Modeling of GRACE-Derived Groundwater Information in the Colorado River Basin

Groundwater depletion has been one of the major challenges in recent years. Analysis of groundwater levels can be beneficial for groundwater management. The National Aeronautics and Space Administration’s twin satellite, Gravity Recovery and Climate Experiment (GRACE), serves in monitoring terrestrial water storage. Increasing freshwater demand amidst recent drought (2000–2014) posed a significant groundwater level decline within the Colorado River Basin (CRB). In the current study, a non-parametric technique was utilized to analyze historical groundwater variability. Additionally, a stochastic Autoregressive Integrated Moving Average (ARIMA) model was developed and tested to forecast the GRACE-derived groundwater anomalies within the CRB. The ARIMA model was trained with the GRACE data from January 2003 to December of 2013 and validated with GRACE data from January 2014 to December of 2016. Groundwater anomaly from January 2017 to December of 2019 was forecasted with the tested model. Autocorrelation and partial autocorrelation plots were drawn to identify and construct the seasonal ARIMA models. ARIMA order for each grid was evaluated based on Akaike’s and Bayesian information criterion. The error analysis showed the reasonable numerical accuracy of selected seasonal ARIMA models. The proposed models can be used to forecast groundwater variability for sustainable groundwater planning and management

Recent La Plata basin drought conditions observed by satellite gravimetry

The Gravity Recovery and Climate Experiment (GRACE) provides quantitative measures of terrestrial water storage (TWS) change. GRACE data show a significant decrease in TWS in the lower (southern) La Plata river basin of South America over the period 2002-2009, consistent with recognized drought conditions in the region. GRACE data reveal a detailed picture of temporal and spatial evolution of this severe drought event, which suggests that the drought began in lower La Plata in around austral spring 2008 and then spread to the entire La Plata basin and peaked in austral fall 2009. During the peak, GRACE data show an average TWS deficit of ~12 cm (equivalent water layer thickness) below the 7 year mean, in a broad region in lower La Plata. GRACE measurements are consistent with accumulated precipitation data from satellite remote sensing and with vegetation index changes derived from Terra satellite observations. The Global Land Data Assimilation System model captures the drought event but underestimates its intensity. Limited available groundwater-level data in southern La Plata show significant groundwater depletion, which is likely associated with the drought in this region. GRAC-observed TWS change and precipitation anomalies in the studied region appear to closely correlate with the ENSO climate index, with dry and wet seasons corresponding to La Ni\~na and El Ni\~no events, respectively

Agricultural Drought Monitoring And Prediction Using Soil Moisture Deficit Index

The purposes of this study are: 1) to evaluate the performance of an agricultural drought index, Soil Moisture Deficit Index (SMDI) at continental scale; 2) to develop an agricultural drought prediction method based on precipitation, evapotranspiration and terrestrial water storage. This study applied multiple linear regression (MLR) with the inputs of precipitation from Parameter-elevation Regressions on Independent Slopes Model (PRISM), evapotranspiration from Moderate Resolution Imaging Spectroradiometer (MODIS) MOD 16 and terrestrial water storage (TWS) derived from the Gravity Recovery and Climate Experiment (GRACE) to predict soil moisture and SMDI. The inputs of the MLR model were chosen based on the mass conservation of the hydrological quantities at the near surface soil layer (two meters). In addition, the model also includes seasonal and regional terms for estimation. Comparisons with the US drought monitor （USDM）showed that SMDI can be used as a proxy of agricultural drought. The model exhibited strong predictive skills at both one- and two-month lead times in forecasting agricultural drought (correlation \u3e0.8 and normalized root mean square error \u3c15%)

Assessing Terrestrial Water Storage Variations in Southern Spain Using Rainfall Estimates and GRACE Data

