Iranians have tried to increase water usage by utilizing structures such as water reservoirs. The province of South Khorasan has also accommodated numerous water reservoirs within its boundaries due to the region's water scarcity, playing a significant role in the people's water usage. In the cities of South Khorasan and the city of Birjand, the value of water was more pronounced due to the mentioned characteristics. The architecture style of water reservoirs in this region is influenced by local architecture. Therefore, in the old fabric of the city and in various neighborhoods, we can observe water reservoirs that date back to the Qajar period. Preserving these structures as a cultural and national capital holds a special place in Iranian art, expressing the culture and beliefs of the people. The present study is fundamental in nature and analytically historical in terms of methodology, focusing on gathering data through both field and library research methods. The main issue of the research is to understand the various styles of construction and forms of water reservoirs in the city of Birjand, including the construction process and knowledge of indigenous materials and techniques used in building these reservoirs. The construction techniques and architectural style of water reservoirs hold specific credibility, thus the study further examines various styles, tank shapes, types of domes, stairways, outlets, covering decorations, and materials (brick, stone, lime, saruj).