Ground­wa­ter ori­gin

The ques­tion of the ori­gin of ground­wa­ter has been a top­ic of debate for a long time. Cur­rent­ly, the fol­low­ing types of ground­wa­ter are dis­tin­guished based on their for­ma­tion con­di­tions: infil­tra­tion, sed­i­men­to­genic, juve­nile, con­den­sa­tion, and meta­mor­phic.

The most impor­tant are the ground­wa­ter of infil­tra­tion ori­gin since they meet the require­ments for drink­ing water qual­i­ty and quan­ti­ty. Infil­tra­tion ground­wa­ter is formed from sur­face water of atmos­pher­ic ori­gin. Their source is the infil­tra­tion or seep­age of rain and snowmelt into the Earth. In some cas­es, the recharge of these ground­wa­ter sources involves water that fil­ters from rivers, lakes, reser­voirs, and canals.

Sed­i­men­to­genic waters are also impor­tant. These are high­ly min­er­al­ized (salty) ground­wa­ter found in deep lay­ers of sed­i­men­ta­ry rocks. Their ori­gin is relat­ed to the bur­ial of sea­wa­ter, which has been strong­ly altered under pres­sure and tem­per­a­ture. They can be formed simul­ta­ne­ous­ly with the depo­si­tion of marine sed­i­ments (syn-genet­ic) or their ori­gin may be relat­ed to the pen­e­tra­tion of water from marine basins into pre­vi­ous­ly formed rocks (epi­ge­net­ic). Deposits of indus­tri­al and min­er­al waters (brines) have a sed­i­men­to­genic ori­gin.

Juve­nile (endoge­nous) ground­wa­ter is formed direct­ly from mag­ma. The influx of such water occurs either dur­ing vol­canic erup­tions or from mag­mat­ic bod­ies locat­ed at depth, which can ini­tial­ly con­tain up to 7–10% water. Dur­ing mag­ma crys­tal­liza­tion and for­ma­tion of mag­mat­ic rocks, water is squeezed out and ris­es up through frac­tures and tec­ton­ic fis­sures, reach­ing the Earth­’s crust and some­times emerg­ing on the sur­face. The amount of juve­nile water is small, and they usu­al­ly emerge in a mixed form, as they inter­sect with oth­er types of ground­wa­ter hori­zons.

Con­den­sa­tion waters are formed as a result of the con­den­sa­tion of water vapor in the pores, fis­sures, and oth­er cav­i­ties of moun­tain rocks. The con­den­sa­tion of water vapor is essen­tial for desert areas with lit­tle atmos­pher­ic pre­cip­i­ta­tion, where small thin lens­es of fresh con­den­sa­tion water peri­od­i­cal­ly appear, over­lay­ing saline waters.

Meta­mor­phic ground­wa­ter is formed dur­ing the meta­mor­phism of min­er­al mass­es con­tain­ing crys­tal­liza­tion water or gas-liq­uid inclu­sions. Under the influ­ence of tem­per­a­ture and pres­sure, dehy­dra­tion process­es occur. If these process­es are pro­longed, they lead to the for­ma­tion of liq­uid droplets that enter the gen­er­al geo­log­i­cal cycle of ground­wa­ter.

As men­tioned above, of the dis­cussed genet­ic types of water, infil­tra­tion waters are the most impor­tant, fol­lowed by sed­i­men­ta­ry waters. The rest of the types are pre­dom­i­nant­ly mixed waters, the pro­por­tion of which in the over­all bal­ance of ground­wa­ter is insignif­i­cant.

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