The paper presents the results of the effects of control drainage (CD) on the groundwater table and subsurface outflow in Central Poland. The hydrologic model DRAINMOD was used to simulate soil water balance with drain spacing of 7 and 14 m, different initial groundwater Table 40, 60 and 80 cm b.s.l., and dates at the beginning of control drainage of 1 March, 15 March, 1 April, and 15 April. The CD restricts flow at the drain outlet to maintain a water table during the growing season. Simulations were made for the periods from March to September for the years 2014, 2017, and 2018, which were average, wet, and dry, respectively. The simulations showed a significant influence of the initial groundwater tables and date blocking the outflow from the drainage network on the obtained results. In the conditions of central Poland, the use of CD is rational only when it is started between 1 and 15 March. In this case, the groundwater table can be increased from 10 to 33 cm (7 m spacing) and from 10 to 41 cm (14 m spacing) in relation to the conventional system (free drainage—FD). In the case of blocking the outflow on 1 March, the reduction is about 80% on average in the period from March to September. With a delay in blocking the outflow, the impact of CDs decreases and ranges from 8% to 50%. Studies have shown that the proper use of the drainage network infrastructure complies with the idea of sustainable development, as it allows efficient water management, by reduction of the outflow and, thus, nitrates from agricultural areas. Furthermore, CD solutions can contribute to mitigating the effects of climate change on agriculture by reducing drought and flood risk.

Control drainage (CD) is a common practice implemented to control the water balance of drainage fields by increasing the amount of water retained in soil. Worldwide studies suggest that climate change can reduce the effectiveness of CD solutions, but no study of CD effects has been carried out in Polish conditions yet. In this study, the DRAINMOD (Wayne Skaggs, North Carolina State University, Raleigh, USA) computer simulation model was used to predict the effects of CD on the time horizons of 2021–2050 (near future) and 2071–2100 (far future) assuming the Representative Concentration Pathway (RCP) 4.5 emission scenario. The effectiveness of CD solutions is presented for a drainage network with spacing of 7 or 14 m. Additionally, different dates of blocking the outflow from the drainage network (1st and 15th of March and 1st and 15th of April) and different initial groundwater table conditions (0.4, 0.6, and 0.8 m) were assumed. All simulations for different variants were carried out for the same period, i.e., from 1st of March to 30th of September. The results of climate models indicated that in the area of central-western Poland in the near and far future there will be an increase in air temperatures by 1.02 and 1.97 °C, respectively, and in precipitation by 5.98% and 10.15%, respectively. In addition, there will be a change in the structure of precipitation, especially with respect to the extension of rain-free periods and an increase in the amount of extreme daily precipitation. The effect of climate change will be a decrease in the mean groundwater table in the fields equipped with drainage systems from 2 to 5 cm. In addition, the number of days on which groundwater table will be above the level of the drainage network will decrease. For the drainage network with spacing of 7 m, the time of the groundwater table above the level of the drainage network will decrease by 5 and 7 days in the near and far future, respectively, while for the drainage network with spacing of 14 m, it will decrease by 4 and 7 days. Climate change will also reduce sub-surface outflow. Subsurface outflows will be smaller than those currently recorded on average by 11% and 17% and 12% and 18% for 7 m and 14 m spacing drainage networks, in the near and far future, respectively. The increase in rainfall intensity in the near and far future will result in a fivefold increase in surface outflow in comparison to the present situation. The simulations show that the greatest effectiveness of CD solutions will be achieved by starting the blocking of outflow from the drainage network on the 1st of March. The implementation of CD solutions since April in the near and far future will allow maintaining the groundwater table at the level presently observed for the conventional network (free drainage-FD).

Niniejsza praca omawia istotny problem związany z klasyfikacją i właściwym zdefiniowaniem wielkości pompowni melioracyjnych. Podstawowa definicja wielkości jest bardzo szeroka, zatem ze względu na liczbę objaśniających ją parametrów wymaga precyzyjnego uściślenia. W dotychczasowych ocenach rozmiarów pompowni melioracyjnych posługiwano się na ogół wrażeniami osobistymi opartymi na subiektywnym odczuciu, które z kolei jest oparte na nieznanej liczbie parametrów. Pojawiające się przy tym trudności z określeniem przynależności obiektów do danej grupy wielkości wynikały głównie z luk informacyjnych dotyczących właściwej granicy podziału pomiędzy poszczególnymi grupami. W niniejszej pracy, do klasyfikacji i podziału pompowni według ich wielkości zastosowano takie ich parametry jak: moc nominalna pompowni P w kW, wydajność całkowita Q w m3 · s oraz zasięg oddziaływania pompowni Fp w ha, dla 270 losowo wybranych obiektów melioracyjnych w Polsce. Do rozwiązania problemu wykorzystano jedną z wielokryterialnych metod podejmowania decyzji (MCDM), opartą na mechanizmach logiki rozmytej, noszącą nazwę metody obiektów charakterystycznych (COMET).

