contribute to nitrate and phosphate contamination in states like Punjab and Haryana, affecting ground water. Untreated sewage is a major problem in cities like Mumbai, Delhi, and Kolkata, contaminating surface water bodies 12.

Tamil Nadu and Karnataka: Both states face issues with groundwater depletion and contamination from excessive use of fertilizers and pesticides. Urban areas also struggle with wastewater management, affecting surface water quality 13.

Kerala: Generally, water quality is good, but localized issues such as pollution from unregulated waste disposal can impact specific areas. The state’s focus on sustainable water management has shown positive outcomes 14.

Contaminants: Water sources in India often face contamination from industrial discharges, agricultural runoff (pesticides and fertilizers), and microbial pathogens. Natural contaminants like arsenic and fluoride are also prevalent in certain regions 14.

Regional variability: Contamination levels and types vary significantly; for instance, arsenic is a major issue in West Bengal and Assam, while fluoride problems are more common in Rajasthan and Gujarat. Coastal areas may face issues with salinity and so on may serve as an issue 5.

Infrastructure: Many regions suffer from inadequate or outdated infrastructure, which affects the effectiveness of water treatment and distribution systems. Issues include insufficient treatment facilities, leaking pipes, and poor storage conditions 15.

Management: Water management is often hampered by fragmented regulatory frameworks, lack of coordination between agencies, and insufficient data for effective planning. Enhancing management practices involves better regulation, improved data collection, and investment in infrastructure.

pH: The effect of pH on the chemical and biological properties of liquids makes its determination very important. It is one of the most important parameters in water chemistry and is defined as -log [H⁺] and measured as intensity of acidity or alkalinity on a scale ranging from 0-14. If free H+ are more it is expressed acidic (i.e., pH<7), while more OH^- ions is expressed as alkaline (i.e., pH> 7). In natural waters pH is governed by the equilibrium between carbon dioxide/bicarbonate/carbonate ions and ranges between 4.5 and 8.5 although mostly basic. It tends to increase during day largely due to the photosynthetic activity (consumption of carbon- di-oxide) and decreases during night due to respiratory activity. Wastewater and polluted natural waters have pH values lower or higher than 7 based on the nature of the pollutants 12.

Total dissolved solids (TSD): Dissolved solids are solids that are in dissolved state in solution. Waters with high dissolved solids generally are of inferior palatability and may induce an unfavorable physiological reaction in the transient consumer. The difference in the weight of total solids and the total suspended solids expressed in the same units gives the total dissolved solids. The difference in the weights of Total Solids (W1) and Total Suspended Solids (W2) expressed in the same units gives Total Dissolved Solids 12.

Dissolved oxygen (DO): Oxygen dissolved in water is a very important parameter in water analysis as it serves as an indicator of the physical, chemical and biological activities of the water body. The two main sources of dissolved oxygen are diffusion of oxygen from the air and photosynthetic activity. Diffusion of oxygen from the air into water depends on the solubility of oxygen and is influenced by many other factors like water movement, temperature, salinity, etc., Photosynthesis, a biological phenomenon carried out by the autotrophs, depends on the plankton population, light condition, gases, etc., Oxygen is the major limiting factor in water bodies with organic materials. Dissolved oxygen is calculated by many methods 12.

Alkalinity: Alkalinity is the capacity of water to resist acidification. It should not be confused with basicity which is an absolute measurement on the pH scale. Alkalinity is the strength of a buffer solution composed of weak acids and their conjugate bases. Total alkalinity is measured by collecting a water sample, and measuring the amount of acid needed to bring the sample to a pH of 4.2. At this pH all the alkaline compounds in the sample are "used up". The result is reported as milligrams per liter (mg/L) of calcium carbonate 12.

Electrical conductivity (EC): The electrical conductivity (EC) of water is a measure of the ability of a solution to carry or conduct an electrical current. Since the electrical current is carried by ions in solution, the conductivity increases as the concentration of ions increases. Therefore, it is one of the main parameters used to determine the suitability of water for irrigation and firefighting 12.

Turbidity: Turbidity in drinking-water is caused by particulate matter that may be present from source water because of inadequate filtration or from resuspension of sediment in the distribution system. It may also be due to the presence of inorganic particulate matter in some groundwaters or sloughing of biofilm within the distribution system. The appearance of water with a turbidity of less than 5 NTU is usually acceptable to consumers, although this may vary with local circumstances. Particulates can protect microorganisms from the effects of disinfection and can stimulate bacterial growth. In all cases where water is disinfected, the turbidity must be low so that disinfection can be effective. Turbidity is also an important operational parameter in process control and can indicate problems with treatment processes, particularly coagulation/sedimentation and filtration. No health-based guideline value for turbidity has been proposed; ideally, however, median turbidity should be below 0.1 NTU for effective disinfection, and changes in turbidity are an important process control parameter 12.

