irrigation Archives - The India Climate Observatory

Big water storage wheel

April 29, 2017 by Climate portal editor Leave a Comment

The Central Water Commission, Ministry of Water Resources, Government of India, monitors every day the quantity of water stored (and used from) each of the 91 major reservoirs of the country. It issues a bulletin every week that gives the weekly storage position of these reservoirs – the volume of water, the level of water in the reservoir and the change from the last week, the change from the same date last year and from the average on this date of the last ten years.

The water storage capacity of these 91 reservoirs taken together is 157.799 billion cubic metres (bcm) which is estimated to be about 62% of the total water storage capacity (in other smaller dams and storage structures all over the country) that has been built and is being used, and which is approximately 253.38 bcm. Out of these 91 reservoirs, hydro-electric power stations (with a capacity of 60 megawatts and more) are attached to 37 reservoirs.

In this illustration by Indiaclimate, for the first time the total storage capacity of the 91 major reservoirs has been visually mapped to show reservoir, state and zone capacities relative to each other and the total.

These are the reservoirs with state, reservoir name and full reservoir level in billion cubic metres (bcm). For a good quality file that you can print, write to us.

South zone reservoirs (AP for Andhra Pradesh, TG for Telengana, APTG for Andhra Pradesh and Telegana together, KAR for Karnataka, TN for Tamil Nadu, KER for Kerala): AP, Somasila (1.994); TG, Sriramsagar (2.3); TG, Lower Manair (0.621); APTG, Srisailam (8.288); APTG, Nagarjuna Sagar (6.841); KAR, Krishnaraja Sagra (1.163); KAR, Tungabhadra (3.276); KAR, Ghataprabha (1.391); KAR, Bhadra (1.785); KAR, Linganamakki (4.294); KAR, Narayanpur (0.863); KAR, Malaprabha (Renuka) (0.972); KAR, Kabini (0.444); KAR, Hemavathy (0.927); KAR, Harangi (0.22); KAR, Supa (4.12); KAR, Vanivilas Sagar (0.802); KAR, Almatti (3.105); KAR, Gerusoppa (0.13); KER, Kallada (Parappar) (0.507); KER, Idamalayar (1.018); KER, Idukki (1.46); KER, Kakki (0.447); KER, Periyar (0.173); KER, Malapmuzha (0.224); TN, Lower Bhawani (0.792); TN, Mettur (Stanley) (2.647); TN, Vaigai (0.172); TN, Parambikulam (0.38); TN, Aliyar (0.095); TN, Sholayar (0.143). Total for 31 reservoirs 51.59 bcm

West zone reservoirs (GUJ for Gujarat, MAH for Maharashtra): GUJ, Ukai (6.615); GUJ, Sabarmati (Dharoi) (0.735); GUJ, Kadana (1.472); GUJ, Shetrunji (0.3); GUJ, Bhadar (0.188); GUJ, Damanaganga (0.502); GUJ, Dantiwada (0.399); GUJ, Panam (0.697); GUJ, Sardar Sarovar (1.566); GUJ, Karjan (0.523); MAH, Jayakwadi (Paithon) (2.171); MAH, Koyana (2.652); MAH, Bhima (Ujjani) (1.517); MAH, Isapur (0.965); MAH, Mula (0.609); MAH, Yeldari (0.809); MAH, Girna (0.524); MAH, Khadakvasla (0.056); MAH, Upper Vaitarna (0.331); MAH, Upper Tapi (0.255); MAH, Pench (Totaladoh) (1.091); MAH, Upper Wardha (0.564); MAH, Bhatsa (0.942); MAH, Dhom (0.331); MAH, Dudhganga (0.664); MAH, Manikdoh (Kukadi) (0.288); MAH, Bhandardara (0.304). Total for 27 reservoirs 27.07 bcm

East zone reservoirs (JHR for Jharkhand, ODI for Odisha, WB for West Bengal, TRI for Tripura): JHR, Tenughat (0.821); JHR, Maithon (0.471); JHR, Panchet Hill (0.184); JHR, Konar (0.176); JHR, Tilaiya (0.142); ODI, Hirakud (5.378); ODI, Balimela (2.676); ODI, Salanadi (0.558); ODI, Rengali (3.432); ODI, Machkund (Jalput) (0.893); ODI, Upper Kolab (0.935); ODI, Upper Indravati (1.456); WB, Mayurakshi (0.48); WB, Kangsabati (0.914); TRI, Gumti (0.312). Total for 15 reservoirs 18.83 bcm

