Impacts of global environmental changes on water: challenges for sustainable development

Abstract

This research aims at understanding how human driven global environmental changes in terms of climate and land use are expected to affect the spatial and temporal distribution of water resources. The main questions that thesis asks are: (1) how global climate and land use change are expected to impact the spatial and temporal distribution of the water resources. (2) How human activities like hydropower and agricultural production are likely to be impacted by global environmental changes. (3) How different socio-environmental systems could be adapted to the changing conditions. The thesis is organized in a set of studies aimed at estimating the main practical consequences in terms of hydropower and agricultural production at different geographical scale. It does so selecting the most appropriate tool, from the two main categories of statistical analysis and physical modeling, for each of the specific case studies. A statistical model is utilized to assess the sensitivity of the global hydropower generation to variations in climate. A biosphere model integrated with a routing scheme is utilized to assess the impacts of climate and land use change on the hydrology of the Tapajos river basin, a portion of the Brazilian Amazon. A hydro-energy model was used to assess the possible implications in case of hydropower development in the river system. A crop model was used to analyze the expected impacts to the agricultural productivity in the upper part of the Tapajos basin, one of the most important areas for this economic sector in Brazil. Results show how the global hydropower system is expected to be vulnerable to global changes with specific magnitudes linked to the spatial distribution of climate change and the specific characteristics of the power plants. The Tapajos river basin hydrology is expected to be seriously impacted by climate change, mainly through a delay in the beginning of the rainy season and a reduction of its duration. Land use change, in the specific case deforestation, is expected to partially invert the decreasing trends in river discharge caused by climate change, but causing a consistent increase in flow variability. Moreover, the crop analysis confirmed the expected negative climate change impacts on the agricultural sector in the upper part of the basin, creating the basis for a possible demand for irrigation: an adaptation strategy destined at increasing the anthropogenic pressure on the water resources. The project aims at providing policy makers with a better understanding of the expected future impacts and enhances long-term adaptation strategies. The global hydropower analysis gives an idea of the patterns of vulnerability of this system of production. The basin scale analysis shows how the river flow could be modified by the combined effects of climate, land use change and alternative uses water demand. This confirms that an increasing level of uncertainty should be taken into consideration in case of infrastructural development of the area. This thesis provides a significant contribution to the debate about uncertainty and stationarity in water management. It proves, providing practical examples, how different socio-economic and ecological systems at different geographical scale are interconnected: the dynamics influencing one system affect, directly or indirectly, the connected systems causing a cascade effect.