New observational techniques

Tracers hydrology and flux exchange in páramos

Knowledge about the spatial distribution of water sources and temporal dynamics of water and material fluxes and release mechanisms is needed to represent a holistic response of catchment behavior. Such knowledge can be gained using tracers in conjunction with independently measured hydrometric data (Buttle, 1994; Inamdar et al., 2013). Hydrochemical tracers to identify and quantify contributions of geographic sources, time-domain tracers, such as water stable isotopes to study the fate of water and water age dynamics, and “smart” bio-reactive tracers, like resazurin (Raz), to assess Carbon Dioxide (CO2) dynamics have been successfully applied in the páramo ecosystem (Correa et al., 2017, 2018; Esquivel-Hernández et al., 2018; Mosquera et al., 2016b; Riveros‐Iregui et al., 2018). Correa et al. (2017, 2018, 2019) used a multi-method approach and a large number of natural tracers to analyze the runoff composition at multiple spatial temporal scales. Their findings highlighted the paramount role of soils from different geographic locations to compose the runoff and draw attention into the evident contributions of the freshwater and shallow-groundwater sources, including a quantification of water contributions from the different compartments. These studies additionally pinpointed the variable stream water age, the spatial variability and diverse evolution of hydrological processes under different hydrometeorological conditions. Other researchers used water stable isotopes to evaluate the effect of land use change on rainfall-runoff response (Roa-García et al., 2011), quantify runoff generation (Minaya, Camacho Suarez, et al., 2016), and determine the isotopic composition of high mountain lakes (Esquivel-Hernández et al., 2018). Additionally, mean transit times were evaluated in order to understand catchment dynamics (Mosquera et al., 2016b; Muñoz‐Villers and McDonnell, 2012; Roa-García and Weiler, 2010) and quantify stream water ages (53–264 days) (Mosquera et al., 2016b). Artificial tracers were as well applied in an experimental based 4 days -high resolution sampling campaign in the Colombian páramos. This with the aim to assess the land use impact on the dynamics of dissolved CO2 and potential for CO2 evasion (Riveros‐Iregui et al., 2018). The bio-reactive RAZ -which is reduced to resorufin (Rru) via aerobic cellular respiration (González-Pinzón et al., 2014)- was injected together with chloride into sites with different land cover. Results suggested that most of the outgassing in wetland systems occurs near the stream wetland interface, where the potential CO2‐enriched water flowing out of the wetland mixes in a turbulent form. A high density of carbon-rich peatlands was mapped in the high elevation mountains of the Ecuadorian páramos by (Hribljan et al., 2017) improving sustainable management for national and global carbon accounting. Peña-Quemba et al. (2016), using the portable soil respiration chamber technique in their field experiment revealed that the agricultural management and land use changes were the main drivers of soil-atmosphere exchange of CO2 in the páramo of Guerrero (Colombia). The authors additionally stated that the easy decomposition of organic matter in páramo soils turns them into carbon sinks. Soil respiration is a key factor in the heat balance, the concentration of atmospheric carbon and global ecological changes (Jassal et al., 2007; Veenendaal et al., 2004). Small changes in soil respiration as a potential effect of global warming can determine the shift point where an ecosystem acts as a source or sink for CO2 (Jassal et al., 2007). A recent study revealed that páramos are carbon sources (Carrillo-Rojas et al., 2019). Processes of CO2 emission (100±30 gr m-2 yearly) show that this ecosystem are more susceptible to lose the carbon fixed in the soil (especially dry periods) due to the effects of climate change and vegetation alterations. (Carrillo-Rojas et al., 2019).This would have far-reaching implications for water storage and dynamics, biodiversity and ecosystem services management.

