Numerical modeling of seawater intrusion in the aquifer of Manukan Island

Sarva Mangala Praveena, (2011) Numerical modeling of seawater intrusion in the aquifer of Manukan Island. PhD thesis, Universiti Malaysia Sabah.

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Abstract

This study presents an understanding of seawater intrusion in the low lying area of Manukan Island. A three dimensional numerical model (SEAWAT-2000) was developed based on modeling protocol using low lying area of Manukan Island. SEAWAT-2000 output indicated that there is about 1.4% of freshwater and seawater mixing ratio at sea level in low lying area of Manukan Island illustrates the seawater intrusion problem. Upconing process simulated by SEAWAT-2000 showed the current status of seawater intrusion in Manukan Island is about 14.6% of freshwater and seawater mixing ratio at the beneath of pumping well (W6). Moreover, the calibrated model was also used to predict current and potential extent of seawater intrusion in low lying area of Manukan Island two years with all conditions assumed to remain same as those in December 2009 under different scenarios of varying recharge and pumping rates. The SEAWAT-2000 model's output showed pumping rates are higher than recharge rates in all of the selected scenarios, thereby indicating that overpumping is the main factor behind seawater intrusion in the low lying area of Manukan Island. The seawater-freshwater mixing ratio moves landwards after two years of simulation in Scenario 1. In order to control overpumping in this study area, Scenario 2 has resulted in backward movement of the 1.4% seawater-freshwater mixing ratio towards to coast after two years of prediction. The current contamination of the coastal aquifers by seawater intrusion will be more severe with an impact of El-Nino events on groundwater resources depletion in Scenario 3. Reductions of pumping and recharge rates in Scenario 4 have worsened seawater intrusion problem. With an aid of artifidal recharge, highest hydraulic heads and lowest chloride concentration were observed (Scenario 5). In addition to this, water balance components have illustrated sustainable groundwater management. selected for Manukan Island's current situation will be Scenario 2. In view of the effects of EINino events in the future, Scenario 5 can be implemented to restore groundwater resources. Moreover, a suitable groundwater management plan in Manukan Island must also include economic, social and environmental issues together with further adjustment of pumping rate using water usage data from various parts (restaurant, tourism, office and chalets).!n a nutshell, this study has provided a management foundation for restoration of the groundwater resources of Manukan Island which can be applied in other small islands with similar hydrogeological conditions.

Item Type:Thesis (PhD)
Uncontrolled Keywords:groundwater, seawater intrusion, SEAWAT-2000, recharge, pumping, management
Subjects:T Technology > TC Hydraulic engineering. Ocean engineering
Divisions:SCHOOL > School of Science and Technology
ID Code:10189
Deposited By:IR Admin
Deposited On:13 Jan 2015 11:49
Last Modified:13 Jan 2015 11:49

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