Human Impacts on the Hydrology of Tropical Andean Catchments

Thursday, 9 June 2016
Boris F Ochoa-Tocachi1,2, Wouter Buytaert1, Bert De Bievre3, Rolando Célleri4, Patricio Crespo4, Marcos Villacis5, Carlos A Llerena6, Luis Acosta7, Mauricio Florencio Villazon8, Mario Guallpa9, Junior Gil Ríos2, Paola Fuentes3, Dimas Olaya10, Paul Viñas10, Gerver Rojas11, Sandro Arias12 and Regional Initiative for Hydrological Monitoring of Andean Ecosystems (iMHEA), (1)Imperial College London, Civil and Environmental Engineering and Grantham Institute for Climate Change, London, United Kingdom, (2)Consorcio para el Desarrollo Sostenible de la Ecorregión Andina (CONDESAN), Cuencas Andinas, Lima, Peru, (3)Fondo para la Protección del Agua - FONAG, Quito, Ecuador, (4)Universidad de Cuenca, Departamento de Recursos Hídricos y Ciencias Ambientales & Facultad de Ciencias Agropecuarias, Cuenca, Ecuador, (5)Escuela Politécnica Nacional, Departamento de Ingeniería Civil y Ambiental, Quito, Ecuador, (6)Universidad Nacional Agraria La Molina, Facultad de Ciencias Forestales, Lima, Peru, (7)Superintendencia Nacional de Servicios de Saneamiento, Lima, Peru, (8)Universidad Mayor de San Simón, Laboratorio de Hidráulica (LHUMSS) & Facultad de Ciencias y Tecnología, Cochabamba, Bolivia, (9)Empresa Pública Municipal de Telecomunicaciones, Agua Potable, Alcantarillado y Saneamiento de Cuenca (ETAPA EP), Subgerencia de Gestión Ambiental, Cuenca, Ecuador, (10)Naturaleza y Cultura Internacional, Piura, Peru, (11)Asociación Peruana para la Conservación de la Naturaleza, Chachapoyas, Peru, (12)Servicio Nacional de Meteorología e Hidrología del Perú, Cusco, Peru
Abstract:
Tropical Andean catchments deliver a large portfolio of ecosystem services, including an abundant supply of clean fresh water. At the same time, they are undergoing dramatic changes in land use as a result of local rural development, with potentially serious impact on the hydrological response. The severity of their degradation contrasts strongly with the lack of knowledge about hydrological processes and the strong spatiotemporal gradients of the local climate. Some localised investigations have tried to overcome data scarcity, but the complexity of the Tropical Andes make regional hydrological predictions very challenging.

We present an analysis of data generated from a network of paired catchments to regionalise human impacts on their hydrological response. Currently, over 30 headwater catchments are being monitored by a consortium of institutions in 14 sites across the Tropical Andes. We studied 25 of these catchments (from Ecuador, Peru and Bolivia) covering three of the major Andean biomes (páramo, jalca and puna) and linked their hydrological responses to main human interventions (cultivation, afforestation and grazing). Precipitation and discharge were monitored at high temporal resolution and analysed with indices that capture the most conspicuous hydrometeorological features.

The analysed data clearly reflect the dominant regional climate patterns and the extraordinary wide spectrum of hydrological response behaviour of the Tropical Andes. The catchments range from perennially humid, highly buffered streamflows in the wet páramo to highly seasonal, flashy catchments in the drier puna. The impacts of land use are equally diverse. Cultivation and afforestation affect the entire range of the hydrograph, but low flows in particular. Grazing impacts depend on animal density and catchment properties, and have the largest effect on the hydrological regulation. Overall, human interventions consistently result in an increase of streamflow variability and reductions of both catchment regulation capacity and water yield, irrespective of the hydrological properties of the original biome.

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