Hydrological Information System - Basic Tool in Water ...



Hydrological Information System, Basic Tool in Water Management and Decision Making

Dr. Eram Artinyan, Dr. Dobri Dimitrov

Eram.Artinian@meteo.bg; Dobri.Dimitrov@meteo.bg

National Institute of Meteorology & Hydrology, Sofia

Abstract

The design, set-up and operation of water related information and forecasting systems is of primary importance for the river basin management. The issue is especially valid for the basins shared by two or more countries, as mentioned in the EU Water Framework Directive. The paper deals with the Bulgarian experience in design, setting up and operating of some Information/Forecasting Systems at different Bulgarian river basins as follows:

Modeling and forecast of the Maritza river flow and river basin water and energy budget; the system consists of coupled surface scheme and a distributed hydrological model. It can be provided with historical, real time and forecast input meteorological data. The system is set-up for a large region in Bulgaria – about 34000 km2.

Struma/Strymonas Flood forecasting and warning system; this is Bulgarian – Greek research project targeting detailed investigation on flood formation and flood forecasting due to heavy rainfall phenomena as well as mixed rainfall – snowmelt phenomena. The project includes also installation and operating a system of automatic telemetric hydro-meteorological observation stations. Warning system set-up and operation will follow the research project to ensure better management and safety operation of the Kerkini Lake.

Short-range forecasting of some mountain reservoirs daily inflow; the system is serving the peak energy production using water accumulated at the Southwest part of the Maritza river basin. The system is in operation since late 2000 and uses coupled meteorological-hydrological forecasting models. The use of Limited Area High Resolution meteorological forecasting makes possible two days lead time of the hydrological forecast.

Iskar and Yantra River flows real time monitoring; this project covers two main Danube basin rivers in Bulgaria as a part of the cooperation between Romania and Bulgaria in the field of hydrology.

System for automatic hydro-meteorological data processing, archiving and presentation via Internet/Intranet: It covers mostly the conventional hydro-meteorological data from the Bulgarian territory and presents data in the NIMH intranet environment. Hydro-meteorological data are stored in a database server and made accessible through a web server. This system presents the data in tabular, graphical and mapped views. It was developed in the frame of the Med-Hycos and WOISYDES projects.

Keywords: Hydrology, forecasting, modeling, hydro-meteorological database

Introduction

River basin management is a complex issue comprising variety of tasks and activities of different spatial and temporal scale. Information and forecasting systems are serving the short-term tasks of the river basin management, providing timely information about the development of the phenomena, facilitating water management and decision-making. The tasks become much more complex, when the trans-boundary issue is concerned, because of the necessity to consider in addition different legislation of the countries sharing the basin, different information polices and networks, culture and others.

1. Modeling and forecast of the Maritza river flow and of the river basin water and energy budget.

1. Description of the region

The region under consideration takes one-third part of the territory of Bulgaria – 34000 km2. It covers the central part of South Bulgaria, between the chain of Stara Planina Mountain and the state borders with Greece and Turkey at the south (Figure 1). The climate is continental to Mediterranean in the valleys depending on the dominant atmospheric circulation. It has pronounced altitude variability as the elevation is going from 50 m up to 2925 m at the pick of Mussala in Rila Mountain.

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Figure 1: Map of the Maritza, Arda and Tundja River basins in Bulgaria

2. Objectives of the project

1. Real time monitoring of the natural water balance components and river flow forecast at predefined locations

• One to two days river flow forecast for the most endangered locations.

• To provide real time diagnosis of the river flow over a large region of the country.

• To evaluate the snow height and snow water content in real time

• Soil moisture evaluation for hydrological and agronomical purposes

2. Real time monitoring of reservoirs and channels water balance, and of water table level

• To analyze and predict reservoirs water inflow in order to help the decisions of water supply authorities

• Long term forecast of the underground water level and low-level river flow in order to prevent the shortage of water for irrigation and water supply.

