B-2.1 Subcomponent

Telemetric hydrological and meteorological monitoring networks within operational flood management systems

The earliest possible warning on the expected flood, determination of water level and its changes over time are the basic tasks of the operational flood management

Flush forecasting for the flood management purposes is based upon the knowledge on the current hydrological situation in the protected basins and precipitation forecast. Today, the latter is developed inter alia on the basis of results generated by mezoscale meteorological models, continuously developed and producing increasingly precise quantitative precipitation forecasts. This improves quality of hydrological forecasts, whereby the mathematical hydrological models are used. Proper hydrological modelling cannot be ensured without constant inflow of data from meteorological models and the data generated by the network for measurement of precipitation and water levels at the selected points of the river system.

The hydrological forecasting quality is contingent upon penetration of the precipitation and hydrometrical measurement network and frequency of information update. This is of particular importance in mountain catchments where orography-dependent variation of precipitation is substantial and hydrological phenomena are frequently quite rapid. This concerns mainly the Odra and Vistula catchments.

Today, the IMGW measurement network operated for the flood management purposes comprises chiefly standard precipitation and hydrometric (water gauge) stations. This is not the case in the Upper Vistula catchment, where the automated telemetric VISTEL network has been operated since 1995.

Under normal circumstances, the information from the signalling network are transmitted by radio or telephone to the IMGW Forecasting Offices once or three times a day. The information is produced by observers and based on their measurements and observations. When the flood hazard occurs, i.e. the alert water levels are exceeded or intense precipitation is highly probable, upgrade frequency of precipitation and water level data increases. However, this is not always feasible that is due to practical reasons. IMGW posts are maintained by the part-time observers. The work is not the basic source of income for them, but rather an additional means of support. In the case of protracted flood hazard, these observers cannot make observations every three hours or with smaller interval over a few or more than ten days and nights.

Modern hydrological models require high frequency data updates. This may be ensured exclusively through automation of the observation and measurement network.

Today, the Upper Vistula basin is the only area on Poland, protected by an automated telemetrical flood management system.

The system was developed over the recent years with the financial assistance of the World Bank and the European Union (as part of the EU-PHARE programme). It is systematically expanded and implemented within the operational flood management.

The system was designed and developed by the IMGW Kraków Branch. The relating R&D effort spanned over 10 years. So far, the role of the system was to complement the existing standard signalling network.

During the September 1996 flood, the system capacity was fully verified for the first time. In July 1997 the team of hydrologists vied the measurement data received from the system in the Kraków data collector as fully credible.

The telemetric network includes three types of stations. These are hydrometrical posts, provided for water level measurement, precipitation posts for the precipitation measurement and meteorological posts, earmarked for measurement of wind velocity and direction, air temperature and humidity and precipitation. All VISTEL stations are uniform in terms of equipment and software.

Every hour the telemetric stations are called by the computer control centre in the IMGW Kraków Branch, directly or through the retransmitter network. The stations transmit information on the water level and precipitation volume changes, occurred in the last hour. Data may also be collected more frequently, for instance every 10 minutes, or transmitted upon request at any time. During the recent flood this option was often used, facilitating more precise forecasting of the culmination time.

The VISTEL control centre enables monitoring of all system parameters presented in a graphic form and conversion to such form of the data from all measurement network sensors up to 35 days back. Following each communication session with the measurement station the updated information is transmitted through the IMGW internal computer network to the Operating Hydrological System terminal, located in the Hydrological Forecasting Section.

There, the data is processed by the computer forecasting models and the forecasting models of flood wave transformation. Hydrologists on duty interpret the results and prepare the forecast of the time and size of flood wave culmination, expected in a given profile.Hydrologists from the IMGW Kraków Branch all agree that without the automated network it is not possible to forecast the wave on Vistula of the description as in 1997

The VISTEL stations monitor all crucial points on Vistula and its tributaries down to the Raba river mouth, the measurement profiles in Zawichost and Sandomierz on Vistula and in Nisko on the river San.

