World Colleges Information

Scenario:

->  Monsoon rainfall is the basic resource for water availability in Tamil Nadu. Out of 30 districts in Tamil Nadu, Salem, Dharmapuri, Krishnagiri, Namakkal, The Nilgiris, Kanyakumari districts and parts of Villupuram, Cuddalore and Perambalur districts mostly benefit from Southwest monsoon season (June-September) rainfall. While all the 30 districts in Tamil Nadu are highly benefited from North east monsoon season rainfall (October-December).

->  If any deviation occurs from normal rainfall either during South west monsoon season or during North east monsoon season in an year, the water availability in Tamil Nadu would be always under stake in all the three sources of irrigation viz. tank, canals, and wells. The normal rainfall in Tamil Nadu during cold weather period (January- February) is 46.4 mm, while it is 140.9 mm during hot weather period (March-May) 334.0 mm during South west monsoon period (June – September) and 459.0 mm during North east monsoon period (October – December).

2. Supply and Demand for Water in Tamil Nadu (2025):

• The supply and demand gap for water during 2025 in Tamil Nadu as reported by Palanisamy (2003) is 2.2 MHM. ie. the total water supply is 4.7 MHM, while the demand for water for agriculture (5.2 MHM) and non agriculture (1.7 MHM) is 6.9 MHM. These data indicate that the water resource must be enhanced or there must be a discipline to minimize the water use both in agriculture and non agricultural activities.

• Out of total available water in Tamil Nadu presently, agriculture consumes about 85 percent, while it is 15 percent for domestic and Industry. Central Water Commission estimated the requirement of water for different sectors for the year 2025. Domestic may require about 5 percent of total water availability, while it is 18.2 percent for industry and energy, 73.3 percent for irrigation and 3.5 percent for other uses.

•  Scientific talk given at RMC, Chennai on 23.03.2004 during World Meteorological Day.

•  A decadal analysis was made by Palanisamy (2003) on net irrigated area in Tamil Nadu comparing the net irrigated area of 2000’s with 1970’s. The study indicated that there is no drastic change (-8.0%) in net irrigated area under canals between 1970’s and 2000s while it is -30% for tanks, +93% for wells and -50% for other sources. However the over all data for Tamil Nadu indicated that because of enhanced net irrigated area brought under wells there is 9 percent increase is total net irrigated area in Tamil Nadu during 2000’s (26.9 lakh ha) as compared to net irrigated area existed during 1970’s (24.8 lakh ha).

3. Monsoon rainfall performance in Tamil Nadu:

    A study was undertaken to understand the performance of both monsoon rainfall (Southwest and North east) in Tamil Nadu from the year 2000 (Selvaraju and Balasubramanian, 2004). The study was undertaken for agroclimatic zone wise and the results are presented hereunder.

3.1. North eastern zone:

•  This zone consists of Chennai, Kanchipuram, Thiruvallur, Cuddalore, Villupuram, Vellore and Thiruvannamalai districts.

•  The study indicated that out of eight seasons in four years (South west monsoon and North east monsoon of 2000 to 2003) four districts viz, Kanchipuram, Thiruvallur, Cuddalore and Thiruvannamalai recorded below average rainfall in seven seasons. Overall deviation from normal rainfall in this agro climatic zone was (-) 16.9% for the past eight seasons. Negative anomalies found in at least 3 out of 4 North east monsoon seasons in the past four years in all the districts of this agro climatic zone.

3.2. North western zone:

    This zone mainly comprises of Dharmapuri, Krishnagiri, Salem and Namakkal districts. This zone is to be mostly benefited from Southwest monsoon rainfall. But in the study period between 2000 and 2003 in 3 of the 4 Southwest monsoon seasons, these district did record below average rainfall (-3 to -58%). These district in addition recorded below average rainfall from (-) 3 to (-) 49% in all the four North east monsoon seasons.

3.3. Western zone:

    This zone consists of Erode, Coimbatore, Karur, Dindugul and Theni districts. These districts in Tamil Nadu are well known for low annual rainfall record and the annual average rainfall is around 650 mm. The study indicated that six out of eight seasons had below average rainfall in Erode, Coimbatore and Karur districts. Karur was mostly affected district, recording below average seasonal rainfall in all the eight seasons of the study period from (-) 2 to (-) 76 percent.

3.6. Southern zone:

    Madurai, Ramnad, Vridhunagar, Sivagangai, Tirunelveli and Thoothukudi form this zone. Out of eight seasonal rainfall study from 2000 to 2003, seven seasons had below average rainfall (-) 14 to (-) 76 in Virdhunagar and Thoothukudi districts, while below seasonal rainfall was recorded for six seasons in Madurai and five seasons each in Ramnad and Sivagangai districts respectively. The over all deficiency in the last four years for this agroclimatic zone was (-) 16.9 percent.

3.5. Cauvery Delta Zone:

    This zone consists of six districts viz, Trichirapalli (part of district), Perambalur (part of district), Pudukottai (part of district). Thanjavur, Nagapattinam and Thiruvarur. Nagapattinam and Thiruvarur district recorded deficit rainfall from (-) 3 to (-) 61% in all the eight seasons of study, while it was deficit in six seasons in Trichirapalli, Perambalur and Thanjavur districts. The over all deficit in rainfall at this zone is computed to (-) 16.8 percent over the past four years.

