India is an agricultural country with 80% of its population engaged in agricultural operations. Water is the basic and foremost requirement of agriculture. Though the primary source of water is rainfall, the other sources of water are rain water, surface water and ground water. All three are interlinked. A portion of the rain water How’s in rivers and enters the sea. There are certain rivers flowing through more than one state. In India, Cauvery is one such interstate river. Cauvery originates in Karnataka State and joins the sea in Tamil Nadu. Before independence, there were the Presidencies which were under the direct control of British Governors and native states ruled by native rulers but under the power of the British Government. In order to protect the irrigation interests of the tail end delta ayacut, the then Governor of Madras Presidency thought it fit to enter into an agreement with the Mysore Durbar in 1892. Oh the basis of this agreement any new irrigation project storage or diversion in the upper reaches of the following rivers including Cauvery could be taken up only with the prior permission of the Governor of Madras. For the development of ayacut Cauvery both in the Mysore area and in the Madras Presidency, an agreement was concluded in 1924-1929 between the Governor of Madras and Mysore Durbar. Under this agreement, 1,10,000 acres were to be irrigated in the Mysore area under the newly constructed Krishnaraja-sagar and 3,10,000 acres in Madras Presidency under the Cauvery Mettur Project. The agreement contains a clause providing for a review after 50 years. In case of disputes, it should be referred to arbitration by the Central Government.


In the context of the 1924-1929 agreement, let us try to analyse the technological issues involvled. Agriculture is an operation which requires solar energy and soil moisture, in addition to the sup-porting soil with its macro and micro nutrients. In a tropical region like ours, solar energy is available in plenty throughout the year. The control factor is the soil moisture. Soil moisture is supplied by way of rainfall and supplemented by irrigation. Manavari or rainfed crops depend entire on the rains for their required soil moisture. In the case of dry crops or garden crops, rainfall is supplemented by irrigation. In the case of wet crops like paddy, plantain, sugarcane and betel leaves etc, irrigation becomes the major component contributing to soil moisture. A crop is raised during times when moisture is available in required quantity. As the primary source of soil moisture is rainfall, the crop period is fixed, taking into account the rainfall pattern and covers the period of maximum rainfall. This crop period is called the agricultural season.

Agricultural Seasons based on Rainfall Pattern:

Normally on an all-India bask, the following are the agricultural seasons.

KHARIF (Monsoon) - 15th June to 15th October (Rainy Season)
RABI (Winter season) - 15th Oct. to 15th Feb. (Summer season ) - 15th February to 15th June

But in Tamil Nadu, the traditional agricultural season lasts from August to January known as the Samba Season. In respect of agricultural seasons, the Cauvery Basin divides itself into two distinctly different zones. The upper catchment area consisting of the Ghat Section and the Mysore Plateau receives rain during the summer months of June-July under the influence of South-West monsoon. The lower half consisting of the Tanjore delta in Tamil Nadu receives rains during the months of October, November and December under the influences of North-East monsoon.

A review of the monthly normal rainfall of the 30 climatologically regions in India will reveal this phenomenon: The annual rainfall ranges from 31.1 cm.(Rajasthan West) to 326.5 cm. in coastal Mysore forming an arithmetical average of 139:0 COL, taking the country as a whole. The rainfall during the Kharif season (15th June to 15 October) amounts to 26.6 cm. in Rajasthan West to 252.8 cm. in coastal Mysore leading to an average of 98.75 cm. for the country as a whole. For a study of the trend of monthly rainfall, distribution over each zone, and comparison of this trend among different zones, the annual rainfall of each region is taken as 100% and the rain received during each month is expressed as a percentage of the annual rainfall. For the Kharif season the average is 72.8% taking the country as a whole. It goes upto 89.7% in individual cases like Gujarat. Tamil Nadu receives the least amount - 39.4%. The adoption of Kharif season over the entire country except Tamil Nadu is then based on the rainfall pattern. Though Tamil Nadu does not get adequate rainfall during the Kharif season, during the Samba season (from August to January) it receives 115 cm. out of 100.8 cm. of the annual rainfall. In Tamil Nadu, a district-wise breakup of the monthly normal rainfall also establishes this point. Barring the Kanyakumari District, the Nilgris District, Kodaikanal in Madurai District, Anamalai and Chinnakallar hill stations in Coimbatore District, the annual normal rainfall for the State works out to 96.7 cm. Out of this, 37.5 cm. is received during the Kharif season whereas it receives 73.7 cm. during the Samba season. A station-wise break-up of the 26 rainfall stations in Tanjore District also establishes this point. The annual normal rainfall of the district is 114.8 cm. out of which it receives 36.9 cm. during Kharif season and 933 cm. during Samba seasons. In terms of percentage, it works out to 31.9 and 81 respectively. Thus it can safely be concluded that our forefathers who were adopting the Samba season had been adopting a procedure in keeping with the pattern of rainfall.

