Abstract
Scarcity of information on the water productivity of different water, land, and other ecosystems in Africa, hampers the optimal allocation of the limited water resources. This study presents an innovative method to quantify the spatial variability of biomass production, crop yield, and economic water productivity, in a data scarce landscape of the Pangani Basin. For the first time, gross return from carbon credits and other ecosystem services are considered, in the concept of Economic Water Productivity. The analysis relied on the MODIS satellite data of 250 m and eight-day resolutions, and the SEBAL model, utilizing Monteith’s framework for ecological production. In agriculture, irrigated sugarcane and rice achieved the highest water productivities in both biophysical and economic values. Rainfed and supplementary irrigated banana and maize productivities were significantly lower than the potential values, reflecting a wide spatial variability. In natural landscapes, forest and wetland showed the highest biomass production. However, the transition to economic productivity was low but showed the potential to increase significantly when non-market goods and services were considered. Spatially explicit information, from both biophysical and economic water productivity, provides a holistic outlook of the socio-environmental and the economic water values of a land-use activity, and can identify areas for improvement, and trade-offs in river basins.
Highlights
The competition over water resources is escalating in many river basins, worldwide
The key drivers of the spatial variability were the biophysical characteristics of different land use and land cover (LULC) types while the temporal variability was influenced by the precipitation, and the inter-seasonal/intra-seasonal variation of the climate conditions, during the period of analysis, in the river basin
In the dry year of 2009, the biomass production was suppressed for most of the LULC types, in the lower catchment, while it was enhanced in the land-cover-types, such as irrigated bananas and coffee, afro-alpine and dense forests, and the wetlands that had a sufficient water supply
Summary
The competition over water resources is escalating in many river basins, worldwide. Population growth and increasing food demands to meet local and global needs imposes high pressures on the world’s fresh water resources. More water is required to provide for the increasing energy demands from hydropower and biofuels [1]. Competition over water is not limited to the agricultural, domestic, and industrial sectors and includes the natural environment. While environmental water uses are fundamental for sustainable economic and social development in river basins, it is becoming clear that the natural environment consumes large amounts of the water resources, and that measures are required to safeguard natural capital [4,5,6]
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