In this study, GIS-based system analysis has been performed for the aim of monitoring and managing the sewerage lines. The model has been designed for a proper and efficient application, which have several objectives such as integrating data processing, modeling, analyzing and reporting. Spatial data have been collected from different sources and several different data layers and their related tabular data have been used in this study. Possible usage of GIS for analyzing sewerage system has also been described in the study. Old and newly planned wastewater lines of the study area and, stream channel, maps and basins were also added to the system. Population estimation and drainage water flow of the year 2033 have been calculated. Obtained drainage water flow rate and population were added to the system and used as a new attribute for the analysis. Additionally, appropriateness of the methods for flow calculation and population estimation were also examined in this study. Comparing present and future population as well as flow estimation, feasibility of the system for further thirty years was also discussed.
Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 239 - GIS BASED SYSTEM ANALYSIS FOR URBAN WATER CHARACTERISTICS Dursun Zafer Seker a, b , Akira Yuasa a , Arzu Sakiz c , M. Sedat Kabdasli b a River Basin Research Center, Gifu University 1-1, Yanagido, Gifu-city 501—1193, Japan b ITU, Istanbul Technical University Civil Engineering Faculty 34469 Maslak Istanbul Turkey c IMECE A.S. (International Management Engineering Consultancy and Environmental Technologies Inc.) Firin Sok. No:17/13 Tesvikiye 34365 Istanbul Turkey ABSTRACT In this study, GIS-based system analysis has been performed for the aim of monitoring and managing the sewerage lines. The model has been designed for a proper and efficient application, which have several objectives such as integrating data processing, modeling, analyzing and reporting. Spatial data have been collected from different sources and several different data layers and their related tabular data have been used in this study. Possible usage of GIS for analyzing sewerage system has also been described in the study. Old and newly planned wastewater lines of the study area and, stream channel, maps and basins were also added to the system. Population estimation and drainage water flow of the year 2033 have been calculated. Obtained drainage water flow rate and population were added to the system and used as a new attribute for the analysis. Additionally, appropriateness of the methods for flow calculation and population estimation were also examined in this study. Comparing present and future population as well as flow estimation, feasibility of the system for further thirty years was also discussed. INTRODUCTION Istanbul is the largest city of Turkey. It is situated around the Bosphorous, joining the Asian and European continents and has a population of over 12 million. The city comprises both very rich historical background and modern society. Tarabya, a sub-province of the city located at the Bosphorous on the European side, has been selected as the study area. Istanbul has the largest and most complex sewer infrastructures in Turkey. To manage this system, many different alternatives and master plans were developed in recent years. But in these studies the effective usage of GIS has been ignored and was not integrated in the plans. One of the main aims of this study is to emphasize the importance of GIS usage for the sewer network planning. During the rainy seasons, water level in the stream increases and causes flooding events. In other words, the infrastructure in this area is very complex and needs to be renovated. GIS provides the tools to analyze and consider system-wide impacts that were simply impractical in the past. The challenge is to use the GIS tools effectively to develop specific applications that will allow the City to manage the extremely valuable and important collection system assets. In the study area, the surface area of present stream channels is not enough for receiving pour down storm water. Due to this, during rainy time events of flooding occurred in the area due to rises of water level in the streams. Therefore, a prevention strategy was planned. In the plan, Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 240 - a new stream channel that connects the most down stream part of the existing channel with the newly constructed sand trap pool. Furthermore, two lateral stream collectors that are located left and right side of stream was planned for the wastewater collection in the stream. Mapping, monitoring, modeling, and maintaining are the four most important activities in effectively managing a stormwater and wastewater collection system. Since these activities begin with the letter "M", a management practice which utilizes them can be referred to as a "4M" management approach. A Geographic Information System (GIS) can be used to implement or improve the 4M management strategy. The application was developed using ArcView desktop GIS software (Bramwell and Parikh, 2002). Geographic Information System (GIS) and