DEVELOPMENT OF A DECISION SUPPORT SYSTEM FOR INTEGRATED URBAN WATER MANAGEMENT

Abstract

Urbanization refers to the migration of the people from rural areas to cities due to many reasons, most common being better quality of life and safety, diversity in socio-cultural life, better facilities of education and employment opportunities, medical services, etc. The process of urbanization comprise of individual development of site, replacement of trees and natural cover by buildings and impervious cover. Rapid and unplanned growth of urbanization has many adverse effects on existing water supply sources, hydrology and the micro-environment. High population density results in high water consumption and change in lifestyle of people's increases per capita water demand. Both the factors have created pressure on the existing water supply sources. Besides, deforestation, construction of buildings, roads, parks, and industrialization have significantly affected hydrology and microclimate of the environment. Imperviousness results in a loss of interception and depression storage, a decrease in the potential infiltration, and redirection of flow paths due to change in local slope. This leads high volume of runoff results in flood problems. Therefore urbanization can be characterized by high population density and change in land use dynamics. The main objective of any water supply scheme is reduction in water shortage that can be achieved by increasing water supply by some additional sources; rooftop rainwater harvesting, runoff harvesting, recycling waste water and imported water from other sources. Since many water supply sources will not be able to fulfill ever increasing water demands in the long run, it is essential to check water demands. Some water demand reduction measures include increasing price, metering, public awareness about water savings, and toilet retrofitting. These measures can reduce the water demand by upto 50%. Therefore, water shortage reduction, water demand management, increasing groundwater recharge and runoff reductions must be the part of any water supply strategy for urban area. Traditional water management strategies for different subsystems are being practiced in a fragmented way but inefficient management of one subsystem may have severe impact on other subsystems as all the subsystems of water supply system are interlinked. Therefore, the strategies required for urban water management must be carried out in an integrated way. It is necessary to develop proper and planned infrastructure to overcome the problems of future water demand as well as the sustainability of natural water resources system. This can be done by Integrated Water Resources Management (IWRM) i.e. by ii integrated management of all existing water sources, water conservation techniques, recycling waste water and demand management. IWRM is a complex method that includes different analytical processes that require management of large volume of spatial as well as non-spatial data. The IWRM can be implemented by demonstrating and developing an interactive interface so that, it is readily adopted by the decision makers. This requires a computer aided tool called Decision Support System (DSS). In accordance to the research objective, the essential characteristics of a DSS, as appropriate from water resources study are firstly identified. A comprehensive search on the models and methods of various components of integrated water management was done keeping in view their data need and type of output generated. From the wide literature and other resources available on the Decision Support Systems (DSSs), it is found that most of the DSSs developed are either area specific or problem specific. Many DSSs have been reported on river basin and reservoir planning and management, waste load allocation, irrigation water management and for rural water supply. Very few DSSs have been developed for urban water management considered urban water supply through lake or river, or flood control. There is a need of a DSS for urban area for integrated water management that integrates water supply from different sources as well as demand management, runoff reduction and groundwater recharge. Keeping this in view, a DSS was developed in the present study for Integrated Urban Water Management (IUWM). The prototype DSS developed for water resources planning has been demonstrated for Municipal area of a rapidly growing city "Dehradun" of Uttarakhand state, India. Development of a DSS requires the following processes; preparation of a framework of the DSS, selection of conceptual methods for analytical modules, computer programming for software development, database creation, testing the various components of the DSS, and demonstration of the utility of the developed DSS. Integrated water management needs much spatial and non-spatial information, so the database module has been provided essential features to manage both the data. The conceptual methods for the analytical modules of the DSS have been selected on the basis of data availability, their popularity, functions provided in software language. A user friendly DSS was developed using the object oriented programming language Visual Basic 6.0 and an ActiveX control, MapObjects 2.4 was used to make DSS input and access spatial data in the interface of the DSS. The analytical modules developed for the DSS for integrated urban water management are water supply, water demand, water shortage, runoff estimation, groundwater recharge, rooftop rainwater harvesting and iii Analytical Hierarchal Process (AHP) module. User interfaces were then developed for each method, called module in the DSS. The developed software platform is a prototype of the Decision Support System for Integrated Urban Water Management, which has been abbreviated and called as DSS-IUWM. The study fulfills its objective for the development of a DSS for IUWM. The spatial and non-spatial database was created for the study area. The DSS developed in the study is user friendly, and has capability to handle both the spatial and non-spatial data as input. The main components of the developed DSS-IUWM are data management module, analytical modules and graphical user interface (GUI). The present status of water supply scenario can be studied by the developed modules of water supply, water demand and water shortage. Population forecast module provides options for three methods or population forecasting Arithmetic Increase Method (AIM), Geometric Increase Methoc (GIM), and Incremental In crease Method (IIM). Therefore shortfalls of water can b( forecasted, so that corrective action can be taken at an appropriate time, which is ver3 essential for sustainable development of available water resources. All the information car be retrieved ward-wise. Runoff module has been developed to estimates the weighted annual runoff b3 SCS-CN method and weighted-CN method. Groundwater recharge module has beer developed to compute groundwater recharge as per the norms provided by Groundwater Estimation Committee (GEC, 1997) for rainfall infiltration method. The graphical uses interface for Rooftop rainwater harvesting module provides the flexibility of computir4 the total rooftop rainwater harvesting potential under different efficiencies of buildings tc collect rainwater. All the information can be seen in an integrated way. The GUI developed for eact module are simple, easy to understand and provide sufficient flexibility to users tc increase the adoptability of the DSS-IUWM. Scenario analysis is an important aid ir decision-making when IWRM is to be implemented. AHP module contains user interface for calculations of weights by pair-wise comparison methods and comparing the scenarios by AHP method. The user can analyze the scenarios using from 3rd to 15th criteria. Database for spatial data have been generated in ArcGIS 9.0, whereas tables of non-spatial database have been created in MS Access software. The utility of the DSS have been demonstrated considering different water supply scenarios in the existing and future conditions. In the existing condition, groundwater and surface water are the main water supply sources whereas in future condition integration of rooftop rainwater iv harvesting potential, recycling of water, runoff harvesting and water demand reductions assuming different water demand measures have been considered in a water supply scheme. In the short-term planning, rooftop rainwater harvesting can be a solution to meet the shortfall of water, but to achieve the aim of sustainability a long term planning is required. For long term planning, integration of water demands measures with additional water supply sources may be required. Recycling of waste water is essential to achieve the aim of sustainability. The DSS-IUWM has been developed by integrating different modules, so it can be easily upgraded by adding new modified modules, as per the need of any study area. In general, study has successfully demonstrated the development of the DSS for integrated urban water management, which may be useful to water resources planners and decision-makers.