“COMPARATIVE STUDY OF GROUNDWATER TRENDS AND FACTORS AFFCTING THEM IN MISSISSIPPI RIVER WATERSHED (USA) AND INDO-GANGETIC PLAINS (INDIA)”

Abstract

With increase in urbanization and human needs, more pressure is now being exerted on groundwater resources to meet the increasing demands for public and domestic water supply, irrigation, and industrial uses. As a result, the groundwater level is declining in many parts of the world. Thus it is crucial to identify the regions where the groundwater level is declining as a response to anthropogenic impacts. In this study, the trends in groundwater anomalies were examined and the influence of land use and land cover, crop types, and precipitation on the trends of groundwater levels were investigated in the entire Mississippi River Watershed (MRW), USA and Indo-Gangetic Plains (IGP), India. Changes in regional groundwater storage were estimated from Gravity Recovery and Climate Experiment (GRACE) satellite data and monthly well-log data from United State Geological Survey (USGS) from 2003-2015. Depletion in groundwater level was obtained by removing the water storage as soil moisture, surface water, and snow from GRACE-derived terrestrial water storage changes. Trend analysis was carried out for changes in Land Use and Land Cover, Precipitation and Crops patterns. The spatiotemporal analysis was carried out in three scales: (1) for the entire study area, (2) for the states constituting the study area, and (3) for the sub-watersheds in the area, six USGS hydrologic Unit Code (HUC)-2 watersheds in case of MRW, which provided detailed insights about the groundwater trends in both smaller and larger spatial scales. It was observed that the groundwater level in the Lower Mississippi region is declining at a faster rate as compared to other regions in the watershed due to heavy groundwater-based production of Soybeans in the region. On the other hand, groundwater level is declining in North-western part of IGP, specifically Delhi, Chandigarh, Uttarakhand, Haryana and Punjab because of increasing industrialisation and urbanisation in the region. The variability of precipitation pattern was also studied for the time period of 1900-2017 in this research. It was detected that although the amount of rainfall or rainfall intensity has not changed much in the last 100 years, there has been deviation in the normal monsoon months of the region. The trends obtained in this study for the groundwater regimes, sub-watersheds, and the entire study areas in tandem with changes in spatial and temporal distribution of land use and land cover, crop types, and precipitation helped to identify trends of groundwater storage changes as a response to human activities in the watershed. This thesis is a compilation of satellite data, literature survey, and detailed trend analyses that have been studied thoroughly, during the course, to identify the most affected areas in the study area and come up with a solution to this day-to-day increasing problem.