Waterlogging and coastal salinity management through land shaping and cropping intensification in climatically vulnerable Indian Sundarbans

Abstract

Sundarbans in West Bengal, India located in the eastern coast of the Bay of Bengal is one of the vulnerable zones subjected to abrupt climate change. The region receives 2.7 times surplus rainfall as compared to crop evapotranspiration during monsoon months causing widespread waterlogging of the low lying agricultural fields and impedes the productivity. The present study assessed the effects of different land shaping models namely, farm pond (FP), deep furrow and high ridge (RF) and paddy cum fish (PCF) systems for rainwater harvesting in restoring the productivity of degraded coastal soils in Sundarbans. A water balance was run to estimate the soil moisture, crop evapotranspiration, runoff and water depth in the reservoir during normal, excess and deficit rainfall years. The average annual harvested runoff was 2709, 1650 and 1169m3 per hectare in FP, RF and PCF systems, respectively. The runoff going out of the system was 19.5, 29.1 and 27.75% of the annual rainfall in FP, RF and PCF systems, respectively, whereas in monocrop rice-fallow system it was 34.6% of the annual rainfall. We estimated all the three components of water footprints (WF) i.e., blue WF (WFblue), green WF (WFgreen) and gray WF (WFgray) as an aggregative indicator to evaluate environmental impact. The results indicated that total as well as the components of WF was higher in rice-fallow and rice-rice systems than in each of the land shaping system. Large scale adoption of different land shaping systems increased the cropping intensity and net farm income and there was reduction in salinity during summer and waterlogging during rainy season and overall improvement in soil quality. The dominant soluble salts identified in the study region were NaCl and MgSO4.