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Data collection and management
In the course of this study, or rather the project to which this study contributed, a large set of data has been collected in the study area. The types of data as well as the way they were collected will be detailed in Section 2.2.1. The data were generally stored, processed and analyzed using targeted computer software. This will be described in Section 2.2.2. An evaluation of the data collection and management will be undertaken in Section 2.2.3.
Data collection
Data were mainly collected for three purposes:
– to calibrate/validate the (bio-)physical models;
– to understand the decision-making processes; and
– to characterize the study area and develop a spatial database (Bio-)physical models
The data requirements for bio-physical models are generally well defined, although the input requirements of these models can be minimized once sensitivity analyses have been carried out to determine the relative importance of various input parameters for the parameters that one is interested in. In this study, two (bio-)physical models were used, i.e. SIC – Simulation of Irrigation Canals, a hydraulic model, and SWAP93, a water flow – solute transport model.
SIC was used for the Fordwah Branch and for two secondary canals in the study area. Input data relate mainly to canal geometry, water levels and discharge ratings of structures, see Table 2.7. Data on canal structures were obtained from existing records of PID, while the actual state of channels and structures was determined in the field. Data were procured mostly in collaboration with PID, in some cases through training sessions organized by IIMI and PID (IIMI, 1995b).
Decision-making processes
Basically, two decision-making processes were studied, i.e. the operational management of irrigation managers and PID staff, and farmers’ salinity management. The former was captured in a decisional model, Gateman, which is described in detail in Section 3.2. The latter is documented in Section 4.2.
The operational management of PID staff was studied through interviews and through field observations of discharges and gate operations, see Table 2.9. In addition, a field experiment was conducted with PID staff in which a steady state of the canal was ensured for 2 days, after which a wave was created by increasing the discharge at the head of the study area. The reactions of gate keepers to this positive discharge step were observed and compared with the results of a hydraulic model in order to understand the effects of the operations on discharges and water levels. A restitution exercise took place after completion of the experiment (Litrico et al., 1995). The collaboration with PID on the introduction of a management information system also provided insights into the daily management of the system.
Farmers’ strategies and constraints were first studied by Rinaudo (1994) on the basis of interviews with 278 farmers in 8 tertiary units. A farmers’ socio-economic typology was made on the basis of these interviews and 15 representative farms were selected. Pintus (1995) and Meerbach (1996) did detailed studies for these farms on farmers’ practices related to wheat and cotton, respectively. Data on crop development, farmers’ cultural and irrigation practices, and on yields were collected, see Table 2.10. Advice on recommended practices were obtained from the Punjab Agricultural Department (PAD), which served as a reference to detect atypical practices, which generally occur due to farmers’ constraints, such as credit, water, salinity or inputs. Restitutions took place to discuss the results with the farmers and obtain a better understanding of their management. Farmers salinity management was studied in further detail by Kielen (1996a) through semi-structured interviews and mapping exercises with farmers. The results of soil and water samples that had been obtained in the area were combined with these observations and restituted to farmers (Kielen et al., 1996).
Large-scale surveys to determine soil types and soil salinity were undertaken with the Soil Survey of Pakistan (SSP) and the Directorate for Land Reclamation (DLR). The daily discharges were observed by PID staff, as part of a collaboration on the introduction of a management information system at the main canal level. The tube well water samples were analyzed in the laboratory of SSP. Depth to groundwater table was obtained from secondary data of the SCARP Monitoring Organization (SMO), which is a research institute of WAPDA. A socio-economic characterization of the study area was done for 66 tertiary units in which about 600 farmers were interviewed. The boundaries of tertiary units, which are indicated on maps available with PID, were verified in the field by a retired irrigation manager, as boundaries had been altered substantially. Cropping intensities and genetic salinity were determined through the analysis of LANDSAT and SPOT satellite images (Vidal et al., 1996; Tabet et al., 1997).
Data management
Data were stored in computer databases, using specialized packages such as FOXPRO. In the case of canal water flows, the database was shared with PID. The data were as much as possible geo-referenced through the use of ARCINFO, once the system boundaries had been clearly defined through field observations and remote sensing. In a few cases, the data were made available to a wider audience through reports. This is the case for discharge ratings of the structures in the study area (IIMI, 1995b), tertiary outlet and characteristics and hydraulic details of secondary channels (Tareen et al., 1996), and soil types (Soil Survey of Pakistan, 1997). The satellite images along with a few examples of applications were made available through a CD-ROM, a product of Cemagref, IIMI and SPOT Image.
