Excessive land exploitation in Dumai has been replaced by intrusion seawater in aquifers in the coastal area. This is indicated by the increasing number of society’s wells that turn into brackish. The intrusion has a wide impact on various aspects of life, such as decreasing soil fertility, damage the buildings, and disrupting public health. The aim of this study is to find out the saturated zone of water and the interface of water with fresh water, so it is known that water zones are suitable for daily use. The study used Geoelectrical Resistivity Survey with 1D Schlumberger configuration to determine the zone of aquifer and its thickness. Based on the research that has been done, the results of the boundary of the intrusion zone in Dumai were obtained that there is an intrusion zone boundary of seawater content. This is indicated by the low resistivity value. It is less than 10 ohms, which is found at the zone of less than 1 km from the beach line.

The still low understanding of the concept of students in vocational schools in learning physics, due to the lack of innovative learning, so it needs innovation such as a reciprocal teaching model that implements four independent understanding strategies, namely summarizing the material, compiling questions, explaining, and predicting. The purpose of this research was to determine the improve in understanding of students' concepts in the class applying the reciprocal teaching model with conventional classes at Vocational High School (SMK) Abdurrab Pekanbaru. The population in this research were 130 students spread over five classes and samples were taken by simple random sampling, so that 2 classes of samples were obtained with 52 students. The research instrument was in the form of concept comprehension test questions consisting of pretest and posttest. The Test  in the form of multiple choice reasoned with 4 choices totaling 15 items. The instruments are arranged according to the category of understanding the concepts of translation, interpretation, and extrapolation. Data collection techniques in the form of scores on the concept understanding results obtained from the pretest and posttest scores. The data is processed by descriptive analysis. The results showed that students of class X SMK Abdurrab Pekanbaru in optical material learning, had a difference in increased understanding of concepts. The average score of concept understanding after the implementation of learning in the experimental class was 82.44 with a high category, while the control class was 59.68 with a low category. To that end, the implementation of the reciprocal teaching learning model, is able to better enhance the understanding of physics concepts in optics learning for students in class X SMK Abdurab Pekanbaru.