Agriculture is a major sector in India which contributes around 14% of country's gross domestic product (GDP). Being an agriculture-based country, good quality of water for irrigation has been a prime requisite. Highly growing population and accelerated industrial development are causing anthropogenic pollution to both surface and groundwater on one side and geogenic contamination like arsenic, fluoride, high dissolved solids, sodicity, and iron in groundwater on other side. As a result, ensuring safe water quality for the irrigation has become a major challenge to both the central and state governments. The present irrigation water quality standards being followed in India have been set by the Central Pollution Control Board (CPCB) and Central Ground Water Board (CGWB) in the year 2000. These standards are solely based on four parameters, namely electrical conductivity, sodium percentage, sodium absorption ratio, and residual sodium carbonate, which are quite subjective and many times are not capable to exactly decide the quality of irrigation water particularly when there are large variations in the source water quality. Therefore, in the present paper, an indices-based approach is presented for categorization of irrigation water quality. These indices are mathematical equations that transform water quality data into a numeric value, which describes the quality of irrigation water. The proposed irrigation water quality index (IWQI), which is based on 12 parameters, classifies the water into five categories, viz. excellent, good, medium, bad, and very bad in the same manner as given by the CPCB and CGWB. In order to give proper rating to various parameters of the index, weights are computed using Saaty's analytic hierarchy process (AHP)-based multiple criteria decision analysis (MCDA) approach. This approach minimizes the subjectivity in assessment of weights and improves understanding of water quality issues by generating an overall index to describe the status of water quality. The proposed index will be beneficial for the water management authorities in ensuring safe water to the stakeholders.

Water quality indices are mathematical equations that transform water quality data into a particular number which describe the status of water. A number of water quality indices have been developed by various researchers for categorizing the water quality for different uses. These indices are developed based on classification criteria, sub-indices, and aggregation function. In the present study, a generalized Composite Water Quality Index (CWQI) is developed to classify the water into five categories, viz excellent, good, fair, poor, and polluted. For this purpose, the concentration ranges have been categorized on the basis of the Indian Standards (IS) and Central Pollution Control Board (CPCB) standards and considering International standards of World Health Organization (WHO) and European Commission (EC). Twenty-five water quality parameters are selected based on the social and environmental impacts, and weights are computed using the Saaty's Analytic Hierarchy Process (AHP) Multiple Criteria Decision Analysis (MCDA) tool. These parameters are selected such that the same indices can be used to assess the quality of both surface and ground water. The computed weights minimize the subjectivity in assigning the parameter weights. The proposed index improves understanding of water quality issues by integrating complex data and generates a score which describes the status of water quality. The index will be very useful for the water management authorities to maintain good health of surface water resources.

A water quality index (WQI) is a tool which numerically summarizes the information from multiple water quality parameters into a single value and this information can be used to assess spatial and temporal variations in overall water quality. However, these indices are time and region specific and may be influenced by local factors. In the present study, water quality index has been worked out to assess the spatial and temporal variation of groundwater quality status for future planning and management of North Goa. Data of 19 groundwater samples were collected in the year 2005 during January, March and April, are used for the analysis. The Water Quality Index has been computed using four parameters viz. pH, Total Dissolved Solids, Total Hardness and Chloride. The WQI results show that the overall water quality class is 'good' and water is acceptable for domestic use.

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Yamuna river water quality has been deteriorated from Delhi onwards mainly in Agra and Mathura areas of Uttar Pradesh due to discharge of large quantities of untreated or partially treated wastewater into the river. Groundwater is also saline in these areas. Thus, the resultant poor water quality could worsen the problems of portable water supply to rapidly growing population of these areas. Groundwater and river water respectively is the main drinking water source in Mathura and Agra. Therefore, there is need to investigate the quality of bankside groundwater and surface water in Mathura and Agra as potential source of drinking water and also to assess the interaction between Yamuna river and groundwater. Keeping in view the above points, present study was carried out to assess river Yamuna and-groundwater interaction using isotope in the Agra and Mathura area of Uttar Pradesh, India. Samples of river and groundwater were collected from hand pumps/bore wells along the periphery of the Yamuna River. Analyses of the electrical conductivity (EC), temperature and isotopic composition (δD) demonstrated that the groundwater is highly influenced by the river Yamuna. Groundwater containing seepage component is indicated by low temperature, low EC and depleted isotopic (δD) composition. The influence of river on groundwater is found to decrease with the increasing distance from the river. The contribution of river water to the groundwater is more in Mathura as compared to Agra.