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UNIVERSIDAD POLITÉCNICA DE MADRID DEPARTAMENTO DE SILVOPASCICULTURA ESCUELA TÉCNICA SUPERIOR DE INGENIEROS DE MONTES LAND COVER DYNAMICS AND CLIMATE CHANGE IMPLICATIONS ON WATER RESOURCES IN SOUTH PACIFIC COSTA RICA NUR ALGEET ABARQUERO Ingeniera de Montes DIRECTOR Miguel Marchamalo Sacristán Dr. Ingeniero de Montes 2014 1 2 Tribunal nombrado por el Mgfco. Y Excmo. Sr. Rector de la Universidad Politécnica de Madrid, el día …….. de …………………………… de 2014 Presidente D. ……………………………………………………………………………………………………….. Vocal D. ………………………………………………………………………………………………………………. Vocal D. ………………………………………………………………………………………………………………. Vocal D. ………………………………………………………………………………………………………………. Secretario D. ……………………………………………………………………………………………………….. Realizado el acto de defensa y lectura de la Tesis el día …….. de ………………………………………. de 2013 en Madrid. Calificación …………………………………………………….. EL PRESIDENTE LOS VOCALES EL SECRETARIO 3 4 MENCIÓN DE DOCTORADO INTERNACIONAL INTERNATIONAL DOCTORATE MENTION Esta Tesis ha sido informada positivamente para su defensa en exposición pública por los siguientes investigadores: This Ph.D. Thesis has been positively evaluated for its public defense by the following external reviewers: Prof. Dr. Roger Moussa LISAH Universidad de Montpellier (FRANCE) Dr. Federico Gómez Delgado Organización Meteorológica Mundial San José (Costa Rica) 5 6 ABSTRACT ................................................................................................................................... 9 1. Introduction ........................................................................................................................ 11 1.1. Water and forests in the framework of global change ................................................. 13 1.2. Costa Rica as a study case in the humid tropics ........................................................ 16 1.3. Aims and scope ........................................................................................................... 17 1.4. Study framework .......................................................................................................... 18 2. Forest dynamics in Osa Region, Costa Rica: Secondary Forest is here to stay ........ 19 2.1. Introduction .................................................................................................................. 21 2.2. Material and methods .................................................................................................. 23 2.3. Results ......................................................................................................................... 27 2.4. Discussion ................................................................................................................... 33 3. Monitoring Soil and Water Resources in the Humid Tropics: Tinoco Experimental Catchment (Costa Rica) ............................................................................................................ 37 3.1. Introduction .................................................................................................................. 39 3.2. Material and methods .................................................................................................. 40 3.3. Results and discussion ................................................................................................ 47 4. Implications of land use change on runoff generation at the plot scale in the humid tropics of Costa Rica. ............................................................................................................... 53 4.1. Introduction .................................................................................................................. 55 4.2. Materials and methods ................................................................................................ 56 4.3. Results ......................................................................................................................... 64 4.4. Discussion ................................................................................................................... 67 5. Impacts of climate and land cover change scenarios on water supply in south pacific Costa Rica. ................................................................................................................................. 73 5.1. Introduction .................................................................................................................. 75 7 5.2. Methods ....................................................................................................................... 76 5.3. Results and discussion ................................................................................................ 81 6. General Discussion ............................................................................................................ 89 6.1. Land cover dynamics and the hydrology of water supply priority areas. .................... 91 6.2. Impact of global changes in water resources for rural communities ........................... 94 7. Conclusions ........................................................................................................................ 97 8. References ........................................................................................................................ 103 ANNEX 1 ................................................................................................................................... 115 ANNEX 2 ................................................................................................................................... 119 ANNEX 3 ................................................................................................................................... 125 8 ABSTRACT Water is fundamental to human life and the availability of freshwater is often a constraint on human welfare and economic development. Consequently, the potential effects of global changes on hydrology and water resources are considered among the most severe and vital ones. Water scarcity is one of the main problems in the rural communities of Central America, as a result of an important degradation of catchment areas and the over-exploitation of aquifers. The present Thesis is focused on two critical aspects of global changes over water resources: (1) the potential effects of climate change on water quantity and (2) the impacts of land cover and land use changes on the hydrological processes and water cycle. Costa Rica is among the few developing countries that have recently achieved a land use transition with a net increase in forest cover. Osa Region in South Pacific Costa Rica is an appealing study site to assess water supply management plans and to measure the effects of deforestation, forest transitions and climate change projections reported in the region. Rural Community Water Supply systems (ASADAS) in Osa are dealing with an increasing demand of freshwater due to the growing population and the change in the way of life in the rural livelihoods. Land cover mosaics which have resulted from the above mentioned processes are characterized by the abandonment of marginal farmland with the spread over these former grasslands of high return crops and the expansion of secondary forests due to reforestation initiatives. These land use changes have a significant impact on runoff generation in priority water-supply catchments in the humid tropics, as evidenced by the analysis of the Tinoco Experimental Catchment in the Southern Pacific area of Costa Rica. The monitoring system assesses the effects of the different land uses on the runoff responses and on the general water cycle of the basin. Runoff responses at plot scale are analyzed for secondary forests, oil palm plantations, forest plantations and grasslands. The Oil palm plantation plot presented the highest runoff coefficient (mean RC=32.6%), twice that measured under grasslands (mean RC=15.3%) and 20-fold greater than in secondary forest (mean RC=1.7%). A Thornthwaite-type water balance is proposed to assess the impact of land cover and climate change scenarios over water availability for rural communities in Osa Region. Climate change projections were obtained by the downscaling of BCM2, CNCM3 and ECHAM5 models. Precipitation and temperature were averaged and conveyed by the A1B, A2 and B1 IPCC 9 climate scenario for 2030, 2060 and 2080. Precipitation simulations exhibit a positive increase during the dry season for the three scenarios and a decrease during the rainy season, with the highest magnitude (up to 25%) by the end of the 21st century under scenario B1. Monthly mean temperature simulations increase for the three scenarios throughout the year with a maximum increase during the dry season of 5% under A1B and A2 scenarios and 4% under B1 scenario. The Thornthwaite-type Water Balance model indicates important decreases of water surplus for the three climate scenarios during the rainy season, with a maximum decrease on May, which under A1B scenario drop up to 20%, under A2 up to 40% and under B1 scenario drop up to almost 60%. Land cover scenarios were created taking into account current land cover dynamics of the region. Land cover scenario 1 projects a deforestation situation, with forests decreasing up to 15% due to urbanization of the upper catchment areas; land cover scenario 2 projects a forest recovery situation where forested areas increase due to grassland abandonment on areas with more than 30% of slope. Deforestation scenario projects an annual water surplus