to Interpret RAP Results
RAP, by itself, is only a diagnostic tool. It allows a qualified evaluator
to systematically examine the irrigation project to determine
1. External Indicators, and
2. Internal Indicators
External Indicators will give an indication if it is possible to conserve
water and enhance the environment through improved water management.
The Internal Indicators give a detailed perspective of how the system
is actually operated, and the water delivery service that is provided
at all levels.
interpretation of the results requires one or more irrigation
specialists who clearly understand the options for modernization.
Without a thorough knowledge of these options, the recommendations can
be ineffective, to say the least.
are basic rules:
almost all projects, modernization requires both hardware and management
In general, it is quite possible to provide high levels of water
delivery service to turnouts, without good water control, if the
system is very inefficient and there is a very abundant supply of
water. However, if the system must also be efficient, the only way
to provide good water delivery service is to have excellent control
of the water.
In almost all projects, water delivery service needs to be improved
in order to meet the basic objectives of lower labor costs, less
spill, improved crop yields, and less environmental damage. The
RAP process allows the evaluator to target the appropriate level(s)
on which to begin modernization.
general, there are many very simple changes that can be made in
operational procedures, and numerous others that only require a
moderate investment in capital for hardware changes.
changes must be accompanied by quality control and excellent training.
must clearly understand the difference between Command Area Irrigation
Efficiency and Field Irrigation Efficiency. In projects without internal
recirculation, the Command Area Irrigation Efficiency is generally
lower than the Field Irrigation Efficiency. But in projects with internal
recirculation of water, the Command Area IE may be greater than the
Area IE Benchmarking indicator combines many of the previous indicators
into a single indicator value.
area IE =
expression of irrigation efficiency does not conform to the precise
requirements defined in the ASCE document (Burt et al., 1997), but it
is close enough to give a reasonable estimate of the command area IE.
area irrigation efficiency of 100% is impossible. In general, efficiencies
greater than 60% require internal recirculation of losses - either
as surface water recirculation or from groundwater pumping, or both.
improvement of command area irrigation efficiency can be done in one
of two ways:
first-time losses. These losses occur in two areas:
losses. These include
- spillage from canals and pipelines
- seepage from canals
- phreatophtye water consumption
losses. These include
- conveyance losses in field channels
- surface runoff from fields
- deep percolation in fields, caused by
water in rice fields
of irrigation water application
duration of irrigation water application
is considerable merit in reducing first-time losses, because these
can directly affect required canal capacity, fertilizer loss, pesticide
losses, local water logging, etc. In most projects, seepage from
canals is targeted, although often other components of first-time
losses are more important and cause greater damage to the environment.
first-time losses. Recirculation options include:
recirculation. Surface drains, creeks, and rivers pick up first
time losses that originated as
- seepage or deep percolation that returns to these creeks from
a high water table.
- surface runoff from fields
- spillage from canals.
from the groundwater. This recirculates first time losses that
- field deep percolation.
cases, recirculation is the least expensive and quickest option for
improving project irrigation efficiencies.
very common mistake in modernization is the elimination of first-time
losses with the belief that this will improve project irrigation
..even though those first time losses may already
be recirculated within the project. If this is the case, there
may not be any true water conservation.
other benefits can be obtained from the elimination of first-time
losses such as:
easier operation of the distribution system from lining
- better crop yields through better first-time water management
- less contamination of water due to fertilizers and pesticides.
beginning of the RAP Input sheets, the RAP user is asked to provide
an estimates of field irrigation efficiency for rice and other
crops. These estimates should account for all conveyance losses, field
deep percolation, and surface runoff downstream of the delivery point
from the project authorities.
"14. World Bank BMTI Indicators", a better estimate of Field
Irrigation IE is given - based on a water balance of the project. One
should compare this value against the stated value in Worksheet 1, to
see if the stated value corresponds to the water balance values. In
general, the water balance values are much closer to the truth.
to use Field IE values
Field Irrigation Efficiency is low, one must not necessarily conclude
that the farmers need better education on how to irrigate properly.
In many projects, such training is worthless because project authorities
dictate the schedule and amounts of water delivery, and the farmers
have almost no choice in the matter.
Low field irrigation efficiencies are typically an indication of a
water delivery system that is unreliable, inequitable, and/or inflexible.
Generally, the water delivery system must be improved before significant
field efficiency improvement can take place.
That said, there is one practice that can be implemented immediately
without changing the water delivery system. That is land grading.
Most of the world's irrigation projects use surface irrigation, and
good land grading is important for good in-field distribution uniformity
IE > Field IE,
there is considerable recirculation within the project.
Project Irrigation Efficiency is the key indicator as to whether there
is an opportunity to conserve water. Field Irrigation Efficiency gives
no indication of this, by itself, because much of the field losses
are often re-circulated.
Conservation" in a hydrologic basin (as opposed to a specific
irrigation project) can only be achieves if one of the following occurs:
flows to salt sinks (ocean, localized salty groundwater) is eliminated
ET is reduced (weed and phreatophtye and drain ET is reduced)
water management, even if it does not conserve water in the basin,
has appreciable benefits, including:
Improving downstream water quality.
the TIMING of water usage
the flow rate requirements into a project.
of pumping (sometimes)
crop yields through better timing of applications and less fertilizer
the quality and quantity of flows in rivers and streams immediately
downstream of irrigation diversion points.
of the Interpretation Process
the process of interpretation is as follows:
irrigation efficiencies are examined. Good field efficiencies depend
upon receiving good water delivery service at the field.
irrigation efficiencies are examined. It is very common for irrigation
project personnel to want higher flow rates into the project, although
the inefficiencies may be quite high. An important alternative to
increasing the water supply is to improve efficiencies.
efficiencies are noted, and compared against field irrigation efficiencies.