This paper investigates the relationship between rainfall, groundwater and Gravity Recovery and Climate Experiment (GRACE) data to generate regional-scale estimates of terrestrial water storage variations in the Andalucía region of southern Spain. These estimates can provide information on groundwater depletion (caused by periods of low rainfall or droughts) and groundwater recovery. The spatial distribution of groundwater bodies in southern Spain is complex and current in situ groundwater monitoring methods are deficient, particularly in terms of obtaining representative samples and in implementing and maintaining groundwater monitoring networks. The alternative approach proposed here is to investigate the relationship between precipitation time series and changes in the terrestrial water storage estimated from GRACE observations. The results were validated against the estimated fluctuation in regional groundwater. The maximum correlation between the mean groundwater level and the GRACE observations is 0.69 and this occurs at a lag of one month because the variation in gravity is immediate, but rainfall water requires around one month to travel across the vadose zone before it reaches the groundwater table. Using graphical methods of accumulated deviations from the mean, we show that, in general, groundwater storage follows the smooth, multi-year trends of terrestrial water storage but with less short-term trends; the same is true of rainfall, for which the local trends are more pronounced. There is hysteresis-like behaviour in the variations in terrestrial water storage and in the variations of groundwater. In practical terms, this study shows that, despite the abnormal dryness of the Iberian Peninsula during the 2004–2010 drought, the depleted groundwater storage in Andalucía recovered almost to its pre-drought level by 2016. In addition, groundwater storage and terrestrial water storage show very similar trends but with a delay in the groundwater trendProjects PID2019-106435GB-I00 (Ministerio de Ciencia e Innovación)CGL2015-66835-P (Ministerio de Ciencia, Innovación y Universidades

Large-scale assessment of groundwater reserves and processes in Brazil, South America

As reservas de água subterrânea estão entre os componentes do balanço hídrico com maior incerteza de quantificação. O entendimento da sua disponibilidade ainda é limitado em comparação com outras reservas hídricas como rios, atmosfera, solo e lagos. A busca por esse recurso tem aumentado tanto nas áreas úmidas quanto nas áreas secas. Explorar os processos de interação entre as águas subterrâneas e os rios em aquíferos de grande escala (como o comportamento das reservas em períodos secos, eventos de recarga episódica e variabilidade anual), é de grande interesse para a indústria, a economia e a qualidade de vida da população. O desenvolvimento e a avaliação de ferramentas é um passo inicial para o uso sustentável das águas subterrâneas. O objetivo desta tese é avançar no entendimento de processos hidrogeológicos de grande escala que ocorrem no Brasil em diferentes climas e formações aquíferas a partir de ferramentas inovadoras e complementares de monitoramento in situ, dados de sensoriamento remoto e modelagem hidrológica. Verificou-se que o uso do GRACE para detectar variações nas reservas de água subterrânea para um aquífero sedimentar no semiárido brasileiro apresentou resultados adequados. As reservas de água subterrânea estão entre os componentes do balanço hídrico com maior incerteza de quantificação. O entendimento da sua disponibilidade ainda é limitado em comparação com outras reservas hídricas como rios, atmosfera, solo e lagos. A busca por esse recurso tem aumentado tanto nas áreas úmidas quanto nas áreas secas. Explorar os processos de interação entre as águas subterrâneas e os rios em aquíferos de grande escala (como o comportamento das reservas em períodos secos, eventos de recarga episódica e variabilidade anual), é de grande interesse para a indústria, a economia e a qualidade de vida da população. O desenvolvimento e a avaliação de ferramentas é um passo inicial para o uso sustentável das águas subterrâneas. O objetivo desta tese é avançar no entendimento de processos hidrogeológicos de grande escala que ocorrem no Brasil em diferentes climas e formações aquíferas a partir de ferramentas inovadoras e complementares de monitoramento in situ, dados de sensoriamento remoto e modelagem hidrológica. Verificou-se que o uso do GRACE para detectar variações nas reservas de água subterrânea para um aquífero sedimentar no semiárido brasileiro apresentou resultados adequados.Groundwater volumes are among the water balance components with the greatest uncertainty of quantification, the understanding of its availability is still limited compared to other water reserves such as rivers, atmosphere, soil, and lakes. The search for this continuous supply resource throughout the year has increased in wet and dry areas. Exploring hydrological, hydrogeological, and surface-groundwater interaction processes among these large-scale South American aquifers, such as the dynamics associated with dry periods response, recharge events, and interannual variability, is of great interest to the industry, the economy, and the quality of life of the regional population. And the development and testing of tools for researching these aspects is a primer step for sustainable usage of groundwaters in the South American domain. The main objective of this thesis is to advance in the determination of large-scale hydrogeological process in Brazil, South America in different climates and aquifer formations from innovative and complementary tooling of intensive field monitoring, remote sensing data, and hydrological modeling. We found that the use of GRACE to detect variations in groundwater reserves showed adequate results for a small-scale sedimentary aquifer in the Brazilian semi-arid region. The findings were promising to improve the understanding of droughts at different scales in those areas. GRACE data also showed itself as an essential tool for monitoring groundwater volumes in the other two aquifers in humid subtropical areas and investigated in this thesis (Caiuá Aquifer and SASG). We also found that in those humid subtropical areas, the high soil moisture storage has an important role in the occurrence of large episodic recharge events. Atypical rainfall in winter periods was responsible for the increase in soil moisture that explains the larger events. The changes in aquifer storage caused by episodic recharge events are long-lasting and directly affect low flows in rivers with implications on hydro-climatic variability. We also brought important findings related to groundwater variations in fractured aquifer systems, which are complex to predict. Significant contributions related to groundwater level variations, transit times, regional trends, and interaction with the rivers in the SASG were presented

