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This paper represents the application of a developed water balance model (based on a model which has been prepared in Germany) to estimate the quantity of leachate output in arid and semiarid regions. Field capacity, saturated water conductivity, and waste direct evaporation tests were implemented to characterize the basic hydrologic properties of municipal waste and the effect of climate conditions on leachate production. A test cell in Aradkouh landfill with the area of 32 × 50 m2 was constructed to calibrate and compare the measured values with the results of the model. Since the cell is located in a semiarid climate, evaporation had a crucial role in decreasing the primary leachate quantity. The field capacity of the waste is obtained approximately 32.5% (V/V), which is more than the results of laboratory tests. Besides, the waste permeability of the cell was calculated (1.02 × 10−6 m/s) that is less than the results of experiments. In order to determine the effect of waste settlement in leachate production, an initial rate of settlement and ultimate settlement by using hyperbolic function has been obtained 0.104 and 146.5, respectively. Although aerobic reactions were not prevailing in the cell due to thermal conditions and incompatibility with the observed values, anaerobic reaction decreased the discharged leachate by 10.82%. [ABSTRACT FROM AUTHOR]

Stable isotopes of hydrogen and oxygen are often used for water balance calculations of lakes. We present an approach combining the lake water balance with an isotope mass balance to constrain the sources and sinks of the water of a small dimictic lake subjected to eutrophication. Meteorological and hydraulic data in combination with measured isotope signatures of the different water compartments enabled to assess the degree of surface water/groundwater interaction and the amount of overland flow into the lake. Groundwater could be excluded as a lake water source, as its water level was always below the lake water level. In the absence of a channelled inflow, precipitation and overland flow were the remaining options, whereby the latter was only active during periods of exceptionally high rainfall. While the groundwater signatures adjacent to the lake showed an influence of lake water, the lake water balance itself indicated that the associated volumetric water loss to groundwater is rather negligible. In the present case, only a combined assessment of hydrological and isotopic data allowed for an accurate characterization of the studied lake and a quantification of its water sources and sinks, highlighting the importance of using more than one methodological approach for such a purpose. [ABSTRACT FROM PUBLISHER]

This study was focused on modeling soil water, carbon (C), and nitrogen (N) dynamics in soil and crop emphasizing uncertainties in model parameterization and the evaluation of potential water stress for silage maize cultivations on a drained field. The CoupModel was applied on different management systems for silage maize ( Zea mays ) in monoculture and undersown with grass ( Lolium perenne L.) on a sandy-humic soil. Four different fertilization levels with 0, 150 kg of mineral-N, 40 m 3 of cattle slurry (72–148 kg N ha −1 year −1 ), and combined slurry/mineral-N (222–298 kg N ha −1 year −1 ) were simulated over five years. Results were based on most plausible parameter combinations regarding simulated biomass obtained from 10,000 runs by the Generalized Likelihood Uncertainty Estimation (GLUE) approach. The uncertainty in model parameterization was reduced significantly by limiting the number of simulations for each treatment sequentially resulting in quartile coefficients of variation ( CV *) < 25% for 26% and 36% of selected input parameters in bi-cropping and monoculture systems, respectively. Average soil temperatures in upper soil depths, the groundwater level, water potentials, and water contents between 10 and 80 cm of depth were reproduced plausibly with the model as well as plant C and N contents. The CV * values of evapotranspiration and total runoff ranged between 0 and 26% and 8–21%, respectively, on half-yearly basis. Significant differences between the cropping systems were found, even though the soil water balance was positive for all systems, and the potential water stress was only minor in bi-cropping systems. [ABSTRACT FROM AUTHOR]

