Understanding landscape-scale patterns of herding is critical in identifying and assessing the impacts of pastoral grazing. Here, a general model of herding is developed based on the Sukuma agropastoral system in the Rukwa Valley, Tanzania. Using this conceptual framework, the factors affecting the maximum distances herds travel from home and the distribution of grazing around pastoral settlements are examined. The distribution of dry season water structured the landscape-scale distribution of grazing throughout the year, not just during the dry season. Water availability strongly affected the distances herds ranged from home in the dry season and the distribution of grazing around pastoral settlements throughout the year. Associations between cattle productivity and herding practices were also examined. Keywords: pastoralism, GIS, Sukuma, Tanzania.