Tamil Nadu - Climate
Tamil Nadu has high dependence on natural resources and faces the threat of climate change and its impacts. Available evidence shows that there is high probability of increase in the frequency and intensity of climate related natural hazards and hence increase in potential threat due to climate change related natural disasters. In the (relative) absence of State level climate models and/or vulnerability studies, as well as low community awareness, Tamil Nadu is potentially mere sensitive and vulnerable to climate change and its impacts.
The State of Tamil Nadu is situated at the south-eastern extremity of the Indian Peninsula, bounded on the east by the Bay of Bengal, in the west by the Western Ghats and in the south by the Indian Ocean,and in the North West by Nellore and Chittoor districts of Andhra Pradesh and Kolar, Bangalore and Mysore districts of Karnataka. It has a coastal line of 922 km and land boundary of 1200 km. It lies between 8° 5? and 13° 35? N latitude and between 76° 15? and 80° 20? E longitude. The State can be divided into two natural divisions namely, the coastal plains and hilly western areas.The Palghat gap of Kerala about 25 km in width in the great western mountain wall is the only marked break to Tamil Nadu. The slopes of the Western Ghats are covered with heavy evergreen forests, that too presently being made grey rapidly with human intervention, thus making it susceptible to animal and human conflict.
The trend of drainage is from west to east into the Bay of Bengal. The river Cauvery rises from the Brahmagiri hill in Coorg district of Karnataka and passes across eastwards across the peninsula into the Bay of Bengal. The Ponnaiyar River rises from Kolar district of Karnataka runs across the State and falls into the sea north of Cuddalore. The Vaigai river from Western Ghats and passes across the State and finally falls into the Bay of Bengal, 16 km east of Ramanathapuram. The proximity of sea influences the climate of the eastern and southern parts of the State whereas hilly orography and inland locations play important roles in modifying the climate over rest of the State. The western portions of the State and the portions bordering with Kerala have a marine climate with mild winters and moist summers and the remaining part of the State has a tropical savanna climate that is hot and seasonally dry.
Out of 13 million hectares of geographical area, about 7 million hectares of land is under cultivation. Of this 55 percent is irrigated and rest is rain fed/ dry land. Among all the States in India, ground water has been harnessed fully in this State. Tamil Nadu has been divided into seven agro climatic sub-zones, three agro ecological zones amd 16 sub agro-ecological zones. The agroclimatic zones are North Eastern zone, North Western zone, Western Zone, Cauvery Delta zone, the Southern zone, High rainfall zone and High Altitude and Hilly zone. The three agroecological zones are the hot semi arid eco-region with red loamy soil, hot sub humid to semi arid eco-region with coastal alluvium derived soils and hot humid eco-regions with red lateritic and alluvium derived soils. This classification helps in the suitable planning and should be made based on these boundaries.
The State mainly receives its rainfall in three seasons, viz. south west monsoon, north east monsoon and pre monsoon season. The normal annual rainfall falling over the State is 958.4 mm. About 50 percent of the total annual average rainfall is received during north east monsoon, while about 31 percent is received during south west monsoon and the balance in the other seasons. The coastal districts receive about 65-75 percent of annual rainfall and interior districts get about 40-50 percent in this season.
Long term studies carried out by Guhathakurta et al, for the period 1901-2005, indicate, that Tamil Nadu is experiencing more dry days than wet days every year. However, there has been a significant increase in heavy precipitation events. Situated along the eastern coast of India, Tamil Nadu has been hit by about 32 cyclonic storms between 1891 to 2006 of which 30 were severe cyclonic storms. The total number of cyclonic storms hitting the Tamil Nadu coast increased to 44 by 2011. A sharp increase by 37.5 percent between 2006 and 2011.
Increase in heavy precipitation events is likely to lead to flash floods, leading to deterioration in soil health due to heavy loss of top soil caused by erosion in hilly areas, and decline in soil organic matter content thereby impacting agriculture in these areas. The other risk that the agricultural system may have to deal with is the emergence of new pests and diseases.
The State over the years has become vulnerable to various natural disasters, which is a matter of serious concern to the planners. Agriculture is the predominant occupation in Tamil Nadu and is highly dependent on the endowment of natural resources and environmental conditions. Because of its geographical position under the climate variability situations, agriculture in Tamil Nadu is affected by frequent cyclones; droughts and flood occurrences. Further, the inter-annual variability in the Inter-State river flow affects surface water resources available for irrigated agriculture.
Tamil Nadu is prone to droughts every 2.5 years. As a result of droughts, summer crops are likely to experience enhanced Evapo-Transpiration (ET), needing larger, more frequent irrigation. The surface water resources are likely to be depleted, creating pressure on ground water, which though may need the needs in the 1st year but recurrent droughts will not enable natural recharge.
Current estimates of Demand and Supply gap of important crops in Tamil Nadu for the year 2010 (estimated by the State Planning Commission) indicated that the State is lagging far behind in the production of various crops. As the production and productivity of crops mainly depend on the climatic conditions that prevail during the growing period, it is important to understand the changes that have happened in the climate and its related impact on agricultural production, and plan agriculture as per the anticipated changes to climate.
|
NEWSLETTER
|
| Join the GlobalSecurity.org mailing list |
|
|
|