At the end of waste disposal in 2005, a temporary mineral system was constructed to cover the waste body of the municipal landfill in Rastorf (N Germany). The aim of this study was to evaluate the effectiveness of this temporary cover system in limiting the infiltration of surface water into the waste body. The numerical modeling for the hydrological year 2012 was performed in FEFLOW 6.0. The required input data for modeling were achieved by laboratory measurements of the saturated hydraulic conductivity and the water retention characteristics of the mineral layers. The assumed initial and boundary conditions were based on in-situ measurements of matrix potential and volumetric water content at three different measuring points by tensiometers, FDR sensors and observed meteorological conditions. The model was applied according to Darcy's and Richards' equations for variably saturated flow. Our results allowed assessing the components of water balance for a temporary cover system, especially water seepage into the waste body. The correlation between the measured and modeled volumetric soil water content in the layered temporary cover system was observed ( R2 = 0.56 to 0.90). Deviations between the measured and modeled values are superficially related to the soil´s heterogeneity. In conclusion, the measured and modeled water balance parameters indicate that the temporary coverage system remains effective in limiting the infiltration rate. However, our studies revealed that the calculated and measured water seepage exceeded the values allowable by the German regulations. Additional studies have to assess variations in the soil water characteristics caused by weather-related wetting and drying cycles and influence of waste settlement changing the profile of slope. [ABSTRACT FROM AUTHOR]

A comprehensive study was conducted to examine the performance and possible changes in the effectiveness of landfill surface covers. Three different profiles of mineral landfill caps were examined. The results of precipitation and flow measurements show distinct seasonal differences which are typical for middle-European climatic conditions. In the case of the simple landfill cap design consisting of a thick layer of loamy sand, approximately 100—200 L m-2 of annual seepage into the landfill body occurs during winter season. The three-layer systems of the two other test fields performed much better. Most of the water which percolated through the top soil profile drained sideways in the drainage layer. Only 1—3% of precipitation percolated through the sealing layer. The long-term effectiveness of the mineral sealing layer depended on the ability of the top soil layer to protect it from critical loss of soil water/critical increase of suction. In dry summers there was even a loss in soil water content at the base of the 2.0 m thick soil cover. The results of this study demonstrate the importance of the long-term aspect when assessing the effectiveness of landfill covers: The hydraulic conductivity at the time of construction gives only an initial (minimum) value. The hydraulic conductivity of the compacted clay layer or of the geosynthetic clay liner may increase substantially, if there is no long-lasting protection against desiccation (by a thick soil cover or by a geomembrane). This has to be taken into account in landfill cover design. [ABSTRACT FROM AUTHOR]

The water balances and the long-term performance of different landfill cover systems have been measured in situ in large-scale lysimeters on the landfill Hamburg-Georgswerder, Germany since 1988. The cover systems including different barrier components for water transport were constructed with state-of-the-art technology and have been excavated at several occasions especially to inspect the structure of the barriers. For the first time, the irreversible impact of crack formation in cohesive soil barriers and geosynthetic clay barriers due to desiccation, shrinkage, ion exchange, and plant root penetration has been observed and quantified in this study. After four years of good performance, these covers began to leak between 90 and 200 mm/year (average precipitation of 860 mm/year). The hydraulic conductivity of the cohesive soil barriers increased from 2×10-10 to 9×10-8 m/s, the daily peaks of the leakage through the geosynthetic clay barriers from initial values around 2×10-11 to 2×10-7 m3/(m2 s). The composite barriers with geomembranes above cohesive soil barriers performed very well, showing no leakage and only very little thermally induced water transport. A capillary barrier also performed well (average annual leakage of 18 mm/year). The data of the past 10 years prove that evapotranspiration can be increased significantly by planting bushes, which also limits the potential leakage through barrier layers. [ABSTRACT FROM AUTHOR]

