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).