In the Handbook of Water Resources in India (2007) several authors bemoan the low per capita water storage in India. These include John Briscoe and RPS Malik (pg. 2), A Sekhar (pg. 63) and RPS Malik (pg. 142), well known and influential names.
Mr. Sekhar, Advisor to the Planning Commission, even says that one of the main reasons for water problems in the country is the low per capita storage. He adds that India has no option but to go ahead with its dam construction programme. This is quite incredible for in the vast number of articles in book (including by these authors and others) the problems discussed and the solutions offered are quite different.
Nevertheless, it may well be that the authors are merely inconsistent in their views. The question may still be posed. Is there merit in the augmenting water storage?
The reason proffered by these authors is that rainfall is concentrated in a few monsoon months making storage inevitable. Further, the per capita water storage in India at about 265 cubic metres (see Tables 1.8 &1.9 and Chart 4 of this report) is much less than that of other countries. While Briscoe and Malik say that arid-rich countries like USA and Australia have over 5,000 cubic metres (m^3), middle-income countries like South Africa, Mexico, Morocco and China have a storage capacity of about 1,000 m^3. Interestingly, Mr. Malik in a later chapter offers somewhat different figures – 1964 (USA) and 753 (South Africa). He also points out that dams on the Colorado (USA) and Murray-Darling (Australia) can store 900 days of river flow; India can store only about 30 days of rainfall.
The comparison is with a select list of countries (why only these and not other countries make it to their list and why global averages are not presented is a moot point but I will let that pass for the moment). The interesting that is that most of the countries mentioned - Australia, Spain, China, USA and South Africa - face varying levels of acute and chronic water-related problems including that of scarcity. Water storage hardly seems such a silver bullet after all.
Mr. Sekhar also suggests the need for a storage capacity of 750–1,000 m^3 per capita though the rationale of that figure is not explained.
In any case, what matters is the ability of a country to meet its requirements - to provide water - and not its storage capability. India’s per capita availability of 1,700 m^3 per capita per annum is considered quite comfortable. As I pointed out earlier, several countries with higher storage have not solved their problems while several countries (e.g. in the Gulf) with less storage manage quite well. In fact if a country can meet it use without storage so much the better.
Since rainfall in India occurs over a few months it is, of course, imperative to store water. Let’s examine this more closely.
Note that the Indian storage estimates – approximately 300 billion cubic metres (BCM) (265 m^3 per capita) - relate to major (more than 10 million m^3) and medium facilities with the former accounting for almost all of it. This excludes the tens of thousands of small storage structures in the country that collectively store considerable quantities of water.
A major source of surface storage is water in the form of snow, something not considered by the authors at all. This is a free and valuable form of storage and the melting of snow provides water in a very regular and dependable manner, though admittedly the water is not accessible the way it is from other sources. Yet it is a form of storage that hardly deserves to be excluded. In another essay in the book (pg. 184) a figure of 200 BCM of annual water flows from snowmelt is mentioned and one can derive a figure of 800 BCM of storage in the form of snow (700 m^3 per capita), a figure hardly to be scoffed at.
Nor is water stored only above the ground. It is stored below the ground (in shallow and deep aquifers) and which provides near-free and low evaporation capability. As is well known by now groundwater is a considerable source of supplies to irrigation, domestic and industrial users. Aggregate storage below the ground would dwarf surface facilities by a large margin.
(Now it is true that other countries storage capacities too will increase if we include all sources but as I have pointed out overall storage per capita may not be a useful way of looking at things.)
There is also the whole issue of the source of water for storage. If water is not being stored today where is it going? Is it flowing to the seas? Recharging groundwater? Or is it evaporating? Surface storage in large dams would make sense only in case of the last of the three. For as the authors themselves recognise water flowing to the seas is not a waste. And if it were to be captured from what goes to recharge groundwater it would be a zero-sum game.
Finally, it is in the Ganga-Brahmaputra-Meghna system that the bulk of the storable potential exists but water shortages are endemic in the arid parts – select regions of north, western, central and southern India. Enhanced water storage is unlikely to benefit these areas.
(This post may be read along with the others on Water.)