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ENHANCEMENT OF WATER RESOURCES MANAGEMENT IN MURES RIVER BASIN Daniela Radulescu 1 ,Ada Pandele 1, Tomas Eidsmo 2, Pavel Tachecí 3 1 National Institute of Hydrology and Water Management, Romania, email: daniela.radulescu@hidro.ro, ada.pandele@hidro.ro 2 DHI a s, Norway, email: tomas.eidsmo@dhi.no 3 DHI a.s., Czech Republic, email: P.Tacheci@dhi.cz Keywords Tarnava Mica river basin, water balance, integrated hydrologic mathematical modelling, MIKE SHE, water resources sustainable use, decision support tools. Abstract Project focuses on strengthening the ability of Romanian authorities to protect the environment by assuring a sustainable use of water resources in particular river basins, like Mures River basin. Within the project framework, observation network of Tarnava Mica river basin (sub-basin of Mures river basin) is optimized, integrated mathematical model focusing on water balance is established using DHI MIKE SHE 2009 software, combined with other tools to be easily used and maintained by Romanian water authorities. A DSS-like tool is established this way. Scenarios of future course of water resources and integrated surface- and groundwater hydrologic regime in Tarnava Mica river basin are produced, resulting in recommendations of measures to be conducted. Experience from Tarnava Mica river basin are intended to be transposed to recommendations for observation network and sustainable water resources management measures applicable in whole Mures river basin and further to the methodology applicable across Romanian territory. This project started in 2009 and will be finished in 2011. It is supported from EEA financial mechanism. Main beneficiaries are National Institute of Hydrology and Water Management (leader of the project) and Mures Water Directorate in Mures River basin. Two Norwegian participants are: The Norwegian Water Resources and Energy Directorate and DHI Norway INTRODUCTION In connection with last socio-economic development, water demands in Mures River Basin have been fluctuating a lot. At the same time, further increase of average annual temperature and amplifying of extremes is expected for Romanian territory. Since 2002 trend of groundwater level across Mures Basin decrease is pronounced. As consequence, there is need for tools which quantify impacts to hydrologic regime at present and for future and enhance the water management in an integrated and consistent way. Those tools need to be combined to decision support system for simulation of water balance course under different future development scenarios. The National Institute of Hydrology and Water Management (NIHWM, the Romanian authority in hydrology, hydrogeology and water management field), become lead-partner of an European Economic Area (EEA) granted project Enhancement of water management resources in Mureş River Basin. The total project cost is 1,476 mil. €. Partners in the project are: the Mures Basin Administration (MWD, water authority, responsible for Mures River Basin), the Norwegian Water Resources and Energy Directorate and DHI Norway.

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Essentially, the project consists of two interconnected parts. The first focuses on enhancement of hydrologic and groundwater observation network. The second focuses on the application of modern modeling instruments for the improvement of water resources management, having as general objective the sustainable use of water resources in the Mures River Basin. Within the project, an integrated surface-subsurface mathematical model is developed as a support tool for the decision-making process in water resources management at river basin level. Through mathematical modeling, there will be simulated and evaluated possible impact scenarios on water resources for the Tarnava Mica River Basin. The implementation of the project aims at the strengthening of Romanian authorities’ capacities in the field of water management, the participation to the protection of the environment through maintaining a sustainable development of water resources. The paper presents briefly the Tarnava Mica river basin, focusing on monitoring surface and groundwater network, the hydrological water balance model, some results of model simulation and the next steps that should be undertaken in order to fulfil the project objectives. TARNAVA MICA RIVER BASIN Tarnava Mica river basin is situated in the central pat of Carpathian depression (Fig. 1). The area of basin is about 2071 km2. The altitude ranges from 240 m a.s.l. (Blaj) to above 1700 m a.s.l. (source area in southern part of Muntii Gurghiu), from which about 80% is situated below 600 m a.s.l. Wide Tarnava Mica floodplain and short tributaries forms prevailing landscape in middle and western part of river basin. North-eastern part of river basin (on east from Sovata town) is formed by mountains, while the rest of the area has just a hilly shape. One large reservoir (Bezid) and one important lake (Lake Ursu) are situated in upper part of river basin. Volcanic layers are indicated in east, in upper part of the river basin. Springs occur frequently there.