Triangular sharp-crested weirs are commonly used to measure low-flow measurements in open channels. The flow over such a V-notch is proportional to the height of water above the weir on the upstream side. Therefore, it is relatively easy to calculate the flow from standard equations by using only recordings of water levels. Thus, these types of weirs can provide inexpensive measurements of flow volumes and resulting nutrient loads from subsurface drainage systems and associated conservation practices. The objective of this study was to develop appropriate weir equations for a 22.5° V-notch weir developed for a new tubular water level control structure in a controlled drainage system (CD). Analyses using this weir, with three typical slope angles of 30°, 45°, and 60°, were also conducted. There were no significant differences in the fitted parameters across the three analyzed slope angles. The coefficient of determination (R²) values were 0.9955, 0.9981, and 0.9980, respectively. However, the best-fitted equation for a 22.5° V-notch weir was for a slope angle of 45°. The flow equation was Q = 0.2235H^2.4182, with Q in liters per minute and H in centimeters. This equation can be used for measuring flow through tubular-controlled drainage structures.

Water meadows in river valleys are a source of very valuable forage. Due to their specificity, an appropriate approach to water management is required. This study assessed the impact of the reclamation of a traditional gravity irrigation system, aimed at saving and reducing water loss from meadows through controlled drainage. The main purpose of this study was to evaluate the investment in drainage system restoration in the context of improving the yield of fodder hay in water meadows under changing hydrometeorological conditions. The analysis was performed on the basis of meteorological and hydrological data from 30 years in the period 1989–2018. The research was conducted on the basis of two assumptions. The first concerned management of meadows without the use of subsoil irrigation based only on the amount of water supplied from rainfall. The second variant assumed deficit irrigation based on periodic water meadows with systems of ditches and drainage channels that supplied water depending on the currently available amount of water in a nearby river. The field research was performed during the crop season of 2019 and 2020. Drainage restoration investment allowed the amount of water supplied to the meadows to be increased. In the analysed period, on average, almost 30 mm of water was delivered through the ditch system. There was also an increase in hay yields of 32%. However, the investment costs, which amounted to EUR 23,382.48, were too high for this type of farm production. A positive net present value (NPV) was obtained only for 25% of cases of hydrometeorological conditions (first quartile). For the other years, the investment was not profitable.

In this paper, research on improving the economic efficiency of 38 drainage pumping stations was undertaken. Particular attention was paid to the effectiveness of activities without considering any expenditures. Energy costs for this type of machine are usually high, approximately 45% of the total maintenance cost. The main assumption of this work was the selection of appropriate energy tariffs to reduce operating costs. Liquid transport in any economy consumes significant amounts of electricity, estimated at 20–30% of the total electricity production. The optimization of the energy consumption of pumping processes is, therefore, very important. While analyzing the choice of energy tariffs, we designed profitability ratios (PR) specifically for different daily time zones. With the forecasted distribution of energy demands for different daily time zones (usually 2 or 3 zones), it was possible to compare multi-zone tariffs with 24 h tariffs. The profitability of the tariffs was decided by the value of the PR indicator. The lower, the better. In practice, this meant that the analyzed multi-zone tariffs, in most cases, are more profitable compared to single-zone tariffs. In the Polish energy system, each entrepreneur, depending on the connection power, has a right to choose a particular energy tariff from three tariff groups, i.e., high (A), medium (B), and low (C) voltage. In the case of land reclamation pumping stations, energy tariffs are usually from groups B and C. The choice of tariffs largely depends on the contracted capacity and is determined by tariff regulation. Nowadays, the current energy system forces entrepreneurs to declare a connected power load at the level corresponding to the maximum use of the production potential. Lack of knowledge of the hydrological regime, quite common for land reclamation pumping stations, usually results in overestimating the contracted capacity. When comparing the effect of changing tariffs, it was found that the profitability of this method is significant. The four-year study period (2010–2013) showed that active energy in the multi-part tariffs of groups B and C is on average 10.2% cheaper than in the single-part tariffs and varies in a wide range from 2% to 20.4%. The analysis carried out on 38 drainage pumping stations shows that for only five pumping stations could changing the current tariff be unjustified. In the other cases, the four years of analysis demonstrates that changing the current energy tariff could reduce electricity costs by approximately 5%., i.e., approximately PLN 124,000 per year (approximately EUR 27,000).