Land use changes have dramatically affected the water quality and biological productivity of streams and associated watersheds, particularly within the Brazilian Amazon Basin, where deforestation and extensive agriculture have led to increased surface water flow and nutrient losses from watersheds, including headwater catchments. It is thought that economic and socio-demographic factors have played critical roles in structuring these changes; in particular, household decisionmaking, driven by environmental factors, government policies, and knowledge of land use and water quality are important components driving land and water use choices in small watersheds. These uses have specific outcomes for the water quality found in streams draining small watersheds, particularly the quantity and type of nutrients that are important for the biological productivity of stream ecosystems. As a result, this study evaluates the role of household needs and activities, land and water use, and perception of water quality in affecting the water quality of small watershed streams in an agricultural settlement near Altamira, Brazil. The importance of two kinds of watershed land cover gradients are assessed: amount of forest in a watershed and amount of non-forest in a watershed, as pasture or cacao plantations, which are the two most predominant land uses near Altamira. Examination of water quality and stream water dissolved nutrient concentrations (carbon, nitrogen, phosphorus) at watershed stream outflow points, using standard sampling techniques, provides a summary of the impact of watershed land use on stream water quality. In addition, interviews with small farmers provide information on household structure and knowledge of the relationship between land use and water quality. Remote sensing analyses and a geographic information system are being used to generate information on larger spatial patterns of watershed land use changes. The investigators hypothesize that external market factors, such as prices for agricultural goods, and increasing water needs from agriculture are the predominant factors driving land use and subsequent changes in water quality and stream water dissolved nutrients.
The results of this study will provide valuable insights into household land use and environmental change in terrestrial and aquatic ecosystems. In addition, as small streams are widespread in the Amazon Basin and provide important resources for many Amazonian inhabitants, including food and drinking water, the results of this research will provide insights to minimize detrimental impacts on water quality, particularly through understanding how household agricultural land and water use affects the underlying water quality and health of streams. While focused on land use changes in the Brazilian Amazon, this research also addresses land use issues worldwide, as local Amazonian watershed changes ultimately scale-up to affect worldwide ecology, such as global nutrient cycles, and economy, such as agriculture and trade. As a Doctoral Dissertation Research Improvement award, this award also will provide support to foster independent research by a doctoral student.