Fig. 1 Localisation of Tarnava Mica River Basin

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Shallow groundwater body in Tarnava Mica floodplain is situated in 2-15 m thick alluvial layers of sand, gravel, medium-fine with lenses of sand and clay. Below this layer, impermeable layer of clay and marble in depth of 5-15 m was found, insulating shallow GW body from deeper systems. According to the general data available (coming from Water management 1960-1990 data, updated by NIHWM in 1995) groundwater body has following features: depth of hydrostatic groundwater levels between 1 – 5 m, hydraulic conductivity ranged between 40 – 50 m/day and transmisivity between 400 – 500 mp/day.

Fig.2. Tarnava Mica river basin – surface (triangle) and groundwater (cross) monitoring stations AIMS OF MODELLING WORK IN FRAME OF THE CURRENT PROJECT The aim of integrated modelling is to establish a tool which quantify impacts to hydrologic regime at present and for future and enhance the water management in an integrated and consistent way. The tool is to be combined to decision support system for simulation of water balance course under different future development scenarios. We may define modelling work in frame of the project in following consecutive steps:

• Establishing hydrological model focused on long-term water balance of “current status” in Tarnava Mica river basin.

• Application of model and its results (temporal changes in water resources in Tarnava Mica river basin) for different future scenarios and its mutual comparison.

• Further use of calibrated model and its results in frame of the project: o as a basic part of DSS-like tool for automated scenario results generation o to prove the effect of enhancement of observation network at Tarnava Mica

river basin o as a base for whole Mures river basin assessment o as a base and pilot study for building a methodology for whole Romanian

territory.

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As a first step, deterministic distributed integrated hydrologic mathematical model is being established for Tarnava Mica river basin in frame of the current project. The reason lies in need for clear, straightforward solution, based on repeatedly available results and methods easily applicable in engineering routine work. We are dealing with water balance of a river basin, where no part of hydrologic cycle is dominating others (surface as well subsurface part is important). This river basin is formed by several parts differing in character and regime, where fully distributed hydrologic model presents enormous advantage. Model should be valid for scale of a river basin in units of thousands of square kilometres, allowing generalisation to scales of large river basins. MIKE SHE 2009 Water Movement modelling system is used for building the current mathematical model of Tarnava Mica river basin. This modelling tool allows to use different levels of a detail of individual hydrological process description. HYDROLOGIC CONCEPT OF TARNAVA MICA WATER BALANCE MODEL Prior to the building a model itself, general concept of water movement and water balance in river basin area should be established, based on available data and knowledge. From a point of view of water resources modelling, we may distinguish three main building blocks in Tarnava Mica river basin:

• Groundwater body: shallow groundwater body in permeable layers along Tarnava Mica river channel in bed of the valley.

• Slopes: remaining part of valley (slopes, upper hilly part and part of floodplain). This part is able to store just a minor portion of ground water resources, but is important for forming runoff response of the river basin.

• Mountains: mountain areas in north-east part of the river basin area. The bedrock is formed by fractured volcanic layers with frequent occurrence of springs.

There are also some other important structures in river basin: reservoir Bezid, lake Ursu, Balauseri polder, river channel itself and individual water users included into model. Taking into consideration all information and data gathered for Tarnava Mica river basin, provisional concept of water movement across Tarnava Mica river basin area is established. It is expected, that main storage of water is formed by groundwater body along Tarnava Mica river channel. It is the main source for river baseflow in periods between precipitation events. Oscillation of groundwater level during the year (in a range up to 5 m) is visible in most of the observation wells. It is clear, that main resource of water, feeding this groundwater body is snow melt in spring period, when groundwater level rapidly increases. The most important area of snow accumulation during the winter period is mountain area in north-east. This area forms a source for Tarnava Mica and several tributaries, as well as a number of springs. Precipitation events occurring during the year cause only short-term increase of discharge in river channel and mainly supply moisture content in soil profile. Only rarely high-flow peaks comparable to the melting period are reached in summer. For modelling of water resources at Tarnava Mica river basin are the most important:

1. Correct setting of overall hydrologic balance (the most important items are precipitation input, outflow and evapotranspiration)

2. Correct setting up of rainfall-runoff mechanism for different parts of a river basin 3. Groundwater flow, groundwater level oscillation in permeable layers along river

channel, plus proper approximation of exchange of water between river channel and this groundwater body

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MODEL SCHEMATIZATION AND INPUT DATA MIKE SHE modelling setup allows to use different schematisations for individual processes of hydrologic cycle. Keeping in mind project aim (water resources and hydrologic balance), following schematisations, available in MIKE SHE, were selected:

• Overland flow: diffusive wave approximated by 2D finite difference scheme • River flow: 1D hydrodynamic simulation in river channels (MIKE 11 HD) • Unsaturated zone: 2 layer simplified water balance model • Evapotranspiration: computation of actual evapotranspiration based on potential rate

and actual soil moisture conditions • Saturated zone: 3D finite difference scheme for approximation of Boussinesq

equations • Snow melt: degree-day-factor method

The most important time series for calibration and validation of the model are precipitation, discharge and groundwater level. Based on those rules and summary of data available we should take in consideration period of 1987-2009. Length of the period (23 years) relies on a) necessity of establishing of correlation relationship of time series for periods of data gaps and also b) this period will be divided and both sub-periods simulated individually by model during calibration and validation process. Based on analyse of minimum and maximum values of annual precipitation totals and air temperature, period for model calibration (1987-1999) and validation (1999-2008) were set. Input data Several types of measured data were used for setting up of correct schematisation and parameters. These data were made available from different sources and concern mainly the next listed inputs:

• Digital elevation model was built based on grid raster data provided by MWD. Original grid of 10 m cell size was interpolated to 200 m grid cells (Fig. 3).

• Main river branches were included to the river network model (Fig. 4) build using MIKE 11 HD software. As only rare data were available, general schematisation of river channel, based on field survey, was conducted.

• A digital soil map covering the area of Tarnava Mica river basin was available from NIHWM (Fig. 5). Individual soils were categorised according to hydrologic groups (NRCS), soil texture classes, soil classes and soil types. Hydraulic parameters were tabulated for every of 11 categories. Land use map was available from MWD in form of shapefile, based on Corine LU 2000 product. Cathegories were aggregated to 7 main vegetation types. Time series of main vegetation parameters were used, based on literature retrieval.

• Extent of floodplain groundwater body (given by shape file), hydraulic parameters from tests in individual wells and also measured time series of groundwater level in wells were available from NIHWM database. For modelling purposes, 27 wells were selected, having time series of observation available in period 1987 – 2008 (Fig. 6). In June 2010 MWD conducted field survey of other spring and well locations for purposes of the project. There was measured depth of groundwater level in 76 wells (overall average depth 2.74 m) situated mainly in groundwater body (along Tarnava Mica river) area. There was also measured discharge from 10 springs (average 0.28 l/s), mostly situated in upper, mountain part of the river basin.

• Daily precipitation totals were available in 14 gauging stations (6 stations of

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meteoinstitute, 8 stations of MWD/NIHWM). Also daily average air temperature were available in 12 stations and reference evapotranspiration data in 4 stations. Time series were processed, gaps were filled by means of linear correlation. Fully distributed fields for every day in simulation period were interpolated from station data and used as an input to MIKE SHE model. Lapse rates (change according to the elevation) were established for precipitation and temperature.

• Daily average discharge were available in 8 stations of MWD/NIHWM. Time series are used for comparison of simulated model results with real data for calibration as well as validation period. Data for 103 water users (surface as well as ground water) were processed and put in model.

