# Sentinel-1 and -2 Based near Real Time Inland Excess Water Mapping for Optimized Water Management
## 2 Materials and Methods  
### Study Area  
The study area is 5913 km\({}^{2}\) in the southeast of the Great Hungary Plain, enclosed by the Tisza, Koros and Maros rivers and the Hungarian-Romanian border (Figure 1). The elevation is between 77 and 107 m (above Baltic mean sea level). The vulnerability to inland excess water of the area falls in the categories moderately endangered or strongly endangered [11].  
Figure 1: Study area of inland excess water mapping.  
The areas that are most vulnerable are southeast of the city of Oroshaza, the low-lying plains in the west, the valley of the lower Tisza and the areas close to the K\(\ddot{\text{o}}\)ros river. There is a close relation between these areas and the regularly flooded regions prior to the 19 th century river regulations [15]. Due to the geomorphological characteristics of the Maros alluvial fan, IEW can also develop on the higher areas, which can cause significant damage at the border of the alluvial fan [2].  
The development of inland excess water in the study area is favored by the fact that 84% of the soils are clayey, 50% of them have poor water absorption and unfavorable water management characteristics, and their upper, middle and lower layers are easily saturated. Eighty eight percent of the agricultural land is arable land, which is because more than 75% of the soils are fertile chernozem. The build-up area ratio in the study area is 5%.  
The development of IEW is closely, but not exclusively, related to the period with high precipitation in January, February and March. For this reason, our research period is focused on, respectively, March 2016 and March 2018 (Figure 2). In 2016, during the period between January and March the precipitation was continuously above the 1971-2000 long-term average for that period, while in February it was even twice as high as normally. After the high precipitation period in the second half of February, between March 14-20, just before and during the satellite data acquisition, also quite a lot of rain fell. The temperature of 5-10 \({}^{\circ}\)C was several degrees above the normal temperature in February and March, causing increased evaporation.  
In February 2016, everywhere on the Great Hungarian Plain inland excess water developed. In March, IEW in Hungary peaked at a maximum 82,427 ha [43]. The year 2016 can be considered a moderate IEW year in terms of total area covered by water.  
In February, as well as in March 2018, the precipitation was twice as high as the national long-term average between 1971-2000 for those months. In fact, in the south part of the study area, the precipitation was already above the seasonal average in January. At the end of February, a cold period with precipitation started, which resulted in a considerable layer of snow. The warmer period in the middle of March caused the snow to melt and the soil to get saturated by melting water. Also, substantial rainfall fell during March, especially on the 18 th. The satellite imagery from March 28, 29, 30 and 31 used in the study shows the development of IEW at the end of March. The total area covered  
Figure 2: Daily precipitation and temperature data on the study area between 01 January–31 March in 2016 and 2018 respectively and the deviation of the monthly precipitation amount from the 1971–2000 climatic normal value based on a summation of the 5 closest meteorological stations (Hungarian Meteorological Service, OGIMET) (the colored days on the x-axis show the remote sensing data acquisition dates in 2016 and 2018).  
by IEW in Hungary was 73,184 ha [43], slightly less than in 2016. This year should also be considered a moderate IEW year.