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Adequate water resource management is essential for fulfilling ecosystem and human needs. Nainital Lake is a popular lake in Uttarakhand State in India, attracting lakhs of tourists annually. Locals also use the lake water for domestic purposes and irrigation. The increasing impact of climate change and over-exploration of water from lakes make their regular monitoring key to implementing effective conservation measures and preventing substantial degradation. In this study, dynamic change in the water spread area of Nainital Lake from 2001 to 2018 has been investigated using the multiband rationing indices, namely normalized difference water index (NDWI), modified normalized difference water index (MNDWI), and water ratio index (WRI). The model has been developed in QGIS 3.4 software. A physical GPS survey of the lake was conducted to check the accuracy of these indices. Furthermore, to determine the trend in water surface area for a studied period, a non-parametric Mann–Kendall test was used. San’s slope estimator test determined the magnitude of the trend and total percentage change. The result of the physical survey shows that NDWI was the best method, with an accuracy of 96.94%. Hence, the lake water spread area trend is determined based on calculated NDWI values. The lake water spread area significantly decreased from March to June and July to October at a 5% significance level. The maximum decrease in water spread area has been determined from March to June (7.7%), which was followed by the period July to October (4.67%) and then November to February (2.79%). The study results show that the lake’s water spread area decreased sharply for the analyzed period. The study might be helpful for the government, policymakers, and water experts to make plans for reclaiming and restoring Nainital Lake. This study is very helpful in states such as Uttarakhand, where physical mapping is not possible every time due to its tough topography and climate conditions.

Irrigation tanks are perceived to contribute significantly to irrigation, agricultural production, and environmental sustainability. Realizing the significance of this perception, this paper analyses why farmers should invest in wells when irrigation tanks underperform. If the availability of water in tanks is poor, tanks perform poorly, and water becomes scarce. Farmers respond by increasing the number of private wells. If farmers do not invest, they stand to forgo an income of INR 12,430-12,775 per hectare per year. Therefore, farmers should be helped to construct wells.

Fertilizers may leach through the vadose zone and eventually reach groundwater in agriculturally intensive areas. Thus, the main focus of this study was to investigate Nitrate-N load and vulnerability of groundwater resources using in-situ observed hydrogeological data. Soil water flow and contaminant transport equation was numerically simulated using HYDRUS 1D for constant head and atmospheric top boundary conditions. Sub-surface materials were distributed based on the lithologs of the target area. Observed water table locations were considered as bottom boundary condition to respective numerical domain. The time taken by Nitrate-N to reach groundwater table was considered to estimate vulnerability index. The results show that Nitrate-N load is higher in constant head boundary conditions than atmospheric boundary conditions. The eastern part of the study area shows high vulnerability than northern part followed by western part. In-situ observed nitrate concentrations were well matched with simulated results. The high vulnerability in eastern and northern part is due to alluvial sandy lithologs and very shallow groundwater table. These findings are in line with the observed low water table depths, less runoff, and higher hydraulic conductivity of the vadose zone material in these area. In western part, forest cover dominated land use causes low pollution vulnerabilities to groundwater resources. This study may help to frame agricultural and soil-water conservation practices with more sustainable remedial techniques.