Drivers of peatland water table dynamics in the central Andes, Bolivia and Peru

Abstract

Cushion plant dominated peatlands are key ecosystems in tropical alpine regions of the Andes in South America. The cushion plants have formed peat bodies over thousands of years that fill many valley bottoms, and the forage produced by the plants is critical for native and nonnative domesticated mammals. The sources and flow paths of water supporting these peatlands remain largely unknown. Some studies have suggested that glacier meltwater streams support some peatlands, and that the ongoing loss of glaciers and their meltwaters could lead to the loss or diminishment of peatlands. We analysed the hydrologic regime of 10 peatlands in four mountain regions of Bolivia and Peru using groundwater monitoring. Groundwater levels in peatlands were relatively stable and within 20 cm of the ground surface during the rainy season, and many sites had water tables 40–90 cm below the ground surface in the dry season. Topographic and groundwater elevations in the peatlands demonstrated that the water source of all 10 peatlands was hillslope groundwater flowing from lateral moraines, talus, colluvium, or bedrock aquifers into the peatlands. There was little to no input from streams, whether derived from glacier melt or other sources, and glacier melt could not have recharged the hillslope aquifers supporting peatlands. We measured the stable water isotopes in water samples taken during different seasons, distributed throughout the catchments, and the values are consistent with this interpretation. Our findings indicate that peatlands in the study region are recharged by hillslope groundwater discharge rather than stream water and may not be as vulnerable to glacial decline as other studies have indicated. However, both glaciers and peatlands are susceptible to changing thermal and precipitation regimes that could affect the persistence of peatlands.

A review of groundwater in high mountain environments

“…Several studies have examined the hydrologic function of wetlands and meadows in high mountain catchments (Chignell, Laituri, Young, & Evangelista, 2019; Chimner et al, 2019; Cooper et al, 2010, 2019; Lowry, Loheide, Moore, & Lundquist, 2011; Millar, Cooper, & Ronayne, 2018; Mosquera, Lazo, Célleri, Wilcox, & Crespo, 2015; Mosquera et al, 2016; Polk et al, 2017; Streich & Westbrook, 2019). Due to their excess of water and decreasing permeability with drying, wetlands can self‐regulate to keep the water table near the land surface (Rezanezhad et al, 2016).…”

Meteorological Controls on Water Table Dynamics in Fen Peatlands Depend on Management Regimes

“…When the water level is above the soil surface, in the absence of peat as a matrix, the surface specific yield could be assumed to be one (Dettmann and Bechtold, 2016b) and thus showing a lower response to precipitation and VPD. According to Cooper et al (2019) once water table is near the soil surface, water table response becomes limited. Thus, this difference in water table position between the drained and the rewetted fens, is a major control over how the sites differ in their response to meteorological forcing.…”

“…Meteorological factors such as temperature, precipitation and relative humidity may affect the water table in peatlands through several processes such as recharge and evapotranspiration (Bridgham et al, 1999;Ferone and Devito, 2004;Menberu et al, 2016;Cooper et al, 2019). The combined effect of air temperature and relative humidity on evapotranspiration and thus on water table fluctuation can be understood by computing the vapor pressure deficit (VPD).…”

Reframing Pastoral Practices of Bofedal Management to Increase the Resilience of Andean Water Towers

“…Bofedales vary in size according to their geomorphological setting and hydrological conditions (Squeo et al 2006). The water that replenishes bofedal systems may include contributions from surface hydrology (eg lakes and streams), springs, precipitation (including surface runoff), and glacier outflow (Polk et al 2017;Cooper et al 2019). In pastoralist communities, herein emphasized, the water is sustained by the construction of canals and waterways to redirect hydrological flow and infiltration.…”