In recent years there has been growing evidence that the Earth's climate will become warmer in the 21st century, which raises the essential question: What impacts will global warming have on the environment and human activities? Warming will cause hydrologic changes that will affect freshwater resources with cascading effects on ecological and human systems. These are among the most significant potential impacts of climate change. As the climate warms, there will be changes in the nature of global precipitation, evaporation, snowpack, streamflow and other factors that will affect freshwater supply and quality. Climate change will present challenges to water utilities, and planning now could prevent freshwater crises in upcoming years. Areas of research on water resources and climate include: