The European Union Water Framework Directive obliges each country to monitor the groundwater level as it is an important source of drinking water, but also an important part of agriculture. A water budget is used for assessing the accuracy of the groundwater level determination. The computations of the water budget are based on evapotranspiration and the state of land surface hydrosphere. On the basis of the determined water budget, statistics and the prognosis for the next 12 months can be computed. In this paper, all the components of the water budget, such as precipitation, surface run-off and evapotranspiration, are studied for the three tested locations in Poland: Suwalki, Zegrzynski and Tarnow cells. The resultant water budget was also determined and presented graphically. On the basis of the water budget research, a prognosis was determined using AutoRegressive Integrated Moving Average (ARIMA) models with the parameters (2,0,2). A comparison between actual water budget data and a prediction prepared for 2015.08–2016.08 indicated that analysing a 12-month period provides a satisfactory prediction assessment.

Previous geoid/quasigeoid models calculated for the area of Poland were based on the traditional "remove-compute-restore" procedure. One of the modifications of this method is the least squares modification of Stokes' formula with additive corrections method (LSMSA), which was developed at the Royal Institute of Technology (KTH) in Stockholm in Sweden. The modified Stokes integral combines the regional terrestrial gravity data with a global geopotential model (GGM) giving the approximate geoid heights. To obtain the gravimetric geoid, four additive corrections, topographic, downward continuation, atmospheric and ellipsoidal, are calculated and applied. This paper presents the results of computation of a new gravimetric geoid model for Poland using the KTH method. In computations terrestrial gravity anomalies derived from nine different gravimetric data sets, global geopotential model EGM2008 and global elevation data SRTM v. 4.1 were used. The determined gravimetric geoid model was evaluated with GPS/levelling points of the Polish ASG-EUPOS network. After fitting the geoid model to the GPS/levelling data using a 7-parameter model, the standard deviation of differences was estimated to 2 cm. where the term N GM reflects the contribution of the geopotential model coefficients, while N ∆g represents the contribution of the Faye'a anomalies (∆g) after removing the effects of the geopotential model. The term N H is called the indirect effect on the geoid, and accounts for the change of equipotential surface after the terrain reduction is applied to ∆g. The term N ∆g can be calculated using the Fast Fourier Transform or the least squares collocation method (Łyszkowicz, 2012;Kryński, 2007). Accuracy of the last quasigeoid model computed from gravimetric data and geopotential model EGM08 by the collocation method after fitting to the vertical reference height system in Poland is accurate to ± 1.4cm (Łyszkowicz, 2010). ARTICLE INFOBut at the same time, there are no geoid models for Poland computed using the LSMSA method (least squares modification of Stokes' formula with additive corrections). In order to determine the next geoid model for Poland, this method was used in this paper. The method was developed at the Royal Institute of Technology (KTH) in Stockholm and is also known as the KTH method. This method was successfully applied for a gravimetric geoid determination in several countries. The results of the regional geoid modelling using the KTH method were given among others in

This study deals with the analysis of temporal gravity variations in central Poland, deduced from multiple sources and covering the period from 2002–2016. The gravity data sets used comprise GRACE monthly solutions, GLDAS land surface models and absolute gravimeter measurements from the FG-5 gravimeter located in Józefosław, Poland. All data are corrected using standard processing methods in order to include the same gravity effects. After removing the annual and semi-annual components from all data using least-squares spectral analysis and seasonal-trend decomposition, the deseasoned time series are derived and examined for signatures of extreme hydrological events. The signatures of several severe drought and flood conditions affecting Poland and central Europe are identified. A complementary correlation analysis is performed to assess the level of agreement between different data sources. A higher correlation is shown when the analysis is restricted in the 2009–2012 period that includes the 2010 extreme flood and 2011 increased precipitation events, both affecting Poland.

Results of three campaigns of Baltic Sea Level Project and further studies reveal the GPS and spirit levelling data possibly contain errors which affect SST and W L 0 computations. For that reason, the old data were revised and additionally, in spring 2015, the new GNNS campaign was carried out at tide gauges in Swinoujscie, Ustka and Wladyslawowo. The study concerns computation of the local average geopotential value W L 0 using water level data at the three tide gauges, geoid undulations from a global geopotential model EGM2008 and ellipsoidal heights from GNSS observations, which were obtained using revised data from three campaigns of .