The South Atlantic has recently experienced region-wide droughts. There is concern that water scarcity may become more common or prevalent due to a warming climate. Problems associated with water scarcity are compounded by under-developed water allocation policy in the historically water abundant South Atlantic. This dissertation examined the potential causes of water scarcity related to changes in average streamflow from 1934-2005, 1934-1969 (Mid-20th Century) and 1970-2005 (Late-20th Century). Second, the contribution of climate versus anthropogenic drivers of change in mean annual streamflow in the Late 20th Century was evaluated using Budyko curves. Third, hydrologic drought was characterized in the South Atlantic and changes in drought characteristics were assessed over multiple time periods. Fourth, water interconnections, which form an important component of water infrastructure and water management, were assessed for the potential to transfer water from a drought free to a drought stricken area. Results showed that streamflow abruptly shifted from a drier regime in the Mid-20th Century to a wetter regime in the Late-20th Century with trends of significantly decreasing streamflow since 1970. Climate contributed to increased streamflow during the Late-20th Century throughout the South Atlantic; whereas human factors varied between basins and either amplified or decreased the climate change effect on streamflow. Human impacts were equivalent to or exceeded climate impacts in some basins. Seventy-one percent of drought events were shorter than 6 months with a recurrence interval of 6 years. Less than 7% of droughts were longer than one year, yet these longer duration droughts resulted in region-wide water scarcity. There were few significant temporal trends in drought characteristics over the studied time periods. The short interconnection distances (median=11.6 km) rarely extended beyond the spatial extent of multi-year droughts; interconnected water systems were simultaneously in drought 98±3% of the time from 2000-2008. Water managers face many challenges with a steadily growing demand and fluctuating long-term and short-term water supply needs that can be partially met through interconnections. Decision-making will benefit from monitoring changes in climate, human activities, and streamflow, as well as continually assessing the ability of current water infrastructure to perform under normal and adverse conditions.Doctor of Philosoph
