PERIURBAN AGRICULTURAL DYNAMICS AND INTEGRATED WATER MANAGEMENT: THE EXAMPLE OF A WATER CATCHMENT IN THE METROPOLITAN REGION OF SÃO PAULO (BRAZIL)

Abstract

Megacities development is putting an increasing pressure on water resources in their periurban areas. It raises the challenge of the competition between potable water supply and irrigated agriculture, in a context of rapid land use changes, which results in increased pressures on water availability and quality. This is the case of the Tietê-Cabeceiras catchment in the Metropolitan Region of São Paulo (Brazil), the only metropolitan catchment where agriculture is being represented in the water committee - the negotiation and discussion body for water management. A diagnosis was implemented to analyze agricultural water uses: production areas, farming and cropping systems were identified by interviewing local experts and farmers. Water harvesting in these areas competes with two other main functions: irrigated crop production and poor population housing. Inadequate sanitation arrangement in the settlements is responsible for the degradation of water quality. The landscape of this 1690 km² basin is structured by two main determinants: hydro-geomorphology and urban pressure. 7,400 hectares are cultivated, mostly with irrigated horticulture. Irrigation relies on conventional aspersion by individual pumping. Agriculture water consumption is roughly 3,3 m3/ha (29% of the total flow). While agriculture competes with domestic water uses, it also provides some environmental and social services: it contributes to the preservation of forest fragments, prevents illegal urban land occupation and helps keeping a social network counterbalancing the negative social effect of urbanization. The functioning difficulties of this newly created catchment committee make it hard for the institution to play properly its role as a discussion body. It thus only played a minor role in resolving two recent conflicts involving agriculture. In this periurban context, agriculture evolution towards sustainable practices is difficult to anticipate and the technological solutions advocated by many probably require various accompanying incentives: The new institutional arrangement for water and urban management provides the adequate basis to develop an action plan for agriculture.