A water footprint approach to guide water resource management in data-scarce regions: A case study for the Upper Ewaso Ng'iro Basin, Mount Kenya

Résumé 0

Due to population growth and agricultural intensification, water scarcity is increasing in the Upper Ewaso Ng'iro Basin. Quantitative information is needed to improve the management of this resource, but is a challenge due to lack of hydrometeorological data. Using water footprint thinking, a pragmatic approach applying available information and simple assumptions was used to estimate blue and green water availability and consumption for different land uses and activities. Despite the attention it receives, flower production makes up a small component of the basin's water footprint (1.4% of blue water consumed, roses used 0.73%), although the drastic impact of horticulture on low flows during dry periods is recognized. Surface water evaporation from irrigation dams containing captured floodwaters or pumped groundwater has a water footprint comparable to greenhouse horticultural production itself. Small-scale irrigation was estimated to use 71.4% of the blue water consumed, while total commercial horticultural production was estimated to use 8.2%. Direct human consumption was estimated at 3% and livestock and wildlife consumption at 4.2% of consumed blue water. Labour opportunities were almost 10 times higher for roses than for maize per hectare and per m³ of water consumed. Water productivity in terms of selling price was 128 times higher for 1 tonne of roses than for 1 tonne of maize. This approach can be used in data-poor regions to advance understanding between multiple stakeholders (such as between farmers, pastoralists and conservationists) for participatory management, and to better understand the basin's water balance to estimate exploitable water resources.