Terrestrial water storage changes over the Pearl River Basin from GRACE and connections with Pacific climate variability

AbstractTime-variable gravity data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are used to study terrestrial water storage (TWS) changes over the Pearl River Basin (PRB) for the period 2003–Nov. 2014. TWS estimates from GRACE generally show good agreement with those from two hydrological models GLDAS and WGHM. But they show different capability of detecting significant TWS changes over the PRB. Among them, WGHM is likely to underestimate the seasonal variability of TWS, while GRACE detects long-term water depletions over the upper PRB as was done by hydrological models, and observes significant water increases around the Longtan Reservoir (LTR) due to water impoundment. The heavy drought in 2011 caused by the persistent precipitation deficit has resulted in extreme low surface runoff and water level of the LTR. Moreover, large variability of summer and autumn precipitation may easily trigger floods and droughts in the rainy season in the PRB, especially for summer, as a high correlation of 0.89 was found between precipitation and surface runoff. Generally, the PRB TWS was negatively correlated with El Niño-Southern Oscillation (ENSO) events. However, the modulation of the Pacific Decadal Oscillation (PDO) may impact this relationship, and the significant TWS anomaly was likely to occur in the peak of PDO phase as they agree well in both of the magnitude and timing of peaks. This indicates that GRACE-based TWS could be a valuable parameter for studying climatic influences in the PRB

Drought rapidly diminishes the large net CO2 uptake in 2011 over semi-arid Australia

Each year, terrestrial ecosystems absorb more than a quarter of the anthropogenic carbon emissions, termed as land carbon sink. An exceptionally large land carbon sink anomaly was recorded in 2011, of which more than half was attributed to Australia. However, the persistence and spatially attribution of this carbon sink remain largely unknown. Here we conducted an observation-based study to characterize the Australian land carbon sink through the novel coupling of satellite retrievals of atmospheric CO2 and photosynthesis and in-situ flux tower measures. We show the 2010–11 carbon sink was primarily ascribed to savannas and grasslands. When all biomes were normalized by rainfall, shrublands however, were most efficient in absorbing carbon. We found the 2010–11 net CO2 uptake was highly transient with rapid dissipation through drought. The size of the 2010–11 carbon sink over Australia (0.97 Pg) was reduced to 0.48 Pg in 2011–12, and was nearly eliminated in 2012–13 (0.08 Pg). We further report evidence of an earlier 2000–01 large net CO2 uptake, demonstrating a repetitive nature of this land carbon sink. Given a significant increasing trend in extreme wet year precipitation over Australia, we suggest that carbon sink episodes will exert greater future impacts on global carbon cycle

