Impact of climate change on the Mahanadi river basin

The Mahanadi River delta plain covers 0.9 x 10 km and lies between 85 40' : 86 45' E and 19 40' : 20 35' N. The catchment area of the river covers 1.42 x 10 km. The sediment yield of the Mahanadi catchment is around 200-400 tonnes/km. It has an average annual rainfall of 1572 mm and 70% of this during the SW monsoon season.

In the recent past, the years 2001 and 2003 were marked by very high floods in the Mahanadi River. In July, 2001 very high floods passed for four continuous days (July 17 to July 20) when water discharge exceeded 39,000 cumsec and the recorded highest discharge was around 40,868 cumsec. For a few days in August and September 2003, very high floods passed when water discharge fluctuated between 31,000 to 38,200 cumsec.

Orissa meteorological subdivision has gained importance because of the recent observations which show that impact of CC is more vulnerable to Orissa. Analysis of instrumental climate data revealed that the mean surface temp over India has warmed at a rate of 0.4 deg cet per century (Rao, 1995). The increasing trend of temperature in Mahanadi river basin of Orissa meteorological subdivision due to CC is more severe. Rao (1195) found that the surface air temp over this area is increasing at a rate of 1.1 deg per century which is more than double of that of entire India.

The impact of CC may also be more severe for Orissa met subdivision because of its position at the coast of the Bay of Bengal. A slight change in the pressure anomaly of the sea can have a severe impact on the precipitation of Orissa, which results in increase of hydrologic extremes in that region. Recent past records of Orissa with a flucturating weather condition and the high occurrence of hydrologic extremes show that this the most affected region of India due to CC.