Kerman has crossed the red line in water resources, and is expected to face serious problems in drinking water supply in the coming four years. However, the authorities are making efforts to control the crisis through construction of underground dams.
Despite the rainy season, Kerman has received the lowest rainfall in recent years. Subsidence of the plains, reduction in area under cultivation and poor quality of agricultural produce, are among the problems as a result of the consecutive drought. A major part of the water is also wasted due to evaporation or water flow into the salt marshes thus becoming unusable, Mehr News Agency reported.
Hamideh Habibi, Kerman weather forecaster said in the present conditions, rainfall is not favorable in Kerman. To solve the problem of water shortage, “we should move towards modern methods of water harvesting, supply and maintenance.” New methods like cloud seeding should also be employed, but to implement the plan, the existence of adequate rain clouds and weather humidity is essential, she added.
Also a high amount of water evaporates at the time of transfer for irrigation purposes, “so we need new transfer and irrigation methods to prevent evaporation.”
Meanwhile, it appears that some experts in Kerman have found ways to resolve the water crisis: by constructing underground dams. The dams have been constructed in such a way that there is minimum amount of water wastage “in the time of water retention.”
Ingenious Method
An underground dam is a wall constructed to save underground water from pouring into the sea so that it can be put to human use. Underground dams are an ingenious Brazilian method for storing water during wet periods for dispersal during dry times. Essentially, they are similar to above ground dams except that their reservoirs are full of sand to prevent evaporative loss. Water is stored in the porosity of the sand and extracted when needed during dry periods.
Underground dams are relatively easy to make and cheap to construct. Assuming a porosity of 30 to 35% for loose sandy alluvium, the stored water volume for a typical underground dam is around 2,000 cubic meters but can be much larger. In semi-arid regions, these volumes are a significant resource and can supplement water for irrigation.
During dry weather the groundwater behind the dam remains because it is trapped by the plastic barrier and sheltered from evaporation by the alluvium. Water is extracted through a large diameter well emplaced a meter or so upstream of the dam. In some cases, salt extracting plants are grown in the alluvium immediately upstream of the dam. Regular removal of these plants helps prevent salinity from building up in the groundwater.
New Structures
The new method of dam construction was put on the country’s agenda four years ago. Although the structures are common in other parts of the world, in Iran they are still new. The method is especially beneficial in desert regions and arid provinces where the rate of water evaporation is high. The underground dam capacities are less than the regular dams but they have the lowest dissipation, said Mohammad Arab, deputy of natural resources and watershed department of Kerman.
Low cost of construction, hygienic water and durability of the structures are among their other benefits. Several underground dams have been built in the province and the trend continues.
