"Drought is a natural hazard, often with significant societal, economic, and environmental consequences. Public policy issues related to drought range from how to identify and measure drought to how best to prepare for, mitigate, and respond to drought impacts, and who should bear associated costs. Severe droughts in 2011 and 2012 in Texas and the midcontinent region, the current drought in California and parts of other western states, and 15 years of dry conditions in the Southwest have fueled congressional interest in drought and its near-term effects on water supplies and agriculture, as well as in long-term issues, such as drought forecasting and possible links between drought and human-induced climate change. […] One question is whether the parts of the United States, in particular the American Southwest, including California, may be experiencing the beginning of a modern-era megadrought. Because such megadroughts occurred previously, there is the possibility of a return to the long-term drought conditions experienced in previous centuries. Further, some postulate that droughts could be exacerbated if the future climate is warmer due to the buildup of greenhouse gases in the atmosphere. Predicting the severity and persistence of severe drought over a specific region of the country, however, is not yet possible more than a few months in advance because of the many factors that influence drought (e.g., precipitation, heat, soil moisture). The prospect of extended droughts and more arid baseline conditions--possibly exacerbated by greenhouse gas-driven warmer temperatures--in parts of the United States may challenge existing public policy responses for preparing for and responding to drought."
CRS Report for Congress, R43407
National Agricultural Law Center: http://nationalaglawcenter.org/