"IWA best practices are very well developed, are used in many projects and many case studies have proved great success. Especially dividing network in DMAs and even simple work with measurement results have caused fast increase of NRW and leakage reduction efficiency in many companies. The operators usually have developed their own methodology for data evaluation in order to prioritize the leakage detection in DMAs with non-acceptable leakage level.
The approach, the usual used indicators and their target values are very varied in the Czech Republic and usually we can meet certain insufficiency in the process of permanent evaluation of leakage level in the DMAs compared to the IWA methodology. A large majority of Waterworks in the Czech Republic evaluate primarily NRW distribution in the DMAs based on the balance of inflow and invoiced water in time step of 1 or 3 months. Systematic evaluation of leakage level based on night inflow evaluation is quite exceptional. A check of flow diurnal patterns in SCADA is sometimes used, however it is usually not supported by an automatic process and it has become more demanding on the gradual increase of the DMA number.
The approach to the control of leakage detection actions based on such data differs a lot as well. Very easy performance indicators or principles are usually used for prioritization of DMAs. We can meet with evaluation and limit values of % of NRW, unit leak [m3km-1year-1], % of night flow from day demand, etc. The operators usually can keep such targets quite easily in some DMAs and almost always have some DMAs where they cannot meet the targets even if they invest enormous effort. So, quite often is used strategy of “keeping of existing leakage level”, i.e. leakage detection is done in a zone with “significant” increase of NRW % compared to the previous time period."