Groundwater Depletion in the Middle East from GRACE with Implications for Transboundary Water Management in the Tigris-Euphrates-Western Iran Region

In this study, we use observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to evaluate freshwater storage trends in the north-central Middle East, including portions of the Tigris and Euphrates River Basins and western Iran, from January 2003 to December 2009. GRACE data show an alarming rate of decrease in total water storage of approximately -27.2 plus or minus 0.6 millimeters per year equivalent water height, equal to a volume of 143.6 cubic kimometers during the course of the study period. Additional remote-sensing information and output from land surface models were used to identify that groundwater losses are the major source of this trend. The approach used in this study provides an example of ''best current capabilities'' in regions like the Middle East, where data access can be severely limited. Results indicate that the region lost 17.3 plus or minus 2.1 millimeters per year equivalent water height of groundwater during the study period, or 91.3 plus or minus 10.9 cubic kilometers in volume. Furthermore, results raise important issues regarding water use in transboundary river basins and aquifers, including the necessity of international water use treaties and resolving discrepancies in international water law, while amplifying the need for increased monitoring for core components of the water budget

Statistical prediction of terrestrial water storage changes in the Amazon Basin using tropical Pacific and North Atlantic sea surface temperature anomalies

Floods and droughts frequently affect the Amazon River basin, impacting transportation, agriculture, and ecosystem processes within several South American countries. Here we examine how sea surface temperature (SST) anomalies influence interannual variability of terrestrial water storage anomalies (TWSAs) in different regions within the Amazon Basin and propose a statistical modeling framework for TWSA prediction on seasonal timescales. Three simple semi-empirical models forced by a linear combination of lagged spatial averages of central Pacific and tropical North Atlantic climate indices (Niño 4 and TNAI) were calibrated against a decade-long record of 3°, monthly TWSAs observed by the Gravity Recovery And Climate Experiment (GRACE) satellite mission. Niño 4 was the primary external forcing in the northeastern region of the Amazon Basin, whereas TNAI was dominant in central and western regions. A combined model using the two indices improved the fit significantly (p< 0.05) for at least 64% of the grid cells within the basin, compared to models forced solely with Niño 4 or TNAI. The combined model explained 66% of the observed variance in the northeastern region, 39% in the central and western region, and 43% for the Amazon Basin as a whole, with a 3-month lead time between the climate indices and the predicted TWSAs. Model performance varied seasonally: it was higher than average during the wet season in the northeastern Amazon and during the dry season in the central and western region. The predictive capability of the combined model was degraded with increasing lead times. Degradation rates were lower in the northeastern Amazon (where 49% of the variance was explained using an 8-month lead time versus 69% for a 1-month lead time) compared to the central and western Amazon (where 22% of the variance was explained at 8 months versus 43% at 1 month). These relationships may contribute to an improved understanding of the climate processes regulating the spatial patterns of flood and drought risk in South America.©Author(s) 2014

Statistical prediction of terrestrial water storage changes in the Amazon Basin using tropical Pacific and North Atlantic sea surface temperature anomalies

Floods and droughts frequently affect the Amazon River basin, impacting transportation, agriculture, and ecosystem processes within several South American countries. Here we examine how sea surface temperature (SST) anomalies influence interannual variability of terrestrial water storage anomalies (TWSAs) in different regions within the Amazon Basin and propose a statistical modeling framework for TWSA prediction on seasonal timescales. Three simple semi-empirical models forced by a linear combination of lagged spatial averages of central Pacific and tropical North Atlantic climate indices (Niño 4 and TNAI) were calibrated against a decade-long record of 3°, monthly TWSAs observed by the Gravity Recovery And Climate Experiment (GRACE) satellite mission. Niño 4 was the primary external forcing in the northeastern region of the Amazon Basin, whereas TNAI was dominant in central and western regions. A combined model using the two indices improved the fit significantly (<i>p</i> < 0.05) for at least 64% of the grid cells within the basin, compared to models forced solely with Niño 4 or TNAI. The combined model explained 66% of the observed variance in the northeastern region, 39% in the central and western region, and 43% for the Amazon Basin as a whole, with a 3-month lead time between the climate indices and the predicted TWSAs. Model performance varied seasonally: it was higher than average during the wet season in the northeastern Amazon and during the dry season in the central and western region. The predictive capability of the combined model was degraded with increasing lead times. Degradation rates were lower in the northeastern Amazon (where 49% of the variance was explained using an 8-month lead time versus 69% for a 1-month lead time) compared to the central and western Amazon (where 22% of the variance was explained at 8 months versus 43% at 1 month). These relationships may contribute to an improved understanding of the climate processes regulating the spatial patterns of flood and drought risk in South America

Inter-comparison of ground gravity and vertical height measurements at collocated IGETS stations

International audienceVertical displacements and time-varying gravity fluctuations are representative of various deformation mechanisms of the Earth occurring at different spatial and temporal scales. The inter-comparison of ground-gravity measurements with vertical surface displacements enables to estimate the transfer function of the Earth at various timescales related to the rheological properties of the Earth. In this paper, we estimate the gravity-to-height changes ratio at seasonal timescales due mostly to hydrological mass variabilities. We investigate this ratio at nine sites where Global Navigation Satellite System (GNSS) and Superconducting Gravimeter continuous measurements are collocated. Predicted gravity-to-height change ratios for a hydrological model are around-2 nm/s²/mm when there is no local mass effect. This is in agreement with theoretical modeling for an elastic Earth's model. Spectral analysis of vertical displacement and surface gravimetric time-series show a coherency larger than 50% at seasonal timescales at most sites. The obtained gravity-to-height change ratios range between-5 and-2 nm/s²/mm for stations Lhasa, Metsahovi, Ny-Alesund, Onsala, Wettzell and Yebes. At Canberra and Sutherland, this ratio is close to zero. Finally, at Strasbourg site the coherency is low and the ratio is positive because of local mass effects affecting gravimetric records