3. Short description of the models used

1. High precision short-range numerical weather prediction model – ALADIN

Aladin short-range NWP model has been operating at the NIMH since May 1999. The numerical weather prediction model ALADIN () - has been used as operational model in Bulgaria since June 1999. The weather forecast for 48 hours over the Balkan Peninsula is computed twice a day using as initial conditions the predictions for 12 and 00 UTC of the French global model ARPEGE (Action de Recherche Petite Echelle Grande Echelle). The horizontal resolution of ALADIN is approximately 12 km, with 31 levels vertically. The model is widely used in Europe.

2. Land Surface Scheme – ISBA (Interface Soil Atmosphere Biosphere)

The ISBA surface scheme was developed for the climate, mesoscale and prediction atmospheric models used at Météo-France (). It aims to represent the main surface processes in a relatively simple way: it solves one energy budget for the soil and vegetation continuum, and uses the force-restore method (Deardorff, 1978) to compute energy and water transfers in the soil. Evapotranspiration is computed through four components: interception by the foliage, bare soil evaporation, transpiration of the vegetation (with a stress function computed using the method proposed by Jarvis (1976) and sublimation of the snowpack. Two fluxes of water in the soil are computed: a surface runoff (RO) and drainage (D) (Figure 2). ISBA was coupled with the distributed hydrological model Modcou (Habets et al. 1999a, 1999b).

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Figure 2: ISBA land surface scheme coupled with MODCOU macroscale hydrological model.

3. Distributed regional scale hydrological and hydro-geological model – Modcou

The macro-scale hydrological model MODCOU was used in several applications (Ledoux et al., 1989). MODCOU takes into account a surface and the underground layers. The surface routing network is computed from the topography, using a geographical information system (Golaz, 1995). The surface and underground domains are divided into grid cells of size 1, 2, and 4 km. The transfer between two grid cells is estimated by using the topography. The surface runoff computed by ISBA is routed to the river network (Figure 3) and then to the gauging stations using isochronous zones with a daily time step. The drainage computed from ISBA contributes to the evolution of the groundwater table, which evolves according to the diffusivity equation. The exchanges of water between the groundwater table and the river are computed according to simple relations (Ledoux, 1980). At the end, the flows from the surface layer and from the groundwater table form the riverflow at the gauging stations.

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Figure 3: River network (blue) and area with existing water table (red). Gauging stations are shown with green squares.

4. Achieved project objectives

1. Analysis of the project feasibility

The overall analysis has shown that except the precipitation field estimation, which contains the higher error, all other fields could be used without special transformation. To correct the effect of the precipitation field on the water balance the measured precipitations could be used through sequential update of the soil moisture and other ISBA variables with that ones computed by using measured precipitations.

2. Automated field preparation

For the implementation of the two dimensional surface scheme and the distributed hydrological and hydro-geological model two-dimensional fields of meteorological variables are needed. In this case, most of them come from the ALADIN HRM but the precipitation field being the most critical is also computed on the base of near real time measurements. The real time processing of all the required fields has to be automated in order to supply the models with the needed input information.

3. Adaptation of ISBA-MODCOU coupled system for using Aladin precipitation fields

The use of Aladin precipitations only was expected to produce largely overestimated runoff, caused by the overestimated precipitation. That is because the initial conditions (soil moisture, soil temperature, snow density and height) had to be corrected after one or two days of surface scheme integration. The values for the re-initialization were taken from another ISBA integration having a delay of one or two daily steps (Noilhan, 2002), which was using measured precipitations instead of Aladin outputs.

5. Conclusion

• High resolution, short-range outputs from Aladin model can be used for the purpose of hydrologic modeling.

• For the forecast use, it is not possible to avoid inclusion of real and near-real time measured precipitations.

• The update of the ISBA land surface scheme variables (soil moisture, soil temperature, snow height and density etc.) have to be made at the shortest possible intervals, which is driven by the availability of new real time 2D precipitation fields.