Evapo-transpiration - The Index of Water Requirement of the Crop

Another salient point to be considered is the temperature and its resultant agronomical effect, evapo-transpiration which is an index of the requirements of water by plants. Evapo-transpiration is influenced not only by temperature but by the number of sunshine hours, humidity and wind velocity. Though the number of maximum possible sunshine hours is primarily determined by the latitude of an area, it is further influenced by the actual cloud cover during the day-time period. Thus, there is sharp reduction in the number of actual sunshine hours in Karnataka and Kerala during June-July compared to those obtained in Tamil Nadu during these months. A comparison of data for the three regions in Cauvery Basin will reveal the sharp differences in the evapo-transpiration and rainfall pattern, which are the indices of water required by plants and the supply of available water to plants. The net surplus or deficit during each month can be taken as a rough guide for indicating the need of supplemental irrigation for the plant in question.

In Karnataka and Kerala the Kharif crop is raised on lands which have good drainage facilities. Due to the well-spread rainfall pattern, a crop comes to maturity in the Kharif season.

For the Rabi season, required soil moisture is built up in the soil in advance so that almost without further rains, the Rabi crop comes to maturity. The moisture available in the humid air in the Rabi season is also utilized by the plant.

The pattern of soil moisture supply in Samba season follows a distinctly different pattern. The soil should be repeatedly ploughed and exposed to the sun for drying up by the solar heat and activated by the solar light. The longer the period of this plugging and exposure to solar heat and light, the better it would increase the capacity of the soil for the absorption, retention and release of water as soil moisture. By such a process, the field capacity of the soil is increased and its water release characteristics improved.

It would be useful to consider in detail how soil moisture is generated and retained in the different seasons. It would, perhaps, then give an idea of the total unsuitability of adopting the Kharif season in Tamil Nadu.


Rainfed Conditions:

(a) Method of Development of Soil Moisture during Kharif Season:

@FIRSTPAR = Lands with well-drained soil and subsoil structures are taken up for cultivation during this season. Rain is well spread throughout the season.

Very little soil culture is done for the three seasons through ploughings and exposure to the solar heat and light. Seeds are drilled in rows along plough lines 3 to 5 cm. deep immediately after rain. Utilizing the soil moisture developed on the top layer of the soil, germination takes place. The land is periodically ploughed by way of intercultivation and the soil between the rows of seedlings is loosened. Initially, the depth of plough is small but subsequent ploughings are taken to greater depths evidently to create soil moisture in the soil depth very near to the grass roots. This inters 'Cultivation continues for about 3 months till the plant grows to a height of about 2 feet.

Thus, the soil moisture is developed and arranged to be within the reach of the grass-roots during the growth period.

(b) Method of Development of Soil Moisture during Rabi Season:
The black and humus soil with less drainage facilities are reserved for cultivation during the Rabi Season. The Kharif rains fall over these lands. The lands are periodically ploughed and the rain water allowed to soak into the soil. The plough depths are increased during further periods so that the entire monsoon rain soaks down, reaching the moisture level already existing in the soil. By the time the South-West monsoon comes to a close, a continuous capillary column of water is established from deeper depths to the top of the soil. The seeds are drilled into the soil (not necessarily in rows as in the case of Kharif crop). The seed germinates availing the soil moisture on the top layer of the soil. As the plants grow upward, the roots pierce downward to greater depths. The roots suck the soil moisture already developed and made available with certain amount of suction force, and grows further. The grown up roots are able to exert increasingly greater suction pressures depending on further growth of the plant and the roots extending both in depth and on the sides. This is a continuous process till the plants come to maturity. As the period is winter, the water vapor present in the humid air is also absorbed by the plant through its leaves. This supplements the supply of moisture from the soil below.