Evaluation of the data collection and management
There is no lack of data per se for the irrigation systems of the Indus Basin, but there are many complaints about the accuracy, the accessibility, the timeliness, and the inability to relate different data sets due to differences in sampling methods, a lack of geo-reference, and the fact that the primary data are often contained in bulky handwritten registers. This is perhaps a good synthesis of the many remarks made by authors who have attempted to interprete and analyze data collected by the various government organizations in Pakistan (Ahmed and Chaudry, 1988; Federal Cell, 1990; World Bank, 1994; IIMI, 1995a).
The following excerpts from two different sources give a flavour of some of the frustration felt by different authors:
« There are at present no means of knowing the discharges of outlets from day to day and month to month. Unless there is definite proof to the contrary it is assumed that the discharges of outlets are always equal to their permissible. But a glance at the annual efficiency diagrams of any channel will show how erroneous this assumption is. What is wanted is a permanent and continuous record of the actual daily discharges of all outlets on a canal system. Then and only then, equitable distribution of water can be ensured » Erry (1936) « … appropriate accounting of water is of fundamental importance to the process of investment planning. The discharge data of the rivers and tributaries are inconsistent and published with several years’ delay. Records of water diversions to the distributaries/minors and outlets are either not kept or inaccessible. Similarly, the groundwater monitoring data and information collected under other monitoring programs is not cataloged systematically and is stored in paper registers, which makes the data inaccessible. The WSIPS [Water Sector Investment Planning Study, Federal Planning Cell, 1990] found that investment planning is constrained severely by unavailability of the information about resource base, its use, and other technical parameters necessary for planning » World Bank (1994).
The publication of Erry (1936) was intended to advocate the volumetric assessment of actual delivered irrigation water to farmers. Implementation of this would have imposed tremendous requirements on the existing data collection system of the PIDs. The quote from the World Bank publication (1994) provides evidence of the fact that information in the irrigation system is still an important problem. A number of points can be made to address this issue.
Firstly, great strides have been made around the world, particularly in industry, in the development of information systems, made possible through the rapid advances in computer technology. In addition, the development of Geographical Information Systems (GIS) has provided better opportunities for geo-referencing of data and of combining incongruent data sets. These information techniques have so far hardly been made use of in the Indus Basin irrigation system, but can offer great opportunities in the future in the management of the system (Rey, 1996; Federal Planning Cell, 1990) . In the context of this study, the introduction of a management information system was undertaken on a small scale in collaboration with PID (Rivière, 1993; Rey et al., 1993). This experience emphasized the difficulty in daily collecting and communicating information on water levels and discharges for a 75,000 ha irrigation system.
Secondly, the size of the system and the number of parameters that are relevant for the performance of irrigated agriculture necessitate or even dictate that information requirements are kept to a minimum. Only those data that can be processed and analyzed should be collected. A visit to any of the government departments in Pakistan will convince anybody that collecting information does not imply that it will or can be used. The use of computer models can be useful to determine and minimize these requirements. By carrying out sensitivity analyses, those parameters likely to influence the performance of the irrigation system can be identified. This will be demonstrated in Chapters 3 and 4 of this study.
Thirdly, better use can be made of existing data bases or routine data collection. This has been done in Pakistan by processing and analyzing these data and making them available to a wider audience through publications. The best examples of this are perhaps the book on irrigated agriculture by Ahmed and Choudry (1988) and the book on hydraulics by Ali (1993) . Another way of doing this is by processing these databases with modern techniques, such as computerized databases and geographical information systems (Asif et al., 1996). In this study, use has been made of data collected by government agencies. This was generally done in collaboration with IIMI, which provided opportunities to mix field expertise and manpower with modern information techniques (e.g. Soil Survey of Pakistan, 1996).
