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Table 8.1 Some examples of stakeholders and their targets in the water
productivity framework as related to agriculture
Stakeholder
Deinition
Scale
Target
Plant physiologist
Dry matter/
transpiration
Plant
Utilization of light
and water resources
Nutritionist
Calorie/
transpiration
Field
Healthy food
Agronomist
Yield/
evapotranspiration
Field
Suficient food
Farmer
Yield/supply
Field
Maximize income
Irrigation engineer
Yield/irrigation
supply
Irrigation scheme
Proper water
allocation
Groundwater policy
maker
$/groundwater
extraction
Aquifer
Sustainable
extraction
Basin policy maker
$/
evapotranspiration
River basin
Maximize proits
Adapted from Molden et al. ( 2003 ).
Question 8.7: Consider a microlysimeter with a diameter of 10 cm, a depth of 5 cm,
illed with sandy soil with a porosity of 40% and a water content of 30% (i.e., ¾ of the
pores is illed with water).
a) What is the weight of the contents of this lysimeter (use Table 2.2 )?
b) The microlysimeter is used during a night in which the average dewfall is 0.03 mm h -1 .
Suppose that we want to keep track of the dewfall every ive minutes. What is the
resolution for the weight measurement needed to attain this resolution?
c) What is the needed resolution (answer of question b) relative to the total weight?
8.3 Water Productivity at Field and Regional Scale
8.3.1 Introduction
In an increasing number of regions the claims for fresh water by agriculture, indus-
tries, households and nature reserves exceed the amounts of fresh water available, thus
demanding a better management of fresh water. Because irrigated agriculture is by far
the biggest consumer of fresh water, increasing water productivity in irrigated agricul-
ture is a logical way to save water (IWMI, 2007 ). Water productivity (WP) relates to
the value or beneit derived from the use of water. Deinitions of WP are not uniform
and change with the background of the researcher or stakeholder involved ( Table 8.1 ).
For example, obtaining more kilograms of dry matter per unit of water transpired is a
key issue for plant breeders. However, at basin level, policymakers may wish to maxi-
mize the economic value of the irrigation water used (Molden et al., 2003 ).
This case study presents nominal WP values based on the yield/evapotranspi-
ration ratio of an irrigated basin in a semiarid region of India and combines ield
 
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