The discharge into the Mosoni branch of the Danube according to the intergovernmental Agreement should be 43 m³s^-1, which is composed by the discharge released to the Mosoni branch of the Danube through the intake structure at Čunovo and the discharge through the seepage canal. Discharge measurements are carried out downstream of the intake structure on the Slovak territory at 0.160 rkm and upstream of lock No. I on the Hungarian territory. The average daily discharges were agreed after the joint evaluation of joint discharge measurements performed at both profiles. In the evaluation the data measured just downstream of the intake structure were considered (Fig. 1-4).

The monthly characteristics of the amount of water released into the Mosoni Danube through the intake at Čunovo in the hydrological year 2002 were as follows:

The average annual discharge was 39.5 m³s^-1.

The flow rate in the right side seepage canal was measured at two sites as well. The first is on the Slovak territory at Čunovo; the second is placed on the Hungarian territory at lock No. II. In the evaluation the data observed at lock No. II were considered.

The monthly characteristics of the flow rates recorded at lock No. II were as follows:

The average annual flow rate was 1.93 m³s^-1. There was a continuous slow decrease of discharge observed in the seepage canal during previous years, so the hydrological conditions did not allowed continuous releasing of 3 m³s^-1, which are envisaged in the Agreement. However, after the flood in March 2002 significant increase of seepage water amount can be observed. The increase of flow rate in the seepage canal is related with fine sediments erosion from the reservoir bottom during the flood.

The monthly characteristics of the total flow rate released into the Mosoni Danube, consisting of the amount of water released by the intake structure at Čunovo and amount of water in the right side seepage canal were as follows:

The total average annual flow rate was 41.42 m³s^-1.

Taking into consideration the hydrological circumstances for discharging water into the Mosoni Danube during the flood periods in March and in August 2002 (23-28.3.2002, 13-22.8.2002, from August 16 to August 22 was the intake structure at Čunovo even closed) only, the total average annual flow rate was 42.75 m³s^-1. Based on the evaluation it can be stated that the average annual discharge into the Mosoni Danube envisaged in the Agreement was fulfilled.

1.3. Water distribution on the Hungarian territory

 The goal of the water distribution on the Hungarian side is to provide continuous water supply into the inundation area, into the river branches on the flood-protected area and into the Mosoni Danube.

1.3.1. Water supply into the inundation area

The inundation area on the Hungarian side can be supplied by water from two sources:

a.)   Through two openings in the Danube riverbank, by manipulating the water level increased by the submerged weir and the Dunakiliti dam. The total inflowing discharge is measured at Helena profile.

b.)   From the seepage canal through the lock No. V.

Joint flow rate measurements by both Parties were performed at the Helena profile too. The measurements were jointly evaluated and average daily flow rate data were accepted.

The monthly flow rate characteristics at Helena profile in the hydrological year 2002 were as follows:

* - during the flood event (15-17.8.2002) the flow rate was set to 0 m³s^-1, and it was taken into account in the flow rate of the Danube

The average annual flow rate was 76.9 m³s^-1.

The monthly flow rate characteristics at the lock No. V:                                                                     

The monthly flow rate characteristics of the total amount of water released into the inundation area in hydrological year 2002 (Fig. 1-5a, Fig. 1-5b):

* - during the flood event (15-17.8.2002) the flow rate at Helena was set to 0 m³s^-1, and the amount of water flowing through this profile was taken into account in the flow rate of he Danube

The water supply into the Mosoni Danube is secured from the seepage canal through the lock No. VI (Fig. 1-6). The flow rate is measured at the profile downstream of the lock.

The monthly characteristics of the flow rates through the lock No. VI in hydrological year 2002 were as follows:

The average annual flow rate in the Mosoni Danube at lock No. VI. was 21.8 m³s^-1.

During the non-vegetation period low water period was simulated in the Mosoni Danube as well. This was reached by redirecting of a large part of the water from the seepage canal into the inundation area through the lock No. V., while the water amount taken from the Danube upstream Dunakiliti was reduced.

Besides the water supply function the lock No. I has also a flood protection function. It prevents floods to enter the flood-protected area.

1.4. The Danube water level characteristics on the Čunovo-Vámosszabadi stretch

According to the prevailing influence the Danube stretch between Čunovo and Vámosszabadi can be divided into four different sections. These sections can be characterised by data obtained from the following gauging stations: Rajka and Hamuliakovo, Dunakiliti, Doborgaz and Dobrohošť, Dunaremete and Gabčíkovo. Vámosszabadi and Medveďov.

