Water resources and extreme events in the Awash basin: economic effects and policy implications: report prepared for the Global Green Growth Institute by Smale, R, Walker, O, Vadheim, B, Hope, R, Hope, R, Charles, K, Hall, J, Dadson, S, Borgomeo, E, Kebede, S, Alamirew, T, Bekele, F, Mengistu, A, Beyene, S