(c) Method of Development of Soil Moisture during Samba Season:
The soil is repeatedly ploughed and exposed to the solar heat and light right from February to July. Thus the soil gets not only a good title but is also energized in the sense that water, when added, is retained in greater quantity, as a series of layers over the individual soil particles, thus increasing the field capacity of the soil. Addition of fine soil during the ploughings adds to the increase in field capacity of the soil. These fine soils are retrieved during the summer period from reservoir beds, tank beds and ponds. Addition of compost on the soil, especially those from cow-dung and urine and human night soil, adds gummy substance to the soil which help to bind the individual particles into podzols. In this process, capillary columns and cavities are created in the soil structure. These phenomena go to increase field capacity. The humus particles, by themselves, contain more pore spaces compared to soil particles. This again increases the field capacity.

When the final ploughings are over and seeds drilled into the soil either before the rains or after the rains, the pore spaces and capillary columns, together with the individual soil particles, retain the water particles! Water is taken beyond the forces of gravity and the water particles are brought up with the capillary action and surface tension. The germination of the seeds takes place and the sprouting grow, leaving the roots to probe downward, seeking moisture from the soil. Proliferation of the roots takes place. The growth continues till sufficient supply of moisture is available, or is replenished by way of further rains. Otherwise, the plant gets into a stage of dormancy of no growth and no wilting. This continues for about a month till the heavier rains are received during October. The rain water is stored in the root zone depending upon the depth to which soil has been cultured, texture structure and energy level. The excess water, if any, is allowed to drain away as surface run-off water or to percolate to deeper depths and join the ground water storages. The plants grow during November-December, availing the moisture from air and come to maturity in January.

Summer Conditions:

During this period, there is not sufficient rain to develop soil moisture without supporting irrigation supply. Depending upon the capacity of the top soil in the root zone to contain water (Higher Field Capacity), based on its texture structure and humus content, the effectiveness of utilization of irrigation water takes place.


@FTRSTPAR — from the earliest period of history, then, the Cauvery Basin was functioning under two different climatic environments. Each region had its own agricultural season. The administrative machinery represented by the ruling kings in different periods did their best to conserve and distribute the water by strengthening the riverbanks, putting up anicuts and canals. But no one tried to change the agricultural season. When the Cauvery-Mettur Project was brought in to use, the change in agricultural season was introduced in the old delta ayacut of Tanjore District. The new ayacut developed under the Cauvery-Mettur Project in Pattukotlai area is under the Samba season. But as a part of the stabilization efforts of the old delta ayacut, a part of the new water potential created under the Cauvery Mettur Project is utilized. And hence, the change in the agricultural season was introduced over part of the delta ayacut. The season was made to synchronise with the Kharif season. In due course, this has come to be known as 1 the Kuruvai season. The 1924-1929 Agreement provision fixing the water requirements 'or Tamil Nadu during the months of June and July was meant to cater to the ayacut under Kuruvai crop. Let us now briefly see the consequences of this change in the traditional agricultural seasons.

Increase of water into the sea:

Significantly, the change in the agricultural, season has led to a number of problems leading to the present Cauvery Crisis. The original Samba season promoted optimum use of water. During the rainy months of October, November and December the rain water could be stored in the field itself thus minimizing the rate of drainage of water into the sea. For the Samba season, see dings are prepared in August and transplantation is completed before the heavy rains start. The paddy crop takes root and is, thus, prepared to receive the heavy down pour under the influence of the North-East monsoon during October-November. The old story, regarding the method in which a poetess blessed a King may be relevant in this regard. Awayar blessed the King "Let the bunds rise". When asked to explain her cryptic saying she said if the bunds rise, water will raise in the field, the paddy will rise, the peasant will rise, the kingdom will rise and as a result the king will rise in stature. When the Kuruvai season was brought in, the harvest and transplantation operations had to be conducted during the October-November periods. As such, water could not be stored in the field: Hence, even the limited rainfall received in the area causes drainage problems. Drainage relief measures, like straight cuts, brought the seawater nearer the ayacut lands. Other measures like deepening and widening of drainage courses do not help the situation and do not offer significant relief.