The 1997 flood finally confirmed all the VISTEL design assumptions relating to the system structure, telecommunications and installation arrangements, software and technical suitability of the equipment used. Therefore, one may accept that VISTEL should be perceived a model solution, also for the Monitoring, Forecasting and Warning System, covering the entire territory of Poland.

The built-up and maintenance of telemetric flood management networks is extremely expensive. Nonetheless, the per annum cost of the system development equals just a few basis points of the losses caused by a catastrophic flood on the protected area.

The question as to by how much the flood losses may be reduced through the use of data provided by telemetrical flood management network cannot be answered without the relevant research and analyses. No such research or analyses were ever conducted in Poland, primarily due to the lack of complete estimates of various elements of flood damages. The loss reduction is for sure substantial though, if nothing else due to optimisation of rescue operations, hence decrease of the relating costs.

In the recent history of Poland, the large-scale floods occurred in 1972, 1974 and 1980. The long peaceful time that followed tranquillised the authorities and the calls of experts, demanding funds for flood management, including development of telemetric flood management networks were neglected. It was only the tragic - especially on the Odra - flood of 1997 that changed this situation. However, this is relatively typical in the entire world. In many countries the telemetrical flood management networks were put in place after disastrous floodings. This was the case in France (the flood on Loire), in Germany (the flood on Rhine), in the USA and Canada.

Work on the SMOK concept started in the end of 1997. The countrywide hydrological and meteorological monitoring network will be just one element of the planned system. The network will consist of approximately 1100 individual installations, including 516 hydrometrical stations, 246 precipitation stations, 217 meteorological stations and 60 automated synoptic stations, some of them being also the collecting Centres of the system. Other stations include Regional Data-collecting Centres, located in the IMGW Branches in Pozna? , Warsaw, Bia??ystok, Gdynia, Wroc? aw, Katowice, S? upsk and Kraków, radio repeaters and retransmitting stations. The exact number of the latter two will be determined only following completion of the System Technical Design. The stations for measurement of the unsaturated ground layer water level (30) will constitute a conceptually new element of the network.

Distribution of the measurement station in Poland will not be even. The greatest density network will be developed in Southern Poland. This is because it is there where the flood waves on the Odra and Vistula form and the mountain regions are most threatened with disastrous natural phenomena.

At the system design, much attention is paid to ensuring of data flow continuity. In particular, this concerns the hydrometrical stations, most vulnerable to destruction or damage in the case of flood. All hydrometrical stations will be constructed and equipped so as to satisfy the data flow continuity requirement. However, a certain group of stations, referred to as "indestructible" will be particularly protected in terms of their location, construction, power supply and telecommunications. An additional protection measure will derive from special type of such stations' maintenance organization in the time of flood. Majority of hydrometric stations in Southern Poland, nearly all stations on the Odra and Vistula and the estuary sections of their largest tributaries will be available to the data collectors through at least two independent communication channels.

The system operating regime will be similar to that of VISTEL. Data-collecting Centres will call stations every hour in Southern Poland and every 3 hours in Central and Northern Poland. One data collection cycle will take the maximum of 20 minutes. Local Data-collecting Centre will send aggregate messages to the Regional Data-collecting Centres in the IMGW Branches, which in turn will transmit the data to the System Head Office in Warsaw. From the level of Local Centres and upwards the data will be immediately used for the flood management and made available to the users.

The effects expected

The Component delivery will result in establishment of a sound, robust system, to a large extent independent from weather conditions and external data sources, providing hydrological and meteorological measurements and observations. The system configuration will enable access to measurement data with a predetermined interval and raster, adequate to the potential and existing threats. The system will feed data to complex meteorological and hydrological models, delivered under other components. The data system will be conveyed to all users operating within the hydrological and meteorological management system and exchanged with foreign organizations.