About the Author

Pabitra Mukhopadhyay
Civil Engineer (Kolkata)

Pabitra is an Honors graduate in Civil Engineering from Jadavpur University, Kolkata. He has specialized in the field of River Hydraulics working for more than two decades training rivers, protecting banks and beaches and fighting erosion of the river banks/beds. He has worked with Bio-Engineering models involving mangroves using them as tools for cost effective and natural means of anti-erosion technology.His work is mostly concerning the extremely morpho-dynamic Hugly estuary with Bay of Bengal In course of his work, he got exposed to indegenious people of the Sunderban wetlands, who are fighting a losing battle against agressive Industrialization. Pabitra loves to read and write and he is full of crazy ideas. He believes that he has a tryst with the strange river-country south of Bengal.

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Blue Water

Published 19th January 2011 - 0 comments - 4983 views -

If the new water paradigm has introduced the idea of Virtual Water, it has also brought in new insight into real water, H2O. We now see this physical and material water in a very different way compared to what we used to half a century ago. What necessitated such radical change in our outlook towards global water, I wish to come back in a later post. For now I want to talk about Blue-Green Water. My day’s post is about Blue Water.

For a brief recapitulation of the Global Hydrological Cycle, we may remember that we have roughly 37216000 cubic kilometers of freshwater in global water balance of which 29000000 cubic kilometers are frozen in polar ice caps. This leaves 8216000 cubic kilometers of non-ice water (either liquid or vapor) in earth’s water reservoirs, namely:

1. Aquifers: 8000000 cubic kilometers

2. Lakes: 100000 cubic kilometers

3. Rivers: 2000 cubic kilometers

4. Atmosphere: 13000 cubic kilometers

5. Soil Moisture: 100000 cubic kilometers

6. Biosphere: 1000 cubic kilometers

Soil Moisture is also called sub-soil water or ground water and is sometimes mistakenly thought as inclusive of aquifers, which it is not. Sub-soil water is the water just underneath the soil, normally the water that is available if someone digs up earth a few feet only. This water table can be several 100 feet deep in some places and normally the deeper it is, the cleaner it is too on account of mechanical straining through interstices of the soil grains/particles. Aquifers are normally water entrapped between two successive layers of clayey or impervious soil or between two layers of sub-surface rock layers and are often quite deep. The common misconception between ground water and aquifers is mainly due to their occurrences at varying depths. For example in a place aquifer water can be available at 200 feet depth and the tube well that extracts it we call deep tube well whereas in another place, ground water can be available at 300 feet depth and the tube well that extracts it we call shallow well. So a shallow well can be deeper than a deep well. Quite confusing! So an easier way to differentiate between ground water and aquifer water is by their chemical environment. Ground water is aerobic and Aquifer water is anaerobic in nature of environment.

We see from above that all the mighty rivers of the world do not add up to an impressive total. Lakes and soil each contain 50 times as much fresh water and aquifers contain 4000 times as much. River water is most accessible as it flows past us, Lake water is next most accessible but we need to go to it. Ground water and aquifer water demand some hard digging for access. But what about 13000 cubic kilometers of water in atmosphere? Is it limited in wishful prayer at rain clouds? What about 1000 cubic kilometers of Biosphere water? Is it only for the crocodiles and mangroves?

The current paradigm of water is to classify it as observable and unseen water in the freshwater cycle. Blue water is the water that  is observable, water that we see flowing in rivers or stored in lakes. It is also the water in sub-soil and aquifer and all these waters have a common characteristic: they flow from higher to lower planes under gravity and ultimately fall in seas and oceans. You may wonder how lake water can flow, but it does actually. The whole land water regime is a continuum and connected to oceanic water through ground water table as shown in the picture below.

