Paute River Basin (Ecuador)
The Paute Basin is located in the southern highlands of Ecuador in a segment of the Andes Mountain Range and covers an area of 6,439 km2. This basin is part of the headwaters of the Amazon basin, which delivers its waters through the Santiago River. In total, there are 18 hydrographic sub-basins (Figure 1).
The basin elevation ranges from 500 to 4,600 metres above sea level (m a.s.l.). The available slope information covers approximately 80% (5,128 km2) of the total area. The sub-basins without slope information are Río Negro and Baja del Río Paute. The slope morphology of the interior of the valleys is very steep: approximately 60% of the area has a slope over 25% and 30% of the area has a slope greater than 50% (CG Paute, 2008).
According to Vanacker et al. (2007), the main outcropping rocks of the Paute basin are consolidated volcanic (75%) followed by sedimentary rocks (16%) of Upper Miocene to Lower Pleistocene Age and unconsolidated fluvial (4%) and glacial (5%) sediments from Lower Pleistocene to present-age. The basin is located within the Inter-Andean depression; the eastern part is situated in the Cordillera Real and the western part is situated in the Cordillera Occidental. The Eastern Cordillera is composed of metamorphic rocks, whereas the Western Cordillera is mainly composed of marine sedimentary rocks of the Middle to Upper Miocene (Coltorti and Ollier, 2000). The middle area is dominated by sedimentary rocks (Noblet et al., 1988) where the older deposits are covered by volcanic rocks of Middle Pliocene to Lower Pleistocene Age, which create a volcanic plateau (Hall and Beate, 1991).
The soils of the Paute River Basin are composed of variable parent materials due to the high lithological diversity. They contain materials from recent origin such as volcanic ashes and ancient materials such as volcanic, metamorphic, volcano-sedimentary and sedimentary rocks. In higher altitude areas in a large part of the basin (internal slopes and flanks of the Andean mountain range), the pyroclastic material is formed by recent volcanic ashes and constitutes the source material of the soils. The depth of this pyroclastic layer varies from few centimeters to several meters and acts as an agent for forming aerial deposits or as a drag material in accumulation events (colluvium, alluvial and/or alluvial colluvium). The ancient materials (metamorphic, volcano-sedimentary and sedimentary rocks) constitute the soil-forming agent in the humid highlands of the mountain range, in the dry and temperate lowland areas of the inter-Andean valley, and in the low and humid outer flanks of the eastern mountain range and Amazonian sub-Andean zone.
According to Vanacker et al. (2007), climate and topography have developed soils with heterogeneous characteristics. In this way, at high altitudes Andosols and Histosols prevail. In the interior valleys of the Paute River Basin, where the climatic conditions are drier and warmer, Vertisols have developed on clay-rich Tertiary sedimentary rocks. In the transition zone between the interior valleys and the hillslopes, Cambisols and Luvisols are found, which are the most fertile soils of the region. Due to the rugged topography and the intense geomorphic activity on the hillslopes, Regosols and Cambisols are commonly observed.
The landscape is heterogeneous, with forests and páramo ecosystems (high-elevation peatland) at higher elevations. In the middle of the basin, rivers flow through narrow valleys. Trees typically cover the slopes of these valleys (where introduced species such as eucalyptus and pine are observed), while the riverbanks are covered by grasslands. Urban development has occupied low slope areas, for example the cities of Cuenca and Azogues. The most eastern part of the Paute River Basin is cover by a páramo ecosystem at higher altitudes and by tropical primary forest and vegetation in the Amazon basin downstream.
Table 1 presents a summary of vegetation types in the high, middle and lower part of the Paute River Basin, including the areas covered by each of these vegetation types.
Table 1: Vegetation within the Paute River Basin
Source: Mapa de Formaciones Vegetales del Ecuador Continental, Sierra, 1999.
The land use and vegetation cover are related with the altitudinal floors of the Paute River Basin. In general, the vegetation in middle and lower basin is reduced because the high anthropic intervention. On the other hand, the vegetation in the upper part of the basin maintains important areas of natural vegetation, which some of them have been declared under special protection. The following table describes the land use within the Paute River Basin.