2. Struma / Strymonas Flood Forecasting and Warning System

Struma is a mountain river flowing from North to South, from Bulgaria through Greece up to the Aegean Sea. It generates flush floods of snowmelt – rainfall type mainly in the late spring. Following the strong demand of Greece a project was started aiming to build the basis of a flood warning system, which should facilitate reservoir management downstream Bulgarian border, allow secure handling of the floods in Greek territory and generally decrease the flood hazard. The activities planed include installation of automatic telemetric hydro-meteorological observation network, review of the results of relevant projects, analysis of historical hydro-meteorological data, design and calibration of flood forecasting models, prove the possibility to issue flood warnings with certain lead-time and accuracy.

1. Introduction

Struma is collecting waters from four countries (Yugoslavia, Bulgaria, Macedonia and Greece), flowing from North to South up to the Aegean Sea. Considerable part of the river basin is situated in northwest Bulgaria (fig. 4.), having an area of more than 10000 km2 and average elevation about 900 m a.s.l. It is a mountain basin with steep slopes and relatively small concentration time, generating flush floods of snowmelt – rainfall type mainly in the late spring. Flood warnings are needed generally for the Greek lowlands to facilitate reservoir management downstream, allow secure handling of the floods in Greek territory and generally decrease the flood hazard.

Some real steps in organizing flood forecasting/warning system for the Struma river basin started in early 1990, when project briefs prepared by one of authors of this paper were presented to the Greek side. The WMO expert Dr. Alesh Svoboda during his advisory mission in 1992 prepared a project document related to flood forecasting for the Bulgarian-Greek border basins of Mesta and Struma, calling for UNDP support. The AUA Greek experts Prof. Karakatsoulis and Dr. Mimidis prepared in 1990 project proposal for Struma/Strymonas Flood Warning System. As a result the joint Bulgarian-Greek Intereg II – Phare CBC Committee found the problem as important one and gave start to research activities to be implemented by Bulgaria and Greece, which should prove the possibility to issue flood forecasts and warnings with acceptable for the practice lead-time and accuracy. For that purpose, the Bulgarian Phare CBC Program organized an international tender (project BG9803-030202) for delivery and installation of equipment for the Struma Flood Warning and Forecasting System in late 1999. The Greek company ScientAct SA was selected and successfully installed the equipment in early 2001 with the assistance of the National Institute of Meteorology and Hydrology, which is beneficiary of the project.

It should also be noted that the development of the WMO Med-Hycos project significantly facilitated the above one providing guidance, practices and the first automatic telemetric station in the basin (Figure 4).

The present paper is giving information on the activities of the side in the design and establishment of the telemetric hydro-meteorological observation network, analysis of historical hydro-meteorological data, design of hydrological forecasting model, first practical results, etc.

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Figure 4: Telemetric observation network

2. First Results

The first results achieved by the Bulgarian team include:

• The telemetric observation network set-up and the operational data collection system. The system started functioning and collecting hourly averages of all the observed hydrological and meteorological parameters in January 2001;

• Analysis of relevant historical data set was completed. It includes review of 30 years series of daily averages of discharges, daily precipitation totals, snow heights, air temperature daily means and maximums observed at certain stations in the region. Different type of descriptive information, important for the design and calibration was also collected. That is valid for the hydrographic characteristics of the basin, information about the major soil classes in the basin, major anthropogenic impacts of the hydrological regime, etc. Examples of the work carried out in that direction are presented below. Separately the pluviograph data (rainfall intensity – Figure 8) were processed, which are unfortunately available for a few stations situated in the lowland and working only during the warm season. Relevant single flood waves (Figure 7) (using hourly discharges from limnigraph records) were analyzed as well, to determine more precisely the concentration time and flood peak discharge. The most important result here is that the southern parts of the basin usually start working first, due to the intensive snowmelts and rainfalls, caused by Mediterranean cyclones moving from South to North.