The two routes of Blue Water flow, namely surface and sub-surface, taken together are very important, especially when considering the hydrological based projections of water needs to a growing world population, food production and other water related services such as navigation and hydro-power generation. The flows of blue water resources represent the availability of water for use to satisfy the needs for socio-economic development in human societies. These flows constitute about 40 000 cubic kilometers per year (km³/yr) which have been subject to manipulations, by humans and other living organisms such as beavers, to make water available where and when it is in demand. These controls of blue water are in the form of dams, reservoirs, canals, pipelines, irrigation systems, water purification plants, etc. and constitute a large component of human water services across the entire globe.

Locally, regionally and globally the entire science of water resources engineering focuses on the influencing of blue water for human supply and demand. The steady flow of rivers and streams represents the available accessible section of the flow of blue water. Two basic components can be discerned in this regard:

• The flow from natural storage in lakes.

• Groundwater flow into rivers and streams.

Both these components support the dry season flow in any locality, whether it is a river basin or a hydrologic regime in a region. Throughout the centuries an additional volume of blue water was added via storage in human made reservoirs. This increased the availability of blue water from 40 000 km³/yr to 62 500 km³/yr. For instance, the states with the largest number of dams, built for various purposes, include the United States with 50; the Commonwealth of Independent States (CIS) (former Soviet Union) 34 (although the former Soviet Union only declared the 132 hydro-electric dams under control of the Ministry of Energy and Electrification to ICOLD, whereas the dams built by the Ministry of Agriculture is estimated to be between 2 000 and 3 000); Canada 26; Brazil 19; Japan 19; Turkey 11 (this includes the Greater Anatolia Project (GAP) is completed); China (People’s Republic of China) 11 (this includes the Three Gorges Dam Project which is World’s largest capacity Hydro-electricity power generation facility); Germany 9; Italy 9; Switzerland 9 and Argentina 8. Note that many of the states with the largest amount of dams, that increased the amount of blue water, are developing states. This also suggests that the increase of blue water resources were not the sole responsibility of developed states, but that states in all the regions across the entire GLOBE were, and still is, involved in the increase of blue water availability. The construction of dams is therefore one of the most important actions on the part of humans regarding the increase in global blue water resources. Yet, with the changing water paradigm, this increase in blue water will be provided by other means such as Water Demand Management (WDM).

To cut a long story short (or till the time I come back on it), the Blue Water based Demand management is the current challenge that we face. Our traditional water resource management had regularly and persistently concluded that future water demands would exceed actual water supplies, mainly due to the unchecked advancement of the three dead end drivers as explained in my last post. This was called supply sided management (SSM). In terms of current social science theory, this form of management tends to focus on what has been defined as a first order resource scarcity - i.e. the scarcity of a natural resource such as water. Supply Sided Management was the dominant mode of water development and management in the United States of America (USA) prior to the 1980’s, with the Bureau of Reclamation (BoR) and Army Corps of Engineers (ACoE) being the main instruments. Significantly, these organizations spawned a global paradigm due to the fact that they trained many of the hydraulic engineers who subsequently went on to construct the world’s largest dams.

No offence meant to American Technological prowess, but this SSM (mainly consisting of huge dams/reservoirs, having gigantic pipelines such as the Namibian supply line from Okavango River) were essentially flawed because beginning in the mid-1980s absolute and per-capita water use started to decline, in spite of population growth and increased economic development. For instance, in the USA, water withdrawals declined by nearly 10 % from 610 km³/yr in the 1980s to 554 km³/yr in 1995. Per-capita freshwater use also decreased by more than 20 % by 1995 from its 1980 levels in the USA.

For now, I shall conclude that big Water Resource Management Plans (WRMPs) are now rightfully needed to be replaced with Water Demand Management (WDM) which is basically cutting down on wasteful use and providing reasonable amount of water where it is needed most. Understanding Blue Water is the key to that.


Reference: PERSPECTIVES OF GLOBAL WATER BALANCE AND REGIONAL WATER RESOURCES by R. Meissner and P.M. Mampane, African Water Issues Unit, University of Pretoria, South Africa

Picture: Self drwan by author

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