In contrast, the drainage of water into the sea in a river system with a huge ayacut in the
delta portion cannot completely be avoided. The adoption of the Kuruvai season for agriculture has increased the quantum of water wasted into the sea both through the Coloroon below the Lower Anicut as well as the various tail-end regulators built across the drainage courses from the delta ayacut.

Increase in demand for water:

The adoption of the Kharif season has resulted in a greater demand for water due to excessive evapo-transpiration. during June and Jury when rainfall is also low. The higher the evapo-transpiration, the greater the production of try matter. Water is the control factor here. It is water which would otherwise be utilised more economically that is wasted due to the adoption of the Kharif Season.

Development of New Genes to Resist Wet Harvest Conditions and the Resultant Deterioration in Grain Quality:

The Kuruvai crop comes for harvest during October, November when the rains are at their heaviest under the influence of North-East monsoon. The plants lodge and the grains, together with the stalks, get wet. The grains germinate under wet conditions. In order to get over these difficulties, the Agricultural Department attempted to develop new varieties of seeds so that

- the stalks do not lodge
- and grains do not germinate under wet conditions.

These new genetic types like ADT 27 etc., were brought out in quick succession to meet this challenge. Short stalks with grains covered with thick husks were brought forth. The net effect was that these species were not of a high quality, from a consumer's point of view. Also, they spoiled due to the rains and wetness during the harvest. A knowledgeable farmer of Tanjore giving a talk over All India Radio, Thirchirapalli said "We have to search out buyers for our Kuruvai crop. For the Samba crop, the buyers come in search of us".

Insufficient and Delayed Supply to Tail End Areas of the Old Delta:

The introduction of the Kuruvai season has resulted in an insufficient and delayed supply of water to tail-end areas of the old ayacut. Due to the excess requirement of water in June-July under the Kharif season, it is not only difficult to meet the timely requirement of the ayacut in the upper reaches, but highly, impossible to meet the requirement of the lower down ayaculs in the delta itself. In a delta distribution system with a major storage reservoir like Mettur, it should have been possible for the engineering authorities in charge of water regulation in the delta area to meticulously ensure supplies to tail-end reaches. But for the introduction of Kharif season in part of the delta ayacut, it should have been possible to ensure equitable supply to the delta ayacut lands in proper time to start cultivation under the Samba season. Now, the tail-end ayacutdars under the delta ayacut are not able to start cultivation in proper time in the Samba season, with the result that the young crops get caught in the rains and do not take proper roots and are washed away at times due to the rains. (The new ayacut in Pattukottai area which is under Samba season does not get supply in proper time to start cultivation. In an irrigation Seminar conducted in May 1974, the ryots of Pattukottai represented that they have been, enbtoc, shoved into the category of tail-end ryots. Due to the introduction of Kharif season over part of delta ayacut the Kharif crop ayacut get precedence over the New ayacut. Hence it results in handicap to the New ayacut.

In view of all this the upper catchment area of Cauvery Basin lying in Tamil Nadu did not get enough attention in the matter of augmenting irrigation facilities during the post-independence period of the Five Year Plans. The supplies to Tanjore delta ayacut have been consistently safeguarded. The introduction of Kharif season has boosted up artificially the requirement of water for irrigation. Hence the taking up of irrigation schemes in Coimbatore, Salem and North Madurai District The sinking of ground water table levels in Coimbatore District can be traced to the inadequacy of the number of storage and diversion works across the drainage courses in the area. It may not be out of place to say that this has a bearing on the current farmer agitation taking roots in those areas.


Now coming to the crisis proper, the difficulty hinges round the introduction of the Kharif season in the Tanjore Delta. If we revert back to the Samba season, cutting off our demand for water in June and Jury, the relationship between the upper regions and Tamil Nadu will become normal Based on the rainfall pattern, Kerala and Karnataka could have Kharifand Robi crops from June to February. Tamil Nadu could have Samba crop from August to January. Based on the available surface water and water to be lifted from the alluvial bed of Tanjore Delta, a second crop during the period February-April could be had. The much needed pulses, oilseeds and cotton could be had over a portion of the delta ayacut if not over the entire delta area. This second crop will enjoy the facility of avoiding risk in the matter of water supply as there is no rain expected during this period there is no risk of speculation in the matter of irrigation supply. Such a lifting of ground water will lower the water table with the result that the soil could be properly dried and processed to receive the next Samba crop after an interim follow period of about 3 months. By such a process, the soil will keep its potency and optimum production could be expected. The chances for development of salinity and alkalinity in the delta ayacut can be reduced to a great extent by availing the dry summer period. Certain consistent practices need to adopted in this regard. A fair sharing of resources, in keeping with the specific requirements of the different parts of the Cauvery delta, is in order. It also means considering the various zones of the delta as an interconnected area and planning cooperation on this basis.

