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Spring constitutes one of the primary water resources in some parts of the world, such as the Indian Himalayas. However, these remain imperfectly surveyed and delineated far and wide in most areas worldwide. Due to natural and anthropogenic factors, the springs are under great threat. All over the globe, springs have left as data deficit and have not relatively gained considerable attention in comparison to other systems like rivers, streams, lakes, and wetlands. This is also true for India, where most of the research is usually centered on groundwater, rivers, lakes and wetlands. This manuscript presents an overview of studies carried out on various themes of spring water systems, such as characteristics, classification schemes, and different empirical and analytical methods at international and national levels. A comprehensive overview of the literature identified the demand for an integrated approach of different empirical and analytical methods to strengthen the understanding of spring hydrology in the Himalayan region and elsewhere. Research highlights: Springwater system protection needs a forewarning of imminent contamination and thus, an integrated approach of conceptual and management-related groundwater models should be developed in India on a large scale. Empirical and analytical approaches should be used to attain an inclusive understanding of springwater hydrology and water quality. Himalayan springs should be studied considering the current updated classification schemes to obtain a comprehensive understanding of them. Monitoring of data and simulation models should be developed to establish an integrated and comprehensive understanding of Himalayan spring hydrogeology and hydrology. [ABSTRACT FROM AUTHOR]

• Indian Northwestern Himalayan lakes are sole sources of water at many locations. • Anthropogenic alterations have an adverse impact on lake water quantity and quality. • Tourism and land use land cover changes have led to degrading lake systems. • Void in knowledge of hydroecology of lake systems inhibits sustainable management. • Need for holistic lake studies with long term hydroecological monitoring. The Himalayas are dotted with a multitude of freshwater lakes of varying sizes. These lakes serve as the sole source of water for multiple major human settlements in the region and a backbone to socio-economic services. Here, we provide a comprehensive review of the available literature on hydro-ecology of important lakes in the Indian Northwestern Himalayas (INWH). Numerous studies have been performed in the past but are reported in regional journals, scientific reports of government research institutions and local conference proceedings with a very few publications in the international journals. We attempt to synthesize the available scientific knowledge in view of topography, climate, hydrology, water quality, land use land cover (LULC), sedimentation, climate change, and other anthropogenic influences. Our review reveals that INWH lakes are adversely affected by multiple anthropogenic influences including, population growth, LULC modifications and deforestation, urbanisation, intensified agricultural, wastewater disposal, excessive freshwater abstraction, and tourism. It is leading to a widespread decline in water quality and adverse impacts on the ecological status of lakes across the INWH region. Signals of climate change impacts are also reported in the region, evident as a significant reduction in precipitation and warming of temperature in historical records, along with projections of an increasing rate of change in future climate. Sustainable management of INWH lakes to preserve their unique hydroecological attributes will require integrative limnological studies that include climate, hydrology, water quality, and ecology. It will provide a body of evidence for developing conservation practices and policies to protect the INWH lakes, prioritise restoration activities, and sustain their role as socio-economic assets. The studies need to prioritise long-term field-based limnology research and high-frequency, high-density monitoring stations while developing practices and policies to alleviate the immediate threats from LULC, water abstraction, and human perturbances. [ABSTRACT FROM AUTHOR]