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Decision Support System for Irrigation Water Management B. Srinivasa Rao, P. Anuradha Centre for Good Governance, Hyderabad, India E-Mail: srinivasaraob@cgg.gov.in, anuradha@cgg.gov.in Web site: www.cgg.gov.in Abstract Water is a scarce resource and there is a growing importance in efficient use of water in agriculture. Hence, techniques for monitoring irrigation water use and productivity are becoming increasingly vital. Developing irrigation potential over a command area requires considerable efforts both in terms of time and money. Advances in remote sensing, GIS and modeling have offered water resource researchers and managers a novel way for obtaining accurate spatial data on actual water use, water demand, allocation and distribution of water, and crop yield. The main crux of the development of the irrigation management is the optimization of irrigation water requirements which requires proper irrigation scheduling based on the crop water requirements of different crops sown over an area during that particular season. In order to improve irrigation management in Andhra Pradesh, this project is done to improve the existing decision support systems for irrigation management, thereby improving the efficiency of the existing system and thus ensuring judicious distribution of the water distribution services to all areas. Decision Support System (DSS) has been developed such that it provides the Water Management Authorities with a well-structured, user-friendly, practical and complete Management Information System (MIS). It assists the decision makers in taking the right decisions on the basis of good comparison of different strategies under various scenarios, and combines the benefits of Geographic Information Systems, expert systems and simulation models. 1.0 Background A vast majority of the population in India depend on agriculture for their livelihood. Agriculture accounts for a third of India's Gross Domestic Product (GDP) and it is estimated that 73% of the available water resources are consumed in this sector. India receives about 1200 mm of average annual rainfall, which is unevenly distributed and seasonal in character warranting the need for development in Irrigation Management. Efficient and accountable irrigation leads to a greater investment in terms of inputs by farmers, a shift to high-value crops, intensification of agriculture and increased employment. Irrigation, therefore, can be considered a lead input in agricultural and rural development. Andhra Pradesh is the fifth largest state in India and like other states in the county, the economy is predominantly agrarian. The agriculture sector contributes to over a third of the State's Gross State Domestic Product(GSDP) and provides livelihood for over 70 per cent of its' population. The state is blessed with many major rivers, the most important being the Godavari, Krishna, Vamsadhara and Pennar. 2.0 Krishna River Basin The focus of this paper will be the Krishna River which flows through the states of Maharashtra and Karnataka before entering Andhra Pradesh. The dependable flow in this river has been estimated at 2130 Thousand Million Cubic (TMC) foot, out of which Maharashtra, Karnataka and Andhra Pradesh are entitled to 585, 734 and 811 TMC foot of water respectively in any water year, on the basis of 75 per cent dependability flows. Four major irrigation projects have been constructed on the river by the Government of Andhra Pradesh viz., Priyadarshini Jurala, Srisailam, Nagarjunasagar and Prakasam barrage to harness the allocated dependable water flows. The total Storage Capacity and Command Area under each of these projects is shown in Table 1. 
These projects irrigate about 39.40 Lakh Acres of land in Andhra Pradesh state covering three geographical regions comprising Rayalaseema, Telangana and Coastal Andhra . The region wise Command Area irrigated by the projects is shown in Table 2. 
Due to the construction of major irrigation projects on the river during the last 5 years by the Governments of Maharashtra and Karnataka which are the upper riparian states, inflows into Andhra Pradesh have drastically reduced. The problem has been further compounded by reduced rainfall in the catchment area of the river resulting in reduced inflows in the river. The trend of inflows into the river recorded at one of the projects over the last 10 years is shown in Figure 1. The water flowing into Andhra Pradesh is not sufficient to serve the command area that the projects are supposed to serve. The problem has been further compounded due to poor irrigation efficiency, inadequate system maintenance and lack of accountability. Currently, irrigation systems in the State function at only 35-40 per cent efficiency. This compares poorly with both the internationally accepted standard of 57 per cent as well as the best practice efficiency of nearly 70 per cent achieved by the superior irrigation systems of Israel. The main causes of poor irrigation efficiency are poor maintenance of the surface irrigation network and the use of outdated irrigation technology. Ensuring reliable canal releases and balancing them with the demands for water has proved difficult, with the results that crops do not receive the adequate quantities of water at the proper time. In all the project command areas, there is significant amount of canal water wastage due to untimely release and lack of regulatory measure at the outlets.  Figure 1 Trend of Inflows This scarcity of water has led to competing claims from farmers of different geographical locations and the cropping pattern devised by the Government to ensure equitable distribution of water is not practiced by the farmers. This has made it imperative to develop a Decision Support System (DSS) to enable decision making for rational distribution of water to the command areas. 