Rodrigo Abarca del Rio

In 2000, the World population was 6.2 billion people; it reached 7 billion in 2012, and is expected to reach 9.5 billion (± 0.4) in 2050, 11 billion (± 1.5) in 2100, according to the 2012 UN projections (Gerland et al, in Science 346:234–237, 2014). The trend after 2100 is still one of global demographic growth, but after 2060, Africa is the only continent where the population would still increase. The amount of water consumed annually to produce the food necessary to meet the needs of the populations varies greatly between countries, from about 600 to 2500 m3/y per capita (Zimmer  in L’empreinte eau. Les faces cachees d’une ressource vitale. Charles Leopold Meyer, Paris, 2013), depending on their wealth, their food habits, and the percentage of food waste they generate (on average, 30% of the food produced is wasted). In 2000, the total food production was on the order of 3300 million tons (in cereal equivalents). In 2014, it is estimated that about 0.8 billion inhabitants of the planet suffer from hunger (FAO in World agriculture: towards 2030–2050. FAO, Rome, 2014. http://www.fao.org/docrep/004/Y3557E/y3557e00.HTM) 2014) and do not get the nutrition they need to be in good health or, in the case of children, to grow properly (both physically and intellectually). This food deficit was on the order of 40 million tons of cereal equivalents in 2014. The number of inhabitants with a food deficit was about 0.85 billion before the 2008 crisis and was decreasing annually, but it increased abruptly after 2008 up to 1 billion inhabitants, and is slowly decreasing now. Assuming a World average water consumption for food of 1300 m3/y per capita in 2000, 1400 m3/y in 2050 and 1500 m3/y in 2100, a volume of water of around 8200 km3/y was needed in 2000, 13000 km3/y will be needed in 2050 and 16500 km3/y in 2100 (Marsily in L’eau, un tresor en partage. Dunod, Paris, 2009). Can bioenergy be added to food production? Will that much water be available on earth, and where will it come from?  Is climate change going to modify the answers to these questions? Can severe droughts occur? Can there be conflicts related to a food deficit? Some preliminary answers and scenarios for food production will be given in this paper from a hydrologist viewpoint.

We predict flood events by fitting two simple logistic regression models between mesoscale rainfall and El Niño-Southern Oscillation (ENSO) index with local scale flooding into the Biobío River Basin in Chile from 1948 to 2002. Two different and complementary logistic models were studied: Logit and Probit. The models perform alike suggesting that the methodology is robust. The best model is most accurate during the autumn over 80% hit rate and in winter 66% hit rate, which are the seasons with high risk of floods. This work represents a first step in the development of a complete hydrological framework for the Biobío River Basin. The Logit distribution shows better results; thus, we suggest to use this distribution to relate flood events with mesoscale precipitation and ENSO index in the Biobío River Basin. Finally, these results explain the flood events and its relation with risk management. In forthcoming studies we will extend the methodology over this region and Chile taking advantage of the availability of higher resolution (temporal and spatial) weather products along with investigating climatic patterns and Intergovernmental Panel on Climate Change (IPCC) climate change scenarios.

In  ungauged  basin,  space-based  information  is  essential  for  the  monitoring  of  hydrological  water  cycle,  in
particular in regions undergoing  large flood  events where  satellite  data  may  be  used  as input to  hydrodynamic
models. A method for near 3D flood monitoring has been developed which uses synergies between radar altimetry
and high temporal resolution multi-spectral satellite. Surface Reflectance from the MODIS Terra instrument are
used to map areas of open water as well as aquatic vegetation on a weekly basis, while water level variations in the
inundated areas are provided by the radar altimetry from the Topex / Poseidon (T/P) and Envisat satellites. We
present this synergistic approach to three different regions: Niger Inner delta and Lake Tchad in Africa, and Ganga
river delta in Asia. Based mainly on visible and Near Infra Red (NIR) imagery is suitable to the observation of
inundation extent. This method is well adapted for arid and semi arid regions, but less for equatorial or boreal ones
due to cloud coverage.
This work emphasizes the limitations of current remote sensing techniques for full 3D-description of water storage
variability in ungauged basins, and provides a good introduction to the need and the potential use of the future
SWOT (Surface Water and Ocean Topography) satellite mission.

Located within the Altiplano at 3,686 m above sea level, Lake Poopó is remarkably shallow and very sensitive to hydrologic recharge. Progressive drying has been observed in the entire Titicaca-Poopó-Desaguadero-Salar de Coipasa (TPDS) system during the last decade, causing dramatic changes to Lake Poopó’s surface and its regional water supplies. Our research aims to improve understanding of Lake Poopó water storage capacity. Thus, we propose a new method based on freely available remote sensing data to reproduce Lake Poopó bathymetry. Laser ranging altimeter ICESat (Ice, Cloud, and land Elevation Satellite) is used during the lake’s lowest stages to measure vertical heights with high precision over dry land. These heights are used to estimate elevations of water contours obtained with Landsat imagery. Contour points with assigned elevation are filtered and grouped in a points cloud. Mesh gridding and interpolation function are then applied to construct 3D bathymetry. Complementary analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) surfaces from 2000 to 2012 combined with bathymetry gives water levels and storage evolution every 8 days.

The analysis of variability in Atmospheric Angular Momentum (AAM) and Length of day (LOD) of Abarca del Rio et al. [Ann.Geophys.18 (2000) 347 ] is extended to investigate a possible connection with solar activity fluctuations from interannual to secular time scales. The southern oscillation index and records of sea surface temperature are used as proxy series in this analysis during the era prior to the availability of AAM analyses. At  interannual times scales, the variability in AAM and LOD agrees with that in solar activity with regard to the decadal cycle in the stratospheric quasi biennial oscillation and solar activity but whose phases are slowly shifting from one another with time, while the stratospheric quasibiennial cycle agrees with the solar quasibiennial cycle, though led by 6years. At decadal times scales, AAM varies statistically with the solar decadal cycle over much of the last century since 1930–1940. The decadal mode in AAM is suggested here to be generated by upward propagation of surface atmospheric modes, from the surface throughout the troposphere through the stratosphere. Equatorial Sea Surface Temperature (SST) variability may be considered a proxy index for AAM variability because of the relationship to the El Nino/SouthernOscillation; its analysis over the last three centuries (1730–2000) and that of LOD since 1830 confirm the agreement found over the last part of the 20th century,as well as the general disagreement before.