How to Interpret RAP Results

The 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

The 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.

The 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.

Here are basic rules:

1. In almost all projects, modernization requires both hardware and management changes.

2. 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.

3. 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.

4. In 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.

5. All changes must be accompanied by quality control and excellent training.

6. One 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 Field IE.

The Command Area IE Benchmarking indicator combines many of the previous indicators into a single indicator value.

Command area IE =

This 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.

A command 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.

In short, improvement of command area irrigation efficiency can be done in one of two ways:

1. Reduce first-time losses. These losses occur in two areas:

   1. Conveyance losses. These include
      - spillage from canals and pipelines
      - seepage from canals
      - phreatophtye water consumption

   2. Field losses. These include
      - conveyance losses in field channels
      - surface runoff from fields
      - deep percolation in fields, caused by

      • standing water in rice fields

      • non-uniformity of irrigation water application

      • excess duration of irrigation water application

There 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.

2. Recirculate first-time losses. Recirculation options include:

   1. Surface 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.

   2. Pumping from the groundwater. This recirculates first time losses that originated as
      - seepage
      - field deep percolation.

In some cases, recirculation is the least expensive and quickest option for improving project irrigation efficiencies.

At the 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.

But in "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.

How to use Field IE values

1. If the 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 of water.

2. If
                Project IE > Field IE,
                     Then there is considerable recirculation within the project.

3. The 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.

4. "Water Conservation" in a hydrologic basin (as opposed to a specific irrigation project) can only be achieves if one of the following occurs:

   • Water flows to salt sinks (ocean, localized salty groundwater) is eliminated
     

   • Excess ET is reduced (weed and phreatophtye and drain ET is reduced)

5. Good water management, even if it does not conserve water in the basin, has appreciable benefits, including:

   • Improving downstream water quality.

   • Improving the TIMING of water usage

   • Reducing the flow rate requirements into a project.

   • Reduction of pumping (sometimes)

   • Improving crop yields through better timing of applications and less fertilizer leaching.
     

   • Improving the quality and quantity of flows in rivers and streams immediately downstream of irrigation diversion points.
     

Summary of the Interpretation Process

In general, the process of interpretation is as follows:

1. Field irrigation efficiencies are examined. Good field efficiencies depend upon receiving good water delivery service at the field.

2. Project 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.

3. Conveyance 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.

4. The attributes of water delivery service are examined for each level.

5. The appropriateness of hardware and operator instruction is reviewed.

6. The 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.

7. Where 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 is adopted.

With 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 projects….and PLC implementation without that foundation is almost guaranteed to fail.

Typically, the key steps for modernization are:

1. Eliminate 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.

2. All 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.

3. Examine 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 goal.

4. The 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.

5. The next steps, more or less in order of sequence, are to improve the following areas:

   1. Understanding 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.

   2. Communications at all levels. This starts with human-human communications - often with radios.
      

   3. Mobility 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.
      

   4. Flow 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 projects.
      

   5. Existence 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.
      

   6. Improved 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.
      

   7. Re-organization 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.
      

   8. Remote monitoring of strategic locations. Such locations are typically buffer reservoirs, drains, and tail ends of canals.
      

   9. Remote 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.
      

   10. Provision for spill, and the recapture of that spill, from the ends of all small canals.

What may 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.

Another 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 ruled out…..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.