Geographically speaking 75 percent of Iran has a dry, arid, and semi-arid climate. As the water crisis worsens in scale and scope, it seems construction of underground dams is a dire need and necessity, more so because of the disadvantages of surface dams.
Iran has a continental type of climate, with cold winters and hot summers across the plateau. On the plateau, the annual rainfall does not exceed 30 centimeters (12 inches), with the deserts and the Persian Gulf littoral areas receiving less than 13 centimeters (5 inches). In spite of the fact that in the past several years huge amounts have been invested in dam construction to collect surface and rain water, the measures have not produced the desired results nor helped the government in reducing the dangerous water crisis. According to experts, building surface dams, which are normally huge structures, is not economically viable in most cases as they are far from urban areas because of which costly transmission networks ought to be installed to supply end-users with their water needs. In addition, evaporation of water is normally high in dams. Add to this the fact that dams have almost always endangered the biodiversity in their proximity.
Due to these and other valid reasons, specialists recommend subsurface dams whose pluses seemingly outnumber their drawbacks, Fars news agency reported at the weekend. Such dams have many merits that surface dams lack. For instance, land is not submerged to store water and there is no danger of breaching due to natural or manmade disasters. In addition, the surface area can be used in the same way before and after construction of the subsurface dam. Building subsurface dams does not require much funding and expertise since they are mostly simple structures that can be set up without the need for skilled and costly human resources.
Secondly, the evaporation rate is marginal due to the near constant temperature in the reservoir; furthermore, they are more eco-friendly as they do not degrade species and their habitats. Last but not least, unlike surface dams whose collapse spell human and economic disaster on a large scale , underground dams do not cause that much damage in case things go wrong. Moreover, such dams hardly incur heavy costs. Given the economic merits, there are many underground dams in the world, namely in Brazil, India, the US and Japan, to name but a few.
However, these dams have to be under constant control as their reservoirs are smaller than normal dams. Problems with underground dams reported in the past, including sedimentation, flooding, collapse, and salination, occurred because of human error, as well as the immaturity and complexity of geological features.
A subsurface dam is a facility that stores groundwater in the pores of strata and uses groundwater in a sustainable way. In some cases they are also built to prevent saltwater from intruding into a freshwater aquifer. Underground dams are typically built in areas where water resources are minimal and need to be efficiently stored, such as in deserts and on islands like the Fukuzato Dam in Okinawa, Japan. They are most common in arid areas of Brazil while also being used in southwestern United States, Mexico, India, Germany, Italy, Greece and France.According to a recent review of the construction of underground dams, the scale of underground dam projects has grown. In terms of water quality, long-term monitoring was carried out after construction of underground dams on Miyako Island, Japan. To deal with any problems, countries must share information and experience in constructing underground dams.
