Impact on hydrodynamics of the estuarine region of Mahadayi (Mandovi) river due to change in flow pattern

Abstract

A proposal to construct a dam on the river Mahadayi (Mandovi) for power generation would change the hydrodynamics of the estuarine stretch of the river. Using DYNHYD, the hydrodynamic model of WASP developed by the USEPA, several space and time dependent parameters were estimated in the stretch of approximately 80 km from the mouth of the river close to Panaji City up to the village of Sonali. The model was calibrated through the observed and predicted salinity values at various segments for summer and monsoon flows in the river. The channel flow variations in the river and estuarine zone, as well as flow velocities, effect on salinity have been predicted for pre‐ and post‐project scenarios. The natural variation in the river flow during a year was from 1.3 cum/s to 824 cum/ s. In the post project scenario, the variation ranged from 18.3 cum/s to 724 cum/s, respectively. The results indicated that predicted impact of salinity changes in the estuarine portion of the river Mandovi will be marginal. A stretch of about 12.5 km from Usgaon Pali village to Amone village may change from mesohaline to oligohaline during summer due to the construction of the dam.

Keywords:

• Hydrodynamics
• Mahadayi river
• flow pattern
• salinity