Karl Marx argued that the underlying cause of all wars was competition for resources. Oil may have been the impetus of many Western forays into the Middle East, but could water become our next casus belli? It’s unlikely that water will be the direct cause of any armed conflict in the near future—negotiating water rights has historically been found to bring countries together rather than tearing them apart—but that might not always be the case. Here are seven regions where growing demand for water could result in problems.