Pollutant runoff: Industrial activities and agricultural practices contribute to water pollution through runoff 2. Factories often discharge pollutants like heavy metals, chemicals, and sediments into water bodies. Similarly, agricultural expansion increases the use of fertilizers and pesticides, which can leach into waterways, causing nutrient pollution and algal blooms. These blooms can deplete oxygen in water, harming aquatic life 8.

Wastewater discharge: Industrial processes generate wastewater that may contain harmful substances 2. If not properly treated, this wastewater can enter rivers, lakes, and oceans, leading to contamination with toxic compounds and heavy metals 6. This can affect aquatic ecosystems and potentially enter the human food chain 8.

Erosion and sedimentation: Agricultural expansion often involves land clearing and tillage, which increases soil erosion. Eroded soil can be carried into water bodies, leading to sedimentation. High sediment levels can cloud water, reducing light penetration and affecting aquatic plants and animals 8.

Temperature changes: Industrial activities can alter water temperatures through the discharge of heated water or the alteration of natural waterways. Elevated temperatures can disrupt aquatic ecosystems, affecting species that are sensitive to temperature changes 8, 9.

Alteration of water flow: Both industrialization and agriculture can alter natural water flows. Industrial activities may involve damming or redirecting rivers, while agricultural practices can change land use patterns. These changes can affect the natural flow of water, impacting sediment transport and the health of aquatic habitats 9.

Government initiatives: Programs like the National Rural Drinking Water Programme (NRDWP) and the Jal Jeevan Mission focus on improving water access and quality. These initiatives have led to improvements in infrastructure and monitoring systems 25.

Rainwater harvesting: Rainwater harvesting promoted through policies and incentives involves capturing and storing rainwater to supplement traditional water sources and enhance groundwater recharge. 25

Legislation and standards: India has established water quality standards under the Bureau of Indian Standards (BIS) and various regulations, such as the Water Prevention and Control of Pollution Act, 1974. However, enforcement and adherence to these standards can be inconsistent 25.

Monitoring systems: Organizations like the Central Pollution Control Board (CPCB) and State Pollution Control Boards (SPCBs) are responsible for monitoring water quality. They conduct regular assessments, but issues like limited coverage, inadequate data sharing, and delays in reporting can impact effectiveness 26, 27

Technological advances: There has been increased use of remote sensing and data analytics for water quality monitoring. These technologies have improved the precision and efficiency of monitoring but require further scaling and integration 25.

Northern India: States like Uttar Pradesh and Bihar face significant challenges with arsenic and fluoride contamination due to natural geological sources. Studies such as those by the Geological Survey of India have highlighted high levels of these contaminants in groundwater (BGS, 2014).

Southern India: States like Tamil Nadu and Karnataka have issues related to industrial pollution and high nitrate levels from agricultural runoff. Research published in ‘Environmental Monitoring and Assessment’ has documented these concerns Mohan et al., 2021 28.

Urban vs. rural disparities: Urban areas, such as Delhi and Mumbai, often struggle with sanitation-related issues affecting water quality, while rural areas may suffer from inadequate water treatment infrastructure Kumar et al., 2018 23.

Remote Sensing and GIS: These technologies help in monitoring water bodies, assessing pollution sources, and managing water resources.

Water quality sensors and IoT devices: Deployed in various locations for real-time monitoring of parameters such as pH, turbidity, and contaminants.

Advanced treatment technologies: Includes methods like membrane filtration, UV treatment, and advanced oxidation processes to improve water quality.

Enhanced monitoring: Regular and comprehensive water quality assessments are crucial for timely intervention and management.

Infrastructure investment: Increased investment in water infrastructure is needed to address deficiencies and ensure equitable access.

Public awareness: Education and awareness programs can help communities adopt practices that reduce water contamination and improve conservation.

Waterborne diseases 30: Contaminated water is a major cause of diseases like cholera, dysentery, and hepatitis A. The World Health Organization and the Indian Council of Medical Research report that these diseases are prevalent in areas with poor water quality (WHO, 2021; ICMR, 2022)

Chronic health issues: Long-term exposure to contaminants such as arsenic has been linked to cancer, cardiovascular diseases, and developmental issues in children. Research by the Indian Institute of Toxicology Research provides extensive data on these health impacts 31.

Economic impact: Waterborne diseases impose a substantial economic burden on healthcare systems and affect productivity. Studies estimate that poor water quality costs India billions annually in healthcare expenses and lost labor World Bank, 2020 30

Government Programs: Initiatives like the Jal Jeevan Mission aim to provide safe and adequate drinking water through improved infrastructure and management 7.

Community Efforts: Localized efforts, including rainwater harvesting and community-managed water systems, are improving water access and quality in many regions 7.

Technological Advances: New technologies for water purification and monitoring are being introduced to address contamination and ensure safe drinking water.