mapping are now moving to the desktop. ArcView is a sophisticated desktop mapping software that promises to bring the power of GIS to the average PC user. In this study, ArcView applications in typical activities associated with the management of wastewater collection systems are described. ArcView is an effective tool for routine display and plotting of collection system maps, querying the GIS database, development of sewer system hydraulic models, and conducting computerized maintenance management. The proposed methodology is illustrated by an example (Robbins and Philips, 1996). Geographic Information System (GIS) is a system of hardware, software, personnel and data used for storage, retrieval, mapping and analysis of geographic data. Spatial features are stored in a coordinate system, which refers a particular place on the earth. Descriptive attributes in tabular form are associated with spatial features. Spatial data and associated attributes in the same coordinate system can then be layered together for mapping and analysis. GIS can be used in many different applications. GIS is used for wide range of applications like sewerage. GIS provides us to transfer the sewerage data to the system and processing, modeling, monitoring and rapid maintenance of the system. Modeling of an existing sewerage system can be used to analyze the existing situation easily and determine the areas, which require new pipelines and their routes and the pipelines, which are insufficient, and needs replacement. Additionally, GIS gives very well visual effect of sewerage system that makes it more understandable. In this study, initially the data has been gathered and transferred into the required GIS databases. The collected data includes existing and planned wastewater network systems, existing and planned sections of stream channels, catchments and maps of a chosen area. After the GIS database is set up, the system has queried and analyzed by using attribute tables. Population data of Istanbul has been prepared by using census data record and past population estimation studies. After transferring calculated population and flow values into the system it showed that the wastewater system is adequate for future flows (2033). The results are supported by the simulation where INFOWORKS simulation program has been used by using GIS data. Therefore, a new stream channel that is to be installed between the end of existing channel and constructed sand trap pools were planned together with two lateral stream collectors that are to be located at both sides of the stream (Sakiz, 2003). Some of the goals of conducting such a study are; • Matching and analyzing existing and planned wastewater interceptors • Analyzing the system for ability of working • Population analysis and comparison growth over time Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 241 - • Prediction of population data for future and analyzing the system with future population data to be acceptable • Simulation for small area of project • Alternative analysis by changing current configuration During the study, • All data was analyzed and prepared for ArcView. • Tables are formed and those contains: o Catchment area containing Basin IDs, area (hectare), population density (person/hectare), population, flow rate. o For planned interceptors: Manhole table containing manhole IDs, ground level, invert level, distance between ground and invert level, X co-ordinates and Y co- ordinates. Pipe table containing inlet manhole, outlet manhole, distance, section and pipeline gradient. o Planned channel table containing section, distance, width, height, flow rate and depth of water in the channel. • Catchments areas are processed. • Existing wastewater system is shown in the project window. DATA and METHODOLOGY Geographic Information Systems (GIS) can be easily used for the infrastructure application as well as many other areas. GIS, allows to user to collect, store, manipulate, analysis, visualize and maintenance every kind of data in a rapid way. In this study data that collected in the different formats have been transferred in the same format and then stored in GIS database. These processes have been done by means of Microstations software. Data related to study area are; existing and planned wastewater lines, existing and planned part of stream channels, basins, neighborhood boundaries and different kinds of maps. After the data preparation different layers have been formed. To evaluate and analysis the newly planned wastewater lines, attribute tables were formed. In these tables, radius and distance of the lines are also defined clearly. Catchments of wastewater lines formed and hydraulic calculations have been carried out with the calculated value of flow rate. Present situation of the system, maximum flows rate that system can carry and suitable pipeline radius has also been calculated. By means of elevation data, Digital Elevation Model of the study area was also been produced. 3D of the study area has been formed easily by means of used GIS software, then planned sewage lines on the streams and the around streams are merged into this model. 