Matthew Rodell

Satellite-based estimates of groundwater depletion in India

Groundwater is a primary source of fresh water in many parts of the world. Some regions are becoming overly dependent on it, consuming groundwater faster than it is naturally replenished and causing water tables to decline unremittingly. Indirect evidence suggests that this is the case in northwest India, but there has been no regional assessment of the rate of groundwater depletion. Here we use terrestrial water storage-change observations from the NASA Gravity Recovery and Climate Experiment satellites and simulated soil-water variations from a data-integrating hydrological modelling system to show that groundwater is being depleted at a mean rate of 4.0u2009±u20091.0u2009cmu2009yr-1 equivalent height of water (17.7u2009±u20094.5u2009km3u2009yr-1) over the Indian states of Rajasthan, Punjab and Haryana (including Delhi). During our study period of August 2002 to October 2008, groundwater depletion was equivalent to a net loss of 109u2009km3 of water, which is double the capacity of India’s largest surface-water reservoir. Annual rainfall was close to normal throughout the period and we demonstrate that the other terrestrial water storage components (soil moisture, surface waters, snow, glaciers and biomass) did not contribute significantly to the observed decline in total water levels. Although our observational record is brief, the available evidence suggests that unsustainable consumption of groundwater for irrigation and other anthropogenic uses is likely to be the cause. If measures are not taken soon to ensure sustainable groundwater usage, the consequences for the 114,000,000 residents of the region may include a reduction of agricultural output and shortages of potable water, leading to extensive socioeconomic stresses.

Remote Sensing of the Terrestrial Water Cycle: Lakshmi/Remote Sensing of the Terrestrial Water Cycle

Reviewed by: Melissa J. Rura Ph.D. Contributing Editor, Photogrammetric Engineering & Remote Sensing (PE&RS). This collection from the American Geophysical Union (AGU) brings together research and researchers from across disciplines and the world to examine the how satellite data is used to expand our knowledge about the terrestrial water cycle and quantify its spatial and temporal variations. This particular text comes directly from the AGU Chapman Conference on Remote Sensing of the Terrestrial Water Cycle held in February 2012. This book is one Monograph (206) in the Geophysical Monograph Series published by Wiley in cooperation with the AGU. In particular, the book is divided into seven sections all of which relate directly to the terrestrial water cycle. Each individual chapter within each section is independent research contributed by different researchers that are grouped together by topic that do not necessarily and generally do not build upon each more comparable in the world of fiction to short stories than a novel and should be read as such. Section 1 addresses the remote sensing of precipitation with two literature reviews, the first on Rain / no rain classification (RNC) algorithms based on passive microwave sensors and the second review is on the Climate Prediction Center Morphing (CMORPH) techniques including the development and future directions. An application chapter considers work to improve the measure of precipitation in mountainous regions through research using Global Satellite Mapping (GSMap) algorithm and Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI). Finally, there is a discussion of quantitative precipitation estimates (QPEs) for error characterization and quantification in terms of the TRMM and Global Precipitation Measurement Mission (GPM). Section 2 addresses the remote sensing of evapotranspiration (ET) with two case-studies. The first case-study uses the 3Temp. model to ET based on Moderate Resolution Imaging Spectroradiometer (MODIS) data. It tests this method regionally, also looking for spatial and temporal trends within the Jinghe River Basin in the southern part of the Loess Plateau in China. The second case-study centered in the Lower-Colorado River Basin in a region of interest in southern California looked at ET using a Remotely Sensed Energy Balance (RSEB) model to investigate effects on the invasive Tamarisk species. Section 3 addresses surface water remote sensing. The first chapter is a case study looking at the Central Congo Basin’s Terrestrial Water Storage (TWS) changes using multiple satellite measures including, among others, the Gravity Recovery And Climate Change Experiment (GRACE) mission data. Chapter 10, Downstream Hydraulic Geometry (DHG) estimates are derived for the entire Yukon River Basin using software designed to measure river widths through algorithms applied to imagery data in conjunction with Digital Elevation Model (DEM) discharge estimates. The final chapter in this section is a report from the Jet Propulsion Lab on ongoing Surface Water Ocean Topography (SWOT) research. This particular study repurposed of the Terminal Descent Sensor (TDS) from the Mars Science Laboratory, which is a 35.75 GHz Dopplar Radar. This repurposed Kaband radar was deployed in bridge based river observations and preceded KaSPAR airborne radar. Section 4 addresses remote sensing of snow and the sensors best suited for its detection. The first chapter is a literature review of snow cover depletion in hydrologic applications and the change in remotely sensed data, its uses, and how it has changed the understanding of, especially snow extent measures. Next, a chapter discussing snow cover observations using the Visible /