1. Introduction
Tropical mountainous ecosystems are recognized as providers of valuable
ecological and hydrological services (Viviroli et al, 2007). In Central
America, the Páramo, a high‐elevation tropical grassland ecosystem,
extends over ~ 200 km2 in Costa Rica
and Panama, with ~50% of this area located within the
Chirripó National Park between 3,100 and 3,820 m asl (-83.49°, 9.46°).
Vegetation mostly consists of 0.5 to 2.5 m tall bamboo dominated
(Chusquea subtessellata ) grasslands, covering up to 60% of the
total Páramo area in Costa Rica (Fig.1a). The climate is controlled by
the northeast trade winds, the latitudinal migration of the
Intertropical Convergence Zone (ITCZ), cold continental outbreaks (i.e.,
northerly winds), and the seasonal influence of Caribbean cyclones.
These circulation patterns produce two rainfall maxima on the Pacific
slope, one in June and one in September, which are interrupted by a
relative minimum between July-August, known as the Mid-Summer Drought,
due to intensification of trade winds over the Caribbean Sea (Magaña et
al., 1999; Waylen, 1996). The wettest season extends from May to
November (contributing up to 89% of the annual precipitation), whereas
the driest season is from December to April (Fig. 2a; Esquivel-Hernández
et al., 2018). The surface water system of Chirripó is characterized by
a lake district which comprises approximately 30 lakes of glacial origin
and streams flowing down the Caribbean and Pacific slopes (Fig 1b). Lake
catchments are characterized by steep slopes that promote rapid
hydrological responses such as fast water‐level changes. Input of water
to these glacial lakes is mostly controlled by the seasonal inputs of
rainfall, which mix up with stream and subsurface waters. In April 2015,
the Chirripó Hydrological Research Site (CHRS) was installed with the
goal of advancing the understanding of the hydrological functioning in
the Central American Páramo using environmental tracers (i.e., water
stable isotopes) in combination with hydrometric data. A detailed map of
CHRS is available in Esquivel-Hernández et al. (2019).