Summary: Land use is a key factor controlling the hydrological behaviour of catchments. Changing land use therefore can have an important influence on the local hydrological cycle. Validated and process-based hydrological models are suitable tools to quantify the impact of a change in land use on the hydrological processes. In this study, the physically based catchment model WaSiM-ETH (Water Balance Simulation Model) was applied to a mesoscale lowland catchment in northern Germany (Hunte river, 2141km2 at gauge Oldenburg). Model calibration and validation showed that WaSiM-ETH well represented the discharge of the main Hunte river while the discharge dynamics of a few lowland tributaries whose catchments are characterised by peaty soils and intense artificial drainage could not be represented. The purpose of this study was twofold; on the one hand to analyse the sensitivity of WaSiM-ETH to changes in land use observed in the decade 1990–2000, and on the other hand to quantify the impact of land use change projected for the future in terms of land use scenarios available to the public. The results showed that WaSiM-ETH is hardly sensitive to the slight changes observed in the last decade of the 20th century. By contrast, water flows simulated by WaSiM-ETH are clearly impacted by agricultural land use scenarios which were developed based on IPCC scenarios. However, the results also show that it is not sufficient to focus on agricultural land use, only. The proposed reduction of agricultural land leaves open the final land cover after land use change, e.g., forest or urban areas. This study demonstrated that WaSiM-ETH was more sensitive to the choice of the final land cover than to the difference in the scenarios (e.g., A1F1 versus B1). Therefore, we recommend to precisely define change in agricultural land use as well as the final land cover in order to estimate the realistic impact of land use change on hydrological behaviour. [Copyright &y& Elsevier]

The article presents a study on the water balance of Mining Lake Plessa 117 in Lusatia, Germany, using stable isotopes. It states that the application of stable isotopes was possible since the water exchange in the catchment area had obtained steady-state conditions after the abandonment of mining activities in 1968 and the filling of the voids and aquifers by re-rising groundwater in the years thereafter. It discusses that diverging slopes of the Evaporation Line and the Global Meteoric Water Line demonstrated as evaporation from the late catchment area.

A method is presented to assess lake water-groundwater interactions by modelling isotope signatures of lake water using meteorological parameters and field data. The modelling of δ18O and δD variations offers information about the groundwater influx into a meromictic Lusatian mining lake. Therefore, a water balance model is combined with an isotope water balance model to estimate analogies between simulated and measured isotope signatures within the lake water body. The model is operated with different evaporation rates to predict δ18O and δD values in a lake that is only controlled by weather conditions with neither groundwater inflow nor outflow. Comparisons between modelled and measured isotope values show whether the lake is fed by the groundwater or not. Furthermore, our investigations show that an adaptation of the Craig and Gordon model [H. Craig, L.I. Gordon. Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, E. Tongiorgi (Ed.), pp. 9-130, Consiglio Nazionale delle Ricerche, Laboratorio di Geologia Nucleare, Pisa (1965).] to specific conditions in temperate regions seems necessary. [ABSTRACT FROM AUTHOR]

Abstract: This study presents the modelling approach and impact assessment of different strategies for managing wetland water resources and groundwater dynamics of landscapes which are characterised by the hydrological interactions of floodplains and the adjacent lowlands. The assessment of such impacts is based on the analysis of simulation results of complex scenarios of land-use changes and changes of the density of the drainage-network. The method has been applied to the 198km2 Lower Havel River catchment as a typical example of a lowland–floodplain landscape. The model used consists of a coupled soil water and groundwater model, where the latter one is additionally coupled to the surface channel network. Thus, the hydrological processes of the variable saturated soil zone as well as lateral groundwater flow and the interactions between surface water and groundwater are simulated in an integrated manner. The model was validated for several years of significantly different meteorological conditions. The comparison of lateral and vertical water balance components showed the dominance of lateral flow processes and the importance of the interactions between surface water and groundwater for the overall water balance and the hydrological state of that type of landscape. The simulation of land-use change scenarios showed only minor effects of land-use change on the water balance and groundwater recharge. Changes of groundwater recharge were particularly small within the wetland areas being part of the floodplain where interactions between surface water and groundwater are most pronounced. Alterations in vertical groundwater recharge were counter-balanced by the lateral interaction between groundwater and surface water. More significant deviations in groundwater recharge and storage were observed in the more peripheral areas towards the catchment boundaries which are characterised by greater groundwater distance from the surface and less intense of ground water–surface water interactions. However, the simulation results assuming a coarsening of the drainage network density showed the importance of drainage structure and geometry for the water balance: The removal of the artificial draining ditches in the floodplain would result in significant alterations of total groundwater recharge, i.e., less recharge from winter to early summer and an increase of groundwater recharge during summer and autumn. Furthermore the different effects of groundwater recharge alterations on the dynamics of groundwater stages within the wetland areas close to the floodplains compared to the more peripheral areas could be quantified. Finally, it will be discussed that a well-adjusted co-ordination of different management measures is required to reach a sustainable water resources management of such lowland–floodplain landscapes. [Copyright &y& Elsevier]