Central zone reservoirs (UP for Uttar Pradesh, UTT for Uttarakhand, MP for Madhya Pradesh, CHT for Chhattisgarh): UP, Matatila (0.707); UP, Rihand (5.649); UTT, Ramganga (2.196); UTT, Tehri (2.615); MP, Gandhi Sagar (6.827); MP, Tawa (1.944); MP, Bargi (3.18); MP, Bansagar (5.166); MP, Indira Sagar (9.745); MP, Barna (0.456); CHT, Minimata Bangoi (3.046); CHT, Mahanadi (0.767). Total for 12 reservoirs 42.30 bcm

North zone reservoirs (HP for Himachal Pradesh, PUN for Punjab, RAJ for Rajasthan): HP, Gobind Sagar (Bhakra) (6.229); HP, Pong Dam (6.157); PUN, Thein (2.344); RAJ, Mahi Bajaj Sagar (1.711); RAJ, Jhakam (0.132); RAJ, Rana Pratap Sagar (1.436). Total for 6 reservoirs 18.01 bcm

The IMD’s shaky monsoon math

August 7, 2014 by Climate portal editor Leave a Comment

Over eight weeks of recorded monsoon rain, the district-level data available with the India Meteorological Department (IMD) portrays a picture that is very different from its ‘national’ and ‘regional’ advice about the strength and consistency of rainfall.

In its first weekly briefing on the monsoon of August 2014, IMD said: “For the country as a whole, cumulative rainfall during this year’s monsoon (01 June to 30 July 2014) has so far upto 30 July been 23% below the Long Period Average.” Out of 36 meteorological sub-divisions, said the IMD, the rainfall has been normal over 15 and deficient over 21 sub-divisions.

Readings for each district that has reported rainfall consistently for eight weeks. The columns represent the percentage value of actual rainfall for each district against their normal rainfall for eight weeks.

However, we have compiled a far more realistic reading of the monsoon season so far, from the IMD’s own data. For the 614 individual readings from districts that have regular rainfall readings, we have the following: 86 districts have registered scanty rainfall (-99% to -60%); 281 districts have registered deficient rainfall (-59% to -20%); 200 districts have registered normal rainfall (-19% to +19%); and 47 districts have registered excess rainfall (+20% and more).

Moreover, using our running weekly district-level monsoon meter – the details of which and the reasoning for which you will find in here – we see that there was a substantial dip in the number of districts registering ‘deficient 2’ rainfall, which is less than 21% of the normal and lower, during the seventh week of rain, that is the week of 17 to 23 July. But the general trend returned the following week, 24 to 30 July.

What this means, and the bar chart we have provided to illustrate the 614 individual values leaves us in no doubt, is that 367 out of 614 districts have had meagre rain for eight weeks. This also means that over eight weeks where there should have been rainfall that – as the IMD predicted in early June – would be around 95% of the ‘long period average’, instead three out of five districts have had less than 80% of their usual quota.

Our running weekly district-level monsoon meter to aid governance decisions shows the overall trend has not changed substantially in the last fortnight despite good rains during the seventh monsoon week.

Unfortunately, the press and media – in particular the business and financial media – persist in reporting ‘national’ deficits and whether monsoon 2014 will ‘make up’ the average in the remaining period. This approach must be corrected by the IMD’s departmental divisions as it incorrectly makes popular the notion that total rainfall over a designated number of weeks is the most important monsoon metric (See ‘Why there is no ‘normal’ in our monsoon’). Of course it is not so, as different crops follow their own crop calendars according to the agro-ecological regions they are grown in, and require optimum rain at certain times during their respective crop calendars.

The following examples show why such reporting can be misleading:

From Reuters: “August rains hold the key to India’s major summer crops such as rice, soybean, cane and cotton, after a wet end to July failed to make up fully for a dry start to the four-month monsoon season. A late revival shrank the shortfall in rain to around 10 percent below average in July, the India Meteorological Department’s update showed on Thursday, a sharp improvement from the 43 percent deficit in the first month of the season.”

