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A comparison of water flux measurements: Passive wick-samplers versus drainage lysimeters
Abstract
Quantification of soil water flow is a prerequisite to accurate prediction of solute transfer within the unsaturated zone. The monitoring of these fluxes is challenging because the results are required to answer both scientific and practical questions regarding protection of groundwater, sustainable management of agricultural, forestry, mining or set-aside industrial areas, reducing leachate loss from landfills or explaining the fate of environmentally harmful substances. Both indirect and direct methods exist for estimating water-flux rates and have been used with varying success. In Europe, the use of direct lysimetry methods for measuring water and solute fluxes in soils has increased in recent years. This technique ensures reliable drainage data, but requires relatively large investment and maintenance expenses. Other research groups, especially in the USA, have developed alternative techniques. In this paper we compare the functioning of a passive-wick sampler, especially the deep-drainage meter type (DDM), with two different types of drainage lysimeters (weighing and non-weighing) under field conditions in Germany for the measurement period from May 2004 until April 2009. The study showed that under sandy soil conditions no significant differences occurred between the measurements from DDM and both drainage lysimeter types. Only in periods with increased precipitation was there a tendency of drainage over-estimation by the DDM in comparison with the lysimeters tested. For longer periods, no significant differences in the amount of drainage or the pattern of drainage formation were found between weighing and non-weighing gravitation lysimeters. The practical use of DDMs is restricted because the groundwater level must be >2 m from the soil surface. Suggestions are made for the technical improvement of the DDM as well as the testing of the device with more cohesive soils.
... These meters are simple to operate and are a useful tool for measuring drainage and solutes (Gee et al. 2009;Norris et al. 2023). Meissner et al. (2010) evaluated drainage differences between DFMs and lysimeters, and identified that further research was required to evaluate the role of DFMs in measurements of water quality and drainage in less free draining soils. Very few published studies have evaluated nutrient losses using DFMs (Norris et al. 2023). ...
... They reported it was more challenging to repack soil to replicate natural flow conditions in the heavy-textured soils, concluding the use of DFMs on clay loams is less appropriate than on freer draining soils. Similarly, Meissner et al. (2010) reported that DFMs work well in sandy soils, while other studies also reported high variability in drainage with DFMs and wickbased samplers (Zhu et al. 2002;Gee et al. 2009;Herath et al. 2014), requiring sufficient samplers to account for variability. ...
... We agree with Norris et al. (2023) that if DFMs become more widely available, that technical skill is needed to interpret the data. Several suggested improvements to DFMs have been reported, including the use of a one-way valve system to prevent backflow from temporary high water tables and reducing the constructed depth of the DFM (Meissner et al. 2010). From our experience, several potential improvements could be made to the DFMs including automating some components with digital recording and interfaces, providing compartments for multiple samples, and use of emerging sensor technology for water quality. ...
Context
Agricultural land use is intensifying globally. Irrigation and other farm practices associated with intensification, such as cultivation, grazing, and fertiliser application, can increase nutrient losses. Variable rate irrigation (VRI) systems manage irrigation to spatially variable soils and different crops (zones). We lack knowledge on nutrient losses under zone-specific irrigation for mixed-cropping systems (combined crop and livestock grazing).
Aims
This study evaluated drainage, nitrogen, and phosphorus leaching losses under zone-specific irrigation for a temperate mixed-cropping system.
Methods
The study site had sheep grazing and crops including peas, beans, wheat, turnips, plantain, and ryegrass-white clover pasture. It had a variable-rate centre-pivot irrigator for two soil zones (free draining Zone 1; poorly drained Zone 2). Drainage flux meters (DFMs) collected drainage leachate, and samples for measurement of nitrogen (N) and phosphorus (P) concentrations. Soil water balance data and statistical modelling evaluated nutrient leaching losses over 5 years.
Key results
The mean leaching load of NOx-N (nitrate + nitrite) across 5 years was 133 (s.d. 77) and 121 (s.d. 97) kg N/ha/year for Zone 1 and Zone 2, respectively. Similarly, the mean leaching load of reactive P across all years was 0.17 (s.d. 0.30) and 0.14 (s.d. 0.14) kg P/ha/year for Zone 1 and Zone 2, respectively. The nitrogen concentrations and loads generally had greater uncertainty in Zone 2.
Conclusions
The DFMs worked well for the free draining sandy soil. However, fewer samples were collected in the silt soil, requiring the statistical modelling developed in this study. This study gave a reasonable estimate of annual leaching load means, but the indicators of their within-year variation were not reliable, partly due to differences in sampling frequency. With some exceptions, there was generally more NOx-N leaching from the free draining Zone 1. VRI provided a system to control irrigation-related drainage and leaching in these soil zones.
Implications
Drainage flux meters are more reliable in well-drained than in poorly drained soil. Given the lack of published studies, this study has improved knowledge of nutrient losses under zone-specific irrigated mixed-cropping systems in a temperate climate.
... For studies on the effects caused by climatic changes, long-term measurement series under comparable boundary conditions are required. Lysimeter are especially suited to investigate water and solute fluxes in soils [47,[53][54][55][56][57]. They enable us to investigate the effects of a changed climate based on long-term measurement series [54,[58][59][60]. ...
... They were constructed in the form of a sheet steel vessel with a quadratic surface area of 1 m 2 and a total depth of 1.25 m. A drainage pipe (inner diameter 63 mm) was installed inside the filter layer (25 cm thick filter layer-sand over gravel over stone gravel) to collect the seepage and to discharge it into a storage tank located at the lysimeter cellar [53,63]. The lysimeter vessels were filled with soil material from an agricultural site located 15 km to the west in 1981. ...
... The soil type of the topsoil (0-30 cm) and subsoil (31-100 cm) was characterized as loamy sand (LS). During manual filling of the lysimeters, special emphasis was placed on restoring the soil structure of the extraction site within the lysimeter [53]. In the course of previous coupled investigations in lysimeters and in small catchment areas it could be shown that, despite the design deficiencies of the NWLYS type used here with regard to seepage formation and capillary rise, reliable results can be obtained with regard to the water and solute balance of sandy soils studied [53,63]. ...
As a result of global climate change, heavy rainfall events and dry periods are increasingly occurring in Germany, with consequences for the water and solute balance of soils to be expected. The effects of climate change on nitrogen and carbon leaching were investigated using 21 non-weighable manually filled lysimeters of the UFZ lysimeter facility Falkenberg, which have been managed since 1991 according to the principles of the best management practices and organic farming. Based on a 29-year dataset (precipitation, evaporation, leachate, nitrate and dissolved organic carbon concentrations), the lysimeter years 1995/96, 2018/19, and 2003/04 were identified as extremely dry years. Under the climatic conditions in northeastern Germany, seepage fluxes were disrupted in these dry years. The reoccurrence of seepage was associated with exceptionally high nitrogen concentrations and leaching losses, which exceeded the current drinking water limits by many times and may result in a significant risk to water quality. In contrast, increased DOC leaching losses occurred primarily as a result of increased seepage fluxes.
... Measuring these fluxes is a challenge because the results are required not only for scientific but also practical questions regarding the impact of climate change on water resources, the sustainable management of agricultural, forestry, mining or set aside industrials areas, the reduction of leachate loss from landfills, and for explaining the fate of environmental harmful substances (Meissner et al., 2010a). A suite of methods for measuring water and solute flux in and below the root zone have been developed and critically reviewed (Meissner et al., 2010b;Fuehr et al., 1998;Gee and Hillel, 1988). However, until now, there is no standard method available for measuring soil-water flux (Gee et al., 2009). ...
... However, the construction and maintenance of large drainage lysimeters (especially the weighing type) is expensive. To tackle this problem, new lysimeter techniques have been developed during the last years (Hertel and von Unold, 2014;Meissner et al., 2010b). ...
... Afterward starts the design of the lower boundary conditions, it means free drainage or suction-controlled drainage. The advantages and disadvantages of both methods are discussed in the literature and are not the topic of this paper (Bednorz, 2017;Groh et al., 2016;Meissner et al., 2010b;Peters and Durner, 2009;Abdou and Flury, 2004). If the free drainage is preferred, the lower 15À20 cm of soil in the monolith is removed and replaced with a graded filter layer made of quartz sand and gravel (0.1À0.5, 0.71À1.25, ...
