AGUACRUZ: Water, Landscape, and Cities. Hydrological and landscape ecology modelling for the green and blue future of Santa Cruz de la Sierra (Bolivia)

The expansion of cities is an emerging and critical issue for the future of the planet. Cities and their residents depend on peri-urban and rural landscapes for ecosystem services as well as for economic and social benefits and, ultimately for health and quality of life. On the other hand, it is increasingly evident, in the world of science as well as for the actors of city governance, that urban environments need a green infrastructure approach in order to mitigate the critical state of the environment particularly in the fast growing cities of developing and industrialising countries. Water is one of the most important resources provided by the urban and periurban landscapes and directly or indirectly connected with the quality of environment and life. Santa Cruz de la Sierra is the first city in Bolivia (the second in Latin America) in population growth and soil sealing. It is estimated that over the next five years, the current 2.6 million people (2015) could double: food, energy and water requirements will be completely altered by this change. In particular, water available to the city, mostly from the Piraí river basin, is expected to be totally inadequate to support such a powerful urban development. The objectives of the project AGUACRUZ, financed by the Italian Agency for Cooperation and Development, were selected through a collaboration process between the Government of Santa Cruz de la Sierra, the NGO ICU (Italy) and the University of Florence. Main objectives were: a. to re-structure and harmonize the existing data on the landscape ecology, hydrological, and functional aspects of the Piraí river basin under the light of re-composing the urban rural divide; b. build hydrological scenarios for the future of the basin by introducing a landscape ecology approach to the simulation of actions for the sustainable management of the rural, urban and peri-urban landscape; c. involve stakeholders and local actors in decision-making processes oriented to increase the resilience of urban-rural landscape interconnected to the basin of the river Piraì and the city of Santa Cruz. Five scenarios have been tested by using SWAT (Soil and Water Assessment Tools) modules and assessing the changes in landscape metrics and hydrological determinants. The scenarios were selected along a rural to urban gradient by simulating actions of forest sustainable management, (re) afforestation, agroforestry, urban forestry, and implementation of green infrastructure components. The results indicate that the integrated actions in rural-urban system can lead to a substantial reversal of the trend towards a decline in water supply for the city. From a governance and planning perspective the proposed actions have been configured as to induce (i) an integrated Landscape Ecological Planning, seeking to maintain healthy ecosystems, reconnect fragmented natural and semi-natural areas and recover damaged habitats; (ii) the preparation and approval of departmental regulations for the incorporation of green infrastructure in the municipalities; (iii) the implementation of the socio-environmental challenges by developing and consolidating economic activities (as agroforestry systems) that generate satisfactory income in rural and periurban communities.