Dagargala (also spelt dagar gala or dakarkala) in Hinduism is an abbreviated form of Udakargala, which denotes the science of locating subsoil water veins, i.e. udaka, daka, daga, with the help of argali (a wooden stick) an art still practiced in several parts of the Indian subcontinent. Its antiquity is traceable as early as the 6th century BC. In Vanupatha Jataka, it is stated that Buddha, in one of this earlier lives, i.e. Bodhisattva, as a merchant, while passing through a wilderness without water, comes across a lump of Kusha (grass). When he dug a hole there, water gushed out.
A fairly detailed account of his science is described in chapter 53 of Brihat Samhita by Varahamihira captioned ‘Dagargala.’ However, Varahamihira was not the first to dwell upon this subject. He refers to the writings of Sarasvata and Manu from which much of the material must have been drawn. These were available to Bhattotpala (early 9th century CE) who sites passages from them. However, they are no longer traceable. As a result Brihat Samhita is now the only source of information on dagargala.
The indications of the presence of underground water are primarily vegetal. These include the presence of a certain tree in a waterless tract, characteristics of an aquatic vegetation in a waterless region, grass growing in abundance in a grassless plain or a grassless patch in the midst of soil with abundant grass, a thorny tree in the midst of thornless ones or vice versa, a branch of a tree being bent or dry, a tree showing unnatural symptoms in its fruit bearing and blossoming pattern, two or more trees growing conjointly, sprouting corns that are perishing, growing abundantly or looking pale in a single field, etc.
Source - Encyclopedia of Hinduism Volume IV - page 267 - IHRF
Source - Encyclopedia of Hinduism Volume IV - page 267 - IHRF