A lysimeter is a device to collect drainage water for mass and solute balances and fills the gap between laboratory and field-scale studies. There is a tendency in the international literature that this measuring technique is increasingly used to investigate the effects of climate change on land and water resources. These studies include simple nonweighable lysimeters as well as highly sophisticated weighable lysimeters. The objective of the paper is to demonstrate different lysimeter types and how they can be used to investigate the effects of climate change. On the basis of case studies, the determination of soil water balance parameters such as precipitation, actual evapotranspiration, soil moisture, and the leaching behavior of the environmental relevant nutrient phosphorus will be explained and evaluated regarding sustainable soil management strategies under the conditions of climate change.
... Their drainage flux and therefore their lower boundary has to proceed as in the natural soil, whereas the effect of the lower boundary got discussed controversially in literature. On the one hand, suction controlled devices got emphasized to work better than free draining lysimeters (Vereecken and Dust, 1998;Zhu et al., 2002;Gee et al., 2009;Peters and Durner, 2009;Barkle et al., 2014) and on the other hand studies by Meissner et al. (2010) yielded that there are no significant differences between both types for longer observation periods. Each of these effects or a combination of these problems could lead to deviations between the water regime of the lysimeter and the investigated field (Hagenau et al., 2015). ...
... Climatically, the testing site got assigned to the temperate zone of Central Europe within the transition zone from maritime to continental climate [average annual precipitation: 524.5 mm (1968Falkenberg); annual mean temperature: 9.2°C (1994Falkenberg)]. The design of the three investigated NWGL according to Meissner et al. (2010) is illustrated in Fig. 2. ...
... Above the drain pipe and the filter layer, the lysimeters were filled disturbed, but horizon-wise separated in 1983 (topsoil: 0-30 cm; subsoil: 31-100 cm) with soil substrates from the local region Bretsch (Fig. 1), 5 km in the east of Lü ckstedt (Meissner et al., 2010). Analyzed soil physical properties were taken from Godlinski (2005) (Table 1). ...
The transfer of lysimeter-based water balances to field scale is still a challenge, whereby the reliability of measured data from non-weighable gravitation lysimeters (NWGL) is more questioned than the transferability of data from more modern lysimeter devices. The hypothesis of this study was to predict the water regime of a drained arable field (81 ha) based on measurement results of three neighboring (distance of 20 km northern Altmark region Saxony-Anhalt, Germany) NWGL (surface area of 1 m2, depth of 1.25 m) for three hydrological years (HY) from 11/1/2012 to 10/31/2015. For the first two HY, manually collected monthly outflow rates from the NWGL were comparable to registered (data logger) drain rates of the field. But NWGL outflow was underestimated as compared to field drainage in the third HY. This deficit in the lysimeter water balance was caused by heavy rain events in summer 2014 in combination with wind and interception by the crop canopy (Zea maize). Precipitation did not match the NWGL surface whereas this canopy effect did not play a role at the field site. Thus, further numerical simulations of the soil water flow with the HYDRUS 1D/2D-software package, which were based only on input data determined at the NWGL (stand precipitation, potential evaporation/ transpiration) without taking into account the canopy effect, described registered outflow of the field adequately for the whole observation period. But determining precipitation matching the NWGL surface, which was not registered due to the missing weighing mechanism, is absolutely required to interpret deviating measured outflow rates.
... The most accurate means of quantifying nitrate losses is to capture drainage from below the crop rootzone, and one way to achieve this is through the use of drainage fluxmeters (DFMs). These devices collect soil water by applying a 'passive' suction maintained by an inert wicking material such as fibre glass (Ben-Gal & Shani 2002;Gee et al. 2002;Meissner et al. 2010). When this material is 'wet up', a hanging water column is created which maintains the lower soil boundary of the device at a pressure less than atmospheric (Gee et al. 2009). ...
... This pressure-head replicates the capillary forces in the ambient soil. While DFMs lack the ability to actively control tension compared with devices such as tension lysimeters (Singh et al. 2018), the units are much simpler to operate and have been shown to be an appropriate tool to mimic the soil's capillary conditions for quantifying water and solute fluxes (van der Velde et al. 2005;Green et al. 2006;Gee et al. 2009;Meissner et al. 2010). They also have the benefit of being smaller, simpler in design, and passive; that is they collect drainage without the need for an external application of tension. ...
Commercial cropping farms in New Zealand (NZ) showed highly variable rates of nitrate-N leaching losses (13–148 kg/ha/year) across sites, cropping systems and seasons. Losses were measured at 1.2 m below the soil surface using a network passive-wick drainage fluxmeters (DFMs) which were installed across nine commercial farms between August 2014 and June 2016. Sites were located in the Canterbury, Manawatu, Hawke’s Bay, Waikato and Auckland regions and monitored for a period 51 to 72 months. Twelve DFMs were installed at each site and drainage volumes were validated using an established soil water balance model. At seven sites, losses were calculated using measured drainage and measured concentrations, and at two sites losses were calculated using modelled drainage and measured concentrations. Nitrate-N was the predominant form of inorganic N (96.7–99.9%) in drainage water and annual losses averaged 52 kg/ha/yr for mixed cropping systems with livestock grazing (n = 6) and 101 kg/ha/yr for mixed cropping systems with a focus on vegetable production (n = 3). While not broadly representative of all NZ cropping land uses, results from this study do, nevertheless, suggest that when drainage occurs, nitrate losses may be considerable under the land uses represented here (> 70 kg/ha/y).
... After the installation at the lysimeter station, a 25-cm-thick filter layer (sand over gravel over stone gravel) was placed at the bottom of the vessels. A PVC-drainage pipe (inner diameter 63 mm) was installed inside the filter layer to collect the seepage and to discharge it into a storage tank located at the lysimeter cellar (Meissner et al. 2010). In the year 1981, all lysimeters were filled manually with disturbed soil material from four different agricultural sites in eastern Germany, representing sand (S), loamy sand (LS), loam (L) or silty loam (Si) both in topsoils and subsoils (Table 1) of the Elbe river catchment (Godlinski et al. 2004). ...
... The layers were compacted manually to obtain a bulk density as in the field site. After this filling procedure, the lysimeters were irrigated to accelerate the setting process (approximately 100 mm irrigation water per year; Meissner et al. 2010). Saturated hydraulic conductivity (K S ) measured in 1981 (before filling into the lysimeters) varied only slightly more than a 10-potency among the different soil texture types. ...
This study aimed to demonstrate the impact of phosphorus (P) mineral fertilization on topsoil P content and P leaching. We evaluated 83 datasets from 25 years from lysimeter experiments involving different cropping systems (winter crop, summer crop and autumn tillage, harvested grass) or unfertilized fallow, four types of soil texture, and three levels of applied mineral P fertilizer. A positive monotonic and significant correlation was indicated between P in the topsoil determined by the double lactate method (PDL) and the yearly flow-weight total (TP) concentrations in leachates with Spearman rank correlations rs (rs > 0.183) and probability (p) < 0.05. The present German recommended rates of P mineral fertilization are proposed insufficient to protect fresh and marine waters from undesired P pollution and eutrophication. A long-term reduction of excess soil P is urgent along with other measures to mitigate high P inputs to surface and ground waters.
... The inputs used to measure water balance are irrigation, precipitation and capillary rise from groundwater. Evaporation, transpiration, drainage and surface runoff are the outputs (Blume et al., 2010a(Blume et al., , 2010bMeissner et al., 2010). ...
... Lysimeters must be deep enough to promote root development (Hagenau et al., 2015;Meissner et al., 2010), with a minimum area of 2 m 2 to account for soil variability (Aboukhaled et al., 1982). Moreover, crop population, height, irrigation and fertilization should be similar between lysimeters and the surrounding area (Gebler et al., 2015). ...