From Bloomberg: “Monsoon crops are sown from June and harvested from October. The country had less than 40 percent of average rains in the first six weeks of the monsoon season that runs through September. The shortage shrank to 23 percent by end-July. Oilseed planting in India is poised to slump as much as 24 percent to the lowest since 2002 after a weak start to the monsoon.”

From The Hindu: “With the country receiving good rain in July, monsoon deficiency has gone down to 23 percent, the MET department on Friday said. While the monsoon deficiency at the national level in June was 43 per cent, by July end it has come down to 23 per cent. Central India, which saw little rain in June, has by now seen some good rain. It received 402.2 mm of rainfall as compared to expected rainfall of 477.7 mm with a deficiency of 16 per cent, much lesser compared to other parts of the country.”

From Business Standard: “According to the India Meteorological Department (IMD), the rains managed to recoup much of the June losses due to strong revival over the central and western regions, and parts of northern India. Weather officials said the momentum of July would continue till about August 10 and then slacken a bit.”

From Mint: “India’s July rain deficit narrowed to 10% of the long-term average for the month, marking a recovery from the driest June in five years, the India Meteorological Department (IMD) said, as kharif crop sowing picked up in tandem. The shrinking of the rainfall deficit in July comes at a time when policymakers have been concerned about the impact of a below-average monsoon on foodgrain production and inflation. The June-September monsoon accounts for more than 70% of the annual rainfall in India and irrigates crops grown on half the country’s farmlands.”

Decoding reservoirs for the rest of us

July 21, 2014 by Climate portal editor Leave a Comment

Every week, the Central Water Commission releases to the public and to government departments the numbers that describe how much water is stored in 85 reservoirs in India. These are the reservoirs designated as nationally important, because of their roles in providing water for large irrigated command areas and for generating hydro-electric power (37 of these dams).

These readings are taken as the authoritative compilation of the current weekly state of water storage, and are widely used in government. Amongst the uses is to recommend the rationing of water consumption in the states and urban settlements. Another use is to help determine what advice to broadcast to our farmers about when they can sow seeds (if their fields are irrigated by the canals that radiate outwards from these dams).

But of course these are only 85, even if they are the biggest. Whether Bargi in Madhya Pradesh is half full does not interest in the least a farmer in Purnea, Bihar. Whether Tungabhadra in Karnataka is filling up well in the last two weeks is of no consequence to the residents of Rohtak in Haryana. That Yeldari in Maharashtra has water at a level very much lower it should be at this time of the year does not affect the cultivators of Virudhanagar, Tamil Nadu.

Bihar has 24 large dams (and groundwater) and Tamil Nadu has 116 while Madhya Pradesh has 898 large dams other than Bargi, but we have no weekly or monthly information about how much water these hold, in the first week of June or at end July. And this is what we don’t know for all the 4,839 dams – in the national register of large dams – that are not amongst the list of 85. The Central Water Commission tells us that it uses the combined readings for the 85 large dams because, with their total of about 155 billion cubic metres (bcm) of water storage (if they are all full), they form a large portion of the approximately 254 (bcm) of total reservoir storage available in India (excluding tanks, ponds and traditional water storage structures). But, for the smallholder cultivator and the town council of a Class 2 urban settlement, it is the 50 million cubic metres reservoir in the next taluka that they depend on for water, not on any of the big 85.

What can we then do with the weekly reservoir storage bulletin from the CWC? My approach is to treat it as an indicator of the collection of rainfall by reservoirs in the same meteorological region and agro-ecological zone. When the list is divided into ten groups, by reservoir size, we see far more clearly the effect of the last two weeks of rainfall on the storage levels. Until we can persuade state and central governments to invest in widespread and cheap monitoring of as many of our water storage receptacles as possible, we may use the CWC bulletin as an indicator.

By Rahul Goswami

The panel of charts shows water storage ranges (at full capacity of the dams) for the groups of reservoirs. Starting with the smallest first: 56 million cubic metres (mcm) to 176 mcm (tenth group); 184 mcm to 380 mcm (ninth group); 399 mcm to 523 mcm (eighth group); 524 mcm to 735 mcm (seventh group); 767 mcm to 927 mcm (sixth group); 935 mcm to 1.436 billion cubic metres (bcm) (fifth group); 1.456 bcm to 1.994 bcm (fourth group); 2.171 bcm to 2.676 bcm (third group); 3.046 bcm to 5.378 bcm (second group); 5.649 bcm to 9.745 bcm (first group).