Evaluación de estimaciones satelitales de precipitación nívea en la cuenca superior del río San Juan, Argentina

Abstract

The Tulum, Ullum and Zonda oasis concentrates more of 90 per cent of the population in the San Juan province and depend almost exclusively of surface water resource, whose origin is snow melting at Andes Mountain. Between 2010 and 2019, with the exception of the years 2015 and 2016, the volume
of water that flowed through this river presented annual values between 675Hm³ and 1 120Hm³, categorized as very dry-to-dry hydrological cycles with amounts less than 1 200Hm³ necessary for activities in The oasis. Due to the lack of a historical record of snow precipitation in the upper basin of the San Juan River, estimates based on GPM Final IMERG (Integrated Multi-satellitE Retrievals for GPM - Global Precipitation Measurenment) satellite information were used. These were compared with the daily measurements of a Chilean meteorological station close to the international limit (2014-2020) and with the annual water volume of the San Juan River (DJUA), considered as snow index by Poblete and Vera (2019). The spatial distribution of the snow cover of the Final IMERG GIS raster data was also compared with MODIS (Moderate
Resolution Imaging Spectroradiometer) images in the snowfall events of the year 2020. The association between the observed precipitation data, grouped annually, with the DJUA presented a very strong positive linear correlation, with a significance level of 95%. Based on the linear regression model, the
forecast for the hydrological year 2020-2021 of 882 Hm³ was obtained. The observed and estimated daily data have no correlation; the total estimated annual accumulated precipitation and the volume of water of the San Juan River show a low correlation, without statistical significance. This result could be due to the punctual data, since in a visual analysis of raster data a high concordance was observed in the spatial distribution between the estimated GPM precipitation and the snow cover in MODIS images for the 2020 snow period.