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Figure 5: Struma river basin hydrographic curve

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Figure 6: Struma river basin longitudinal profile

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Figure 7: Single flood wave analysis (hourly)

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Figure 8: Rainfall intensity/duration curves

• The first modeling was elaborated (Sosedko et al, 1990; Dimitrov, 2001). It is not practical to relay on the telemetric data as an input for the hydrological forecasting model because of the short concentration time (for some flood events less than 24 hours). Two days ahead meteorological forecast is used as first approximation of the precipitation and air temperature fields. Experiments were made with two types of simulation models using daily values: the Ukrainian SNEG2 (Sosedko et al, 1992; Dimitrov and Stanev, 1994); the Norwegian version of HBV (Stanev and Saelthun, 1993, 1994). Example of the results is presented below (fig. 10).

• It is foreseen that the real time rainfall/snowfall telemetric data will not be used directly as an input for the hydrological forecasting model. Meteosat satellite data and elevation gradients will be used for the spatial analysis of the precipitation fields. The analysis of the historical data set shows that the density of the observation network is not sufficient because of the mountain landscape conditions.

• Finally, the real time observations of the river levels will be used for dynamic adaptation of the discharge forecast using Kalman filtering or other stochastic approach.

Short Range Forecasting of Mountain Reservoirs Inflow

With the developing of the marketing economy in Bulgaria, the demand for more reliable hydrological information and forecast is continuously increasing. First, the energy production decided to finance the development and set-up of a system for short range forecasting of the daily reservoirs inflow. Four cascades located at the southwest mountain part of Bulgaria were found important for such kind of forecasting services. The reservoirs of those cascades are not big and have relatively complex system of operation, producing only peak energy at certain time in the morning and evening. Most of them are equipped with powerful pumps reversing water at night using cheap energy produced by “Kozloduy” nuclear power plant. The project has been started at late 1998 with the following objectives:

• At least two days ahead forecasts of daily reservoir inflow is issued every day, to facilitate the optimal planning of their operation.

• Improving the management of the reservoirs and cascades operation by optimal planning of peak energy production and reverse pumping.

• Making the exploitation of the reservoir cascades more secure by optimal planning the retention volumes in case of floods.

|Hydrological forecast with increased lead time, two days ahead| |Adjustment of flood forecast by real time |

|meteorological forecast: | |hydro-meteorological observations |

|Limited Area High Resolution Meteorological Forecasting Model | |Spatial analysis of the precipitation fields |

|“ALADIN” | |applying METEOSAT data |

|Two days ahead meteorological forecasts of air temperature and| |Uses the hourly data obtained from the telemetric |

|precipitation | |stations, elevation profiles and satellite data |

| | |about the entire river basin |

| | | |

|Hydrological Rainfall/Snowmelt - Runoff |

|Forecasting Model |

|Takes into account snowmelt processes, interception, evapotranspiration, infiltration, uses simple routing procedures and |

|gives one day ahead forecast, according to basin concentration time |

| | |

|Final adjustment of hydrological forecast using |

|dynamic adaptation stochastic models |

Figure 9:Principle scheme of the modeling concept

One of the first tasks of the project (Dimitrov, 2001) was inventory of derivation channels and pumping facilities to clarify the water collection schemes at each complex and its corresponding watershed (example of that type of information is given in Fig.11). The historical hydro-meteorological information in the reservoirs watersheds was also reviewed as well as the availability of real time hydro-meteorological data, which could be used for the verification of the meteorological forecasts and adaptation of the hydrological forecasts. Certain operational data collection system was designed and set-up, comprising:

• Daily inflow/outflow of 11 reservoirs;

• Air temperature/humidity, wind speed/direction, observed three times per day as well as daily precipitation totals and snow heights at 12 meteorological stations (collected daily);

• Daily precipitation totals and snow heights, weekly snow water content and coverage at 24 precipitation gauges (collected weekly);

• Daily instantaneous discharges at 42 water level gauges located at rivers that are more important and derivation channels (collected weekly for the dynamic calibration of the sub-basin forecasting hydrological model).