Satellite Gravimetry Applied to Drought Monitoring

Near-surface wetness conditions change rapidly with the weather, which limits their usefulness as drought indicators. Deeper stores of water, including root-zone soil wetness and groundwater, portend longer-term weather trends and climate variations, thus they are well suited for quantifying droughts. However, the existing in situ networks for monitoring these variables suffer from significant discontinuities (short records and spatial undersampling), as well as the inherent human and mechanical errors associated with the soil moisture and groundwater observation. Remote sensing is a promising alternative, but standard remote sensors, which measure various wavelengths of light emitted or reflected from Earth's surface and atmosphere, can only directly detect wetness conditions within the first few centimeters of the land s surface. Such sensors include the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) C-band passive microwave measurement system on the National Aeronautic and Space Administration's (NASA) Aqua satellite, and the combined active and passive L-band microwave system currently under development for NASA's planned Soil Moisture Active Passive (SMAP) satellite mission. These instruments are sensitive to water as deep as the top 2 cm and 5 cm of the soil column, respectively, with the specific depth depending on vegetation cover. Thermal infrared (TIR) imaging has been used to infer water stored in the full root zone, with limitations: auxiliary information including soil grain size is required, the TIR temperature versus soil water content curve becomes flat as wetness increases, and dense vegetation and cloud cover impede measurement. Numerical models of land surface hydrology are another potential solution, but the quality of output from such models is limited by errors in the input data and tradeoffs between model realism and computational efficiency. This chapter is divided into eight sections, the next of which describes the theory behind satellite gravimetry. Following that is a summary of the GRACE mission and how hydrological information is gleaned from its gravity products. The fourth section provides examples of hydrological science enabled by GRACE. The fifth and sixth sections list the challenging aspects of GRACE derived hydrology data and how they are being overcome, including the use of data assimilation. The seventh section describes recent progress in applying GRACE for drought monitoring, including the development of new soil moisture and drought indicator products, and that is followed by a discussion of future prospects in satellite gravimetry based drought monitoring

Analysis of long-term terrestrial water storage variations in the Yangtze River basin

In this study, we analyze 32 yr of terrestrial water storage (TWS) data obtained from the Interim Reanalysis Data (ERA-Interim) and Noah model from the Global Land Data Assimilation System (GLDAS-Noah) for the period 1979 to 2010. The accuracy of these datasets is validated using 26 yr (1979–2004) of runoff data from the Yichang gauging station and comparing them with 32 yr of independent precipitation data obtained from the Global Precipitation Climatology Centre Full Data Reanalysis Version 6 (GPCC) and NOAA's PRECipitation REConstruction over Land (PREC/L). Spatial and temporal analysis of the TWS data shows that TWS in the Yangtze River basin has decreased significantly since the year 1998. The driest period in the basin occurred between 2005 and 2010, and particularly in the middle and lower Yangtze reaches. The TWS figures changed abruptly to persistently high negative anomalies in the middle and lower Yangtze reaches in 2004. The year 2006 is identified as major inflection point, at which the system starts exhibiting a persistent decrease in TWS. Comparing these TWS trends with independent precipitation datasets shows that the recent decrease in TWS can be attributed mainly to a decrease in the amount of precipitation. Our findings are based on observations and modeling datasets and confirm previous results based on gauging station datasets

Satellite Gravimetry Applied to Drought Monitoring

11.1 Introduction...261 11.2 Satellite Gravimetry...262 11.3 Gravity Recovery and Climate Experiment...263 11.4 Hydrological Science Enabled by GRACE...264 11.5 Unique and Challenging Aspects of GRACE Data...265 11.6 Disaggregating and Downscaling GRACE Data...266 11.7 Drought Monitoring with GRACE...268 11.8 Future Prospects... 272 Acknowledgments....274 References.... 27