Evaluation of water provisioning services in the upper Guayllabamba River Basin applying the InVEST water yield model

Ecosystem services have been highly underestimated in decision making, in the formulation of economic policies, in markets, prices, production habits, consumption and land use practices. Population growth, the expansion of the agricultural frontier and changes in land use have affected water sources and ecosystems. Therefore, the aim of this study was to evaluate the water provisioning services in the upper Guayllabamba River Basin using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. The study area is located in Ecuador's northern inter-Andean region and occupies an approximate area of 6846.67 km2 with an altitudinal range between 637 to 5897 m.a.s.l. For the water yield model, various sources of information were used: i) a network of 133 pluviometers with historical records from 2001 to 2014, from the Instituto Nacional de Meteorología e Hidrología (INAMHI), the Empresa Pública Metropolitana de Agua Potable y Saneamiento(EPMAPS), the Regional Initiative for Hydrological Monitoring and Andean Ecosystems (iMHEA), The Quito Water Fund (FONAG) and the Secretaría del Ambiente (SA) ii) unprocessed and corrected satellite precipitation data (TRMM V7) iii) annual reference evapotranspiration (ETo), iv) flow data in 12 subbasins, and v) land use/land cover. The InVEST model execute a spatially distributed surface water balance at a scale of 1 km2 with an annual time scale. The results of the study have been represented in water yield maps and can support the delimitation of water conservation zones and identify the properties that could be purchased in the future by EPMAPS, FONAG and other institutions allowing them to guard and focus on the development and sustainable management of water resources. Water yield can reach values as high as 1500 mm/year in the high elevation areas near mountains such as Antisana (5704 m.a.s.l), Cayambe (5790 m.a.s.l), Pichincha (4784 m.a.s.l). Similarly the smallest water yield values can be as low as 500 mm/year in the northwest part of the basin and Guayllabamba Medio sub-basin (637 m.a.s.l).