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Water Productivity

Page history last edited by Maya Rajasekharan 14 years, 10 months ago

Water productivity in the major river basins of the world are below potential:

The Basin Focal Projects (BFPs) provide a rich source of data on water productivity. The Nile BFP expects to generate data for the entire basin with a resolution of 1km. The Andes BFP is generating high resolution surfaces of water productivity based on estimates of biomass. Water productivity appears well below its potential in most basins and there is considerable scope for improvement. Estimates suggest the potential water productivity of wheat is approximately 2 kg/m3, but it is rare to find systems with productivity greater than 0.4 or 0.6 kg/m3 (exceptions occur in parts of the Ganges, Yellow River and Nile delta). This is the case for many other staple foods such as rice, sourghum or millet. 


Water productivity, a partial measure of productivity, is defined as output per unit of water depleted, where output can be measured in physical or value terms. In practice, BFPs estimated water productivity in terms of the amount of agricultural output, typically kilograms of rice or maize, per unit of water evaporated or transpired in agricultural production. Water productivity estimates ranged from 0.8 kg/m3 for irrigated rice in the Mekong delta to 0.5 kg/m3 for maize in the São Francisco Basin, to 0.05 kg/m3 for rainfed maize in the northern part of the Volta Basin. Crop water productivity showed substantial spatial and temporal variability even in areas with seemingly similar climates. This is not surprising when we consider that land productivity (yields) show similar variability. There is some interest here in using spatial mapping of water productivity to ascertain whether practices in areas of high productivity might be suitable for areas of lower productivity. Often, water productivity is lower in wetter areas than in drier areas. Water productivity in irrigated areas in the Karkheh Basin, for example, was lower than in rainfed areas. One explanation is that about half of irrigated areas have become salt-affected, lowering yields. Integration of livestock with rainfed crop production in the Karkheh resulted in levels of water productivity that were relatively high for that basin. (In these cases, livestock were fed grass or crop residues, not grain.) In the Volta Basin, water productivity of rainfed agriculture followed a similar pattern: it tended to increase as rainfall decreased. In contrast, in the Mekong Basin, where water is relatively abundant, a focus on water productivity was thought to be less useful than a focus on trade-offs among major water uses, for example, the possible negative effects on downstream fisheries that may arise from increased use of water to generate hydropower. Water productivity in rice production was found to be largely driven by factors affecting land productivity, for example, rice production technology and input use. Read More...............


Livestock water productivity

Livestock systems are large consumers of water in most river basin systems of the world, especially in Africa. However, there is insufficient understanding of livestock–water interactions and thus low livestock productivity. Recent advances in data availability and methodologies increase the possibilities of accounting for water flow through livestock systems to identify total water productivity of livestock containing systems.  A special issue of Rangeland journal highlights various technologies and the premises required to reverse the negative trends of water depletion and land degradation practices that would enable improving water productivity. Read More….


Water for fish [Fisheries Water Productivity]

Water productivity estimates are now available to indicate benefit per unit volume of water consumed for various food production systems. For example, on an average 1 m3 of water is consumed or lost to the atmosphere in the form of evaporation to produce 1 kg of wheat and 0.29 kg of pork meet. But no good estimates exist for the water consumed to produce a kilogram of fish. The figures still need to be calculated, but it is clear that little or no water is consumed in the production of fish. Fish naturally live in water and production is not depended on water consumed, but water provided within an ecosystem. This complexity often takes fish away from the basin water productivity concept and leaves contributions of fisheries resources in basin water management under valued or excluded. However, it is clearly established that variations in water flow can change fish production- positive variations lead to positive changes and vice versa. Fish needs to be approached differently in a water productivity framework. We propose distinction between three production systems to lessen the complexity- capture fisheries; aquaculture and integrated aquaculture. Read More....


Fisheries productivity and its contribution to overall agricultural production in the Lower Mekong Basin:

Fish and fisheries provide livelihoods and food security to 60 million people living in the MekongRiver Basin. However, there are major uncertainties in estimates of fisheries production and its value in the LowerMekongBasin due to shortcomings in the data. Catch surveys underestimate the production, and consumption based estimates are regarded as more reliable indicators. Mekong Basin Focal Project combined official statistics with several consumption bases estimates to examine the spatial and temporal trends in capture fish and aquaculture production and value. The highest estimates of production are from 42 kg/capita/year in Laos to 65 kg/capita/year in Cambodia, the latter figure being comparable to consumption in Japan. Production is dominated by capture fisheries in Cambodia (where it is concentrated around the Tonle Sap and the Mekong), Laos and Thailand. In Vietnam, aquaculture dominates production, and is concentrated around the main rivers in the delta and along the coastal strip. A full report is currently in press for publication as a CPWF Working paper. Please read the draft final version here. 



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