Abstract

The consumption of gari (or roasted cassava granule) is connected to a chain of impacts on the water resource in the country where cassava crop is grown, processed and consumed. The aim of this paper is to assess the impact of gari consumption on the water resource of Nigeria. The paper elaborates on two types of impact: evaporation of infiltrated rainwater for cassava plant growth (green water use) and the abstraction of ground and/or surface water for processing, including that of consumption at household level (blue water use), while water pollution impacts during processing and consumption (at households) are neglected. Using the 2007 cassava production estimates for Nigeria as baseline, the water impact related to the consumption of gari either as snack or as “eba” (gari reconstituted with hot water to form a dough-like paste) is estimated at 10.52 x 10⁹ m³, out of which 0.38% is due to the use of blue water and 91.3% is due to the use of green water (no dilution water impacts measured in this paper). Under the traditional farming practices, the major volume of water needed to grow the cassava plant is from rainwater. For the total water needed in gari consumption starting from cultivation, the water used in the processing and consumption (at household level) is a significant fraction (about 0.4%) of the soil moisture used to grow the cassava plant. However, the impact of this fraction is often significant: One, it is the blue water (abstracted from surface and/or sub-surface sources) that is often scarcely available and two, it is this blue water sources that are also polluted by the waste flows from the processing and consumption sites.

Key words: Water footprint, virtual water, water resource, blue water, green water, roasted cassava granule (or, gari), Nigeria.