Interpreting discrepancies between discharge and precipitation in high‐altitude area of Chile's Norte Chico region (26–32°S)

Abstract

[1] The water resources of high-altitude areas of Chile's semiarid Norte Chico region (26-32°S) are studied using surface hydrological observations (from 59 rain gauges and 38 hydrological stations), remotely sensed data, and output from atmospheric prediction models. At high elevations, the observed discharge is very high in comparison with precipitation. Runoff coefficients exceed 100% in many of the highest watersheds. A glacier inventory performed with aerial photographs and ASTER images was combined with information from past studies, suggesting that glacier retreat could contribute between 5% and 10% of the discharge at 3000 m in the most glacierized catchment of the region. Snow extent was studied using MOD10A2 data. Results show that snow is present during 4 months at above 3000 m, suggesting that snow processes are crucial. The mean annual sublimation ($80 mm a À1 at 4000 m) was estimated from the regional circulation model (WRF) and data from past studies. Finally, spatial distribution of precipitation was derived from available surface data and the global forecast system (GFS) atmospheric prediction model. Results suggest that annual precipitation is three to five times higher near the peak of the Andes than in the lowlands to the west. The GFS model suggests that daily precipitation rates in the mountains are similar to those in the coastal region, but precipitation events are more frequent and tend to last longer. Underestimation of summer precipitation may also explain part of the excess in discharge. Simple calculations show that consideration of GFS precipitation distributions, sublimation, and glacier melt leads to a better hydrological balance.

Glacier contribution to streamflow in two headwaters of the Huasco River, Dry Andes of Chile

“…As a result, melting of the seasonal snowpack is the major component of the water balance at the regional scale, as shown by Favier et al (2009).…”

“…Glaciers are often perceived as important water reservoirs in the region, but no quantitative study allows such a statement. Favier et al (2009) showed that, at the regional scale, the main water source is the seasonal snowpack. However, the authors pointed out the fact that glacier contribution needs to be further addressed, because few data were available in high-altitude catchments where glaciers exist.…”

The Andes climate and weather

“…level, however, the westerly flow is no longer blocked by the Andes but rather forced to ascend, resulting in pre-frontal precipitation enhancement over the subtropical Andes as far north as 30 • S (Barret et al, 2009;Viale and Norte, 2009). Indeed, the few high-altitude records suggest that orographic air uplift produces 2-3 times more annual precipitation up in the Andes relative to the coastal values at the same latitudes (Falvey and Garreaud, 2007;Favier et al, 2008).…”

Estimating Spatial Distribution of Air Temperature from Meteorological Stations Using Atmospheric Model

“…It has an important orographic influence (Favier, Falvey, Rabatel, Pradeiro, & Lopez, 2009) with a Mediterranean rainfall regime and precipitation occurs predominantly in winter months, during the passage of frontal systems from the southern Pacific (Falvey & Garreaud, 2007). The interannual variability of precipitation is strongly influenced by the El Niño Southern Oscillation, with higher than average amounts during the warm phase (Rutllant & Fuenzalida, 1991).…”