GIS/GPS mapping technology provides a very cost effective method of meeting the guidelines and calculating the total information required for decision makers. This paper aims to integrate Geographic Information System (GIS) and data acquired using low-cost GPS in one system and develop a precise methodology that is reliable for environmental studies at Majmaah region. The research focuses on monitoring and mapping the groundwater quality parameters at the study area. Portable GPS instrument with reasonable accuracy was used to measure the coordinates of non-defined water wells in the form of the latitudes and longitudes. A methodology for using these data to locate those positions accurately and merge them in GIS system was developed. The system was developed mainly for environmental studies (characterization of groundwater quality parameters) using a satellite image and the calculated GPS data aiming to produce a dynamic system that is capable of map the changes in any groundwater parameter on different times. However, other uses could be: defining the contaminated soil zones, and the same for flooding areas, as GIS will help in selecting the most appropriate locations to dig new wells, construct dams or produce sensitivity environmental maps for the study area. The resulted contour environmental maps can be helpful to illustrate a clear picture and quantities of needed areas for preservation. The system can be updated and modified easily and remains useful and helpful for supporting the decision making to identify, monitor and plan other environmental studies at the region.