Assessing hydrological impacts of tree-based bioenergy feedstock

Abstract

This chapter provides a methodology for assessing the hydrological impacts of tree-based bioenergy feedstock. Based on experience gained in South Africa, it discusses the tasks required to reach an understanding of the likely water resource impacts associated with the development of a tree-based bioenergy industry, from individual tree water use rates to national-scale impacts on water resources. It is intended to be a generic methodology not just for South Africa but with more general applicability to tree-based bioenergy developments worldwide. Why is such a methodology important? Firstly, because large-scale changes in land-use (e.g. changes from existing vegetation to future bioenergy feedstock plantations) constitute a change in plant species, and consequently a change in the structure and functioning of the vegetation growing on the land. This has implications in terms of how different vegetation types use water, and how changing patterns and amounts of water-use impact the availability of water in rivers, and the resultant downstream users of that water. Secondly, there may be legal requirements specific to a particular country for determining the water resource impacts of a proposed future land-use. Finally, the growing importance of sustainable, integrated water resource management is acknowledged globally, and proven methods that strive towards this end, through the quantification of land-use driven water resources impacts, are increasingly required.