Table of contents :
1. Introduction
1.1 Salinity and sodicity in the Indus Basin
1.2 Statement of the problem
1.3 Outline of the study
1.4 Limitations of the study
2. Research Locale
2.1 Description of the Chishtian Sub-Division
2.1.1 Physical environment
2.1.2 Irrigation system
2.1.3 Farming systems
2.2 Data collection and management
2.2.1 Data collection
2.2.2 Data management
2.2.3 Evaluation of the data collection and data management
3. Irrigation system management: from the main canal to the tertiary unit
3.1 The irrigation agency: objectives and decision-making processes
3.1.1 General principles of canal irrigation management
3.1.2 Irrigation management activities
3.1.3 Scope for interventions
3.1.4 Physical system constraints
3.2 Methodology
3.2.1 General framework
3.2.2 Developing a hydro-dynamic model (Step 1)
3.2.3 Developing a regulation module for operations at the main canal (Step 2)
3.2.4 Water distribution indicators
3.3 Improving operations at the main canal level
3.3.1 Analyzing the official and existing operational rules at the main canal level (Steps 3 and 4)
3.3.2 Simulating the existing operational rules (Step 5)
3.3.3 Simulating the impact of the official operational rules on the water distribution (Steps 6, 7, 8)
3.3.4 Identifying the scope for an equitable water distribution by changing the operational rules (Steps 6, 7, 8)
3.3.5 Identifying the scope for redirecting canal water supplies to areas with salinity or sodicity problems (Steps 6, 7, 8)
3.4 Improving water distribution at the secondary canal level
3.4.1 Analyzing the official and existing water delivery patterns: principles of water distribution (Step 3)
3.4.2 Management interventions in the outlet characteristics: analyzing the local impact on the offtaking discharge (Step 4a)
3.4.3 Management interventions in channel and structures: analyzing the global impact on water distribution in secondary canals (Step 4b)
3.4.4 Assessing the effect of management interventions on the water distribution at the secondary canal level
3.5 Analyzing the impact of interventions at the main and secondary canal level on water deliveries to tertiary units
3.5.1 Water deliveries to tertiary units as a function of the inflow of secondary canals
3.5.2 Combining and comparing the effect of main and secondary canal interventions on water deliveries to tertiary units
3.6 Conclusions
4. Farmers’ salinity and sodicity control: from the field to the tertiary unit
4.1 Salinity and sodicity processes: a brief description
4.1.1 Pathways leading to soil salinity and sodicity
4.1.2 Effects on soils and crops
4.2 Objectives and constraints of farmers dealing with salinity and sodicity
4.2.1 Farmers’ classification of salinity and sodicity
4.2.2 Farmers’ strategies and measures to cope with salinity and sodicity
4.2.3 Scope for irrigation management interventions to help farmers in dealing with salinity and sodicity
4.3 Methodology
4.3.1 Unsaturated flow of water and solutes: basic principles and description of SWAP93
4.3.2 Predicting the sodium hazard
4.4 Analyzing the effect of irrigation on soil salinity and crop transpiration
4.4.1 Calibration and validation of the model
4.4.2 Sensitivity analysis
4.4.3 The effect of irrigation quantity and quality on soil salinity and transpiration for existing conditions
4.4.4 The effect of farmers’ irrigation practices on soil salinity and transpiration
4.5 Predicting the effect of irrigation on soil sodicity and soil degradation
4.5.1 Predicting the soil sodicity risk
4.5.2 The effect of sodicity on soil degradation
4.6 Predicting soil salinity and sodicity at the level of the tertiary unit
4.7 Conclusions
5. Irrigation management for improved salinity control: towards an integrated approach
5.1 Developing a framework for the integrated approach
5.1.1 Introducing the economic component of the integrated approach
5.1.2 General framework to analyze the effect of canal irrigation management on salinity and sodicity
5.2 Methodology
5.2.1 Identification of relevant parameters /variables
5.2.2 Operationalizing the integrated approach
5.2.3 Performance indicators
5.3 Irrigation management interventions and their effect on soil salinity and sodicity: application to the Fordwah Branch and Distributary
5.3.1 Irrigation management and salinity control in the Fordwah Distributary: actual situation
5.3.2 Improving the salinity control for the Fordwah Distributary
5.3.3 Evaluation of the impact of canal irrigation management on cropping intensities, salinity and sodicity for the Fordwah Distributary
5.4 Evaluation of the integrated approach
5.4.1 Product evaluation
5.4.2 Process evaluation
5.4.3 Perspectives
6. Summary and conclusions
6.1 Irrigation system management interventions for improved salinity and sodicity control: lessons from the case study in Pakistan
6.2 General application of the developed integrated approach to irrigation management
