Object Based Modelling for the Irrigation Suitability using Hydrogeochemical Parameters and Land use Dynamics in the Lower Ganga

The north Indian Ganga basin is one of the densely populated basins of the world. Most agricultural and industrial contaminants drained throughout the river length are likely to be accumulated in the lower part of the Ganga basin. We used ten derived irrigation suitability parameters, which are obtained from 495 sampling points locations, besides using long term climate data (GLDAS_NOAH025_M) using “Technique for Order of Preference by Similarity to Ideal Solution” (TOPSIS) model to get the irrigation suitability map. Multi-Criteria Decision Making (MCDM) using TOPSIS helps make the best choices from the available finite number of alternatives based on their ranking. The obtained entropy weight for irrigation suitability parameters such as Electrical Conductivity (Ec), Sodium Adsorption Ratio (SAR), Magnesium Hardness (MH), Sodium Percent (Na%), Total Hardness (TH), Kelly’s ratio (KR), Permeability Index (PI), Chloride concentration (Cl−), Groundwater Level Fluctuation (GWLF), and lang factor (Df) are found to be 0.08, 0.14, 0.02, 0.02, 0.04, 0.08, 0.01, 0.32, 0.29 and 0.01 respectively. We find that SAR, Cl−, and GWLF controls the water quality for irrigation in the Lower Ganga basin since these parameters have relatively higher entropy weights (more than 0.10). The results obtained from the computed performance index or the closeness coefficient show that the area percent having very good, good, and very poor groundwater quality in the Lower Ganga basin is 34.67%,42.36%, and 22.97%, respectively. The LULC change pattern indicates that the percentage change of water and agricultural land was -11.96 and -0.86%, whereas an increase in the settlement area of 131.42% for the period between 2000 and 2015.

Hydrometeorological Consequences on the Water Balance in the Ganga River System Under Changing Climatic Conditions using Land Surface Model

United Nations Sustainable Development Goal (SDG) ensures adequately accessible water and management for all. Due to the rapid increase in population and industries along the Ganga river, it is necessary to estimate the water budget for fulfilling the demand for water in the future. The M-K test conducted on the Noah-Land Surface Model data for 72 years results in maximum declining trend of water budget in the Yamuna Lower (Q=-3.82BCM/year), and minimum in the Damodar sub-basin (Q=-0.10BCM/year). All the sub-basins show increase in groundwater level (mbgl) except the Kali Sindh, which shows decreasing trend (Q=-0.07 m/year). The extreme severe groundwater drought were estimated using Standard Groundwater Level Index (SGWLI), of the values for the Ram Ganga Confluence (SGWLI=2.44;2005), Upper stream of Gomti (SGWLI=2.06;2014), Ghaghra (SGWLI=2.22;2005), Ram Ganga (SGWLI=2.28;2005), Yamuna Lower (SGWLI=2.13;2007), Kali Sindh (SGWLI=2.30,2.67;2002,2003), Chambal Upper (SGWLI=2.30,2.20;2001,2003), Son (SGWLI=2.02;2010), Gandak (SGWLI=2.37;2010),Kosi (SGWLI=2.08;2012), Damodar (SGWLI=2.72;2010), and Bhagirathi (SGWLI=2.06;2014) were obtained for a period of 1996 to 2016 using a total of 62,050 observed well data.The obtained in-situ point data are converted into the surface raster using geostatistical technique. Our results show declining trend in the water budget of all the 19 sub-basin of the Ganga basin, and also the groundwater drought in several parts. Policy makers will benefit from our findings as they can use them to further UN Sustainable Development Goals such as ending poverty (SDG-1), hunger eradication (SDG-2), clean water & sanitation (SDG-6), socioeconomic development (SDG-8) and climate action (SDG-13) all of which must be accomplished before 2030.

Modified hydrologic regime of upper Ganga basin induced by natural and anthropogenic stressors

Climate change and anthropogenic activities pose serious threats to river basin hydrology worldwide. The Ganga basin is home to around half a billion people and has been significantly impacted by hydrological alterations in the last few decades. The increasing high-intensity rainfall events often create flash flooding events. Such events are frequently reported in mountainous and alluvial plains of the Ganga basin, putting the entire basin under severe flood risk. Further, increasing human interventions through hydraulic structures in the upstream reaches significantly alter the flows during the pre-and post-monsoon periods. Here, we explore the hydrological implications of increasing reservoir-induced and climate-related stressors in the Upper Ganga Basin (UGB), India. Flow/sediment duration curves and flood frequency analysis have been used to assess pre-and post-1995 hydrological behaviour. Our results indicate that low and moderate flows have been significantly altered, and the flood peaks have been attenuated by the operation of hydraulic structures in the Bhagirathi (western subbasin). The Alaknanda (eastern subbasin) has experienced an increase in extreme rainfall and flows post-1995. The downstream reaches experience reservoir-induced moderate flow alterations during pre-and post-monsoon and increasing extreme flood magnitudes during monsoon. Furthermore, substantial siltation upstream of the reservoirs has disrupted the upstream–downstream geomorphologic linkages.