Are Artificial Barrages Necessary to Prevent Saline Incursion? A Modelling Approach to Restore the Healthy Ecosystem of the Vembanad Lake

Abstract

The Thanneermukkom Bund was constructed to prevent salt water intrusion in the low lying areas of the Kuttanad region which increase the paddy cultivation twice in a year.Without it, paddy cultivation would be limited to once a year.This barrier has created many adverse environmental effects such as the proliferation of aquatic weeds, pollution accumulation and deterioration in fishery catch.Thus, it became imperative to manage the salt intrusion in the upstream regions of the Vembanad Lake without impairing the natural flushing.We have implemented a well-validated 3-dimensional Finite Volume Community Ocean model with an accuracy of greater than 90% in tides, greater than 80% in currents and greater than 90% in salinity for the sustainable management of Vembanad Lake.Several model experiments/runs were conducted with varying discharges to obtain less than 2 PSU (freshwater) south of the barrage if the barrage was open.The model results revealed that 20 m3/s of cumulative discharge from southern rivers could overwhelm the salinity intrusion to the south of the barrage.While incorporating the influx from Muvattupuza river, the minimum cumulative discharge from the southern rivers was reduced to 15 m3/s.