Spatio-temporal analysis of hydrological connectivity of floodplain wetlands in the Ganga Plains, India

The Ganga Plain (GP) is one of the largest alluvial floodplains in the world, where river meanders and floodplain wetlands are crucial surface water resources that support millions of people. Nearly 80% of GP wetlands are geographically isolated wetlands (GIWs), meaning that precipitation provides most of their water. These GIWs shrink and develop into vegetative patches as a result of groundwater extraction in the surrounding regions. This study has utilized geostatistical approaches to analyse hydrological connectivity and rainfall patterns for three decades at the sub-basin scale, transecting different hydroclimatic regimes. Hydrological connectivity, defined as the water-mediated transfer of matter and energy within or between hydrological cycle components, was evaluated using two methods: (i) structural connectivity, which is determined by terrain slope/ruggedness, and a rainfall-NDVI-weighted C factor map normalized by the Soil Index, and (ii) functional connectivity, which combines flow accumulation data to link rainfall patterns, connectivity, and water movement. We have mostly used freely available datasets from Google Earth Engine and processed them using cloud computing.

The initial finding revealed that 44% of wetlands in the Ganga Plain (GP) are classified as unstable, declining, lost, or intermittent, with an accuracy of 84%, emphasizing their susceptibility to deterioration. Rainfall in the GP varies significantly by location, ranging from 3000 mm in the north to 500 mm in the southwest, altering hydrological connectivity even more. Disruptions in this connectivity cause an unstable water flow, affecting wetland functionality and stability. The study highlights the importance of targeted actions in preserving hydrological connectivity across climatic zones and maintaining sustainable wetlands.

 

Keywords: Google Earth Engine, Ganga Plain, Wetlands, Hydrological Connectivity.