The modeling concept is very similar to that given at Fig. 9 (Dimitrov, 2001). The difference is that the sub-basins along the derivation channels and reservoirs are much smaller (with area varying from 40–60 to 200-300 km2), their concentration time is several hours, no automatic telemetric observation network is available, so some reasonable lead-time of the hydrological forecast might be obtained only using the high resolution meteorological forecast of air temperature and precipitation.

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Figure 10: Simulation of the daily discharges (1986, 1983)

The hydrological forecasting model is calibrated for the most important sub-basins, where observations of air temperature, precipitation and discharges are available and for each of the reservoirs’ watersheds. The final product – two days ahead hydrological forecast is available in several competitive variants:

• Direct forecast of the reservoirs inflow, considering it as discharge at certain river cross section;

• Composed forecast of the reservoirs inflow obtained by separated forecasting of the derivation channels and their sub-basins contributions;

• Adaptive scheme adjusting the above two variants.

The project implementation has faced a number of difficulties as follows:

• It was difficult to find suitable historical data for the calibration of the sub-basins at the higher elevation zone, because of the lack of meteorological observations there and the low quality hydrometric data during the winter;

• The calibration faced another difficulty, due to the considerable difference between the meteorological forecasts and meteorological observations at the high mountain zone, which is especially valid for the precipitation;

• The operational evaluation of the reservoirs inflow is performed based on the produced energy and overall water balance of the respective reservoir/cascade. That was very often source of errors, existence of false peaks of the inflow, etc.

The operational exploitation of the forecasting system started in early 2001. The evaluation of the system performance and accuracy is promising. The general conclusions are that many improvements should be done both in the meteorological and hydrological forecasting models to increase the forecasting accuracy and reliability as well as to meet the demands of the practice.

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Figure 11: Principle scheme of “Batak” cascade (reservoirs “Batak” “Golyam Beglik”, “Shiroka Plyana”)

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Figure 12: Hydro-meteorological data and hydrological forecasts visualization software

Iskar and Yantra River flows real time monitoring

5 Objectives

Installation of automatic system for observation the level of main tributaries of the Danube in Bulgaria and creation of public information system for hydrological information through publishing in the Internet and, on this basis to provide free access in real time to the data for a wide circle of interested authorities, business and civil organization, population and relevant subject from the Republic of Romania

6 Outputs/Results

In the project framework, an investigation was made for the choice of the places for installation of two automatic hydrometric stations in the lower reaches of the major tributaries of the Danube in Bulgaria – Iskar River and Yantra River. The places had been prepared in advance and automatic stations for water level, water temperature, precipitation and air temperature were installed. The information is transmitted through GSM modem to branch Pleven of NIMH, where it is stored in a database and is published in (Figure 13) Internet (pleven.meteo.bg). Computer equipment was bought and proper software for the project requirements was installed.

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Figure 13: Web site images of the real time water level data - Belyanovo and Orehovitsa hydrological stations

System for automatic hydro-meteorological data processing, archiving and presentation via Internet/Intranet

For the purpose of hydro-meteorological data monitoring within an Intranet environment a special technology was developed. The system (Figure 14) consists of three main parts:

8 Access database file

The Access database stores:

• Vectorial geographical information of the hydro-meteorological objects: basins, watersheds, rivers, stations

• Metadata about the objects: coordinates, relationship between objects, addresses etc.