3D model of the study area and planned sewage lines is given in Figure 1. One of the projected lines, which is called as A line is also given in the figure 2. For the future situation analysis, this is the main target of the study, as the first step the population for 30 years was estimated. To estimate population precisely, census information of the past years should be examined carefully. For this, census information of Istanbul that belongs to the previous years and some prediction study that had been already done were used. Because of the slight differences between population increase of Turkey and Istanbul, to make population estimation for Istanbul is very difficult Demographic data from the year of 1927 up to present have been used. In the year of 1993, for the master plan, population estimation scenarios were examined and the most suitable one was selected. Different population Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 242 - estimation calculation methods have been conducted and the most appropriate one was selected. Together with these methods two different calculation methods were also used to calculate population estimation to show the differences. In this study natural increase ratio equation was used. In this equation; Figure 1. 3D model of the study area sewerage channels Using this equation estimated population for the 30 years was applied to the basins and flow estimation was carried out. After then obtained flow values and calculated basin population were added to the attribute tables. After the values related to the year of 2033, comparing and analyzing between present and future will become easier. Results were supported with the simulation program named Infoworks. In the simulation, data obtained from GIS were used and results showed that the system can work for another 30 years (Sakiz, 2003). Figure 2. General view and Attribute Table of Line A From the calculation population density for the year 2033 was found 300 person/ha. Using this value, system could be used until the year 2033. If the system is not able to carry this value for prior to 2033, a limit value would have been applied for the system to evaluate the possible results. Five catchment areas and a query example are given in Figure 3. Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 243 - Figure 3. Query example The project data are: • Maps (roads, buildings and levels) • Neighborhood boundaries • Existing wastewater interceptor data • Planned wastewater interceptor data • Existing stream data • Planned channel data • Calculation data • General Directorate of Istanbul Water and Wastewater Administration (ISKI - Istanbul Water and Sewer Authority) project criteria • Population data Wastewater Flow Calculation Wastewater lines around the river have been considered. Related data layers are of manholes (nodes) and pipelines (lines). Another layer named here as Basins is reorganized for both present and future situation. There are three sub-basins that give wastewater flow to the planned sites. For the comparison, present and future flows are also calculated in the basin basis. Here, for the wastewater flow calculation, daily water usage and population density was taken as 250 l/s and 200 person/ha respectively. The formula used for the calculation and results obtained are given in the table 1. In this study industrial usage is not considered. Q house = (q*N)/(24*3600) Q groung =0.1*F B = 5 / P (1/5) {P = (N/1000)} Q pik = B * Q house + Q ground Where q is the amount of wastewater per one person per a day, N is the population in the basin, F is total area and B is the Babbit coefficient. Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 244 - Table 1. Wastewater flows for the basins Basin Area (ha) Population Q house (l/s) Q ground (l/s) B Q pik (l/s) A08a 70.74 14088 40.74 7.04 2.95 127.13 A08b 67.11 13422 38.84 6.71 2.97 122.23 A08d 10,68 2136 6.18 1.07 4.30 27.62 Population Estimation The population of Istanbul in 1980 was 4.78 million and increased more than 55% reaching 7.45 million in 1990. This rapid increase of population has affected several facilities and declined their services. Between 1990 and 2000, the rate of population growth in Turkey was 1.83% whereas, 3.31% in Istanbul showing high rate of population growth in the city. The differences in population between Istanbul and Turkey are given in the Figure 4. Figure 4. Comparison of the population increases both Turkey and Istanbul. Ratio of population increment should be precisely defined for the population estimation. The predicted population for Istanbul falls down the real increments. In the last master plan (1993), three different population estimations were performed according to three different scenarios. They are lower, medium and high increment on the population. In this study population estimation was done according to the lower scenarios because the region lies in one of the old settlement of Istanbul and its population is almost in a saturated state. Calculation is done with the following equation. Pn=Po.e r.n Where, Pn is the second and Po is the first of two successive numbers, e = 2.7182818 (coefficient), n is the difference between to census, r is the population increase (SIS – State Institute of Statistics). In the calculation increment factor is taken as 1.6% between the year of 2000 and 2020 and 0.6% between the year of 2020 and 2040. Using previous equation and increment ratio, populations are estimated for the basins in the study area. After this process flows are calculated once more and results are given in the Table 2. 