Water balance is an important tool to evaluate water deficit or excess in crop systems. However, few studies have evaluated the water balance of vegetation grown on the residues from potash mining because the high sodium chloride levels of the residues hinder agricultural development. Therefore, this study aims to measure the water balance components in eight non-weighing lysimeters installed on a potash tailings pile in Heringen (Werra), Germany. These lysimeters were filled with different mixtures of household waste incineration slags and coal combustion residues, resulting in 4 different substrates with two repetitions. Manual seeding was performed using 65% perennial ryegrass (Lolium perenne L.), 25% red fescue (Festuca rubra L.) and 10% Kentucky bluegrass (Poa pratensis L.). Environmental conditions were monitored using an automatic weather station; ground-level and 1-m-high rain gauges. Precipitation and drainage were recorded weekly following the initial saturation of the lysimeters. Water balance components were determined for two hydrological years based on the expression: ET (mm)?=?P - D, where ET?=?evapotranspiration, P?=?precipitation and D?=?drainage. In addition, evapotranspiration was studied using the standard FAO Penman-Monteith equation and Haude's method. The lysimeter water balance measured in 2014 revealed an actual evapotranspiration rate of 66.4% for substrate 1, 66.9% for substrate 2, 65.1% for substrate 3 and 64.1% for substrate 4. In 2015, evapotranspiration ranged from 65.7% for substrate 4 to 70.2% for substrate 1. We observed that the FAO Penman-Monteith and Haude's evapotranspiration models generally overestimated the water use of the green coverage by 67% and 23%, respectively. Our study suggests that an evapotranspiration cover for potash tailings piles may decrease brine drainage from these piles and reduce soil and water contamination.
... The lysimeters are square in shape and 1 m 2 in size, with a depth of 1.25 m. The soil is from former agricultural land from the local region (Germany, federal state Saxony-Anhalt, 52.50 N, 11.39 O; 37 m above sea level), situated approximately 12 km southwest of the lysimeter station (Meissner et al., 2010). The proportions of sand, silt and clay in the topsoil are 73.6%, ...
... They can be used to simulate small-scale effects of processes and transfer these to larger scales, enabling an objective and comparative assessment (Müller, 2015). Due to the close geographical proximity of all three of the experimental sites, the entire area under investigation is located in the continentally influenced climate area of the temperate zone, with a long-term precipitation level of 540 mm and maximum precipitation falling in June and July (Meissner et al., 2010) and a long-term average temperature of 8.5 C (longterm mean from 1961 to 1990). Changes in air temperature and precipitation levels during the study are shown inFig. ...
Greenhouse gases (GHG) cause damage to the biosphere and atmosphere, and essentially lead to a reduction in fertilization efficiency. Different slurry application techniques can influence the emission of GHG. In the years 2014 and 2015, two parallel trials (sites: Lückstedt and Kossebau) and one lysimeter trial (site: Falkenberg) were set up in Central Germany (federal state: Saxony-Anhalt) in order to investigate the influence of the slurry strip-till method on ammonia (NH3) and nitrous oxide (N2O) emissions when compared to surface slurry incorporation. The effect of the nitrification inhibitor (NI) (PIADIN®) on GHG emissions was also examined. NH3 was measured using a combination of passive samplers and the Dräger Tube method (DTM). N2O was measured using the closed chamber method (CCM) both in the maize row and in the interrow space. In the two years of the experiment, NH3volatilization fluctuated between 0.6 and 3.5 kg NH3-N ha⁻¹. In 2014, the slurry strip-till treatments in Lückstedt emitted significantly less NH3 than surface slurry incorporation. In 2015, at the Kossebau site NH3 volatilization was significantly lower in the treatments with NI than those with no NI. In both years, N2O emissions were between 0.5 kg and 2 kg N2O-N ha⁻¹.
... For the recent study lysimeter 30 (Lys 30, not fertilized) and lysimeter 117 (Lys 117, fertilized) were used. The lysimeters were filled with soil substrate from a former agricultural field plot [33]. The material was separately taken as surface (0-30 cm) soil and subsurface (31-100 cm) soil, separately homogenized and filled in 10 cm layers in the lysimeters [33]. ...
... The lysimeters were filled with soil substrate from a former agricultural field plot [33]. The material was separately taken as surface (0-30 cm) soil and subsurface (31-100 cm) soil, separately homogenized and filled in 10 cm layers in the lysimeters [33]. From 1983 to 1990 they were used for investigations considering crop yield maximization. ...
This study aims on identifying growth site and plant part specific element patterns in sunflower (Helianthus annuus).
Sunflowers (H. annuus) were planted in small-scaled plots under field conditions on a metal-contaminated and a non-contaminated site over a vegetation period of 170 days. Nitric acid soluble contents of Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, S, Th, U, and Zn were determined in roots, stems, leaves, and heads of sunflowers harvested in regular time intervals during the vegetation period. Bioavailable and total contents of the mentioned elements were determined in the corresponding soil taken at the day of sowing and after the last harvest.
At first, hierarchical agglomerative cluster analysis was used to investigate the similarities and differences between elements in sunflower parts based on 16 elements and 78 samples. Thereby two clusters were formed, containing separated from each other the sunflower samples from the contaminated and the non-contaminated site. Therein several smaller sub-clusters were found, containing the single plant parts: roots, stems, leaves, and heads.
Forward stepwise linear discriminant analysis was used to verify the clusters of plant parts and to identify the elements which show the highest discriminating power in the data with respect to the sunflower parts and the plots on which the sunflowers were grown. A linear discriminant model based on Mn, Ca, Fe, Ni, U, and Zn out of the 16 measured elements allowed distinguishing between the tissue types from the contaminated and non-contaminated site (correct classification of 91.7%). By plotting the autoscaled data of these most discriminating elements the plant part and site specific element patterns could be displayed. Furthermore an explanation is given how the bioavailability of elements in soil and plant physiology influence these element patterns.
... Ceramic suction cup lysimeters are efficient under stable soil moisture conditions, but the obtained data can be affected by soil heterogeneity [15]. Pan lysimeters may suffer from dispersal flow issues in the upper soil that reduce data collection efficiency [16], whereas the associated resin bags are effective for solute absorption (e.g., NO 3 À ) from the soil solution but cannot continuously monitor mineral N concentrations [17]. ...
... The inclusion of the wick allows the device to capture more drainage than pan lysimeters, with the intent of making these passive-wick lysimeters more accurate in quantifying deep soil drainage [24]. When compared to other lysimeter types, studies show that passive-wick lysimeters record greater drainage during high-precipitation events [25]. ...
A growing human population requires sustainable solutions to regulate and dispose of municipal wastewater. Water treatment facilities in northern Idaho are permitted to apply reclaimed wastewater to forest land during the growing season at specified monthly hydraulic loading rates. We assessed the spatial and temporal variability of drainage below the rooting zone between non-irrigated (control) and irrigated (effluent) stands during the growing and dormant seasons in 2021. No drainage was observed during the two months of annual seasonal drought, but large magnitudes of drainage were recorded during the dormant season (38–94 cm), which was consistent with seasonal precipitation. The overall effect of effluent treatment on the drain gauge measurements did not differ from the controls, as effluent only increased the drainage at some facilities. The measured drainage averaged from 35 to 62 cm among facilities. We then used the drainage measurements to calibrate hydrological models (Hydrus-1D and Water Erosion Prediction Project [WEPP]) and predict the drainage in 50 measurement plots distributed evenly among five forest water reclamation facilities. As with the observed drainage, there were no statistically significant growing season differences in the predicted monthly drainage during the growing season between the effluent and control plots, suggesting the successful use of hydrologic models to support the measured drainage findings. While both models struggled to accurately predict the quantity of drainage during the dormant season, they both successfully predicted that drainage would continue through May. WEPP also successfully predicted that the treated plots began to drain in September and October following late-season irrigation at some facilities. The models showed that the prescribed crop coefficient used by the Idaho Department of Environmental Quality was adequate in avoiding drainage during the peak summer months.
... Each treatment contained one weighable lysimeter (± 10 g) and two lysimeters that were not weighable (Prasuhn, 2016). Taken together, the lysimeter system used here can be classified as a large, weighable, free draining, and monolith lysimeter (Meissner et al., 2010). ...
... In principle, soil moisture is an important factor in the interconnection between matter and energy in the soil-plant-atmosphere system; it is also a key factor controlling the ecosystem's structure [5][6][7]. Soil moisture exists in the unsaturated zone between the soil surface and the groundwater surface [8]. Vegetation also participates in the soil water cycle. ...
