46
2. Formulating
the
Problem
the later release of that water for beneficial uses. Thus reservoirs are generally classified according to whether they were designed for a single purpose or for multiple purposes; single-purpose reservoirs are usually simpler
in design and operation than are multipurpose ones.
In those reservoirs built with flood control as a major purpose, it is essential that the reservoir capacity reserved for storage of flood water be
emptied as soon as practical after the flood. In some cases, because of a
definite seasonal pattern of floods, stored floodwater may also be retained,
at least to the extent possible, for later conservation uses. In those reservoirs
built for conservation uses, stream flow in excess of current requirements is
stored in the reservoir and not released until later when it is needed. In
this manner reservoirs serve the multiple purpose of flood prevention in
times of high flows and supply of necessary water in times of low flows.
The release of stored water may be used for many purposes, such as energy
generation, irrigation, municipal water supply, and others. All of these
uses are generally referred to as conservation uses, since the excess water is
conserved, or stored, for them.
Consider first the benefits from irrigation water. If the willingness to pay
some contract price, or the market price, is the determining factor for the
value of irrigation water, then Di jt multiplied by the price is the value of
the irrigation water from reservoir j in month i of year t. On the other hand,
if the "with or without" principle is to be used in determining the revenue
from irrigation water, as discussed in Section 1.3, the benefits are calculated
by comparing the situation without the project to the conditions that will
prevail with the irrigation water.
In such an analysis farms having similar soil, size, and transportation
costs are grouped together. For each homogeneous group of farms, average
production coefficients, costs, and returns for various potential agricultural
activities are estimated. Based upon information from homogeneous farm
groups and availability of resources, relations such as the following can be
prepared for each group both before and after the introduction of irrigation
water:
#net =
Σ Σ PklVkiqkl — Σ Σ!) CkiyklQkl
Ar—1 2-1
*-l 2-1
where
Rnet = net revenue per unit volume of water from the irrigation water
Cki = cost per ton of crop k by method I
pki = market value per ton of crop k by method I
qu = net consumptive use of irrigation water (area per unit volume) in
each growing season for crop k by method I
yki = production of crop k by method I
2. Formulating
the
Problem
the later release of that water for beneficial uses. Thus reservoirs are generally classified according to whether they were designed for a single purpose or for multiple purposes; single-purpose reservoirs are usually simpler
in design and operation than are multipurpose ones.
In those reservoirs built with flood control as a major purpose, it is essential that the reservoir capacity reserved for storage of flood water be
emptied as soon as practical after the flood. In some cases, because of a
definite seasonal pattern of floods, stored floodwater may also be retained,
at least to the extent possible, for later conservation uses. In those reservoirs
built for conservation uses, stream flow in excess of current requirements is
stored in the reservoir and not released until later when it is needed. In
this manner reservoirs serve the multiple purpose of flood prevention in
times of high flows and supply of necessary water in times of low flows.
The release of stored water may be used for many purposes, such as energy
generation, irrigation, municipal water supply, and others. All of these
uses are generally referred to as conservation uses, since the excess water is
conserved, or stored, for them.
Consider first the benefits from irrigation water. If the willingness to pay
some contract price, or the market price, is the determining factor for the
value of irrigation water, then Di jt multiplied by the price is the value of
the irrigation water from reservoir j in month i of year t. On the other hand,
if the "with or without" principle is to be used in determining the revenue
from irrigation water, as discussed in Section 1.3, the benefits are calculated
by comparing the situation without the project to the conditions that will
prevail with the irrigation water.
In such an analysis farms having similar soil, size, and transportation
costs are grouped together. For each homogeneous group of farms, average
production coefficients, costs, and returns for various potential agricultural
activities are estimated. Based upon information from homogeneous farm
groups and availability of resources, relations such as the following can be
prepared for each group both before and after the introduction of irrigation
water:
#net =
Σ Σ PklVkiqkl — Σ Σ!) CkiyklQkl
Ar—1 2-1
*-l 2-1
where
Rnet = net revenue per unit volume of water from the irrigation water
Cki = cost per ton of crop k by method I
pki = market value per ton of crop k by method I
qu = net consumptive use of irrigation water (area per unit volume) in
each growing season for crop k by method I
yki = production of crop k by method I