Remote sensing and new technologies

Remote sensing has been used in hydrology for estimating hydrometeorological states and fluxes (Kumar and Reshmidevi, 2013), such as precipitation, land surface temperature, near surface soil moisture, snow cover, water quality, landscape roughness, land use and vegetation cover. Schmugge et al. (2002) used primarily remote sensing technique to define evapotranspiration and snowmelt runoff. In the páramos, applications have been related mainly to precipitation detection, land use and vegetation cover mapping, and to evapotranspiration estimation. Improvements in the spatial-temporal estimation of precipitation were possible thanks to a number of methodologies, ranging from the identification of the best satellite products, model images (Ballari et al., 2018; Manz et al., 2017; Nerini et al., 2015; Ulloa et al., 2017, 2018) and use of dense and/or extensive rain gauges networks (Manz et al., 2016; Sucozhañay and Célleri, 2018), to the use of more sophisticated equipment such as radars and disdrometers (Orellana-Alvear et al., 2017; Padrón et al., 2015). Precipitation forecasting and projections use statistical and dynamical downscaling applications (Campozano et al., 2016a; Ochoa et al., 2016) and forecasting of daily precipitation occurrence (Urdiales and Célleri, 2018). The RADARNET-SUR is the first weather radar network located in tropical high mountains. It was installed to complement an existing sparse rain gauge network (Bendix et al., 2016; Orellana-Alvear et al., 2017). The radar successfully detected the relatively low frequency of heavy rain (particles diameters between 1 and 2 mm) and confirmed the high occurrence of drizzle. Raindrop size spectra were characterized with the radar observations, confirming spatial variations across páramo sites. Particularly the use of satellite products in the high mountains showed that Integrated Multi-satellite Retrievals for GPM (IMERG) has a superior detection and quantitative rainfall intensity estimation ability than Multi-satellite Precipitation Analysis (TMPA) (Manz et al., 2017). The latter enabled to reveal the existence of different regimes (unimodal, bimodal, and three-modal) and helped to comprehend the precipitation and cloud dynamics and generation processes of precipitation (Campozano et al., 2016b). Regarding land use and vegetation cover, deforestation and landscape transformation was detected with the comparison of LANDSAT and ARDAS satellite images (Muñoz-Guerrero, 2017). Those images helped to detect crop expansion, especially regarding to the conservation of forests and wetlands (Muñoz et al., 2018a). The occurrence of wetlands was characterized in the Colombian páramos, with remote sensing derived data (Estupinan-Suarez et al., 2015). Lastly fires and their intra- and inter-annual variability, that affect the páramo, was also analyzed through Landsat and MODIS imagery (Borrelli et al., 2015). The energy-balance model METRIC with Landsat and MODIS-Terra imagery provided a robust first estimate of spatial-temporal changes of evapotranspiration (Carrillo-Rojas et al., 2016), which was further greatly improved measuring energy fluxes with an Eddy-covariance tower, one of the highest in the world (Carrillo-Rojas et al., 2019).

Citizen science and participatory monitoring networks

Long-term monitoring of water quantity and quality is often criticized for being unaffordable and challenging in low-income and remote regions (Rufino et al., 2018). Novel strategies allow the participation of new actors (e.g., actors with a non-research oriented profile) in scientific projects; their participation is usually referred to as citizen science. The inclusion of local stakeholders changes the traditional monitoring approach, from intensive-highly specialized in experimental sites to a polycentric and collaborative network with large spatial coverage and a wider range of data collector profiles (Buytaert et al., 2014, 2016). The second option involves the horizontal management of information and massive distribution of knowledge. The participation of stakeholders has proven to be an effective tool to reduce costs while providing hydrological data with sufficient quality (Weeser et al., 2018), and generating locally relevant knowledge to tackle the data scarcity in regions such as the tropical Andes (Ochoa-Tocachi et al., 2018). Regional monitoring networks such as the Regional Initiative for Hydrological Monitoring of Andean Ecosystems (iMHEA, Célleri et al., 2009; Ochoa-Tocachi et al., 2018) integrate locals (land and water users and government offices), academic institutions and other minor monitoring networks. iMHEA generates and analyses information about the impact of land use changes on the hydrological response of mountain catchments with high spatial and temporal resolution, yet short time series (Buytaert et al., 2016; Ochoa-Tocachi et al., 2016b, 2018). Particularly in páramos, the network studies watershed interventions and common land-use activities such as cultivation, grazing, and afforestation with exotic species, as well as connectivity pathways and effects of land use to downstream users (Ochoa-Tocachi et al., 2018). With this collaborative project the authors were able to detect regional patterns such as increases in variability of stream flow and decreases in the water yield of the catchments. Furthermore, decreases in the regulation capacity of the catchments (effect of livestock grazing) and impacts on the base flows (effect of afforestation with exotic species and crops) were evidenced (Ochoa-Tocachi et al., 2016b). With results such as the above mentioned, it is demonstrated that broad networks with scientific and non-scientific actors provide opportunities for data collection, generation of knowledge and support to water management policies (Buytaert et al., 2016).