I would start with this paper:

http://www.nbpol.com.pg/wp-content/uploads/downloads/2011/02/EnvironmentalImpactOfOilPalm.pdf

Hi Tamasha,

Oil Palms are one of the highest oil-yielding plants, and offer good economic returns. The crop water requirements are about 1-2 litres/palm/day in nursary stage to 200-400 litres/palm/day during the main growing season. They grow well when the ground  water level is in  the order of 1.5 to 2 m below ground level. So, certainly they impact the ground water table, but not much work has  been done  in this direction. Ground  water pollution is expected mainly from the fertilizers and pesticides used for their growth. Following are few papers:

http://wwf.panda.org/what_we_do/footprint/agriculture/palm_oil/environmental_impacts/soil_water_pollution/

http://iosrjournals.org/iosr-jestft/papers/vol8-issue7/Version-3/A08730109.pdf

http://thescipub.com/PDF/ajassp.2009.1788.1799.pdf

http://pedology.ac.affrc.go.jp/specialI/SI55-3/12_Sabiham.pdf

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.390.6861&rep=rep1&type=pdf

Thanks a lot for your details Pradeep and Guy.