Estimation of Spatio-Temporal Variations in Water Balance Components and Nutrient Transport for Indian River Basins Using Statistical Analysis and Hydrological Modeling
Kansara, Prakrut, Civil Engineering - School of Engineering and Applied Science, University of Virginia
Lakshmi, Venkataraman, Engineering Systems and Envrionment, University of Virginia
The Indian subcontinent suffers from a decline in water resources per capita and water quality deterioration in the course of recent decades due to exponential population growth. With the impact of climate change being intensified by the increasing anthropogenic interventions, there is a significant risk to the water resources. This dissertation focuses on analysis and modeling of water quantity and quality resources for improving water management in the Indian river basins. In the first study, nine major river basins in India were analyzed utilizing publicly-available satellite and modelled dataset information for the time period from 2002 to 2019. Water balance components - Precipitation (P), Runoff (R), Evapotranspiration (ET), and Total Water Storage Anomaly (TWSA) - were examined for each of these river basins. Time-series of the water balance components demonstrated that all the river basins exhibit strong seasonality with peaks during the Monsoon season (June – September). The seasonal analysis demonstrated that Southern and North-Eastern parts of India experience water deficit due to decreasing monsoonal precipitation combined with increasing ET and decrease in TWSA. I found that 74% of the monotonic trends were associated with ‘Agricultural’ land whereas 19% were associated with ‘Urban’ land. In the second and third studies, a semi-distributed, physically-based hydrological model (SWAT) was built to characterize the catchment hydrology and nutrient transport for the Narmada and Ganga River Basins respectively. Using the flow calibrated hydrological model, I compared simulated and observed Nitrogen (N) at 17 locations inside the Narmada River Basin. Through the calibration of flow parameters at five calibration sites, I obtained a mean R2 of 0.77 during the calibration phase (2001-2010) and mean R2 of 0.76 during the validation phase (2011-2019). The trend analysis revealed that subbasins near the watershed boundaries showed increasing trend for N concentration over the study period. In the third study, using streamflow, N flux and N concentration calibrated SWAT models, I compared simulated and observed N flux and concentration at 92 locations inside the Ganga River Basin. Through multi-site calibration of flow parameters at 3 sites, I obtained a mean R2 of 0.76 during the calibration phase (2001-2010) and a mean R2 of 0.73 during the validation phase (2011-2017) for streamflow. Model results showed that 35 of 650 SWAT simulated subbasins have increasing nitrogen concentration trends with most of the trends in the downstream eastern part of the watershed. For both of these studies, nitrogen contamination can be attributed to anthropogenic activities - specifically farming - as these activities use large amounts of N based fertilizers, excess of which is drained into the river through runoff. For Ganga, point source pollution through industries and urban sewage were significant contributors of nitrogen pollution, but they were not captured due to the data limitations.
PHD (Doctor of Philosophy)
Indian river basins, Water quantity and quality, Nitrogen transport