A spell of heavy rain that followed the Neelam cyclone which resulted in heavy damage to agriculture fields, particularly paddy, has confirmed that exploitation of natural gas has caused land subsidence in the Krishna and Godavari deltas, says a former professor of geology of Andhra University and member of Movement for People Centred Development G. Krishna Rao.
Studying the conditions after the heavy spell of rains between October 29 and November 5, Prof. Krishna Rao pointed out that there was no surface run-off through major rivers and local rainfall alone affected the paddy fields where water crossed 1 to 1.5 metre. Half of the area in the two deltas has been affected. Upland areas like Vijayawada, Eluru, Nidadavolu and Pithapuram, among others suffered damage due to backwaters.
East Godavari received relatively less rainfall, 28.7 cm, compared to 38.9 cm, 37.8 cm and 34.4 cm by West Godavari, Krishna and Guntur respectively but suffered damage in a larger area, 3.4 lakh acres, compared to 2.34 lakh acres, 1.95 lakh acres and 97,000 acres in the three districts.
This was because East Godavari delta area suffered land subsidence over a bigger area compared to other places which conforms to the number of production wells and quantum of hydrocarbons exploited from this region, he said.
This time water logging continued for several days in most of the coastal areas. East Godavari farmers recalled that in the past, before exploration of oil and gas, any amount of rainwater even due to cyclones would get cleared in 24 to 48 hours. Since this is not happening now it is confirmed that elevations of delta lands have reached near sea level, thereby the topographic gradient has come to near zero level and water is unable to flow in to the sea, said Prof. Krishna Rao.
During the November 1996 cyclone, Kakinada received 22.35 cm of rain and 250 villages were inundated. But the recent spell, which is of almost the same quantity affected 500 villages and water remained for several days.
Water-logged
Coastal area is getting water logged even with a rainfall of 5 cm to 10 cm and for several days. Severity of this situation will increase in the next few years as the land is sinking, Prof. Krishna Rao warned.
Sea water is encroaching on the deltas with further sinking of the land and they would turn into wet lands, a stage preceding complete submergence into sea.
Land subsidence has also affected the canals and made the irrigation system defunct in the delta areas. The solution is to evaluate the changed topographic conditions and establishing the gradients in the entire region.
Appropriate designs are to be prepared for the changed topography for effective flow, suggested Prof. Krishna Rao.
“Stopping the sinking process of the deltas is a pre-requisite”, he asserted.
