Development of Groundwater Flow Model in a Coastal Watershed
Authors:-Assistant Professor Sridhar N, Assistant Professor Divagaran R, Madhav S, Harish R
Abstract- The groundwater flow models have been used to demonstrate groundwater movement principles. This paper presents development of groundwater flow model using Visual MODFLOW of the Adappa coastal watershed. In this study, the watershed is divided into three zones and the aquifer properties are assigned based on lithology of the watershed. The assigned aquifer properties, such as hydraulic conductivity: 5 and 10m/day, Specific yield: 0.16 to 0.20 and porosity: 0.25 to 0.4 are given as input to the model. The appropriate engine and solver parameters are chosen based on the requirements and the model is simulated. The boundary conditions are assigned based on the recharge of the study area. The recharge rate from rainfall is 15% in all three zones of the watershed since it is attributed to the presence of clay, clayey sand, and sandy clay. Groundwater model should be calibrated and validated before it is used for any predictions or decision-support. The calibration is made for 1460 days in the period of January 2007 to December 2011 and the period of 2012-2013 is used for model validation process. After running the model, the output of the groundwater flow model is viewed in two dimensions. The calculated vs. Observed head indicates the calculated heads almost matching the observed heads. In this coastal watershed, the groundwater flow direction is towards the sea and the rivers. But in some places along the coastal line, groundwater moves towards the inland area which is due to the inward flow of saline water intrusion and towards the sea near the coastal line. The model also used to simulate possible future changes to hydraulic head or groundwater flow rates as a result of future changes in stresses on the aquifer system.
