Hydrogeologic characteristics of aquifers in Huay Sai Royal development study center and adjacent areas, Amphoe Cha-Am, Changwat Phetchaburi

Abstract

His Majesty King Bhumibol Adulyadej initated to establish Huay Sai Royal Development Study Center as a demonstrated area of deteriorated western area. However, the area still faces lack of water in drought season. The study area is located in Tambon Sam Phraya, Tambon Huay Sai Nua and Tambon Rai Mai Phattana, Amphoe Cha-am, Changwat Phetchaburi. The aims of this study were to explain the hydrogeologic characteristics of aquifers and to create the conceptual model of groundwater and hydrogeologic systems. The results showed that there are three types of aquifer in the study area: floodplain deposits aquifer (Qfd), Permo-Carboniferus metasedimentary aquifer (PCms) and granitic aquifer (Gr). Main groundwater direction of both of aquifers (Qfd and PCms) flow from south-western to north-eastern area. Some areas are found cones of depression due to intensive pumping for agricultural purposes. As a result, the mountainous area in western and eastern areas are the recharge zone and central floodplain is discharge zone. From pumping test analysis, Neuman Method is consistent with Qfd aquifer and Theis Method is consistent with PCms and Gr aquifers. According to transmissitvity, yield potential in Qfd aquifer (ranged from 61.300-91.400 m /d) is better than both of PCms (ranged from 1.840-9.520 m /d) and Gr aquifers (ranged from 0.218-10.000 m /d). Furthermore, water types in study area are calcium-bicarbonate (Ca-HCO₃ ), sodium-bicarbonate (Na-HCO ), calcium-sodium-bicarbonate (Ca-Na-HCO₃ ) and calcium-sodium-bicarbonate-chloride (Ca-Na-HCO₃ -Cl) due to the ion dissolution in Qfd, PCms and Gr Aquifers. The hardness of water is not over than consumption standard, but the water should be treated by boiling.