Water is the foundation of all life on Earth, serving not only as a critical resource for human survival but also playing an essential role in ecosystems, agriculture, industry, and the environment at large. The total volume of water in the universe is approximately 1386 million cubic kilometers, distributed across the planet within four key environmental components: the hydrosphere, lithosphere, atmosphere, and biosphere. This water is unevenly distributed, existing as groundwater, as surface water, and in the form of glaciers. Oceans hold the largest share of Earth’s water, but this water is undrinkable due to its salt content. Only about 2.5% of the total water resources on Earth is freshwater. The present scenario of freshwater availability becomes challenging due to the imbalance in demand and limited resources. The increasing impacts of climate change, however, are reshaping the water landscape, exacerbating shortages, and making sustainable management more complex than ever before. Therefore, monitoring water quality provides valuable insights for the sustainable management of available water resources and helps illuminate complex, dynamic environmental processes. This chapter aims to explore the state of global water resources, analyze the effects of climate change on their availability, and discuss strategies for monitoring, management, and conservation.