• Description of different variables used to create data series, documents and tables

• Links to documents, pictures, tables related to the above mentioned objects

• Data Series of any variable type and time step attached to them

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Figure 14: Information system structure

9 Data Manager application tool

The tool serves:

• To create and maintain the database structure and administrative access

• For adding, updating and deleting geographical objects

• To create new variables

• For editing the objects metadata

• To insert and update Data Series and other documents attached to the objects

• As a tool for graphical and tabular presentation of the data

• For data import and export in ASCII format

10 Web site

The Web site allows an Intranet access to the tabular and graphical views on the database. It has several features:

• An interactive mapping interface to the geographical structures of the database (Figure 15)

• A tree view on the objects relationships

• A tabular representation of the data series

• An interactive graphical presentation of the data series

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Figure 15: Web site main application page

The entire system serves to supply historical and real time information of all hydro-meteorological data collected by the National Institute of Meteorology and Hydrology. It is planned to enhance its analytical potential in the future, in order to include automatic creation of thematic maps :

• Real time and historical water production maps

• Alarm methods for high flood forecast

• Prediction of low water level periods

• Real time soil moisture maps

• Monitoring and alarm methods for the reservoirs input, storage volume etc.

Acknowledgements

Several projects funded by PHARE helped the creation and development of Danube AEWS - 97-5244.00, 99-0207. Struma Warning System was funded by Phare CBC BG9803.03.02.02 and Intereg II funds. The Mountain Reservoir Forecasting System was helped by the National Electricity Company project CDU-9801.

The Maritza River hydrological modeling was developed within the bilateral cooperation between the National Institute of Meteorology and Hydrology of Bulgaria and Météo-France.

The “System for automatic hydro-meteorological data processing, archiving and presentation via Internet/Intranet” was developed initially within Med-Hycos project, then enhanced with the help of a FAO project for Cyprus Water Development Division (WDD) and the WOISYDES project. The Web Interface is developed by Dipl.-Ing. Dejan Lekic (dlekic@meteo.yu) from Ministry for Protection of Natural Resources and Environment of Republic of Serbia.

References

Deardorff, J.W., 1978: Efficient prediction of ground temperature and moisture with inclusion of a layer of vegetation. J. Geophys. Res., 83, 1889-1903.

Dimitrov, D. 2001: Short term hydrological forecasting of the reservoirs cascades Arda, Batak, Belmeken, Dospat. NIMH – Technical report (in Bulgarian), Sofia, 2001.

Dimitrov, D., K. Stanev, 1994: On the possibility for short range forecasting at the Bulgarian mountain part of the Mesta river basin. UNESCO Conf. on Developments in Hydrology of Mountainous Areas, Stara Lesna, Slovakia.

Golaz, C., and C. Cavazzi, 1995: Exploitation d’un modèle numérique du terrain pour l’aide á la mise en place d’un modèle hydrologique distribué. Rapport technique, CIG, Ecole des Mines de Fontainebleau. DEA d’hydrologie, Université PARIS 6. (in French)

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Jarvis, P.G., 1976: The interpretation of leaf water potential and stomatal conductance found in canopies in the field. Phil. Trans. R. Soc. London, Ser. B, 273, 593-610.

Ledoux E., 1980: Modélisation integrée des écoulements de surface et des écoulements souterrains sur un bassin hydrologique. Thesis, Ecole Nationale Superieure des Mines de Paris and Université Pierre et Marie Curie – Paris VI

Ledoux, E., G. Girard, G. de Marsilly, J. Deschenes, 1989: Spatially distributed modeling: conceptual approach, coupling surface water and ground water, NATO, ASI Series C. In: Morel-Seytoux, X. (Ed.). Unsaturated Flow Hydrologic Modeling-theory and Practice, 275 pp. Kluwer Academic, Dordrecht pp. 435-454.

Noilhan, J., 2002: GLASS workshop on land – atmosphere interaction, In

Sosedko, M., K. Stanev, D. Dimitrov 1992: Snowmelt–rainfall hydrograph modelling and forecasting. - Bulg. J. of Meteorology & Hydrology, v.3, No1 (in Russian).

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