Fig. 3 Digital elevation model (200 m grid cell) used as topography input in MIKE SHE model

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Fig. 4 River network setup used in model (black lines with red circles)

Fig. 5 Aggregated soil map, used in model set-up (11 categories)

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Fig. 6 Ground water level (measured depth below surface) in some of wells at Tarnava Mica MODEL CALIBRATION Due to the high complexity of the problem, step-by-step procedure was introduced to ease calibration process. For the first step, selected individual subcatchments of the river basin were treated and calibrated. In the second step, information and values of calibrated parameters from those subcatchments were used to make calibration of whole river basin more straightforward. Based on current knowledge, discharge from Zagar subcatchment was chosen for calibration of parameters of hilly (slope) part of central part of the river basin. Discharge from Sovata subcatchment was calibrated as a representative of mountain (volcanic) part of the river basin. Subcatchment in central part between Balauseri and Sarateni was used for getting first approximation of parameters of ground water body in floodplain. Ground water level observed in 9 wells were used for calibration. Finally, all values were used as initial set of parameters for calibration of a whole river basin. Some examples from a calibration process are given below. Measured (circles) and simulated (black line) values in part of calibration period, in selected flow gauges and observation wells are compared (Fig. 7, 8, 9).

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Fig. 7 Time series of average daily discharge, comparison of measured (circles) and simulated (line) and basic statistics. Tarnaveni flow gauge.

Fig. 8 Time series of average daily discharge, comparison of measured (circles) and simulated (line) and basic statistics. Zagar flow gauge.

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Fig. 9 Time series of groundwater level in 3-days period, comparison of measured (circles) and simulated (line) and basic statistics. Observation well Balauseri F1 and Bahnea F1. Keeping in mind overall focus of the project (hydrologic balance for water resources issues), it is important not to limit calibration process to fitting of measured data, but evaluate also hydrologic balance throughout the simulation period (Fig. 10).

Fig. 10 Simulated hydrologic balance of Zagar subcatchment (1.11.1987 – 30.10.2000). Accumulated height (mm) values in 30 days time step. From results of simulation it is clear, that total accumulated error of simulation is very close to zero. Also amount of water stored in subsurface part of model (unsaturated and saturated zone) is oscillating close to zero for a whole period. PERSPECTIVES Considering the overall objective of the project, one of the main steps undertaken by now is the analysis of the current observation network and, in the same time, the setting up and the calibration of the deterministic mathematical hydrologic model of water balance at Tarnava Mica River Basin.

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A complex MIKE SHE 2009 modeling framework is used for integrated (surface water and groundwater) distributed simulations; furthermore, the hydrologic model will be completed by other specific tools for a easier use to form a decision support system in water management field. Climatic scenario manager will be combined with pre-defined probable scenarios of water use at Tarnava Mica river basin (based on socio-economic models of future development of a region) and also with simple graphical user interface. This set of tools give chance to water management staff in Romanian institutes to operate with project results easily, even being not experts in mathematical modelling. The whole set of tools will be used for long-term prediction of expected scenarios impact on hydrologic regime and water resources in Tarnava Mica River Basin area. Model results will be transferred to maps, tables and time series, comprehensive for planning and management purposes. They will be used for setting of proposals on measures to be undertaken at selected basin area. Experiences from Tarnava Mica River Basin detail simulation study will be transposed to large area extent of entire Mures River Basin (which is based on simular building blocks as Tarnava Mica river basin) , in two directions: • surface water and groundwater observation network sufficiency (analysis and improvement proposals);

• possible impacts of development scenarios on water resources in the area. Then, generally applicable methodology for the Romanian territory will be established.

Dissemination actions concerning the results of the project will at last be taken on frame of the project. REFERENCES Graham, D.N. and M. B. Butts (2005) Flexible, integrated watershed modelling with MIKE SHE. In Watershed Models, Eds. V.P. Singh & D.K. Frevert Pages 245-272, CRC Press. ISBN: 0849336090. E. Radu and C. Radu, 2006: Fresh water and salted water in Pannonian deposits from the south part of the Transylvania depression, Romania *** Water Management in Mures River Basin, first technical Report within the project RO 0019 *** Water balance modelling in Tarnava Mica River Basin, second technical Report within the project RO 0019 ICPA, 2010: Study regarding the characterization of the Tarnava Mica River Basin from the point of view of soils, detailing the hydraulic parameters specific to the major soil types (saturated hydraulic conductivity, water retention curve, hydro-physical indicators)

ANM, 2010: Climatological study regarding the evolution of air temperature (1989 - 2008) and evolution scenarios for the climatic parameters for the 2021 - 2050 and 2070 - 2099 time horizons in the Mures River Basin.