The Principle of Fair Use of Water:

Optimum utility of water for agricultural purposes (i.e.) the maximum production of dry matter per unit of water is achieved only under irrigated dry conditions - popularly known as Garden Cropping - where the soil moisture is maintained within the range of 100% - 30% of the field capacity. But with a view to utilize the excess water actually available either by way of rainfall or the inflow of water from the upper region, wet-root crops like paddy may be taken up. But in the matter of utilization of water for irrigation under wet-foot conditions, the crop period has to be synchronized with a period in which supporting climatic cover like lesser atmospheric temperature, cloud cover, rainfall, high humidity, so that the overall evapotranspiration and the net requirement of water by way of irrigation, after taking into consideration of the useful rainfall during the period, is kept at a possible minimum. This is achieved by adopting Kharif and Rabi seasons in the upper area of Karnataka and Kerala and the Samba season followed by a summer crop (Mast Kodai) in Tamil Nadu and Pondicherry.

The Principle of Equitable Distribution

Considering a unit area of the basin, a certain percentage of the arable part of the land may be brought under wet Crop and another percentage under irrigated dry crop and a third portion under dry/wet crop under rain fed conditions. The unit for such a consideration may be a minor basin or a sub-minor basin. One may take into consideration the rainfall in the area and nature of soil etc. This is to ensure that no part of the basin is left out and no other portion is taking an undue advantage. This is achieved under the "new perspective'' namely the upper area will be able to develop as much as the lower area.

The Principle of Natural Justice:

Every bit of land is entitled fa utilize the quantum of water received on its surface by way of rain-fall. But due to the need for soil conservation and crop development, areas which receive more rainfall are obliged to pass down a portion of the waters to lower down reaches as normal and flood flows. The lower areas which are obliged to pass down the flood received from the upper areas have to adopt the same principles of soil conservation and crop development to make the maximum out of the water flowing through the lower area. This requires starting the crop sufficiently earlier before the floods occur. Under these circumstances, the supply of water at an earlier period is to be let down to the extent required from the upper areas to the lower areas. This is how the lower down riparian are developed as part of the natural justice. Anything contrary to this, by way of riparian rights, will cut across the other principles of fair use and equitable distribution.

Integrated Use of Ground Water, Surface Water and Rain Water:

The water potential in a basin should be reckoned, taking into consideration all the three items of water potential (i.e.) rainfall, surface run-off in the rivers, storages in reservoirs and the ground water stored below ground level.

This "new perspective" takes into account the utilization of rainfall in the upper area during the South East Monsoon, the rainfall in the lower area due to North East Monsoon, the surface run-off in the river and the storages in the reservoirs and the ground water potential in the Delta Area. The ground water potential in the delta portion is proposed to be utilized for the Afasi Kodai crop supplemented by releases from storage reservoirs.

Thus the "new perspective" takes into consideration the integrated water potential in the form of rainfall, surface run-off and ground water.

Principle of Minimum Wastage into the Sea:

In any river system, wastage of water into the sea cannot be completely stopped. The average rainfall of our country is about 139 cm. The average of Tamil Nadu is 100.8 cm. and that of the Interior South Karnataka 124.5 cm. But the annual evaporation is 190 cm. and 180 cm. for Tamil Nadu and Karnataka respectively. Hence Cauvery Basin has to be treated as a deficit area as far as water potential is considered. Thus it may be logical to conclude that theoretically it is possible to utilize the entire water of Cauvery Basin without letting out anything as wastage into the Sea. By adopting the Samba season, the rains received during the North East monsoon could be utilized by storing the same on the paddy field itself and thus the wastage into the sea kept at the barest maximum. It is only such a "new perspective" which would satisfy the principle of minimal wastage into the sea in a water deficit basin.

Author:R. Ramachandran

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