Dileep K. Panda

Spatiotemporal evolution of water storage changes in India from the updated GRACE-derived gravity records

Investigating changes in terrestrial water storage (TWS) is important for understanding response of the hydrological cycle to recent climate variability worldwide. This is particularly critical in India where the current economic development and food security greatly depend on its water resources. We use 129 monthly gravity solutions from NASAs Gravity Recovery and Climate Experiment (GRACE) satellites for the period of January 2003 to May 2014 to characterize spatiotemporal variations of TWS and groundwater storage (GWS). The spatiotemporal evolution of GRACE data reflects consistent patterns with that of several hydroclimatic variables and also shows that most of the water loss has occurred in the northern parts of India. Substantial GWS depletion at the rate of 1.25 and 2.1 cm yr−1 has taken place, respectively in the Ganges Basin and Punjab state, which are known as the Indias grain bowl. Of particular concern is the Ganges Basins storage loss in drought years, primarily due to anthropogenic groundwater withdrawals that sustain rice and wheat cultivation. We estimate these losses to be approximately 41, 44, and 42 km3 in 2004, 2009, and 2012, respectively. The GWS depletions that constitute about 90% of the observed TWS loss are also influenced by a marked rise in temperatures since 2008. A high degree of correspondence between GRACE-derived GWS and in situ groundwater levels from observation well validates the results. This validation increases confidence level in the application of GRACE observations in monitoring large-scale storage changes in intensely irrigated areas in India and other regions around the world.

Quantification of trends in groundwater levels of Gujarat in western India

Abstract The patterns in groundwater level, rainfall and temperature extremes for the western Indian state of Gujarat were examined using water-table records of 555 monitoring wells and daily rainfall and maximum temperature data sets for the period 1995–2005. The results reveal a large number of declining trends in groundwater levels with notable spatial structures; these are unlikely to be associated with the natural climate variability. There is also a noticeable increase in the temperature and rainfall extremes. Our results suggest that the groundwater withdrawal has increased, perhaps due to recurrent droughts and increases in temperature, and this has caused widespread water-table decline that has not been countered by rainfall extremes. Rainfall extremes appear to have caused greater runoff losses in the humid and sub-humid coastal regions, whereas the aquifers of the arid and semi-arid northern regions are more vulnerable to droughts and the warming environment. Editor D. Koutsoyiannis; Associate editor K. Hamed Citation Panda, D.K, Mishra, A., and Kumar, A., 2012. Trend quantification in groundwater levels of Gujarat in western India. Hydrological Sciences Journal, 57 (7), 1325–1336..

Increasing heat waves and warm spells in India, observed from a multiaspect framework

Recent heat waves have been a matter of serious concern for India because of potential impacts on agriculture, food security and socio-economic progress. This study examines the trends and variability in frequency, duration and intensity of hot episodes during three time periods (1951-2013, 1981-2013 and 1998-2013) by defining heat waves based on the percentile of maximum, minimum and mean temperatures. The study also explores heat waves and their relationships with hydroclimatic variables, such as rainfall, terrestrial water storage (TWS), Palmer Drought Severity Index (PDSI), and sea surface temperature (SST). Results reveal that the number, frequency and duration of daytime heat waves increased considerably during the post-1980 dry and hot phase over a large area. The densely-populated and agriculturally dominated northern half of India stands out as a key region where the nighttime heat wave metrics reflected the most pronounced amplifications. Despite the recent warming hiatus in India and other parts of the world, we find that both daytime and nighttime extreme measures have undergone substantial changes during or in the year following a dry year since 2002, with the probability distribution functions (PDFs) manifesting a hotter-than-normal climate during 1998-2013. This study shows that a few months preceding the 2010 record-breaking heat wave in Russia, India experienced the largest hot episode in the countrys history. Interestingly, both these mega events are comparable in terms of their evolution and amplification. These findings emphasize the importance of planning for strategies in the context of the rising co-occurrence of dry and hot events.

Evaluation of an over-used coastal aquifer (Orissa, India) using statistical approaches

Abstract This study evaluates an over-exploited aquifer (Balasor, India) and also explores the possibilities of sustainable management using several statistical approaches. First, bootstrap analysis indicates that groundwater pumping has resulted in the reduction of mean cultivated area as the average irrigation capacity per bore well dropped from 3.74 ha to 1.5 ha within a period of 10 years of operation. However, modelling the groundwater levels using the seasonal autoregressive integrated moving average (SARIMA) procedure showed no evidence of large-scale groundwater withdrawals. The derived models can be used for water table forecasting and also for infilling the missing observations. The empirical relationship among pumping test results indicated that well depth and aquifer thickness significantly influence the discharge from the aquifer. This discharge may have encouraged the resource-rich farmers to exploit the lower aquifer. Based on a contour plot, the zone of groundwater exploitation was estimated to vary from 25 to 60 m below the surface. Therefore, a uniform aquifer exploitation policy needs to be implemented to curb the vertical competition in exploiting the aquifer and to develop sustainable management of the groundwater. Citation Panda, D. K. & Kumar, A. (2011) Evaluation of an over-used coastal aquifer (Orissa, India) using statistical approaches. Hydrol. Sci. J. 56(3), 486–497.