What causes droughts?

What are the human causes of droughts?

• Answer:

  Columbia University scientists have linked recent water shortages in the northeastern United States with human activities. "Researchers at The Earth Institute say the recent water emergencies in some northeastern states resulted from more than just dry weather. They found droughts had a more direct, human cause called demand-driven drought. A recent study, conducted by Bradfield Lyon of the International Research Institute for Climate and Society, Nicholas Christie-Blick of the Lamont-Doherty Earth Observatory and Yekaterina Gluzberg from the university's Department of Ecology, Evolution and Environmental Biology, examined precipitation variability and drought in Rockland County, N.Y., over the last 100 years. The scientists discovered factors such as development, population growth and failing water supply systems played as significant a role as climate in creating the water emergencies. "The balance between water demand and supply is now so finely tuned that even a few months of lower than normal precipitation is sufficient to trigger an emergency," said Christie-Blick. The research appeared in a recent issue of the Journal of the American Water Resources Association."