Abstract: Stand level O3 fluxes were calculated using water balance calculations for 21 Common beech (Fagus sylvatica L.) stands and O3 data from 20 monitoring stations in Southern Germany. For this intention, the daily loss of water by evapotranspiration per stand area was set against the daily O3 uptake. During the last 30 years, O3 uptake ranges between 0 and 187 mmol ha-1 d-1 per stand area. Cumulative O3 uptake (CUO3), ranging between 0.1 and 0.7 mmol m-2 yr-1 per stand area, shows increasing trends since 1971 with considerably greater values at high altitudes. Effects in radial growth were used to derive an initial approximate critical threshold value for O3 impacts on the vitality and growth of mature beech stands in Southern Germany. It is concluded that this concept of O3 flux estimation in combination with dendroecological analyses offers both a site specific and regional applicable approach to derive new critical levels for O3. [Copyright &y& Elsevier]

Simulation models can be efficient tools for several tasks especially in planning. In the USA, the HELP model was developed to simulate the water balance of landfill liner systems, especially of cover systems. HELP version 3 was examined in a German climate in an extensive validation study, and a German adaptation was developed. The validation study consists of three parts: a methodological part (meaning, aims and procedure of validation), a theoretical part (comparison of the modelling approach with the state of science, comparison of documentation, literature and source code), and a practical part (sensitivity analyses and operational validation). In the operational validation, measured and simulated discharges and actual evapotranspiration data of test fields on the landfill Hamburg-Georgswerder from 1988 to 1995 were compared. Limitations, weak points, and errors of the HELP model are shown. The HELP model is a suitable tool for experts in hydrology; but good knowledge of the model and its behaviour and critical review of the simulation results are essential. [ABSTRACT FROM AUTHOR]

The water balance and effectiveness of a landfill cover containing a liner from fine-grained dredged material ('METHA-material') and a drainage layer from sandy dredged material ('METHA-sand') from the Port of Hamburg (Northern Germany) was investigated for 20 years using two test fields (lysimeters), each 500 m 2 in size. The layering within the standard design test field (FS) is identical to the layering of the cover on the landfill, whereas the alternative design test field (FA) was designed to provoke desiccation of the liner. The setup abstained from continuous side walls cutting through the liners in order to allow for material properties representative for the landfill cover, at the cost of possible minor lateral inflows or outflows, which were, however, considered negligible. By example of the lysimeter FA the risk of desiccation-induced failure of a liner from METHA-material under the given climate could be shown. In contrast, the discharges and hydro-chemical parameters measured for the lysimeter FS indicate continuous high efficiency of the liner until today. The average discharge below the liner was 14.9 mm/yr. The entire cover contributes to the good liner performance. Reason are (1) the low hydraulic conductivity of the liner (5 × 10 -10 m/s) and its large thickness (1.5 m); (2) the increased stresses on the liner due to the 2.5 m thick overlaying cover; (3) the 1.0 m thick drainage layer from slowly-draining METHA-sand, allowing for a continuous nearly water-saturated fringe above the liner; and (4) the sufficient amount of plant available water in the recultivation layer., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A large number of environmental management decisions such as the remediation of a mine site require the best possible knowledge of the water balance of the site or the catchment area. For precipitation a large number of observations exists and usually some data are availablewhich are more or less representative for the precipitation conditions in the catchment. However, to close the water balance knowledge about evaporation is also required. This is usually not available from observations. Also bulk formulas cannot be used to reconstruct evaporation for a sufficiently long time, since observations of the input variables are limited as well. In this article an approach is presented showing how local potential evaporation may be reconstructed from other local and non-local atmospheric variables for which long-term observations are available. The method is demonstrated for the planned artificial lakes in the closed down mine sites in the Geiseltal (Germany) and aims at the estimation of the probability distribution of the difference between precipitation and evaporation for the surface water balance. [ABSTRACT FROM AUTHOR]