The South-Eastern hilly regions of Bangladesh possess ample opportunities to study on the environmental geology and natural resources. Water in one of them. Unfortunately water scarcity often is observed during the dry period. The only suitable drinking water remains at the stream which is locally termed as “Chara”. Stream water is a surfacial source of water for domestic and cultivation in small scale. A few streams (chara) having perennial flowing water that can be used for safe drinking water. Some streams have a small annual discharge for the large size of their drainage area. During winter season streams remain dry and local people use reservoir tanks for daily consumption. At the bottom of few hills, some cave is observed as a source of drinking water. The caves are used as a preservation of water during the dry season. Water disperse onto the fine to medium sand through the springs and remain stagnant at the bottom of the hills. People dig some vertical holes to prepare these caves. The geological formation of the bedrock of the hills is sandier towards the north in Khagrachhari and Rangamati districts, allowing water to easily percolate down into the suitable aquifer system and thereby transmitting flow to the springs which are dependent upon groundwater in the dry season in the study areas. The native hilly people use that water for household and drinking purposes. Apart from the natural sources, different national institutions and NGO have installed tube-wells for obtaining safe drinking water.