Changes in woodland characteristics induced by plants and soil greatly affect soil hydrological processes. Stable isotope technology and indoor soil moisture characteristic experiments were conducted at three rainfall levels (3.6, 23.5, and 49.8 mm) to investigate the hydrological processes under six woodlands (two pure forests and four mixed forests). The main influencing factors contributing to these changes were identified in a low mountain and hilly region in central China. The soil waterline equation in this area was soil water δD = 5.626 δ18O − 16.791 (R² = 0.798). The slope and intercept in the soil waterline equation were smaller than the atmospheric waterline equation. From a temporal perspective, the soil moisture content varied in the same trend under different rainfall events, with the maximum and minimum values on the first day after rainfall and the day before rainfall, respectively. However, an overall trend that first increased and then decreased was observed. From a spatial perspective, the soil moisture content increased with soil depth, and the increase rate was in the order of 0–20 cm and 20–40 cm in different soil layers. The soil moisture content in mixed conifer broadleaved woodlands was high. The soil water δD and δ18O in mixed conifer broadleaved woodlands and underground soil were relatively depleted. The effects of soil water-holding capacity, particle size composition, slope, canopy closure, and other factors on soil hydraulic parameters were comprehensively analyzed. The results showed that the extremely coarse sand (1–2 mm) particle content was the main parameter affecting soil-saturated hydraulic conductivity Ks, whereas the slope was the main factor affecting soil water δD and δ18O. In needle-leaved forests, the soil water infiltration form was a rainwater and soil water mixture downward diffusion, whereas the rainwater replaced the original soil water in the needle and mixed conifer broadleaved forests.
... However, this method is limited by its high associated costs and difficulties related to establishing and maintaining the necessary instruments (Voortman et al. 2016). Numerical simulations provide more possibilities for considering different factors under various situations when using unsaturated water flow models (Yang et al. 2021;Raesa and Deproost 2003;Ibrahimi et al. 2014) or integrated models (Luo et al. 2009;Meissner et al. 2010;Kollet and Maxwell 2008;Milly 1982); however, as these models are based on series of governing equations, they are often very complex and have significant requirements for their parameters and solving schemes. In contrast, empirical and semiempirical models derived from measured data, experimental results and theoretical analyses (Gardner 1958;Shah et al. 2011;Willis 1960;Prathapar and Meyer 1993) are commonly used in practical applications. ...
Shallow groundwater evaporation (E g ) is a major component of the hydrological cycle, especially in semiarid and arid locations. Empirical methods are commonly used to estimate Eg. However, most of these methods can only weakly represent E g variations along the soil depth and do not consider the energy driver. In this paper, a temperature coefficient was proposed and incorporated into two preferred empirical models to characterize the impacts of soil temperature and air temperature lags on E g . The method was evaluated using in situ daily data obtained from non-weighing bare soil lysimeters. The results indicated that the models that considered the temperature gradient variable (T) conformed to the changes in the actual E g values with depth more appropriately than the original models, accompanied by 4.3%–8.8% accuracy improvements overall. E g was found to be influenced by the water table depth (H), T, and pan evaporation (E 0 ) in descending order, and strong interactions were found between H and T. Moreover, the impact of precipitation on E g was investigated; measurements from dry days without precipitation revealed the actual E g process, the relative errors in the cumulative E g values derived at different depths demonstrated a positive relationship with infiltration recharge, and the errors related to precipitation induced 6.7%–8.3% Eg underestimations. These results contribute to a better understanding of evaporative losses from shallow groundwater and the typical E g situation that occurs simultaneously with recharge, and they provide promising perspectives for corresponding integrated hydrologic modeling research.
... Based on data-gathering techniques, the methods for estimating groundwater recharge can be categorized in terms of the following (Xu and Beekman 2019): (1) data from surface-related approaches such as remote sensing techniques, land-use change, and evapotranspiration; (2) data from subsurface approaches, including vadose zone methods, methods based on groundwater level data (Nimmo et al. 2015;Cuthbert et al. 2016), and tracer methods (Moeck et al. 2017;Huang et al. 2017); and (3) data related to conceptual approaches such as numerical models and water budget methods. This article is part of the topical collection "Groundwater recharge and discharge in arid and semi-arid areas of China" A wide range of lysimeters have been adapted to capture the groundwater recharge within a prescribed area (Meissner et al. 2010). Lysimeters may be either non-weighing or weighing (Meshkat et al. 1999). ...
Groundwater recharge is critical to water circulation in arid and semi-arid regions. The accurate determination of groundwater recharge is required for assessing water resources and effectively managing groundwater, especially in water-limited areas. Based on field experiments and numerical models in a semi-arid region, this study assessed the effect of non-isothermal flow on groundwater recharge. A lysimeter was used in the Mu Us Desert, northwestern China, to monitor groundwater recharge from 1 June to 30 September 2018. The numerical models (isothermal and non-isothermal models) were calibrated with the measured soil moisture and soil temperature. Groundwater recharge was found to take up nearly 29% of rainfall. The non-isothermal model was capable of accurately assessing groundwater recharge based on the accurate calculation of evaporation. The isothermal model, however, underestimated the groundwater recharge by 13.2% and overestimated the evaporation by 16.2%. The isothermal model overestimated evaporation during the drying process. In contrast, cumulative net recharge was underestimated after heavy rainfall events. It was therefore suggested that the non-isothermal flux should be considered in semi-arid regions, especially when assessing groundwater recharge.
... In 2017, maize was planted which was embedded in a regionally typical crop rotation of sugar beets-winter wheat-potatoes-winter barley-maize. Details on the lysimeter site and management history have been published previously (Meissner et al. 2010;Rupp et al. 2018). The present study investigated a period of one hydrological year starting in the hydrological summer semester in May 2017. ...
Glyphosate (GLYP), the globally most important herbicide, may have effects in various compartments of the environment such as soil and water. Although laboratory studies showed fast microbial degradation and a low leaching potential, it is often detected in various environmental compartments, but pathways are unknown. Therefore, the objective was to study GLYP leaching and transformations in a lysimeter field experiment over a study period of one hydrological year using non-radioactive 13C2-15N-GLYP labelling and maize cultivation. 15N and 13C were selectively measured using isotopic ratio mass spectrometry (IR-MS) in leachates, soil, and plant material. Additionally, HPLC coupled to tandem mass spectrometry (HPLC-MS/MS) was used for quantitation of GLYP and its main degradation product aminomethylphosphonic acid (AMPA) in different environmental compartments (leachates and soil). Results show low recoveries for GLYP (< 3%) and AMPA (< level of detection) in soil after the study period, whereas recoveries of 15N (11–19%) and 13C (23–54%) were higher. Time independent enrichment of 15N and 13C and the absence of GLYP and AMPA in leachates indicated further degradation. 15N was enriched in all compartments of maize plants (roots, shoots, and cobs). 13C was only enriched in roots. Results confirmed rapid degradation to further degradation products, e.g., 15NH4+, which plausibly was taken up as nutrient by plants. Due to the discrepancy of low GLYP and AMPA concentrations in soil, but higher values for 15N and 13C after the study period, it cannot be excluded that non-extractable residues of GLYP remained and accumulated in soil.
... Внутрипочвенный обмен влагой и химическими веществами, обусловленный нисходящим (инфильтрацией, I) и восходящим (испарение грунтовых вод, К) потоками, по мнению многих ученых (Муромцев, 1991;Муромцев и др., 2013;Meissner at al., 2010;Weihermüller at al., 2007), является важнейшим гидрофизическим и гидрохимическим процессом. От соотношения двух разнонаправленных потоков влаги и химических веществ зависят тип водного режима, особенности и интенсивность формирования влаги и химических веществ в почвах, а также их эффективное плодородие. ...
The experimental studies permitted to determine the ratio between infiltration and transpiration of the ground water in a soddy podzolic soil, that accounts for 0.3-0.6 under dried conditions of atmospheric moistening, 2.6-2.9 as an average value for many years and 2.6-2.9 under moderately wet conditions. The loss of potassium, calcium, magnesium, zinc and manganese under the grass stand was calculated as 0.95, 89.0, 37.7, 1.42 and 1.40 kg/ha/yr respectively. Due to capillarity the root layer of this soil receives 0.19 kg/ha of potassium or 20% from its loss with water infiltration, 16.4% of magnesium, 15.0% of calcium, 13.4% of zinc and 9.0% of manganese. It is shown that the water transpiration in case of the close underground water level leads to rupture of capillary links. With increasing the soil thickness in lysimeter the water infiltration and the nitrate leaching become declined both under grass and beangrass stands.
