Transient modelling of lacustrine regressions: two case studies from the Andean Altiplano

Abstract

A model was developed for estimating the delay between a change in climatic conditions and the corresponding fall of water level in large lakes. The input data include: rainfall, temperature, extraterrestrial radiation and astronomical mid‐month daylight hours. The model uses two empirical coefficients for computing the potential evaporation and one parameter for the soil capacity. The case studies are two subcatchments of the Altiplano (196 000 km2), in which the central low points are Lake Titicaca and a salar corresponding to the desiccation of the Tauca palaeolake. During the Holocene, the two catchments experienced a 100 m fall in water level corresponding to a decrease in water surface area of 3586 km2 and 55 000 km2, respectively. Under modern climatic conditions with a marked rainy season, the model allows simulation of water levels in good agreement with the observations: 3810 m a.s.l. for Lake Titicaca and lack of permanent wide ponds in the southern subcatchment. Simulations were carried out under different climatic conditions that might explain the Holocene fall in water level. Computed results show quite different behaviour for the two subcatchments. For the northern subcatchment, the time required for the 100 m fall in lake‐level ranges between 200 and 2000 years when, compared with the present conditions, (i) the rainfall is decreased by 15% (640 mm/year), or (ii) the temperature is increased by 5·5 °C, or (iii) rainfall is distributed equally over the year. For the southern subcatchment (Tauca palaeolake), the time required for a 100 m decrease in water level ranges between 50 and 100 years. This decrease requires precipitation values lower than 330 mm/year. Copyright © 2004 John Wiley & Sons, Ltd.

Accuracy assessment of SRTM v4 and ASTER GDEM v2 over the Altiplano watershed using ICESat/GLAS data

“…The Altiplano watershed is shared by three countries, Bolivia (70%), Peru (26%), and Chile (4%). The climate of this region is semi-arid with low precipitation, and the total amount varies strongly between the north (approximately 750 mm year −1 ) and south (160 mm year −1 ) (Condom et al 2004). The elevation dataset was generated using 33 GDEM v2 tiles for the GDEM version and 5 SRTM v4 tiles for the SRTM version.…”

Computation of the space and time evolution of equilibrium-line altitudes on Andean glaciers (10°N–55°S)

“…Topographic data are extracted from the modified GTOPO30 (1996) digital elevation model (DEM). This DEM is defined by a horizontal grid spacing of 30″ (approximately 1 km) and elevations were shifted by − 28 m to be in better agreement with 1:50 000 maps of central Andes region (Condom et al, 2004). Glaciers are presented on Fig.…”

Evaporation estimation on Lake Titicaca: a synthesis review and modelling

“…The climatology of this region is constrained by the yearly change in eastern and western atmospheric fluxes. It is characterized by a rainy season and a dry season (Ronchail, 1995;Berthier, 2000;Garreaud et al, 2003;Condom et al, 2004). The rainy season takes place during the austral summer, from December to March, and is characterized by an intense convective activity combined with moisture advection from the Amazon basin (Garreaud, 1999;Vuille, 1999).…”