The four sections on the Čunovo-Vámosszabadi stretch are the following:

a)      Čunovo - Dunakiliti section. The water level in this section is impounded since constructing the submerged weir. This impounded section allows the water supply into the right side river branch system. The amount of water released to the river branch system is determined by water level regulation at the Dunakiliti dam. The water level is kept in the mid-water riverbed. The average flow velocities fluctuated in the range between 0.54-2.26 ms^-1. During the hydrological year 2002 discharge over 600 m³s^-1 into the Danube old riverbed was released two times in case of flood. In March the water covered only the lower parts of the inundation area. In August the water covered the whole inundation.
The yearly average water level at the Hamuliakovo gauging station (rkm 1850) was 123.25 m a. s. l. The daily average water level in the Rajka profile (rkm 1848.4) fluctuated from 122.22 to 128.93 m a. s. l. and the yearly average water level was 123.14 m a. s. l (Fig. 1-7a, Fig. 1-7b).

b)     Section between Dunakiliti and Dunaremete. This section of the Danube is not influenced by any measures and the water level is determined only by the flow rate in this riverbed section. In the upper part of this section the water level in the river branches is about 3 m higher than the water level in the main riverbed. The daily average water level at the Dobrohošť gauging station (rkm 1838.6) fluctuated in the range from 116.94 to 124.37 m a. s. l. and the yearly average water level was 117.90 m a. s. l. The daily average water level in the Dunaremete profile (1825.5) fluctuated from 113.38 to 120.26 m a. s. l. and the yearly average water level was 114.18 m a. s. l (Fig. 1-8). The average flow velocities fluctuated in the range between 0.79-2.62 ms^-1.

c)      Section between Dunaremete and Sap. The water level in this section is influenced by backwater effect from the confluence of the tailrace canal and the Danube old riverbed (rkm 1811). The water level changes, especially in the lower part of this section, are influenced by the flow rates in the tailrace canal. The length of the upstream section influenced by the backwater effect depends on the actual flow rate distribution between the hydropower station and the Danube old riverbed. At regular operation it can be stated that the backwater effect reaches the Dunaremete profile (rkm1825.5) at flow rates over 2500 m³s^-1 at Medveďov. The daily average water level at the Gabčíkovo gauging station (rkm 1819) fluctuated in the range from 111.60 to 118.57 m a. s. l. and the yearly average water level was 112.62 m a. s. l (Fig. 1-9). The daily water level fluctuation at Gabčíkovo gauging station in the Danube old riverbed, as a consequence of operation of hydropower station, can reach app. 20 cm.  
During the flood in August the water level culmination at gauging station No. 0002 – Dunaremete pointed out, that the riverbed water transporting capacity significantly decreased. The water level in 1991 was only 5 cm higher then during the flood in August 2002, however the discharge in August was significantly lower (by app. 2100 m³s^-1).

d)     Sap – Vámosszabadi section. The flow rate in this section equals approximately to the flow rate at Bratislava and is additionally influenced by the operation of Gabčíkovo hydropower station. The daily water level fluctuation at this stretch (up to 30 cm) depends on the hydropower station operation. Higher changes occur at low flow rates in the Danube due to the ratio of the total flow rate and the capacity of one turbine, which is put into operation or stopped. The average annual flow rate at the Vámosszabadi – Medveďov profile in 2002 was 2348,66 m³s^-1. The daily average water level at Medveďov profile (rkm 1806.3) fluctuated in the range from 108.84 to 116.88 m a. s. l. and the yearly average water level was 110.84 m a. s. l (Fig. 1-10).

Fig. 1-1a Basic network of gauging stations agreed in the frame of the Joint monitoring		Fig. 1-1b Additional network of gauging stations agreed in the frame of the Joint monitoring		Fig. 1-2 Surface Water - Discharge Bratislava-Devín
Fig. 1-3a Surface Water - Discharge Rajka		Fig. 1-3b Surface Water - Discharge Rajka		Fig. 1-4 Surface Water - Discharge Čunovo-Mosoni Danube
Fig. 1-5a Surface Water - Discharge Helena		Fig. 1-5b Surface Water - Discharge Helena		Fig. 1-6 Surface Water - Discharge Lock No. VI
Fig. 1-7a Surface water level Hamuliakovo - Rajka		Fig. 1-7b Surface water level Hamuliakovo - Rajka		Fig. 1-8 Surface water level Dobrohošť - Dunaremete
Fig. 1-9 Surface water level Gabčíkovo		Fig. 1-10 Surface water level Medveďov