... As indicated by Ilesanmi et al. (2012), these approaches may be broadly classified into direct and indirect measurement. The direct measurement include the use of lysimeters (Ayoade, 1988(Ayoade, , 1988aMeissner et al., 2010), energy balance/budget approach (Adeboye et al., 2009;Farahani, et al., 2007), the soil water budget method (Phene et al., 1990;Evett and Parkin, 2005;Farahani et al., 2007), the use of pan evaporimeters (Ayoade, 1988(Ayoade, ,1988aHowell et al., 1991;Young et al., 1996;Yang et al., 2000;Gavilan et al., 2007), satellite remote sensing (Bastiaanssen et al., 2005;Tang et al., 2009) and the Eddy-Covariance method (Shuttleworth, 1993(Shuttleworth, , 2007. ...
Monthly Relative humidity (RH) models for Enugu and Imo States were developed using statistical analysis (SPSS) based on stepwise method. In this study, the independent variables: sunshine hours, minimum temperature, maximum temperature, rainfall and vapour pressure and the dependent variable (monthly relative humidity) were obtained from Nigeria Meteorological Agency (NIMET) for the years 1991 to 2010. High coefficients of determination R 2 = 0.845 and 0.753 for estimating monthly relative humidity for Enugu and Imo respectively were obtained during model building. The error margin for RH model for Enugu state used in Blaney-Morin-Nigeria(BMN) gave 0.0295-0.1864 whereas the error margin for RH model for Imo state used in BMN gave 0.0312-0.1322. By applying the developed monthly relative humidity in Blaney-Morin Nigeria model to estimate the monthly evapotranspiration from 1991 to 2010 gave a high significant difference. These results are clear evidence of the test of goodness of fit of the models between predicted and measured parameters for monthly relative humidity for Imo and Enugu states.
... Passive capillary wick samplers, which collect soil water samples using a hanging wick to exert matric tension on soil water, have the benefit of allowing for the measurement of both water flux and solute concentration and hence allow the estimation of leaching flux. Passive capillary wick samplers have been used for measuring water flux under a wide range of climatic and soil conditions (Brahy et al., 2002;Boll et al., 1992;Gee et al., 2002;Holder et al., 1991;Jabro et al., 2012;Knutson and Selker, 1994;Meissner et al., 2010). Additionally, PCAPSs have negligible effects on solute concentrations in infiltrating water (Boll et al., 1992;Holder et al., 1991;Knutson and Selker, 1994), making them a suitable tool for measuring NO 3 -N leaching (Brahy et al., 2002;Brandi-Dohrn et al., 1996. ...
Core Ideas
NO3 leaching was quantified by passive capillary wick samplers over 2 yr.
NO3 leaching was three times greater in Year 1 than Year 2 (240 vs. 80 kg N ha⁻¹).
Increased Year 1 NO3 leaching reflected field renovation prior to monitoring period.
There was strong seasonality in NO3 leaching from the field.
Despite fertilizer banding in rows, 60% of NO3 leached from alleys between rows.
Groundwater NO3–N contamination in the Abbotsford‐Sumas Aquifer in British Columbia, Canada, has been attributed primarily to NO3–N leaching from red raspberry (Rubus idaeus L.); however, direct estimates of NO3–N leaching are lacking. This study quantified the magnitude and timing of NO3–N leaching under a commercial red raspberry field over 30 mo (October 2010–March 2013) using passive capillary wick samplers installed below the root zone at three row locations (irrigated row, nonirrigated row, and alley) after the critical period of field renovation and replanting. Substantial NO3–N leaching (240 kg N ha⁻¹) during the first year of monitoring was attributed to the effects of field renovation (including autumn chopping and incorporation of raspberry canes and soil fumigation and spring poultry broiler manure application) in the year prior to the initiation of monitoring. Lower NO3–N leaching (80 kg N ha⁻¹) occurred in the second year of monitoring under typical mineral fertilizer management practices. Strong seasonality of NO3–N leaching was observed in both years, with ∼48% in autumn, 34% in spring and summer, and 17% in winter. Approximately 60% of the NO3–N leaching was attributed to the alleys between raspberry rows, which did not receive mineral fertilizer or irrigation. The high proportion of leaching during spring and summer and from the alleys suggests that growing‐season irrigation practices and alley vegetation management, respectively, would be good targets for the development of improved practices. The samplers were effective in quantifying the magnitude and timing of NO3–N leaching from a commercial agricultural field and informing the development of improved practices.
... In many cases, soil zone techniques to measure NO 3 leaching from the root zone are commonly used on small (<0.05 ha) experimental plots where groundwater zone monitoring is not tractable. For example, NO 3 leaching has been measured directly using passive capillary wick samplers (Meissner et al., 2010) or equilibrium-tension lysimeters (Brye et al., 2001), or calculated by combining soil water NO 3 concentrations from suction lysimeters with estimates of vertical water flow (Vázquez et al., 2005). Nitrate leaching has also been estimated indirectly using NO 3 in the tile-drain effluent as a proxy (Dinnes et al., 2002), from soil N budgets (Errebhi et al., 1998), and by using field-validated numerical models (Nolan et al., 2010). ...
The quantification of groundwater NO 3 loading associated with a specific field or set of management practices so that groundwater quality improvements can be objectively assessed is a major challenge. The magnitude and timing of NO 3 export from a single agricultural field under raspberry ( Rubus idaeus L.) production were investigated by combining high‐resolution groundwater NO 3 concentration profiles (sampled using passive diffusion samplers) with Darcy's flux estimation at the field's down‐gradient edge (based on field‐measured hydraulic gradients and laboratory‐estimated hydraulic conductivity). Annual recharge estimated using Darcy's law (1002 mm) was similar to that obtained using two other approaches. The similarity in the rate of Cl applied to the field and the estimated export flux over the 1‐yr monitoring period (51 vs. 56 kg Cl ha ⁻¹ ) suggested the mass flux estimation approach was robust. An estimated 80 kg NO 3 –N ha ⁻¹ was exported from the agricultural field over the 1‐yr monitoring period. The greatest monthly groundwater mass flux exported was observed in February and March (∼11 kg NO 3 –N ha ⁻¹ ), and was associated with NO 3 leached from the soil zone during the onset of precipitation in the previous autumn. Provided the groundwater recharged from the field of interest can be isolated within a vertical profile, this approach is an effective method for obtaining spatially integrated estimates of the magnitude and timing of NO 3 ⁻ loading to groundwater.
Core Ideas
High‐resolution groundwater monitoring was used with Darcy flux estimation.
The recharge estimate was comparable with two other methods.
This approach accurately estimated loading of Cl tracer.
Nitrate loading exported from individual field was quantified on a seasonal basis.
This approach is appropriate for agricultural fields over vulnerable aquifers.
... Lysimeters are an extremely important tool for the quantification and understanding of the components of the water balance (Goss and Ehlers 2009), because they allow a fairly detailed quantitative analysis of evapotranspiration and deep percolation and, if equipped accordingly, of soil water dynamics. Meissner et al. (2010a) consider lysimetry to be the most important direct method for assessing soil water drainage. Lysimetry is certainly the most accurate tool to measure water and solute fluxes (Meissner et al. 2010b). ...
This study aimed to quantify the water balance components at a grassland and a forest site representative of the Atlantic Forest biome in southern Brazil using drainage lysimeters. Since it was not possible to place mature trees on the forest lysimeter, it was planted with young trees and understory vegetation. Data from this lysimeter and computations with the water balance and the Penman-Monteith equation were then used to assess the values of the water balance components for the mature forest.
Total precipitation during the study period was 2308 mm. In the forest environment, 46% thereof was intercepted by the canopy from where it later evaporated. Hence, much less rain reached the ground than under grassland. Runoff from both sites was <1% of precipitation and therefore not a significant factor in the water balance. Cumulative drainage amounted to 1136 mm from grassland: from the mature forest, it was estimated to be 389 mm. There were two reasons for this low value under forest: Interception prevented a lot of water from reaching the ground, and the actual evapotranspiration from the mature forest was much higher than from grassland (1231 mm compared to 1964 mm).