Table 2: Land use within Paute River Basin
References and further reading:
Bendix, J., Rollenbeck, R., Göttlicher, D., and Cermak, J. (2006). Cloud occurrence and cloud properties in Ecuador. Clim. Res. 30, 133–147.
Buytaert, W., De Bièvre, B., Wyseure, G., and Deckers, J. (2004). The use of the linear reservoir concept to quantify the impact of changes in land use on the hydrology of catchments in the Andes. Hydrol. Earth Syst. Sci. 8, 108–114.
Buytaert, W., Célleri, R., De Bièvre, B., Cisneros, F., Wyseure, G., Deckers, J., Hofstede, R. (2006). Human impact on the hydrology of the Andean páramos
Earth-Science Reviews, 79 (1-2), pp. 53-72. doi: 10.1016/j.earscirev.2006.06.002.
Buytaert, W., and De Bièvre, B. (2012). Water for cities: The impact of climate change and demographic growth in the tropical Andes. Water Resources Research, 48, W08503. https://doi.org/10.1029/2011WR011755.
Campozano, L., Célleri, Ro., Trachte, K., Bendix, J., and Samaniego, E. (2016). Rainfall and Cloud Dynamics in the Andes: A Southern Ecuador Case Study. Advances in Meteorology. https://doi.org/10.1155/2016/3192765.
Célleri, R., Willems, P., Buytaert, W., and Feyen, J. (2007). Space–time rainfall variability in the Paute basin, Ecuadorian Andes. Hydrological Processes, 21, 3316–3327. https://doi.org/10.1002/hyp.6575.
Célleri, R., and Feyen, J. (2009). The hydrology of tropical Andean ecosystems: Importance, knowledge status, and perspectives. Mt. Res. Dev. 29, 350–355, doi:10.1659/mrd.00007.
Célleri, R., Buytaert, W., De Bièvre, B., Tobón, C., Crespo, P., Molina, J., and Feyen, J. (2010). Understanding the hydrology of tropical Andean ecosystems through an Andean Network of Basins. IAHS-AISH, 336, 209–212. https://doi.org/10.13140/2.1.4187.3608.
Coltorti, M., and Ollier, C.D. (2000). Geomorphic and tectonic evolution of the Ecuadorian Andes. Geomorphology 32, 1-19.
Consejo de Gestión de Aguas de la Cuenca del Paute, CG Paute (2008). Plan maestro de la Cuenca del Río Paute.
Hall, M.L., and Beate, B. (1991). El vulcanismo Plio-Quaternario en los Andes del Ecuador. El paisaje Volcanico de la Sierra Ecuatoriana. Estudios Geograficos, vol. 4, pp. 5–17
Instituto Nacional de Estadística y Cencos, INEC (2001). VI Censo de Población y V de Vivienda 2001, Resultados Definitivos, Resumen Nacional.
Instituto Nacional de Estadística y Cencos, INEC (2007). Proyecciones de la Población Ecuatoriana por Áreas y Años Calendario, según Provincias y Cantones Período 2001-2010.
Intergovernmental Panel on Climate Change, IPCC (2013). The Physical Science Basis.
Noblet, C., Lavenu, A., and Schneider, F. (1988). Etude géodynamique s'un bassin intramontagneux tertiaire sur décrochements dans les Andes du sud de l'Equateur: l'example du bassin de Cuenca. Géodynamique 3, 117–138.
Sierra, R. (1999). Propuesta preliminar de un sistema de clasificación de vegetación para el Ecuador continental. Proyecto INEFAN/GEF-BIRF y EcoCiencia. Quito, Ecuador.
Unidad de Manejo para la Cuenca del Río Paute, UMACPA (1995). Estudios Geomorfológico de la Dinámica de los Principales Procesos Erosivos y de Sedimentación de la Cuenca del Río Paute. Cuenca-Ecuador.
Vanacker, V., Molina, A., Govers, G., Poesen, J., and Deckers, J. (2007). Spatial variation of suspended sediment concentrations in a tropical Andean river system: The Paute River, southern Ecuador. Geomorphology 87, 53-67.
Vuille, M., Bradley, R.S., and Keimig, F. (2000). Climate variability in the andes of Ecuador and its relation to tropical Pacific and Atlantic sea surface temperature anomalies. J. Clim. 13, 2520–2535.