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Interpreting discrepancies between discharge and precipitation in high‐altitude area of Chile's Norte Chico region (26–32°S)
Author(s) -
Favier Vincent,
Falvey Mark,
Rabatel Antoine,
Praderio Estelle,
López David
Publication year - 2009
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2008wr006802
Subject(s) - snow , precipitation , glacier , environmental science , surface runoff , weather research and forecasting model , sublimation (psychology) , altitude (triangle) , climatology , atmospheric sciences , hydrology (agriculture) , physical geography , geology , meteorology , geography , geomorphology , psychology , ecology , geotechnical engineering , geometry , mathematics , psychotherapist , biology
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 −1 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.