Temporal dynamics in dominant runoff sources and flow paths in the Andean Páramo

Abstract

The relative importance of catchment's water provenance and flow paths varies in space and time, complicating the conceptualization of the rainfall‐runoff responses. We assessed the temporal dynamics in source areas, flow paths, and age by End Member Mixing Analysis (EMMA), hydrograph separation, and Inverse Transit Time Proxies (ITTPs) estimation within a headwater catchment in the Ecuadorian Andes. Twenty‐two solutes, stable isotopes, pH, and electrical conductivity from a stream and 12 potential sources were analyzed. Four end‐members were required to satisfactorily represent the hydrological system, i.e., rainfall, spring water, and water from the bottom layers of Histosols and Andosols. Water from Histosols in and near the riparian zone was the highest source contributor to runoff throughout the year (39% for the drier season, 45% for the wetter season), highlighting the importance of the water that is stored in the riparian zone. Spring water contributions to streamflow tripled during the drier season, as evidenced by geochemical signatures that are consistent with deeper flow paths rather than shallow interflow through Andosols. Rainfall exhibited low seasonal variation in this contribution. Hydrograph separation revealed that 94% and 84% is preevent water in the drier and wetter seasons, respectively. From low‐flow to high‐flow conditions, all the sources increased their contribution except spring water. The relative age of stream water decreased during wetter periods, when the contributing area of the riparian zone expands. The multimethod and multitracer approach enabled to closely study the interchanging importance of flow processes and water source dynamics from an interannual perspective.

Land use alters dominant water sources and flow paths in tropical montane catchments in East Africa

“…This suggests increased inputs from groundwater through wetlands (SHA-WL) or springs (TTP-SP.a 20 and NF-SP.a) during the rainy season. These findings support our hypothesis that there are temporal changes in the contribution of the different end members in this African tropical montane ecosystem, similar to South American tropical montane catchment (Chaves et al, 2008;Correa et al, 2017). Groundwater end member SHA-WE.b in SHA showed contrasting behaviour, with highest contributions during low flow periods, suggesting that this is a different groundwater source and an important component of baseflow in SHA.…”

“…al., 1990). A quantification of the contribution of different end members in a catchment provides relevant insight into dominant flow paths and stream water sources (Barthold et al, 2010;Burns et al, 2001;Correa et al, 2017;Crespo et al, 2012;Soulsby et al, 2003) or water provenance (Fröhlich et al, 2008a(Fröhlich et al, , 2008b. Application of EMMA in the south-western Amazon revealed, for example, a higher contribution of surface runoff in catchments converted from forest to pasture (Chaves et al, 2008;Neill et al, 2011).…”

“…Alternatively, inclusion of additional end members to increase dimensionality of the end member model may be required to satisfactorily represent the behaviour and stream water sources in these catchments, as observed for an Andean Páramo ecosystem (Correa et al, 2017). The selection of tracers and number of end members is highly subjective and can therefore significantly affect the outcomes of the EMMA (Barthold et al, 2011).…”

“…Most case studies in tropical montane areas are from Latin America (e.g. Correa et al, 2017;Crespo et al, 2012;20 Mosquera et al, 2016b;Roa-García and Weiler, 2010;Timbe et al, 2014;Windhorst et al, 2014), whereas no data is available from African tropical montane catchments.…”

Global Isotope Hydrogeology―Review

“…Storm hydrographs in temperate headwaters remain overrepresented in the primary literature (Table ), relative to the limited land areas and time intervals they encompass (Figure ). Groundwater contributions to streamflow have been quantified in some understudied settings, including cultivated, built, and disturbed landscapes (e.g., Buttle & Sami, ; Gremillion et al, ; Huang et al, ; Sandstrom, ; Tekleab et al, ), polar latitudes (Bishop et al, ; Dahlke et al, ; McNamara et al, ; St. Amour et al, ), glaciated basins (Kong & Pang, ; Williams et al, ), alpine deserts (Sun et al, ), semiarid areas (Camacho Suarez et al, ; Zhou et al, ), tropical high elevations (Correa et al, ; Mosquera et al, ), and the humid (sub)tropics (Burns et al, ; Calderon & Uhlenbrook, ; Litt et al, ; Mortatti et al, ; Muñoz‐Villers & McDonnell, ; Scholl et al, ; Wenjie et al, ). Other works have sampled conditions going beyond just storm hydrographs, studying time intervals encompassing spring freshet (Shanley et al, ; Wang et al, ), extreme rainfall and flood events (Lyon et al, ; Winston & Criss, ), and ecological disturbances (Bearup et al, ).…”