How much groundwater did California's Central Valley lose during the 2012–2016 drought?

We estimate net groundwater storage change in the Central Valley from April 2002 to September 2016 as the difference between inflows and outflows, precipitation, evapotranspiration, and changes in soil moisture and surface water storage. We also estimate total water storage change attributable to groundwater change using Gravity Recovery and Climate Experiment (GRACE) satellite data, which should be equivalent to our water balance estimates. Over two drought periods within our 14-1/2 years study period (January 2007 to December 2009 and October 2012 to September 2016), we estimate from our water balance that a total of 16.5 km3 and 40.0 km3 of groundwater was lost, respectively. Our water balance-based estimate of the overall groundwater loss over the 14-1/2 years is −20.7 km3, which includes substantial recovery during nondrought periods The estimated rate of groundwater loss is greater during the recent drought (10.0 ± 0.2 versus 5.5 ± 0.3 km3/yr) than in the 2007–2009 drought, due to lower net inflows, a transition from row crops to trees, and higher crop water use, notwithstanding a reduction in irrigated area. The GRACE estimates of groundwater loss (−5.0 km3/yr for both water balance and GRACE during 2007–2009, and −11.2 km3/yr for GRACE versus −10 km3/yr for water balance during 2012–2016) are quite consistent for the two methods. However, over the entire study period, the GRACE-based groundwater loss estimate is almost triple that from the water balance, mostly because GRACE does not indicate the between-drought groundwater recovery that is inferred from our water balance.

[1]  C. Shum,et al.  On the postprocessing removal of correlated errors in GRACE temporal gravity field solutions , 2009 .

[2]  Claude N. Williams,et al.  Improved Historical Temperature and Precipitation Time Series for U.S. Climate Divisions , 2014 .

[3]  S. Cosentino,et al.  Dry matter and qualitative characteristics of alfalfa as affected by harvest times and soil water content , 2011 .

[4]  D. Chambers,et al.  Estimating Geocenter Variations from a Combination of GRACE and Ocean Model Output , 2008 .

[5]  Fei Chen,et al.  The effect of groundwater interaction in North American regional climate simulations with WRF/Noah-MP , 2015, Climatic Change.

[6]  A. Aghakouchak,et al.  Global warming and changes in risk of concurrent climate extremes: Insights from the 2014 California drought , 2014 .

[7]  J. Famiglietti.  The global groundwater crisis , 2014 .

[8]  D. Lettenmaier,et al.  Drought in the Pacific Northwest, 1920–2013 , 2016 .

[9]  S. Swenson,et al.  Satellites measure recent rates of groundwater depletion in California's Central Valley , 2011 .

[10]  J. Monteith.  Evaporation and environment. , 1965, Symposia of the Society for Experimental Biology.

[11]  D. Lettenmaier,et al.  Satellite‐based near‐real‐time estimation of irrigated crop water consumption , 2009 .

[12]  Rongjiang Wang,et al.  Significant lateral dip changes may have limited the scale of the 2015 Mw 7.8 Gorkha earthquake , 2017 .

[13]  R. Johnston,et al.  Ground water in the Central Valley, California; a summary report , 1991 .

[14]  C. Shum,et al.  Non-isotropic Gaussian smoothing and leakage reduction for determining mass changes over land and ocean using GRACE data , 2010 .

[15]  Minkang Cheng,et al.  Variations of the Earth's figure axis from satellite laser ranging and GRACE , 2011 .

[16]  P. Mote,et al.  Perspectives on the causes of exceptionally low 2015 snowpack in the western United States , 2016 .

[17]  Peter E. Thornton,et al.  Generating surfaces of daily meteorological variables over large regions of complex terrain , 1997 .

[18]  Fei Chen,et al.  Modeling seasonal snowpack evolution in the complex terrain and forested Colorado Headwaters region: A model intercomparison study , 2014 .

[19]  Daniel Griffin,et al.  How unusual is the 2012–2014 California drought? , 2014 .

[20]  Y. Hong,et al.  Have GRACE satellites overestimated groundwater depletion in the Northwest India Aquifer? , 2016, Scientific Reports.

[21]  B. Scanlon,et al.  Ground referencing GRACE satellite estimates of groundwater storage changes in the California Central Valley, USA , 2012 .

[22]  D. Lettenmaier,et al.  Is climate change implicated in the 2013–2014 California drought? A hydrologic perspective , 2015 .

[23]  Amir AghaKouchak,et al.  Temperature impacts on the water year 2014 drought in California , 2015 .

[24]  Kevin W. Manning,et al.  The community Noah land surface model with multiparameterization options (Noah-MP): 1. Model description and evaluation with local-scale measurements , 2011 .

[25]  C. Faunt,et al.  Groundwater availability of the Central Valley Aquifer, California , 2009 .

[26]  Zhengwei Yang,et al.  CropScape: A Web service based application for exploring and disseminating US conterminous geospatial cropland data products for decision support , 2012 .

[27]  D. Lettenmaier,et al.  A simple hydrologically based model of land surface water and energy fluxes for general circulation models , 1994 .

[28]  Charles F. Brush,et al.  Estimation of a water budget for 1972-2000 for the Grasslands Area, central part of the Western San Joaquin Valley, California , 2004 .