0 1 2 3 4 5 6 1960 1970 1980 1990 2000 Pop. Increase of Turkey (%) Pop. Increase of Istanbul (%) Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 245 - Table 2. Estimated populations and flow values of basins. Basin Population (2000) Estimated population (2020) Estimated population (2033) Q house (l/s) Q pik (l/s) A08a 14088 19401 20975 60.69 175.15 A08b 13422 18484 19983 57.82 165.54 A08d 2136 2942 3181 9.2 37.58 Simulation A model is a representation of the real world. In the GIS world, this occurs through mathematics. A series of mathematical formulas are linked together to explain the works of a particular phenomena. A good model has an ability to predict the outcomes of a set of inputs that would affect the real world. There are two different main models; simulation models and predictive models. A simulation model is used to analyze the known information about a data feature. This could be a stretch of stream, a point source of pollution, or a census tract. A simulation model uses information from the data table associated with the object, plugs that information into a formula, and creates a new result based on the information from one or more variables. A predictive model, on the other hand, is used to predict how a change in a variable will affect other conditions. Once again, this can be applied to any data feature, but it applies more to the attributes of a feature than the feature itself. There is slight difference between simulation and predictive models. Simulation models deal with extracting more information from what is already known about a feature. Predictive models deal with changes that will occur if certain variables of a feature changes. Both these types of models can apply to groups of features or whole coverage, as well. These both have a variety of applications for managing environmental problems. There are several simulation softwares, which are used for simulating hydrological features. In this study Infowork software was used. Simulation is given in Figure 5. CONCLUSIONS If similar studies are done for the whole city, the reliable information about the infrastructure problems of Istanbul can be obtained. By means of these kinds of system several different questions such as, when the problems will start, how the problems will be solved, when the existing system will be insufficient and which areas will need new lines and etc can be answered. During the preparation of master plan of Istanbul, using population and flow estimation values, detailed studies were done and the existing situation of the infrastructure system was determined and solution methods were also developed. Without GIS this process had taken a long time to achieve aforementioned items. By means of modeling option of GIS, system can be analyzed under the different conditions. Also, for the maintenance process, it can be easily done by means of maps produced by collected observation data. GIS also helps for the management process too. The customs of GIS application tools developed to support wastewater-planning process is proven to be effective on providing analytical strength to the end user without requiring Journal of Water and Environment Technology, Vol.1, No.2, 2003 - 246 - extensive GIS background. Strong data processing component built within application model offers quick upgrades to model inputs without requiring time consuming preprocessing. Figure 5. Simulation Results obtained by Infoworks Software GIS provides the tools to analyze and consider system-wide impacts that were simply impractical in the past. The challenge is to use the GIS tools effectively to develop specific applications that will allow the City to manage the extremely valuable and important collection system assets. REFERENCES Bramwell, D. and Parikh, D., 2002. Wastewater Flow Estimating and Planning Tools Using GIS, ESRI 2002 User Conference. Robbins, C. and Phipps, S.P., 1996. GIS/Water Resources Tools Performing Floodplain Management Modeling Analysis, AWRA Symposium on GIS and Water Resources, Ft. Laurdale, Fl. Sakiz, A. , 2003. Sewerage Application And Analyses By Using Geographic Information System, Ms.C. Thesis, Istanbul Technical University, Institute of Science and Technology. Shamsi, U.M. and Fletcher, B.A., 1996. ArcView Applications in Stormwater and Wastewater Management, AWRA Symposium on GIS and Water Resources, Ft. Laurdale, Fl. . 7.04 2.95 12 7 .13 A08b 67 .11 13 422 38.84 6. 71 2.97 12 2.23 A08d 10 ,68 213 6 6 .18 1. 07 4.30 27.62 Population Estimation The population of Istanbul in 19 80 was. (2033) Q house (l/s) Q pik (l/s) A08a 14 088 19 4 01 20975 60.69 17 5 .15 A08b 13 422 18 484 19 983 57.82 16 5.54 A08d 213 6 2942 318 1 9.2 37.58 Simulation A model is