The Vietnamese Mekong Delta has faced a double challenge from surface water resources changes, including: abnormal changes of surface water sources in the upstream and negative impacts from downstream, especially the sea level rise. The former is of the main concern of the An Giang province, one of the two most upstream provinces in the delta. In order to ensure rice production particularly and agricultural production generally as well as to enhance adaptive capacity local residents given the rising influences of the upstream flood, the province has rapidly built the full-dyke systems. The construction of full-dyke system has resulted in both two folds i.e. economic effectiveness and negative impacts on the environment. A study was carried out at case study of An Giang in the period of 2012 and 2013. Interviewing local farmers and monitoring surface water quality (COD, o-PO4^3-, N-NO^3- and total coliforms) were the main approaches in this study. The preliminary result of the study showed that total financial benefit of triple-rice farming systems located inside the full-dyke system was higher than that of the double-rice farming systems located outside the full-dyke system. However, the ratio of benefit - cost of the double-rice pattern was higher than that of the triple-rice pattern. In both study sites, surface water was polluted unlikely for domestic purpose according to the National technical regulation on surface water quality, QCVN 08: 2008/BTNMT. Meanwhile, a small proportion of local people still used surface water for domestic purpose after being treated with a simple traditional treatment method. The pollution of surface water could negatively influence the public health in the study area.