DOHA: Over extraction, sea water intrusion and massive use of pesticides in farms are polluting Qatar's ground water.
The country's present extraction of ground water is estimated to be about four times the average recharge from rainfall. The total quantity of groundwater extraction has increased 327 percent over the last three decades. The number of wells in use for irrigation increased from 660 to 2,981 during the period revealed a research note released by the Friends of Environment Centre (FEC) here yesterday.
High evaporation rate, intrusion of effluents, defective well construction and failure to seal abandoned water are also contributing to the poor quality of Qatar's ground water.
The over-extraction from wells in the same farm or neighbouring farms leads to lowering the water table and consequent up flow of brackish water from the underlying aquifer, thus increasing the water salinity. Though seawater intrusion is a common phenomenon along sea coasts, peninsulas and islands, the problem is more severe in Qatar. The high permeability of the fractured limestone aquifer, containing fresh water, permits rapid intrusion of sea water.
Over-extraction from wells situated along the coasts cause rapid deterioration of water quality. This is evident by comparison of the location of the isosalinity (salt concentration) lines along the coasts for the years 1971 and 2003. For instance, the isosalinity line of 6,000 part per million (ppm) in north and north western Qatar was aligned near the coast in 1971 but shifted inland and was replaced approximately by isosalinity lines of 10,000 and 12,000 ppm in 2003, the report said.
"The return flow from irrigation to the groundwater reservoir is estimated at an average of 25 percent of the gross water application. Although this irrigation return flow increases the recharge to groundwater, it deteriorates the water quality. This is because the percolating poor quality water dissolves salts from the soil and underlying strata and carrier them to the aquifers bearing relatively fresh water".
The farmers in Qatar generally use large quantities of low quality water to wash salts and avoid wilting of plants; and they apply chemical fertilisers to increase the yield. This is another possible contributing factor for groundwater pollution. In the Government experimental Farm, drainage water analysis has shown significant increase in nitrate derived from nitrogenous fertilisers.
The high evaporation rates during summer increases the accumulation of salts in the root zone. Excess irrigation water percolates deeply, carriers with it the accumulated salts to the aquifer and thus, aggravates further the problem of groundwater deterioration.
Groundwater contamination could also result from industrial waste lagoons, underground gasoline and diesel tanks, leaking wastewater pipes, injection of untreated industrial wastewater in to wells, defective wells construction and failure to seal abandoned wells.
By Satish Kanady
© The Peninsula 2010
