Land-Use Differentiated Unit Hydrographs of Thirty Paired Catchments in the Tropical Andes

Abstract:

The tropical Andean provides hydrological ecosystem services to more than 50 million people. Characterizing and quantifying the hydrological impacts of changes in land use or land cover in tropical Andean catchments and ecosystems appear to be a complex task due to the variety of meteorological and biophysical conditions of this region that ultimately result in a huge ecosystems diversity. Moreover, the scarcity of high-resolution hydrological data for the Andean watersheds have hampered the generation of robust evidence for decision makers.

During the last decade, a participatory monitoring network known as Regional Initiative for Hydrological Monitoring of Andean Ecosystems (iMHEA) has been generating high-resolution data of rainfall and streamflow based on the well know approach of “trading-space-for-time”. iMHEA monitors several paired catchments in a regional setting, considering diverse land uses, climatic conditions, and biophysical settings. We monitor rainfall-runoff data at 0.2 mm resolution for rainfall and water level and streamflow time series at 5 min intervals.

These data are used to predict the hydrologic response of catchments using the unit hydrograph (UH) theory, which requires high-resolution catchments rainfall and runoff data. This study proposes to assess the hydrological impacts of dominant land-use types in the tropical Andes using 30 catchments from the iMHEA network. The catchments span in South America throughout Colombia, Ecuador, Perú, and Bolivia. Our results show that it is possible to differentiate the impacts of land-use change and summarize them in unit hydrographs via four main parameters: time to peak, peak magnitude, hydrograph duration, and recession constant.

These results are transferable and allow decision makers used them quickly to provide ex ante hydrological evaluations of different land-use changes, natural infrastructure interventions, and watershed management practices. These summarized data using functional hydrological indices allows democratizing science and improving water resource management in data-scarce regions such as the tropical Andes and beyond.