METHANE FLUX FROM A SUBTROPICAL RESERVOIR LOCATED IN THE FLOODPLAINS OF RIVER YAMUNA, INDIA

Abstract

Tropical and subtropical reservoirs are considered to be a strong anthropogenic source of methane (CH4) emissions worldwide due to high temperature, augmented carbon and nutrient loadings. Thus, CH4 emission estimation from tropical/subtropical reservoirs is critical for preparation of green house gas emission budgets. The Present study estimates CH4 flux from a subtropical freshwater manmade Okhla reservoir located on the river Yamuna, National Capital Region, India. Results showed that Okhla reservoir transformed into a potential CH4 emission source after flooding as the CH4 flux increased by 3.81 orders of magnitude with a net contribution of 171.96 mgm(-2)d(-1). Enhanced CH4 flux is primarily attributed to elevated organic and nutrient loadings to reservoir via river's inflow water, high percentage of shallow areas and presence of dense aquatic vegetation mainly Eichhornia crassipes and Typha angustifolia. These aquatic weeds not only facilitate vascular CH4 transport but also provide substantial amounts of biomass for methanogens to generate CH4. Results also revealed that the summer season exhibited significantly higher CH4 flux (Kruskal-Wallis H-Test; p < 0.05) as compared to monsoon and winter seasons due to prevalence of more favorable water and soil conditions for CH4 emissions including temperature, redox potential, water depth, dissolved oxygen, biological oxygen demand and plant biomass.