The description of the physical parameters characterizing heat transport in the soil medium, especially on a regional scale, requires long-term and high frequency observations of temperature changes in soil profiles. This paper presents a project for a multi-channel, modular and universal data logger for temperature distribution data collecting in the soil profile, based on open electronic components, such as Arduino microcontroller systems and DS18B20 thermometers. The data logger tests were carried out in two profiles. The seven-month tests did not show any errors in the functioning of the measurement set. The presented device requires an average current of 320 µA, which allows for its stable operation on one battery set for about 300 days in temperate climate conditions. The DS18B20 thermometers allow for accurate and stable temperature measurement (the mean absolute error after laboratory calibration was 0.02°C). The cost of a single measurement-registration device was approximately 76 EUR, representing a competitive price in comparison with commercial data loggers. This allows, with relatively low expenditure, the creation of extensive observation networks for the analysis of the heat flow process in high temporal and spatial resolution.
The presented studies focus on changes in groundwater levels and chemistry, and the identification of important factors influencing these changes on short- and long-term scales in urban areas. The results may be useful for rational and sustainable groundwater planning and management in cities. The studies concerned three aquifers: (1) the shallow Quaternary aquifer, (2) the deep Quaternary aquifer, and (3) the Oligocene aquifer in the capital city of Warsaw (Poland). The spatial variability of groundwater recharge was determined and its changes in time were characterized. The characteristics of groundwater levels were based on long-term monitoring series. The results indicate that urban development has caused overall reduction in infiltration recharge (from 54 to 51 mm/year), which is particularly clear in the city suburbs and in its centre, where land development has significantly densified during the last 30 years. Studies of groundwater levels indicate variable long-term trends. However, for the shallowest aquifer, the trends indicate a gradual decrease of the groundwater levels. In the case of the much deeper Oligocene aquifer, groundwater table rise is observed since the 1970s (averagely c. 20 m), which is related with excessive pumping. Based on the studied results, the groundwater chemistry in the subsurface aquifer indicates strong anthropogenic influence, which is reflected in multi-ionic hydrogeochemical types and the occurrence of chemical tracers typical of human activity. The Oligocene aquifer is characterized by a chemical composition indicating the influence of geogenic factors.
We describe a method of calculating one of the basic phenomena influenced by groundwater recharge, namely evapotranspiration (ET). The Operational Simplified Surface Energy Balance (SSEBop) algorithm was applied to calculate actual evapotranspiration (ETa), being modified to include spatiotemporal changes of substrate humidity and so referred to as mSSSEBop. Calculations were performed within the Szkwa and Rozoga River catchments (NE Poland). Quantitative ETa assessment was based on the analysis of Landsat satellite images, hydrometeorological and hydrogeological data. The results obtained for the original SSEBop algorithm and the modified mSSEBop one were compared with the water balance and data from a MOD16A2 dataset. The calculated water balance gave ETa values close to results using mSSEBop (with differences of 9-54 mm/year). In the case of the original algorithm, differences were in range of 42-218 mm/year. When compared with MOD16A2 data, the differences were within the range of -16.7 to 23.2 mm/8 days, with the mSSEBop algorithm giving on average lower ETa sums (~14%) than MOD16A2 while SSEBop gave results higher than MOD16A2 by ~12%. The studies performed indicate that the method presented, using satellite data, gives a reliable, spatial and temporal ETa assessment for the mid latitudes.
Prowadzone w sposób ciągły długoterminowe obserwacje temperatury wody ze źródła na wschodnim stoku Zameczków dostarczyły danych do oceny zmienności tego parametru w czasie. W artykule podjęto próbę interpretacji uzyskanych wyników za pomocą niestacjonarnego, numerycznego modelu transportu ciepła i mieszania wód. Wymagało to opracowania modelu konceptualnego, którego poprawność weryfikowano na podstawie oceny dopasowania obliczonej i pomierzonej temperatury wody. W wyniku tarowania modelu określono średnie wartości współczynnika przewodności cieplnej skał na poziomie 1,4 Wm–1K–1 oraz ciepła właściwego układu woda–skała na poziomie 0,92 kJkg–1K–1, przy wartościach błędu średniego i błędu średniego bezwzględnego wynoszących odpowiednio 0,08 i 0,28°C. Zgodnie z przyjętym modelem zmienność temperatury wody na wypływie można wyjaśnić kondukcją ciepła w strefie sezonowych fluktuacji oraz dopływem wód podziemnych ze strefy neutralnej. Na podstawie obliczeń modelowych udało się określić ilościowy udział wód reprezentujących różne strefy głębokościowe. Rezultaty wskazują, że 67% wód zasilających badane źródło powiązanych jest z płytką strefą krążenia, w której główną determinantą temperatury wody jest kondukcyjny strumień ciepła skierowany prostopadle do powierzchni terenu. Pozostałe 33% dopływu reprezentuje głębszy system krążenia, który można identyfikować ze strefą neutralną. W strefie tej temperatura wody zbliżona jest do średniej rocznej temperatury powietrza, a gradienty temperatury przyjmują niewielkie wartości zarówno w odniesieniu do czasu, jak i przestrzeni.
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Long-term observations of water temperature in the spring on the eastern side of the Zameczki mountain allow collecting a set of data showing variability of this parameter in time. The paper presents an interpretation of this data by a non-stationary numerical model of heat transport and water mixing. Quantitative interpretation of the results required constructing a conceptual model, whose correctness was verified on the basis of evaluation of calculated and measured water temperature. Due to the model calibration it was possible to establish the mean values of heat conductivity of the rocks at 1.4 Wm–1K–1 and the water-rock specific heat capacity at 0.92 kJkg–1K–1 with the mean error and mean absolute error at the level of 0.08 and 0.28ºC, respectively. According to this model, variability of water temperature in the spring can be explained by conductive heat transport in the zone of seasonal fluctuations and by the groundwater inflow from the neutral zone. Based on the model calculations it was possible to determine the quantitative share of waters representing different depth zones. The results indicate that 67% of water recharging the spring is linked with the shallow circulation zone, in which the main temperature determinant is the conductive heat stream directed perpendicular to the terrain surface. The remaining 33% of the inflow represents a deeper circulation system that can be identified with the neutral zone. In this zone, water temperature is close to the annual mean air temperature and the temperature gradients have small values both in space and time .
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Groundwater flow in river valley aquifer is shaped by stresses, which intensity is variable during time. In this case high accuracy of mathematical model demands calculations for transient flow. In this convention was executed model of groundwater flow for the part of the Vistula river valley (central Poland). Aquifer is built of sandily-gravelly sediments of high permeability, which thickness arrives at 40 meters. A numerical finite difference model were built using Visual Modflow software. Discretization of the space in the horizontal surface was executed by orthogonal net, divisive the area on square blocks of 10 meters side length. It were distinguished 10 layers of diverse thickness. Oscillations of surface water level and distribution of recharge were treated as the main criterion for stressperiods marking. After putting of all parameters model was calibrated. The main result of calculations is the spatiotemporal variability of the hydrokinetic state of the aquifer, what gave the base for mass balance computation.
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