Both of these are considered in light of any recirculation (groundwater
or surface) that may occur. The comparison helps to determine where
efforts might be made.
attributes of water delivery service are examined for each level.
appropriateness of hardware and operator instruction is reviewed.
existence of recirculation systems is noted. In many project, installing
surface water recirculation systems in strategic areas is a very
simple way to improve performance and water delivery service.
employees spend their time is an important indication of where changes
can be made. For example, in many projects there is a large staff
of hydrographers who continually take current meter readings at many
locations in the main canals. In general, this inaccurate (due to
the inherent nature of unsteady flows and point-in-time measurements)
work can be completely eliminated if a new strategy for water delivery
modernization, some actions can be taken in parallel with others, but
some actions require a foundation. For example, automation with electronic
PLCs (Programmable Logic Controllers) first requires excellent access
to sites, excellent communications, and a strong infrastructure for
electronic troubleshooting and repairs. They also require a project
that has an excellent maintenance record. In other words, PLC automation
requires a substantial foundation that is often lacking in irrigation
.and PLC implementation without that foundation is almost
guaranteed to fail.
the key steps for modernization are:
the discrepancy between "actual" and "stated"
service. If project managers refuse to accept reality, it is best
to spend time and money on other projects.
levels of staff must understand and adopt the "service mentality".
Of course, this is not done overnight, but modernization concepts
are rooted in this mentality. Without having it, attempts to modernize
a project will typically have minimal benefit.
instructions that are given to operators, and modify them if needed.
A classic example is many Asian projects in which the objective of
cross regulators is to maintain an upstream water level, but the gate
operators must move the cross regulators in strict accordance with
instructions (of specific gate movements) from the office - based
on computer programs or spreadsheets. A simple check in the field
will show that water levels are not maintained properly. The instructions
for the operators must be changed, and they are very simple: "Maintain
the upstream water level within a specified tolerance of a defined
target". The author has never found an operator who is incapable
of determining how much to move the cross regulators to achieve this
first 3 items are the easiest, but they may also be the most difficult
with some senior staff. If the first 3 items cannot be achieved, it
is best to either walk away from a project, or else fire the senior
staff. Of course, changes in the first 3 items may take some training,
study tours, and deep conversations.
next steps, more or less in order of sequence, are to improve the
of what actually happens in the system. An expert can quickly
evaluate a project and because of his/her background, almost immediately
understand cause/effect relationships and the probable level of
service. The operators and supervisors often do not see things
the same way. It is very helpful to install simple dataloggers
and water level sensors at key locations to record spills, flow
rate fluctuations, and water level fluctuations. This is almost
always an eye-opener for operators who can only visit a location
once per day.
at all levels. This starts with human-human communications - often
of staff. In general, a small yet mobile staff is much more efficient
than a large, immobile staff. This is because a small mobile staff
is not responsible for just one or two structures, but must understand
how various structures and actions will impact other areas. Mobility
may be improved with better roads, motorcycles, trucks, etc.
rate control and measurement at key bifurcation points. Note that
"measurement" and "control" are not the same.
Both are needed. There are many combinations of structures and
techniques that provide rapid and accurate control and measurement
of flow rates. This is typically a weak area for many irrigation
of recirculation points or buffer reservoirs in the main canal
system. "Loose" water control may be very adequate in
the main system - as long as there exists a place to re-regulate
about 70% of the way down a canal.
water level control throughout the project. The flow rate control
and measurement (item "d") only pertain to the heads
of canals and pipelines. Downstream of the head, it is important
to easily maintain fairly constant water levels so that turnout
flow rates do not change with time, and so that the canal banks
are not damaged. With the proper types of structures, this is
easy to do without much human effort.
of procedures for ordering and dispersing water. In most modern
projects, one group is responsible for operating the main canal;
another is responsible for the second level, and so on. Each group
then has a very specific service objective. If a main canal is
broken into "zones" with different offices controlling
different "zones", there is almost always conflict between
the zones. Re-organization of the operators is typically necessary.
Also, the complete procedure for receiving real-time information
from the field and responding quickly to requests must typically
be revamped for most projects.
monitoring of strategic locations. Such locations are typically
buffer reservoirs, drains, and tail ends of canals.
manual control of flow rates at strategic locations. These are
the heads of the main canal, and heads of major off takes (turnouts)
from the main canal.
for spill, and the recapture of that spill, from the ends of all
surprise some readers is the complete lack of discussion of canal lining
and maintenance equipment. There is no doubt that maintenance equipment
must be adequate. Canal lining can reduce maintenance and seepage. But
these topics have been discussed for many decades, and the billions
of dollars that have been spent on canal lining have generally not brought
about modernization. This is because modernization is not just a single
action. The items a-j represent a departure from traditional thinking
of "concrete civil engineers" and focus on operations.
missing item is a discussion about downstream control and sophisticated
canal control algorithms. This is because an irrigation project must
walk very well before it runs, and these technologies might be considered
as "high risk". Although the author spends a considerable
amount of professional time on these two subjects in actual applications,
sophisticated controls are only selected after other options have been
..and never before an adequate support infrastructure
exists. There is just no magical pill for modernization and improved
irrigation performance, and simple options often provide excellent results.
It is good
to listen to the operators and try to detect a few things that give
them a tremendous amount of grief. It is sometimes possible to quickly
solve some of these problems. By solving these problems for the operators,
they will become advocates of further modernization efforts.