Ngorongoro Conservation Area (NCA), in northern Tanzania, is a multiple-use area of importance to Maasai pastoralists and wildlife conservation. We adapted the SAVANNA modelling system to the NCA, creating an Integrated Management and Assessment System that allows users to assess responses to alternative management actions. We used the system to conduct fifteen experiments reflecting potential management questions. Results suggest that: the distribution of rainfall throughout the year may have a greater impact on the ecosystem than its quantity; cattle may