Depleted aquifers replenished   
By Mohammad Hussain Khan

LAST year`s flash floods wreaked havoc on livestock and agriculture in Sindh but had some positive impact on soil and ground aquifers. Soil fertility improved greatly while the fast depleting ground aquifers — an important source of irrigation and fresh drinking water — were replenished.

Groundwater level had dropped 30-35 ft in last one decade because of excessive use of tube-wells for irrigation of lands. This caused immense hardship to the rural population which, to a great extent, depended on groundwater aquifers for drinking purpose in absence of any water supply scheme or purification plants.

Drainage and Reclamation Institute of Pakistan (DRIP), Tandojam, which works under the ministry of science and technology, regularly monitors around 100 tube-wells of land owners in districts of Nawabshah, Naushahro Feroze, Matiari and Khairpur which are on the left bank. The institute examines different aspects of groundwater. In recent monitoring following last year floods, it found that fresh groundwater table had improved up to 12-13ft from previous 30-35ft.

According to institute in-charge Mohammad Khan Mari in some areas the table has improved up to 5ft. An old study that is often quoted on groundwater quality by experts, 84-85 per cent of it is brackish. Barring few pockets, groundwater is brackish in most part of the right bank. Freshwater aquifers exist on left bank of the Indus River within a radius of 30-35km, he says.

“We need to utilise this reserve efficiently when there is water shortage in river and canal systems. We can have a good use of it for around four years if we manage it properly”, he emphasises.

An efficient use of this water reserves is being recommended by agriculturists to make it sustainable for a longer period. They say floods did improve land`s fertility and recharged aquifer, important resource of water, and it must be conserved.

Sindh Abagdar Board (SAB) president Abdul Majeed Nizamani and general secretary Mehmood Nawaz Shah stress the need for conducting a baseline study to get exact data of groundwater aquifers and use of systems like drip and sprinkler. Such study should show for how long this reserve will be sustainable. They point out that the rise in water table as high as 5ft could be harmful for plans because it affects their root, and systems like drip and sprinkler can be helpful in water conservation.

According to Mohammad Ahsan Siddiqui, water technologist, geophysical formation of soil in Sindh indicates presence of limestone which blocks penetration of freshwater and hence brackish quality of groundwater. Limestone doesn`t allow rain or floodwater to cross it.

He referred to a study conducted in Sindh during the first tenure of Nawaz Sharif government through Japanese experts. “I assisted experts in that study which established the fact that Sindh`s 80-90 per cent soil has limestone whereas in Punjab land`s quality is better than Sindh`s,” he says.

The quality of subsoil water on the right bank of Indus River is brackish whereas freshwater aquifer is available on the left bank. Yar Mohammad Khuhawar of Sindh University`s High Technology Resource Centre Laboratory says that underground water basically flows towards left side of the Indus and freshwater reserves are found in that pocket.

Environmentalist Naseer Memon says: If you keep on using groundwater excessively in absence of proper recharge mechanism it will badly affect it. If sub-soil water is available by 10ft it is a blessing for farmers. It will serve as important source of drinking water but beyond 10ft it will harm quality of crop barring rice”, he says.

Heavy rainfall and floods serve as main sources for recharging of aquifers but over the last one decade the province has gone through a long dry spell. It forced farmers to opt for massive tube-well operation which dealt a telling below groundwater. Rainfall recharges groundwater aquifers but experts believe that such contribution is not more than two per cent as compared to floods. They stress the need for an efficient management of groundwater aquifer.

Courtesy: The DAWN