... Estimation of NO 3 --N leaching requires measurement of soil solution NO 3 --N concentrations and the estimation of soil water movement. Many studies have examined the advantages and disadvantages of different field methods for measuring soil solution in situ, but there is no standard method (Zhu et al. 2003;Siemens and Kaupenjohann 2004;Fares et al. 2009;Meissner et al. 2010). For example, tension lysimeters provide access to deep soil horizons, and can be sampled daily for near real-time data on soil solution chemistry (Tully and Weil 2014). ...
Meeting food security requirements in sub-Saharan Africa (SSA) will require increasing fertilizer use to improve crop yields, however excess fertilization can cause environmental and public health problems in surface and groundwater. Determining the threshold of reasonable fertilizer application in SSA requires an understanding of flow dynamics and nutrient transport in under-studied, tropical soils experiencing seasonal rainfall. We estimated leaching flux in Yala, Kenya on a maize field that received from 0 to 200 kg ha⁻¹ of nitrogen (N) fertilizer. Soil pore water concentration measurements during two growing seasons were coupled with results from a numerical fluid flow model to calculate the daily flux of nitrate-nitrogen (NO3⁻-N). Modeled NO3⁻-N losses to below 200 cm for 1 year ranged from 40 kg N ha⁻¹ year⁻¹ in the 75 kg N ha⁻¹ year⁻¹ treatment to 81 kg N ha⁻¹ year⁻¹ in the 200 kg N ha⁻¹ treatment. The highest soil pore water NO3⁻-N concentrations and NO3⁻-N leaching fluxes occurred on the highest N application plots, however there was a poor correlation between N application rate and NO3⁻-N leaching for the remaining N application rates. The drought in the second study year resulted in higher pore water NO3⁻-N concentrations, while NO3⁻-N leaching was disproportionately smaller than the decrease in precipitation. The lack of a strong correlation between NO3⁻-N leaching and N application rate, and a large decrease in flux between 120 and 200 cm suggest processes that influence NO3⁻-N retention in soils below 200 cm will ultimately control NO3⁻-N leaching at the watershed scale.
... If wick material is attached to an extension tube, then the extension tube is filled with excavated soil from a hole where the wick lysimeter will be placed. Use of wick lysimeters to measure water flux has been well demonstrated in various studies (Boll et al., 1992;Knutson and Selker, 1994;Rimmer et al., 1995;Louie et al., 2000;Zhu et al., 2002;Siemens and Kaupenjohann, 2004;Gee et al., 2009;Meissner et al., 2010;Jabro et al., 2012). Collection efficiency for wick lysimeter was greater than pan lysimeters (Goyne et al., 2000;Zhu et al., 2002). ...
Core Ideas
Soil solution sampling is essential to better understand water and solute movement in soils.
A review of different types of soil solution samplers is provided in this paper, including: drainage lysimeter or soil column, pan lysimeter, resin bags or membranes, wick lysimeters, suction cup, and suction plate.
Recent developments, modifications, and recommendation criteria are provided for selecting appropriate soil solution extraction samplers.
A number of contaminants including agrochemicals (fertilizers, pesticides), heavy metals, trace elements, and pathogenic microbes along with pharmaceuticals and hormones used in animal production move through the soil and are responsible for degradation of groundwater quality. Therefore, it is essential to sample soil solution for better understanding of movement and environmental fate of various contaminants in soils. We review different soil solution extraction samplers. The soil solution samplers discussed here are: drainage lysimeter or soil column, pan lysimeter, resin bags or membranes, wick lysimeters, suction cup, and suction plate. We have reviewed 304 journal articles representing a wide array of scientific disciplines. A brief history of soil solution monitoring and terminology used for describing various soil solution samplers is also provided. This review classifies literature on the basis of type of soil solution extraction samplers, soil type, land use–land cover (LULC), and analytes measured. Recommendation criteria are provided for selecting appropriate soil solution extraction samplers based on spatial and temporal variation, cost, soil type, amount of disturbance caused during installation of soil solution samplers, and monitoring of leachates involving different cations, anions, carbon, pH, EC, colloids, pesticides, and microbes. Use of advanced techniques with lysimeters for monitoring soil moisture content, soil water potential and flux is also discussed in this review.
... Tipping buckets have also been regularly employed for run-off measurements since the early 1960ies (Pillbury et al., 1962;Edwards et al., 1974;Khan et al., 1997). They are also used in wick samplers 10 and lysimeters for the measurement and sampling of seepage water and for multicompartment sampling (Meissner et al., 2010). TBs are robust, reasonably-priced devices for the discontinuous detection of flow events with a wide spectrum of flow intensities and a high temporal resolution for flow intensities which the bucket was dimensioned for (Habib et al., 2001). ...
Due to climate change, cities need to adapt to changing rainfall and rainwater run-off dynamics. In order to develop an corresponding process based run-off model for pavements, we had to improve the measurement technique to detect run-off dynamics in an appropriate high resolution.
Traditional tipping buckets (TB) have a comparable low volume resolution, capable to quantify the highest intensities in a range of expected flows. This results in varying temporal resolutions for varying flow intensities, especially in low resolutions for small flow events. Therefore, their applicability for run-off measurements and other hydrological process studies is limited, especially when the dynamics of both small and big flow events shall be described.
We improved a TB by coupling it to a balance and called it weighable tipping bucket (WTB). This paper introduces the device set up and the according data processing concept. The improved volume and temporal resolution of the WTB are demonstrated. A systematic uncertainty of TB measurements compared to WTB measurements is calculated. The impact of that increased resolution on our understanding of run-off dynamics from paved urban soils are discussed, exemplary for the run-off and the surface storage of a paved urban soil.
The study was conducted on a permeably paved lysimeter situated in Berlin, Germany. Referring to the paved surface, the TB has a resolution of 0.1 mm, while the WTB has a resolution of 0.001 mm. The temporal resolution of the WTB is 3 s, the TB detects individual tippings with 0.4 s between them. Therefore, the data processing concept combines both the benefits of the balance to measure small intensities with that of the TB to measure high flow intensities.
During a five months period (July to November 2009) 154 rain events were detected. Accordingly, the TB and WTB detected 47 and 121 run-off events. The total run-off was 79.6 mm measured by the WTB which was 11% higher than detected by the TB. 95% of that difference can be appointed to water, which evaporated from the TB. To derive a surface storage estimation, we analyzed the WTB and TB data for rain events without run-off. According to WTB data, the surface storage of the permeable pavement is 1.7 mm, while using TB data leads to an overestimation of 47% due to low volume resolution of the TB.
Combining traditional TB with modern, fast, high resolution digital balances offers the opportunity to upgrade existing TB systems in order to improve their volume detection limit and their temporal resolution, which is of great advantage for the synchronization of water balance component measurements and the investigation of hydrological processes.
... Once installed, the units are designed to remain in the soil for an extended period. A detailed review of the design and functionality of DFM units is provided by Gee et al. (2009) andMeissner et al. (2010). ...
Nutrient losses are an important economic and environmental consideration across the New Zealand cropping sector. Between August 2014 and May 2015 we established a network of passive-wick drainage fluxmeters (DFMs) on commercial cropping farms in the Canterbury, Manawatu, Hawke's Bay and Waikato/Auckland regions to measure loads and concentrations of nitrogen (N) and phosphorus (P) in drainage water below the root zone. Results from this study will provide growers and regional authorities with measured nutrient losses from cropping farms across a range of sites and seasons. The data will help inform our extension work to ensure good management practices are communicated, widely endorsed and adopted by growers and regional councils. The experimental design across the DFM network includes the three sites across four monitor regions, and uses twelve fluxmeters per site. Individual sites were chosen to provide a range of cropping systems, soil types, climatic conditions and management practices relevant to each region. Across the DFM network, measured losses have ranged from 0.2 kg N/ha to 226 kg N/ha and from 0.01 to 0.56 kg P/ha respectively for the period between DFM installation and 30 September 2015. Nitrate-N was the dominant form of N loss while most P was lost as dissolved reactive phosphate. Drainage occurred predominantly (78–100%) over the mid-autumn to early spring period (April to September). The variability in N and P losses among different sites reflect the duration of the monitoring period as well as the wide range of climate, management and soil characteristics. Efforts are ongoing with growers to identify how to reduce nutrient losses. Introduction Optimising nutrient supply is a key management consideration for all farms across New Zealand. Too little supply and crop productivity can be constrained; too much supply and grower profitability decreases and there is a concomitant increase in environmental risks associated with leaching losses. Despite the significance of this issue in New Zealand, there is limited information regarding measured inter-annual nitrogen (N) and phosphorus (P) losses from the root zone of commercial cropping fields. Such information is crucial to informing policy decisions around nutrient losses and supporting the development and implementation of good management practice (GMP) to reduce risks.
