Abstract
Water is an important resource for many activities which includes agricultural production and is something which living things entirely depend on. More than 95% of the surface water in Tamil Nadu has been utilized. In this study, we will analyze the situation of water resources in Tamil Nadu. We will always analyze the impacts of irrigation, rainfall on water resources.
Introduction:
Water is an important asset which provides goods and services which are utilized by agriculture, industry and households. Tamil Nadu is one of the peninsular states of India. It comprises only 2.5% of the total water resources of the country.Agriculture is the main source of livelihood for majority of people living in Tamil Nadu. Tamil Nadu is always known for its achievements in various sectors like agriculture, a lot of variance in the rainfall pattern,declining investment in agriculture, overuse of groundwater still remains a problem. Canals, wells and tanks are the major sources of irrigation in Tamil Nadu excluding sources such as springs, jungle streams etc. Wells and tanks depend upon rainfall for recharge.
Impact Of Rainfall
The first dataset we will be using contains data about annual rainfall in Tamil Nadu. The data is divided season wise into rainfall in hot weather, winter, north east monsoon and south west monsoon. It also contains deviation from the normal rainfall patterns.
As we can see from the figure above, there is high variance in the rainfall pattern in south west monsoon season. Every alternate year, the actual rainfall in south west monsoon was less than the normal rainfall.
The above graph shows actual versus normal rainfall pattern in north east monsson in Tamil Nadu. The actual rainfall kept decreasing from 2005. There has been a sharp decline in actual rainfall in the year 2016-2017.
As seen from the graph, the normal rainfall kept decreasing. The actual rainfall rarely meets the normal rainfall. Though in the year 2018-2019, the actual rainfall was more than the average rainfall or normal rainfall, the exponential decrease in average rainfall in north winter season cannot be neglected.
The actual rainfall in hot weather season is mostly more than the average rainfall. In this graph also we notice a gradual decrease in average rainfall in the year 2018-2019.
This graph shows the total actual versus normal rainfall. The highest percentage deviation is observed in the year 2016-2017 which is 13.6% deviation from the normal.
903.3428571428574
0.3237965335104532 0.507415314545972 0.14822721953379506 0.020613119524306542
The average annual rainfall is 903.34 mm in Tamil Nadu from 2005-2019. Tamil Nadu recieves 50.7% of it's rainfall from North East Monsoon, 32.4% from South West Monsoon, 14.8% from Hot Weather Season and 2% from Winter Season. The rainfall pattern was characterised by many upswings and downswings. The upswings were characterised by good downpur while some years were characterised with scanty rainfall.
Surface Water Resources
For analysing surface water resources, we will be looking at the surface water resources data which have been collected in the year 2020, 2019, 2018, 2017, 2016 and 2015. Now, it is important to understand that the data collected in 2020 was actually the data from 2018-2019. It is the same with all the other datasets also. Each dataset contains the district wise division of number of canals, tube wells, open wells, tanks and resorvours. This will help us in understanding the surface water in Tamil Nadu overrall and district wise.
The above figure shows the distribution of number of canals district wise and the data is also distributed year-wise using the slider above. From year 2017-2013 there was no significant change in the number of canals in any district. In 2018-2017, there was increase in number of canals in Virudhngar,Nilgiris,Sivaganga,Nagapattinam,Ariyar and decrease in number in Tirunelveli,Tiruchipalli,Theni,Thanjavur. In 2018-2019, number of canals in Ariyar again decreased.
The above figure shows the number of tube wells and other wells district wise in each year. There has been decrease in tube and other wells in year 2014-2015. A slight increase was observed in several districts in years 2015-2017. An enormous decrease in the number of tube and other wells in districts like Villupalem, Vellore has been noticed in 2017-2018. There was substantial increase in all the district in 2018-2019.
The bar plot shows the number of open wells in all districts year-wise. Throughout the years 2013-2017, the number of open wells remained more or less the same in number. IN 2017-2018, decrese in number of open wells was observed in Virudhunagar, Thoothukudi,Dindigul whereas increase in number was seen in Theni, The Nilgiris, Ariyalur. In 2018-2019 increase in number was seen in Tirunveli, and decrese in Theni, Nilgiris, Sivaganga.
The above figure shows the distribution of the number of tanks in each district year-wise. Until 2013-2017, there was no major change in number. There was a drastic increase in Virudhunagar, Ariyalur and in other districts a decrease or consistency in number was noticed. In 2018-2019, there was an increase in Tirunelveli, Tiruchirappalli. In other districts a decrease in number was observed.
The above figure shows the distribution of reservoirs in Tamil Nadu year wise. In 2017-2018, a lot of reservoirs were constructed which increased the water sources in Theni, Nilgiris, Thanjavur.
Government measures for water bodies in Tamil Nadu
Public Works Department has been serving for the past 159 years in the construction and maintenance of Irrigation of structures and Government Buildings, massive structures and monuments stand as testimony to our engineering skill.
The water for delta irrigation released from Mettur dam reaches the Grand Anicut situated at Thogur village in Thiruvaiyaru Taluk of Thanjavur District. At Grand Anicut the water has been regulated and distributed to Cauvery, Vennar, Grand Anicut Canal and Coleroon rivers by the divisions of Lower Cauvery Basin circle Thanjavur to irrigate the command area of 4,53,046 acres. During floods the storm water is being diverted to the Coleroon river, the flood carrier, in the Grand Anicut and their by the irrigation systems of Cauvery, Vennar, Grand Anicut Canal are kept intact without any damages.
There was a time when life was centred around waterbodies. Those days are history. As times changed, people lost their connection with waterbodies, leaving them to shrink. As regards Thanjavur district, which has the maximum waterbodies, almost 86 per cent of them are full to the brim. Of the 559 lakes and tanks in the district, as many as 479 are 100 per cent full while 60 waterbodies are 90 to 100 per cent full.