Tanzania, 2012: Violence broke out between farmers and herders in the southeastern Rufiji valley, a region hit hard by drought. "A farmer was killed in a conflict with a herdsman over access to water in the southern regions of Lindi and Mtwara," Lucchetti said. "Five more people died and many more were injured in subsequent violence. According to local sources, violence worsened during the prolonged drought."
Kenya, 2103: Fighting between Borana herders and Burji farmers killed at least 56 people. The conflict was rooted in historic clan rivalries that have exacerbated by competition for water and land in the arid region, Lucchetti explained. "Clashes between the two communities date back to the 1960s and are related to disputes over the use of political power to take control of water and fertile land," he said.
Nigeria, 2014: Riots between farmers and herders killed more than 1,000 people. "At the root of this violence is the issue of access to land and water resources," Lucchetti said.
Population density: More densely populated regions need more water. Water shortages in populated areas cause the risk of a riot to jump by 50 percent.
Proximity to lakes and rivers: In regions were there are no lakes or rivers, drought increases the risk of conflict by 100 percent.
Ethnic tensions: Where different ethnic groups share the same source of water, drought drives up the risk of conflict by 100 percent.