CPWF Research Briefs
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Item Poverty and water management in the Sao Francisco river basin: Preliminary assessments and issues to consider(Other, 2006-11-02) Vosti, S.A.; Torres, M.Of the approximately 17 million who inhabited the SFRB in 2003, about 3.7 million (approximately 21%) were poor by Brazilian standards (living on about one minimum salary or less). Just over four million people lived in rural areas of the SFRB and nearly one-third of them (about 1.2 million) were poor. But the rural poor were not distributed evenly across the SFRB (see Figure 1). The proportion of the rural poor tended to be lower in the southern portion of the SFRB, primarily in the state of Minas Gerais, the mountainous zone where the São Francisco River begins. Rural poverty, by this measure, tended to be higher in the central and northern zones, with some municípios registering proportional rates of poverty well in excess of 50% of the rural population. The depth of poverty matters greatly; Figure 2 depicts the spatial distribution within the SFRB of the extreme poverty, i.e., individuals belonging to households living on less than one-third of the Brazilian monthly minimum salary per person. These extremely poor households are located almost exclusively in the central and northern zones of the SFRB. While poverty is central to our research, training, and outreach mandates, it is also interesting to focus attention on municípios that are less poor, in part because we may learn something from these less-poor municípios that may be useful to their more-poor counterparts. Reviewing Figures 1 and 2, it is easy to identify less-poor municípios in the central and northern zones of the SFRB where rural poverty was especially concentrated. One has to wonder what factors might cause neighboring municípios to have such different rural poverty rates; might water availability have something to do with this? Water Availability in the SFRB While water availability is difficult to define and even more challenging to measure, at any resolution, Figure 3 depicts estimated water availability for the SFRB, by município. Our measure of water availability considers annual precipitation, base evapotranspiration, catchment area upstream, and slope (how likely is rainfall or run-on likely to ‘stay’ on the receiving farm); municípios that appear in darker blue have more available water than those in green or yellow. No seasonal or other water storage, or artificial conveyance of water, is included in this measure of water availability; this measure of water availability may be most useful in areas where irrigated agriculture relies on precipitation as well as on local diversions of direct runoff from the upstream catchment. Two important patterns emerge, one that we have been long familiar with and another that is somewhat surprising. The familiar pattern is that of generally higher measures of water availability in the southern and central zones of the SFRB than in the northern zone; this corresponds to known variations in annual rainfall, which ranges from a high of about 1,500 mm/year in the southern zone to a low of about 500 mm/year in some areas of the northern zone. The surprising pattern is the presence of relatively water-scarce municípios in the high-rainfall southern zone, and some relatively water-rich municípios in the arid northern zone. Other variables in the water availability measure as well as scale of analysis (resolution) explain these differences.Item Choosing the proper spatial and temporal resolution for water management: Don’t forget the ‘Invisible’ factors(Brief, 2006-11-03) Vosti, S.A.; Torres, M.In the search for the proper spatial and temporal resolution at which to manage natural resources, we are generally guided by the flows and stocks of water that we can ‘see’ – rainfall, flowing water, reservoirs, dams, etc. We use what we observe to identify the socially optimal flows/stocks of water, and then suggest the public policy action required to achieve these results. However, there are also some ‘invisible’ factors that need to be included in policy discussions related to water management; one important invisible factor is groundwater (the focus of this brief). The bad news is that groundwater is ‘invisible,’ hence stocks and flows of it are more difficult to measure. The good news is that we are discovering ways to more cheaply measure groundwater stocks/flows and to predict the spatial and temporal effects of groundwater extraction. The SFRB research team has developed a demonstration model capable of examining these effects, and what follows is derived from simulation experiments using that model in the Buriti Vermelho sub-catchment area located near Brasilia. The Buriti Vermelho Sub-Catchment Area The Buriti Vermelho (BV) sub-catchment area is a small watershed comprised of several types and spatial extents of farming activities. Figure 1 depicts the BV site; the precise boundaries of the sub-catchment area are given by the thin black line. Water emerges from about the south-central part of the site, just outside the green patch of cerrado típico (savanna forest) and flows from south to north. Blue circles identify the location and size of capital-intensive centerpivot irrigation schemes, while yellow rectangles identify small farms. Large patches of rainfed agriculture remain in theItem Water productivity at basin level: Methods, benefits, and shortcomings(Other, 2006-11-12) Vosti, S.A.; Torres, M.This research program is part of the CGIAR Challenge Program on Water & Food and is supported by the International Water Management Institute, the Brazilian Enterprise for Agricultural Research (Embrapa), and the Department of Land, Air and Water Resources, the Department of Agricultural and Resource Economics, and the Center for Natural Resources Policy Analysis, all at the University of California, Davis. The views expressed in this research brief need not reflect those of the sponsors.