3.6. High Rainfall Zone:

    The district Kanyakumari is the only one district that falls under this zone. This district is meteorologically known for bi modal heavy rainfall area. Interestingly in all the seasons, except Northeast monsoon 2002, this district recorded below average rainfall from (-) 4 to (-) 83 percent.

3.7. Hilly and high altitude zone:

    This zone is mostly dominated by both South west and North east monsoon seasonal rainfall. Except North east monsoon 2003, in all the seven seasons, the rainfall deficit was from (-) 7 to (-) 64%.

    The over all study indicated the following:

1) Continuous meteorological drought occurred in both seasons of four years study period in all the district of Tamil Nadu against the regular pattern of four years of normal seasonal rainfall followed by one year deficit rainfall. This must be the reason for lesser surface run off in the geographical (130069 km2) area of Tamil Nadu. Scientifically from the information of different types of hydrographs of catchments, it might be due to two reasons.

i) Rainfall intensity is lesser than rate of infiltration and
ii) Volume of infiltered water is lesser than soil moisture deficiency in all the four years of study (eight seasons).

This situation has created water crisis in Tamil Nadu presently.

4. Management of Water Crisis:

Two way approach can be employed to challenge the water crisis.

i) Water management for agriculture

ii) Home stead water management

4.1. Agricultural Water Management:

(*)  It is understood that agricultural sector consumes about 85 percent total water available in Tamil Nadu. High water requirement crops like rice (1200 mm), Sugarcane (2000 mm) and Banana (2000 mm) are largely grown in Tamil Nadu from canal irrigated area, tank irrigated areas and well irrigated area. The need of the hour is to change the cropping pattern from high water requirement crop to low water requirement crops.

(*)  As reported by Palanisamy (2003), the return per unit of water (Rs/m3 water) was above one for rice in all the districts of Tamil Nadu except Pudukottai, Ramnad, Virdhunagar, Sivaganga and Tirunelveli districts.

(*)  Among the districts where more than one was recorded, the highest return per unit of water (Rs/M3 of water) was more with Trichirapalli district (1.55) followed by Erode (1.51) and Coimbatore (1.48). This indicated that rice must be encouraged where it is gives higher yield with less water input.

(*)  Hence there is an urgent need to delineate rice efficient cropping zone in Tamil Nadu and Government encouragement may be given to the farmers where the efficient cropping zone lies. In the non-efficient zone area farmers may be discouraged to grow rice and alternatively some other efficient crops may be introduced in the existing cropping pattern.

(*)  If we examine the productivity of different crops per unit of water in Tamil nadu as reported by Palanisamy (2000) though sugarcane and banana give 2.9 and 6.5 rupees per M3 of water used respectively, their water requirement was on the higher side (2000 mm each).

(*)  However, the other crops like pearl millet, finger millet, groundnut and onion give a return of Rs. 2.2, 2.6, 4.2 and 9.4 respectively with a total water requirement of 450 mm, 500 mm, 450 mm and 400 mm. At the time of water crisis it is wise to switch over to these crops against raising sugarcane, banana and rice to a possible extent.

(*)  In addition to have sound alternate cropping pattern which requires lesser water all water saving techniques so far recommended by Tamil Nadu Agricultural University for various crops must be popularized with the farmers. This includes drip irrigation sprinkler irrigation, surge irrigation alternate furrow irrigation etc.

(*)  Further in drylands of TamilNadu (45% of cultivable area) all the water received from rainfall must be conserved in the soil profile through insitu moisture conservation practices and collection in farm ponds and recycling. For this purpose watershed approach may be meticulously followed with most efficient monitoring.

4.2. Home sted water management:

    Water management at the household is also very important similar to field water management. The following areas are suggested.

i. Harvesting rain water at home

ii. Minimising water requirement at home

4.2.1. Harvesting rain water at home:

    The Government of Tamil Nadu has taken right direction in this regard and provision of rain water harvesting structures in all houses has been completed during August 2003. This impact will be known with in few years on the ground water recharge.

4.2.2. Minimising water requirement at house:

i. The water requirement per man may be reduced to 42 litres/day (Drinking 2 litres, bathing 20 litres washing clothes and toilets use 20 litres). This can be exercised till water situation in Tamil Nadu get improved.
ii. Replacing wornout pipes and taps and closing the leakages in all the water pipes.
iii. Clean the cars and two wheelers with wetted cloth.
iv. Practicing irrigation to home garden in the evening hours rather than in the morning.
v. Using shower for bath rather than water from the buckets.
vi. Using washing machine with full load once in a week.
vii. Reusing the used water for cloth washing to clean the houses and toilets.
viii. Reducing the flushout tank capacity from 10 litres to 5 litres in the toilets.
ix. When drawing water from pipes to containers, close the pipe when ¾th container is filled up so as to avoid over flow.

Conclusion:

    Though there is no loss to water as per hydrological cycle, its availability is becoming scarce across the world including Tamil Nadu. Water use must be minimized both in agriculture and also in home. There may be some ecological imbalance temporarily, but it will get vanished at longer run.