Macedonia develops distribution master plan
In a project financed by the Czech government, Macedonia has prepared a master plan for water supply and distribution for the Macedonian city of Kocani and surrounding area. Vladimir Havlik and Jarmil Vycital from Czech consultancy Hydro Projekt explain the modelling process that was undertaken.The city of Kocani is located in the eastern part of the Republic of Macedonia and spreads over an area of 18.6km2, it has a population of about 32,000 inhabitants. Recently, the city has suffered from insufficient water supply during the summer period due to a shortage of underground water in the existing wells.
The Water Supply and Distribution System (WSDS) was built in order to supply water to three zones in the city itself and to neighbouring villages. The structural state of the aging infrastructure is poor and one of the key problems is that WSDS reveals about 60% of water unaccounted for.
The principal underground water source is a system of wells from which water is pumped into the distribution system. The existing WSDS for the population of the city of Kocani distributes water also to the surrounding villages Orizari, Beli, Trkanje, Dolni Podlog, Gorni Podlog, Mojanci, Grdovci, Pribacevo and Zrnovci.
After storing the underground water from the wells in a collecting reservoir, a main pumping station at Grdovci supplies water through a 5.2km pipeline (diameter 508mm) to a new 300L/s water treatment plant (WTP) that was designed and built in 2004 with a grant from the French government.
A new project, with the principal goal to prepare a Master Plan, was launched for the period of 2004-2005. The main targets of the project were as follows:
- Assessment of the overall conception of WSDS in Kocani from the point of view of current and future demands.
- Elaboration of basic documentation for principal water mains of WSDS for three pressure zones.
- Hydraulic analysis of WSDS with the use of computer model and the results from SCADA. Hydraulic analysis for the current state of operation as well as for future development of WSDS operation for Steady and Extended Period Simulations were performed with the use of the trunk model (demonstrating water supply to neighbouring villages) and the detailed models for the three pressure zones.
- Pipe diameter and pressure optimisation.
- Leakage reduction using a suitable integrated approach.
- Evaluation of the customer information system (CIS) and recommendation for its future development.
- Recommendation for future development of a SCADA system for real time control of the WSDS.
- Elaboration of possible administrative and technical measures for WSDS rehabilitation in a form of priorities (time schedule).
- Financial evaluation of requirements for the reconstruction of water mains.
- Elaboration of basic conceptual documentation for WSDS development.
The geodetic surveying provided not only the information on the WSDS topology, but also a digital model of elevation. Modelling activities relied on the use of a standard computer model, MIKENET from DHI Water & Environment of the Netherlands, which enabled pre- and post-processing visualizations of the data and results.
Moreover, data conversions between different products (CAD and GIS) were available. Three basic scenarios (demand data) were used, namely for the average daily flow rates, Qd,av, maximum daily flow rates, Qd,max and maximum hourly flow rates, Qh,max.
Large data sets from SCADA (from November 2002 to October 2003) as well as from EcoLinks Grant (October 2002) were processed and used for the simulations.
Measured sets of data from SCADA were used for a model calibration.
Representative 7 days period for Extended Period Simulation had been prepared and used for water quality modelling. Both models enabled to simulate water age and chlorine decay.
It was observed that in some parts of WSDS required concentration of residual chlorine (required value cmin = 0.2mg/L according to valid Macedonian standards) could not be guaranteed. Figure 3 shows the results for the average daily flow rate.
The results show that neither the concentration of c=0.5mg/L nor the concentration of c=0.8mg/L in WTP is able to guarantee required residual concentration in the villages.
Theoretically speaking, the concentration c=1.0mg/L could guarantee required minimum concentration cmin=0.2mg/L in most villages, except Trkanje and Banja. However, the concentration in three pressure zones and in some other part of WSDS would be unacceptable high. Hence, to increase the concentration of residual chlorine in WTPs cannot be recommended.
The use of water-quality modelling showed that it would be necessary to install additional automatic chlorination equipment, particularly at Trkanje pumping station, Beli pumping station and/or water tank and Orizari water treatment plant Orizari. The villages of Banja and the supply pipeline via D Podlog to Oblesevo and Ciflik will have to be evaluated into more detail for the future operation.
Prior to final decision, this part of the system should be included into a more systematic measurement of water quality parameters. WSDS optimisation was carried out in order to achieve the best solution for hydraulic behaviour. The project also dealt with a decrease in pressure in order to achieve the leakage reduction. The most important decisions were incorporated into the Pipe Rehabilitation Programme.
Financial evaluation of the highest priority pipe rehabilitation projects (upgrading within 2 years) led to the recommendation that replacement of any mains pipeline must include rehabilitation of residential connections too. However, the investment costs for upgrading of house connections were not included in the estimation.
The main reason was that more accurate information on a real number of house connections and their actual diameters and length needed to be determined before specifying the investment costs. The total required sum for three pressure zones was estimated at about e7 million.
The strategy for development of the master plan for WSDS in the city of Kocani was based on the assumption that the documentation must provide the owner of the asset as well as the operator with a basic conceptual solution. The documentation will provide a basic input data into the City Development Plan and it will be used as the starting point for elaboration of the tender documentation and WSDS upgrading.
The Czech Government gave financial support to this project with the technical cooperation of the operator of Vodovod Kocani. This document should form part of the preparations for documentation, which, in turn, is a prerequisite for receiving financial support from European Commission.