Figure 1: Map of southern Arabia and RASA study sites.
In Southern Arabia’s highland Southern Jol, the RASA Project has documented and dated early water management structures, with important repercussions for prehistoric Arabian resource manipulation and food production. Investigations revealed semi-sedentary occupation by early Holocene people, whose diverse activities included construction of water check dams in the Wadi Sana system (Figure 1.)
Using high-resolution GPS-GIS survey, RASA documented 13 ancient check dams. They are notoriously difficult to date; Yemen’s examples are no exception. In northern Yemen, early agricultural structures usually have been dated by associated settlement (Ghaleb 1990; Edens et al. 2000). Some water management structures clearly have had no recent use, for they can no longer be reached by surface water or canals. Annual precipitation (50–100 mm) is too low for dry-farming, so for at least the past 5000 years, agriculture in southern Yemen has required water management.
Figure 2: Ancient checkdam constructed of domino-aligned slabs, collapsed during flooding.
In the Wadi Sana and its Wadi Shumlya tributary, check dams lie buried in silts deposited 13,000–5000 years ago. Embedded in a gravel bar deposited more than 5000 years ago, an alignment of imbricated bedrock slabs shows the former contour of a check dam (1998-000-B) (Figure 2 destroyed by floods.)
Figure 4: Ancient checkdam remains have slumped into erosional channel but remain embedded in silts in foreground and rear.
Future research will map and explore the purposes of early water management. While agricultural activities cannot be excluded, the Wadi Sana remains predate known Arabian agricultural systems. Other purposes might include flood control, enhanced grazing, and promoting non-cultigen vegetative growth.