Satellites measure recent rates of groundwater depletion in California's Central Valley

 In highly-productive agricultural areas such as California's Central Valley, where groundwater often supplies the bulk of the water required for irrigation, quantifying rates of groundwater depletion remains a challenge owing to a lack of monitoring infrastructure and the absence of water use reporting requirements. Here we use 78 months (October, 2003–March, 2010) of data from the Gravity Recovery and Climate Experiment satellite mission to estimate water storage changes in California's Sacramento and San Joaquin River Basins. We find that the basins are losing water at a rate of 31.0 ± 2.7 mm yr−1 equivalent water height, equal to a volume of 30.9 km3 for the study period, or nearly the capacity of Lake Mead, the largest reservoir in the United States. We use additional observations and hydrological model information to determine that the majority of these losses are due to groundwater depletion in the Central Valley. Our results show that the Central Valley lost 20.4 ± 3.9 mm yr−1 of groundwater during the 78-month period, or 20.3 km3 in volume. Continued groundwater depletion at this rate may well be unsustainable, with potentially dire consequences for the economic and food security of the United States

Satellites measure recent rates of groundwater depletion in California's Central Valley

 In highly-productive agricultural areas such as California's Central Valley, where groundwater often supplies the bulk of the water required for irrigation, quantifying rates of groundwater depletion remains a challenge owing to a lack of monitoring infrastructure and the absence of water use reporting requirements. Here we use 78 months (October, 2003–March, 2010) of data from the Gravity Recovery and Climate Experiment satellite mission to estimate water storage changes in California's Sacramento and San Joaquin River Basins. We find that the basins are losing water at a rate of 31.0 ± 2.7 mm yr−1 equivalent water height, equal to a volume of 30.9 km3 for the study period, or nearly the capacity of Lake Mead, the largest reservoir in the United States. We use additional observations and hydrological model information to determine that the majority of these losses are due to groundwater depletion in the Central Valley. Our results show that the Central Valley lost 20.4 ± 3.9 mm yr−1 of groundwater during the 78-month period, or 20.3 km3 in volume. Continued groundwater depletion at this rate may well be unsustainable, with potentially dire consequences for the economic and food security of the United States

Satellites measure recent rates of groundwater depletion in California's Central Valley

 In highly-productive agricultural areas such as California's Central Valley, where groundwater often supplies the bulk of the water required for irrigation, quantifying rates of groundwater depletion remains a challenge owing to a lack of monitoring infrastructure and the absence of water use reporting requirements. Here we use 78 months (October, 2003–March, 2010) of data from the Gravity Recovery and Climate Experiment satellite mission to estimate water storage changes in California's Sacramento and San Joaquin River Basins. We find that the basins are losing water at a rate of 31.0 ± 2.7 mm yr−1 equivalent water height, equal to a volume of 30.9 km3 for the study period, or nearly the capacity of Lake Mead, the largest reservoir in the United States. We use additional observations and hydrological model information to determine that the majority of these losses are due to groundwater depletion in the Central Valley. Our results show that the Central Valley lost 20.4 ± 3.9 mm yr−1 of groundwater during the 78-month period, or 20.3 km3 in volume. Continued groundwater depletion at this rate may well be unsustainable, with potentially dire consequences for the economic and food security of the United States

Local and global hydrological contributions to time-variable gravity in Southwest Niger

Advances in methods of observation are essential to ensure a better understanding of changes in water resources considering climate variability and human activities. The GHYRAF (Gravity and Hydrology in Africa) experiments aim to combine gravimetric measurements with dense hydrological surveys to better characterize the annual water storage variability in tropical West Africa. The first absolute gravimetric measurements were performed in Southwest Niger, near a temporary pond where rapid infiltration to an unconfined aquifer occurs. As gravity is sensitive both to local and global variations of water mass distribution, the large-scale hydrological contribution to time-variable gravity has been removed using either GRACE satellite data or global hydrology models. The effect of the local water storage changes was modelled using in situ measurements of the water table, soil moisture and pond water level. The adjustment of these simulations to residual ground gravity observations helped to constrain the specific yield to a value ranging between 1.8 and 6.2 per cent. This range of value is consistent, albeit on the low side, with the aquifer water content (6-12 per cent) estimated by magnetic resonance soundings, which are known to slightly overestimate the specific yield in this geological context. The comparison of these two independent geophysical methods shows their potential to constrain the local hydrogeological parameters. Besides, this study evidences the worth of correcting the gravity signal for large-scale hydrology before recovering local water storage parameters

Estudios de Historia de España, 1988, vol. 1 (número completo)

Contenido: Presentación – Sepúlveda en tiempos de Alfonso el Sabio / Antonio Linage Conde – Algunas precisiones sobre los golfines / Isabel J. Las Heras – Otra vez sobre el señorío de Illescas / Hilda Grassotti – Los preliminares de la Guerra de los Cien años y el desarrollo mercantil de la marina de Castilla / María Concepción Rodríguez de Monteagudo – Sobre finanzas y deudas nobiliarias / María del Carmen Carlé – Dos bibliotecas particulares del siglo XV / María Cristina Longinotti – Manifestación de dineros en la aduana de Murcia con Aragón (1493-1494) / Juan Torres Fontes – Traducciones: Fuero de Santander, por María Cristina Longinotti – Reseñas bibliográfica