Identification of the constraints of physical properties on fluid flow rate (as a preliminary study for analysis of changes in subsurface conditions in the KEK Mandalika Lombok)

The KEK Mandalika area, the southern coast of Lombok Island, is an area that is growing up in the tourism sector. The main need for tourist areas is the availability of clean water. The problem that occurs in coastal areas is seawater intrusion. The seawater intrusion can cause the changes in subsurface conditions, especially in groundwater. These changes have an impact on changes in subsurface physical properties, which can be detected by geophysical measurements and modeling based on geoelectric and gravity data. In monitoring the changes of subsurface conditions, it is necessary to observe the constraints based on the value of conductivity, density, viscosity, and fluid flow rate so that physical modeling can be carried out. The method used was an experiment with 11 mixed solutions of groundwater and seawater with different concentrations. The results show that the salinity, conductivity and density have a proportional relationship with viscosity. The higher the viscosity, the lower the groundwater flow rate, and vice versa. Based on these results, the value of the constraints for each variable is obtained, which is conductivity (1.930- 38) mS; density (0.995-1.021) kgm-3 ; salinity (1.06-25.1) ppt; viscosity (0.835-0.876) x10-3 kgm-1s-1 ; fluid flow rate (1292-1388) ms-1 .