... As indicated by Ilesanmi et al. (2012), these approaches may be broadly classified into direct and indirect measurement. The direct measurement include the use of lysimeters (Ayoade, 1988(Ayoade, , 1988aMeissner et al., 2010) and atmometers (Diop et al., 2015), energy balance/budget approach (Adeboye et al., 2009;Farahani, et al., 2007), the soil water budget method (Phene et al., 1990;Evett and Parkin, 2005;Farahani et al., 2007), the use of pan evaporimeters (Ayoade, 1988(Ayoade, , 1988aHowell et al., 1991;Young et al., 1996;Yang et al., 2000;Gavilan et al., 2007), satellite remote sensing (Bastiaanssen et al., 2005;Tang et al., 2009) and the Eddy-Covariance method (Shuttleworth, 1993(Shuttleworth, , 2007. Direct measurement of evapotranspration is usually not feasible in many situations because it is expensive and relatively time consuming (Igbadum et al., 2006). ...
The Blaney-Morin-Nigeria (BMN) model was developed for the estimation of reference
evapotranspiration (ETo) in Nigeria using commonly available meteorological parameters. In the
development of the model, there were some perceived shortcomings which are believed to affect the
reliability of ETo estimation, particularly in some specific locations in Nigeria, due to varying
environmental factors. This study re-examined the model by using the non linear regression model
based on Levenberg-Marquardt Algorithm (Excel Solver) to minimize the error space and generate new
model constants specific for Enugu. A 25-year (1989 to 2014) monthly record of climatic variables (Solar
radiation, Temperature, Relative Humidity and Wind speed) for Enugu were collected from the Nigeria
Meteorological Agency (NIMET), Abuja in Nigeria and used. The newly generated model constants, H
and m, were 392.2 and 1.19, respectively. Reference evapotranspiration for Enugu [
] was
thereafter estimated using the optimized BMN model and compared with that calculated using the
FAO56-PM model [
]. The optimized model showed a more accurate estimation of ET for
Enugu as indicated by the higher correlation coefficient of 0.82 compared to 0.76 for the original BMN,
lower mean absolute error (MAE) of 0.133 compared to 0.42 and root mean square (RMSE) of 0.3641
compared to 0.44. The
of 0.135 obtained using the optimized model was also low showing that the
new model gives a better estimation of ET for Enugu, Nigeria.
... Monitoring hydrological processes with weighable lysimeters was first carried out by the German, von Seelhorst, in 1902. Since that time, many lysimeters have been constructed and used for agricultural and environmental research (Edwards 1986;Schindler et al. 2001;Goss and Ehlers 2009;Meissner et al. 2010;Haferkorn et al. 2011;Prasuhn et al. 2011;Puetz et al. 2011). Lysimeters differ in their construction and management. ...
Quantifying groundwater recharge to aquifers is necessary for agricultural and environmental research. Lysimeters are the main devices for monitoring and quantifying soil water and solute balances and transport processes. However, certain characteristics of lysimeters, high costs and limited flexibility act as restricting arguments. There is a lack of effective and reliable methods for quantifying deep seepage under undisturbed soil and for managing conditions in the field. Soil hydrology measurements provide an alternative way of analysing the soil water and matter status in situ. The method presented here aims to estimate deep seepage and solute leaching in the field based on soil hydrological measurements below the zero flux plane and a calibrated hydraulic conductivity function. This method offers simple handling, flexibility, and costs less than lysimeters. The required soil hydraulic properties are only derived from tension and water content field recordings within the measurement depth. After calibration, no further information about soil properties, weather, management and land use data is required, nor is any other data. Since 1994, the method has been successfully applied at many sites in northeast Germany. A comparison between lysimeter discharge measurements and discharge calculations has confirmed the validity of this method.
... Drainage (D) of irrigation water below the root zone was measured by Passive-wick water fluxmeters (Decagon Devices, Pullman, USA). The working principle, design considerations and field applications of flux meters can be found elsewhere (Gee, 2005;Gee et al., 2009;Gee et al., 2002;Masarik et al., 2004;Meissner et al., 2010). Two flux meters were installed in each experimental plot at 1 m and 1.25 m soil depth. ...
... While accurate ET estimates are essential, ET can be challenging to measure. Numerous approaches have been developed to measure or estimate ET, including lysimeters (Meissner et al., 2010), micrometeorological methods (Anderson and Goulden, 2009;Baldocchi, 2003;Hemakumara et al., 2003), satellite remote sensing (Bastiaanssen et al., 2005;Tang et al., 2009), and water balance methods. While these approaches vary in their spatial/temporal scale and methodological assumptions and accuracy, most require significant observational costs, technical expertise, or have operational difficulties that are too high for most farmers. ...
Standardized reference evapotranspiration (ET) and ecosystem-specific vegetation coefficients are frequently used to estimate actual ET. However, equations for calculating reference ET have not been well validated in tropical environments. We measured ET (ETEC) using Eddy Covariance (EC) towers at two irrigated sugarcane fields on the leeward (dry) side of Maui, Hawaii, USA in contrasting climates. We calculated reference ET at the fields using the short (ET0) and tall (ETr) vegetation versions of the American Society for Civil Engineers (ASCE) equation. The ASCE equations were compared to the Priestley–Taylor ET (ETPT) and ETEC. Reference ET from the ASCE approaches exceeded ETEC during the mid-period (when vegetation coefficients suggest ETEC should exceed reference ET). At the windier tower site, cumulative ETr exceeded ETEC by 854 mm over the course of the mid-period (267 days). At the less windy site, mid-period ETr still exceeded ETEC, but the difference was smaller (443 mm). At both sites, ETPT approximated mid-period ETEC more closely than the ASCE equations ((ETPT–ETEC) < 170 mm). Analysis of applied water and precipitation, soil moisture, leaf stomatal resistance, and canopy cover suggest that the lower observed ETEC was not the result of water stress or reduced vegetation cover. Use of a custom calibrated bulk canopy resistance improved the reference ET estimate and reduced seasonal ET discrepancy relative to ETPT and ETEC for the less windy field and had mixed performance at the windier field. These divergences suggest that modifications to reference ET equations may be warranted in some tropical regions.
... It is not unusual that supposedly identical lysimeters show different results (e.g. Meissner et al., 2010). This is typically due to the natural variation of soil properties, which in turn may lead to differences in the development of the crop grown on the lysimeters, specifically in rooting depth, leaf area and plant biomass. ...
This study looks at the water balance of two identical weighable lysimeters located right next to each other. They contain the same soil and are managed in the same way. Both were planted with maize. The area around them was planted with maize, too, to ensure that the lysimeters were located inside a crop. The only difference between them was that one side of lysimeter 2 was exposed due to a footpath.
... While accurate ET estimates are essential, ET can be challenging to measure. Numerous approaches have been developed to measure or estimate ET, including lysimeters (Meissner et al., 2010), micrometeorological methods (Anderson and Goulden, 2009;Baldocchi, 2003;Hemakumara et al., 2003), satellite remote sensing (Bastiaanssen et al., 2005;Tang et al., 2009), and water balance methods. While these approaches vary in their spatial/temporal scale and methodological assumptions and accuracy, most require significant observational costs, technical expertise, or have operational difficulties that are too high for most farmers. ...
Standardized reference evapotranspiration (ET) and ecosystem-specific
vegetation coefficients are frequently used to estimate actual ET. However,
equations for calculating reference ET have not been well validated in
tropical environments. We measured ET (ETEC) using eddy covariance (EC)
towers at two irrigated sugarcane fields on the leeward (dry) side of Maui,
Hawaii, USA in contrasting climates. We calculated reference ET at the
fields using the short (ET0) and tall (ETr) vegetation versions of
the American Society for Civil Engineers (ASCE) equation. The ASCE equations
were compared to the Priestley–Taylor ET (ETPT) and ETEC.
