water productivity is basically the economic yield divided by the water used by the crop i.e. evapo-transpiration, or sometimes economic yield divided by applied water through irrigation plus rainfall or sometimes economic yield divided by consumptive water use i.e. evapo-transpiration plus drained water out of the root zone.
lot of work has been done, in terms of water use efficiency, applied water use efficiency or consumtive water use efficiency, you can search through google search for these terms or even within RG there are eminent researchers
Water productivity (WT) and water use efficiency (WUE) have same dimension but there are some differences among them. WT are more applicable for field and research but WUE is suitable for research.
The definition as attached by Masaud is in terms of applied water use efficiency, either in terms of rainfall amounts, or irrigation waters or both, this is easy term to compute as Evapo-transpiration value is difficult to use.
Moreover, this term is basically used by planners and economists, as they can handle this term easily
It means that I can compare different agricultural products with industrial products by means of WT. I want to see each cubic meter of water in different sections like industry and agriculture, would produce how much amount of different peoducts.Which one is more economic than the other especially in dry areas.
Neda, very good question raised by you, if we see the water used for one kg of rice production, it is very large, but important from food security point of view.
if rice yield is 6 t/ha, water through ET loss is 60 cm, means 6000 cubic meter of water per hectare. So for 1kg of rice, we need 1 cubic meter of water as ET, 1000kg of water. But for this much ET requirement we need to apply more water as drainage also is taking place, so large amount of water, but we have not to compare with water use efficiency of other sectors, as food security is the vbasic requirement
We can easily compute the water used in a given region if we know the production of different crops in that region, on the method as indicated above
Dr.Kalra, interesting discussion on water productivity. As I understand, the watet productivity gained attention because of competing uses especially in rainfed or limited water supply areas.We can not compare water use in agriculture and industry. We can compare water use and corresponding productivity in different sectors or enterprises in agriculture. In rainfed areas we can use same smount of available water for different crops,in dairy,poultry,horticulture etc.Apart from from food security ,we have to see in which enterprise the farmer can get or generate more income by using the same amount of water.There is another term related to this,i.e.multiple uses of watet.Water from one enterprise can be used or diverted to two or more enterprises.This can further add value or efficiency for water use but some attention has to be paid to contamination or contaminant flow.
Thanks for your all answers. I wanted to show that in dry lands based on WT we can use virtual water. Cause food security is important but what if we have water shortage... therfore we can change crop patterns.
Thanks Dr Subba Rao, stressing on intra-and inter-sectoral choices of utilizing water from raising income purpose, worked on the basis of water productivity
A forthcoming book, titled, Micro Irrigation Systems in India: Emergence, Status and Impacts http://www.springer.com/in/book/9789811003462, edited by me with Dinesh Kumar and A Narayanamoorthy, discusses and provides a detailed review of water productivity and related indicators used in the economics of water management. Pls have a look at.. the book will be on the stands in two weeks time...
I am attaching two papers with a review on water productivity. Below is a cite on a chapter of a very interesting book.
Molden, D., Murray-Rust, H., Sakthivadivel, R. & Makin, I., 2003. A water-productivity fremework for understanding and action. En: Kijne, J., Barker, R. y Molden, D. (Eds.), Water Productivity in Agriculture: Limits and Opportunities for Improvement. CAB International, Wallingford, UK.