Toxicity and Profitability of Rice Cultivation under Waste-Water Irrigation: The Case of the East Calcutta Wetlands

The paper reports the results of an empirical study on the profitability of rice cultivation in the East Calcutta Wetlands region where untreated sewage water from the city of Calcutta, India, is used for the purpose of irrigation during the winter/summer crop. The results show that plots using wastewater containing organic nutrients earn higher profits than those using groundwater. However, we also find the profitability of plots using wastewater negatively affected by the presence of heavy metals such as Chromium, Lead and Mercury that are found in the water and soil. Of the two opposing effects of wastewater irrigation, the positive effects of organic nutrients outweigh the negative effects of heavy metal toxicity. These results support both efforts to conserve the Wetlands, which will generate a number of ecological benefits, as well as to regulate the discharge of heavy metals into the water from households and industries that are located upstream in the city of Kolkata.