Hydrologic Changes in Indian Subcontinental River Basins (1901–2012)

Abstract

Long-term (1901–2012) changes in hydroclimatic variables in the 18 Indian subcontinental basins were examined with hydrology simulated using the Variable Infiltration Capacity model (VIC). Changepoint analysis using the sequential Mann–Kendall test showed two distinct periods (1901–47 and 1948–2012) for the domain-averaged monsoon season (June–September) precipitation. Hydrologic changes for the entire water budget were estimated for both periods. In the pre-1948 period, a majority of the river basins experienced increased monsoon season precipitation, evapotranspiration (ET), and surface water availability (as defined by total runoff). Alternatively, in the post-1948 period, monsoon season precipitation declined in 11 of the 18 basins, with statistically significant trends in one (the Ganges basin), and most (15) basins experienced significant warming trends. Additionally, in the post-1948 period, the mean monsoon season ET and surface water availability declined in eight (with significant declines in four) basins. The results indicate that changes in ET and surface water availability in the pre- and post-1948 periods were largely driven by the changes in the monsoon season precipitation rather than air temperature, despite prominent warming after 1975. Coupled modes of variability of sea surface temperature (SST) and surface water availability indicated El Niño–Southern Oscillation (ENSO) as the leading mode. The second mode was identified as the trend mode for surface water availability in the subcontinental river basins, which was largely driven by SST anomalies in the Indian and Atlantic Ocean regions. This indicates that surface water availability in India’s subcontinental basins may be affected in the future in response to changes in large-scale climate variability.

Strong Influence of Irrigation on Water Budget and Land Surface Temperature in Indian Subcontinental River Basins

“…We used daily wind speed data at 2.5° spatial resolution from the National Centers for Environmental Prediction‐National Center for Atmospheric Research reanalysis, which was gridded to 0.25° using the bilinear interpolation. Daily precipitation and maximum and minimum temperatures from IMD have been widely used in many previous studies in India (Shah & Mishra, , , ). We used daily climate forcing (precipitation, maximum and minimum temperatures, and wind speed) from Sheffield et al () for the parts of the Indus, Ganges, Sabarmati, and Brahmaputra basins that fall outside of India.…”

“…For most of the basins, monthly Nash‐Sutcliffe efficiency is more than 0.8 (Table S2). Shah and Mishra () calibrated the VIC model simulated monthly streamflow for these subcontinental river basins without considering the irrigation. We find that the VIC‐IRR performs reasonably well for monthly streamflow.…”

“…We selected 18 different streamflow monitoring gauge stations located in the Indian subcontinental basins from India-WRIS and Center for Sustainability and the Global Environment. As described by Shah and Mishra (2016), most of these 18 gauge stations are located upstream to large dams and reservoirs to minimize the influence of water abstraction on the calibration and evaluation of VIC-IRR. Six soil parameters of the VIC-IRR were manually calibrated as described in Mishra, Cherkauer, and Bowling (2010) and Shah and Mishra (2016).…”

“…As described by Shah and Mishra (2016), most of these 18 gauge stations are located upstream to large dams and reservoirs to minimize the influence of water abstraction on the calibration and evaluation of VIC-IRR. Six soil parameters of the VIC-IRR were manually calibrated as described in Mishra, Cherkauer, and Bowling (2010) and Shah and Mishra (2016). For most of the basins, monthly Nash-Sutcliffe efficiency is more than 0.8 (Table S2).…”

“…For instance, Narasimhan () argued that ET in India is largely underestimated, and there is a need to reinvestigate the water budget of the Indian basins. Shah and Mishra () used the VIC model to study the long‐term changes in the water budget in the Indian subcontinental river basins, however, without considering the role of irrigation, which can have a prominent influence on the water budget. Here, we use the VIC model with a newly improved irrigation scheme (VIC‐IRR; Bohn & Vivoni, ; Haddeland, Skaugen, & Lettenmaier, ; Haddeland, Lettenmaier, & Skaugen, ) to estimate the influence of irrigation on water budget and LST in the Indian subcontinental river basins.…”