3.0 Decision Support Systems (DSS) Decision Support Systems (DSS) are a specific class of computerized information system that supports organizational decision-making activities. A properly designed DSS is an interactive software-based system intended to help decision makers compile useful information from raw data, documents, personal knowledge, and/or other models to identify and solve problems and make decisions. A DSS can take many different forms and the term can be used in many different ways (Alter 1980). On the one hand, Finlay (1994) and others define a DSS broadly as "a computer-based system that aids the process of decision making." In a more precise way, Turban (1995) defines it as "an interactive, flexible, and adaptable computer-based information system, especially developed for supporting the solution of a non-structured management problem for improved decision making. DSS tools have been used in different situations to assist managers take decisions on complex problems by giving them alternatives and presenting them with tools like 'What if Analsis', 'Scenario Analysis" etc., The objective of the DSS developed under the study is to assist the Government in decision making for the judicious release of water into the canals, distributaries and rationally distribute it to the command area under each project. 4.0 Methodology 4.1 Digitization of Canal & Distribution Network The satellite images taken by Indian Remote Sensing Satellite (IRS) P-6 were processed and geo-referenced. All the four projects on the Krishna River were identified and demarcated. The major canals and distributaries that were visible were digitized using Arc Info. Since the resolution of the images were on a scale of 1:50,000, all the canals and distributaries were not visible. Canal and Distributary Network digitized from the Survey of India Topo Sheets (1:50,000 scale) and field data were used to intricately detail the distribution system and to fill the missing links. 4.2 Crop Water Requirement The crop water requirement in the command area under each canal and Distributary network has been worked out based on the type of crop and taking into account the evaporation and seepage losses. 5.0 Approach 5.1 Users The users of this system are the officials of Agriculture and Irrigation Departments (I & CAD Department, GoAP) and senior government officials in charge of decision making. These officials need to make decisions on the quantity of water to be released to the canal and the rational distribution of it under each project. 5.2 Information required to make a decision The information that would be required is the reservoir storage under each project, the crop water requirements, details of canal and distribution network and water requirement under each of the canals and distributaries. 5.3 Data Used Accuracy of information & knowledge base has been achieved by utilizing data from (1) IRS P-6 Satellite imagery, (2) Survey of India Topo Sheets, (3) Existing Canal and Distributary network, (4) Seasonal crops & water requirements and (5) Details of losses (Evaporation & seepage) 5.4 Software used The DSS has been developed by an unique customized assembly of (1) Arc IMS, (2) Oracle 9i (3) ASP and (4) Arc SDE software tools. 5.5 Structure of the Decision-Making Support System Irrigation water management is related to available water, crop water requirements, command area, cropping pattern, Canal and Distributary network etc. During the irrigation season these data change dynamically. Therefore the decision-making support system for irrigation water management has been developed with the dynamic features by collecting, and processing information dynamically. The structure of the decision-making support system is shown in Figure 2  Figure 2 Structure of the Decision Support System 5.5.1 Information base The information base for the DSS includes data on water resources cropping pattern, crop water requirement, irrigation schedule, Canal and Distributary network including geographical boundaries served by the network. Land use cover and cropping patterns of the command area for all cropping seasons and irrigation water requirements on area basis for all crops sown are the most important information for proper irrigation planning and management. The information on land use and cropping pattern have been extracted with the help of IRS LISS III satellite imageries as well as existing records and stored as different layers in GIS in the form of spatial and non-spatial data. Crop water requirement for different crops is also appended as an information layer along with different data layers of water availability during the entire year. All these determine and affect the irrigation water requirement for different crops. Integrating above data layers along with analytical models can provide a framework for Decision Support Systems (DSS) those can be explicitly designed to support Decision making process for complex irrigation problems. The different spatial layers developed for building the Decision Support System is shown in Figure 3.  Figure 3 DSS: GIS Database 5.6 Work-area set up & Security The software is customized for use by the Senior Officials of the Irrigation and Command Area Development Department of the Government of Andhra Pradesh. This application would be password protected to prohibit unauthorized users to access the information. 6.0 Output The prime out put of this web based application would be a user friendly interface with step by step guidelines for decision making. This system would enable the officials to plan releases of water to the Canal and Distributary network taking into account the water availability, cropping pattern, crop water requirements and geographical distribution. The output showing the villages irrigated by releasing water to a particular set of distributaries is shown in Figure 4.  Figure 4 A Snap shot of the DSS Output 6.1 Unique Aspects of the software:
The e-Development cell of the Centre for Good Governance has developed this system for the Irrigation & Command Area Development (I & CAD) Department, Government of Andhra Pradesh. This Decision Support System has been put into use since January 2005. This is enabling the Government to take decisions based on a scientific basis and thus ensuring timely release of water for irrigation. The system can be replicated for distribution of water in the other river basins in Andhra Pradesh and also other states across India.
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