The ecology of floodwater farming in arid southwestern North America

Abstract

Floodwater farming is the management of sporadic flashfloods for crop production. It is an ancient technique in the arid southwestern region of North America that is currently being reevaluated and adapted. Floodwater-based agro-ecosystems function via (1) hydrostatic manipulations of the physical environment, and (2) synecological manipulations of the plant community. Agronomically productive hydrostatic conditions have been developed by geomorphological alteratiions of the floodplain, including canals, terraces, grids, spreaders, and weirs. These environmental modifications serve to (1) concentrate the runoff from a larger watershed into a strategically located field, and (2) break the erosive force of the incoming water. Traditional floodwater farming in arid America has depended upon ephemeral, drought-avoiding and heat-tolerant genotypes. In addition, native Americans manipulate the wild and weedy flora of floodwater fields by discouraging or protecting and harvesting selected species. As part of traditional subsistence, floodwater farming has undergone a demise in native communities. Techniques are, however, being modified for (1) forage production, and (2) supplemental human food production. As a high risk system, floodwater agriculture is not now competitive with conventional irrigation agriculture in arid lands, but may become so as groundwater pumping costs continue to affect crop production economics.