Mitigation of seawater intrusion in coastal aquifers using coastal earth fill considering future sea level rise.

ABSTRACT

Saltwater intrusion (SWI) is a physical problem that threatens many coastal aquifers all over the world. Saltwater intrusion is increasing with abstraction and rise in sea level. Coastal aquifer protection is essential to protect groundwater resources in these areas. A number of methods have been developed to protect coastal aquifers from SWI. This paper presents the impact of sea level rise on SWI in coastal aquifers and application of coastal earth fill as a new technique to control SWI. Different future sea level rise scenarios were studied and different coastal earth fill with an appropriate soil to extend the coastline towards the sea in order to control SWI was studied using SEAWAT model. The proposed control measure is numerically assessed by Henry's problem and then applied to a real case study of Biscayne aquifer, Florida, USA. For each aquifer, the corresponding relation was developed between the intrusion length of saltwater wedge and the width of fill. The results showed that increasing the fill width resulted in decreasing the intrusion length. In the case of Biscayne aquifer, increasing the fill width by 10, 20, 30, and 40% of the aquifer length resulted in retarding the intrusion to 329, 192, 42, and - 48 m respectively. Using 150- and 300-m fill widths retards the intrusion length by 32.3% and 60.5%. In addition, increasing the fill width to 465 m can retard SWI by 91.3%. This approach is capable to control the future risks of SWI and sea level rise.