Reference ET from the ASCE approaches exceeded ETEC during the
mid-period (when vegetation coefficients suggest ETEC should exceed
reference ET). At the windier tower site, cumulative ETr exceeded
ETEC by 854 mm over the course of the mid-period (267 days). At the
less windy site, mid-period ETr still exceeded ETEC, but the
difference was smaller (443 mm). At both sites, ETPT approximated
mid-period ETEC more closely than the ASCE equations
((ETPT-ETEC) < 170 mm). Analysis of applied water and
precipitation, soil moisture, leaf stomatal resistance, and canopy cover
suggest that the lower observed ETEC was not the result of water stress
or reduced vegetation cover. Use of a custom-calibrated bulk canopy
resistance improved the reference ET estimate and reduced seasonal ET
discrepancy relative to ETPT and ETEC in the less windy field and
had mixed performance in the windier field. These divergences suggest that
modifications to reference ET equations may be warranted in some tropical
regions.
... TBRGs have been often used in hydro-meteorological instrumentation such as rain-gauges or stem flow metres (White and Rhodes, 1970), for run-off measurements (Pillbury et al., 1962;Edwards et al., 1974;Khan and Ong, 1997). They are also used in wick samplers and lysimeters for the measurement and sampling of seepage water and for multi-compartment sampling (Meissner et al., 2010). The major disadvantages of these tipping buckets are: ...
Snow water equivalent is the amount of water contained within a snowpack. It is important to have accurate and timely winter precipitation information for agriculture and especially for flood and stream flow forecasting. Moreover, if the density of the snow is known, then the snow water equivalent data can be used to determine snow depth which is an important parameter for avalanche forecasting (McClung and Schaerer, 1993). In this paper, the design of a new tipping bucket rain gauge (TBRG) and an antifreeze-based attachment have been discussed which would measure rain as well as snow precipitation. The TBRG and the antifreeze-based attachment have been designed to reduce the shortcomings of commercial TBRGs and antifreeze-based attachments. Our TBRG provides faster rain and snow water equivalent data. The highest measurement rate for rain and snow water equivalent is found to be 375 mm/hr and 16.4 mm/hr respectively. The design considerations, field and laboratory trials and results of the TBRG and the antifreeze-based attachment have been discussed in detail in this paper.
... The lysimeters were also filled with sandy loam Luvisol. The study showed that under sandy soil conditions no significant differences occurred between the measurements from drainage lysimeter types (Meissner et al., 2010). ...
The average annual rate of atmospheric precipitation is about 38-40% on the territories of the Republics of Lithuania and Belarus. On agricultural land, with runoff waters various chemical elements leach into the subsoil and cause negative impact on the quality of water bodies. The main objectives of this study were to assess the influence of climate variability on the infiltration of atmospheric precipitation in Lithuania (Vilnius) and Belarus (Minsk). The long-term lysimetric experiment (lysimeter surface area of 1.75-2.0 m2) data of the precipitation infiltration during 1987-2008 was used in the study. It was determined that in 1987-2007 precipitation amount on the studied territory in Lithuania (Vilnius) slightly increased (+10 mm) compared with the climate norm, while in Belarus it significantly decreased (-109 mm), precipitation amount in separate months changed, and it had an impact on the amount of precipitation infiltration. In Lithuania, strong correlation between the amounts of precipitation and infiltrated water was established during the summer period (R2 = 0.77, tr = 99.9%), moderate correlation - in autumn (R2 = 0.48, tr = 99.9%). In Belarus, a strong correlation was established in spring (R2 = 0.978, tr = 99.9%), moderate correlation - in summer (R2 = 0.537, tr = 99.9%), and winter (R2 = 0.592, tr = 99.9%) periods. During 1987-2008 in Lithuania a significant increase (p < 0.05) in infiltration of atmospheric precipitation in the course of the spring period was established. The trend of increased infiltration in summer and reduced infiltration during the autumn period is also established (correlation is insignificant). In Belarus (Minsk), due to lower amount of atmospheric precipitation in 1987-2007, the infiltration decreased during all seasons of the year, but because of the variation of the climatic conditions, no statistically significant trends (p > 0.05) of change in infiltration were established.
... The concentration of the solutes measured by suction cups was influenced by soil structure and composition of the soil in the close surrounding of the suction cup which is highly variable due to the natural soil heterogeneity. Differences between technically equivalent and similarly managed lysimeters have been observed previously by Meissner et al. (2010). Also, Weihermueller et al. (2007) compared three different lysimeter systems, each with two replications, and the means of these provided the basis for comparability. ...
We aimed to assess the dynamics of pore water concentrations of Cd, Co, Cu, Ni, Zn and their controlling factors (EH, pH, DOC, Fe, Mn, and SO42-) in a contaminated floodplain soil under different flood-dry-cycles. Two parallel undisturbed groundwater lysimeters (mean values presented) were used for long term (LT; 94 days) and short term (ST; 21 days) flood-dry-cycles. Reducing conditions under LT lead to low EH and pH, while DOC, Co, Fe, Mn, and Ni increased. Cadmium, Cu, Zn, and SO42- increased under oxidizing conditions during ST. Cobalt and Ni revealed a similar behavior which seem to governed by EH/pH, Mn, Fe, and DOC. Cadmium, Cu, and Zn reveal a similar fate; their dynamics were affected by EH/pH, DOC, and SO42-. Our findings suggest that a release of Cd, Cu, Co, Fe, Mn, Ni, and Zn under different flood-dry-cycles can assumed what might create potential environmental risks in using metal-enriched floodplain soils.
... The concentration of the solutes measured by suction cups was influenced by soil structure and composition of the soil in the close surrounding of the suction cup which is highly variable due to the natural soil heterogeneity. Differences between technically equivalent and similarly managed lysimeters have been observed previously by Meissner et al. (2010) and Haferkorn (2000). Also, Weihermueller et al. (2007) compared three different lysimeter systems, each with two replications, and the means of these provided the basis for comparability. ...
We hypothesize that the dynamics of water soluble arsenic (As), chromium (Cr), molybdenum (Mo), and vanadium (V) in soils might be controlled by the period of flooding due to changes of redox potential (EH), pH, and carriers of metals such as dissolved organic carbon (DOC), iron (Fe), manganese (Mn) and sulfate (SO42 −). Therefore, we aimed to assess the impact of different flood–dry-cycles on the temporal dynamics of pore water concentrations of As, Cr, Mo and V as affected by changes of soil EH/pH and dynamics of DOC, Fe, Mn and SO42 − in a contaminated floodplain soil collected at the Elbe River (Germany). For this purpose a specific groundwater lysimeter technique with two separate lysimeters which served as replicates was used. The groundwater level inside the lysimeters was controlled to simulate different flood–dry-cycles sequentially as follows: the long term (LT) includes 94 days of flooding followed by similar drying term. The short term (ST) comprises 21 days flooding followed by a similar drying term and was repeated six times. The entire experimental period (LT_ST) was about 450 days. The presented data are mean values of both lysimeters.
... The concentration of the solutes measured by suction cups was influenced by soil structure and composition of the soil in the close surrounding of the suction cup which is highly variable due to the natural soil heterogeneity. Differences between technically equivalent and similarly managed lysimeters have been observed previously by Meissner et al. (2010) and Haferkorn (2000). Also, Weihermueller et al. (2007 compared three different lysimeter systems, each with two replications, and the means of these provided the basis for comparability. ...
... Many methods to estimate deep seepage such as direct measurements with drainage lysimeters (Meissner et al., 2010a) and passive wick-samplers (Gee et al., 2009; Meissner et al., 2010b), conceptual (Bethune et al., 2008), mechanistic (Jimenez-Martinez et al., 2009; Lu et al., 2011) and empirical (Selle et al., 2008; Wessolek et al., 2008) modeling approaches and tracer balance calculations (Fragala and Parkin, 2010; Perkins et al., 2011) have been developed and applied at different scales. However, in many cases it is still a challenge to quantify deep seepage with adequate time and effort (cf. ...
Deep seepage estimation is important for water balance investigations of groundwater and the vadose zone. A simplified Buckingham-Darcy method to assess time series of deep seepage fluxes was proposed by Schindler and Müller (1998). In the method dynamics of water fluxes are calculated by a soil hydraulic conductivity function. Measured soil moistures and matric heads are used as input data. Resulting time series of flux dynamics are scaled to realistic absolute levels by calibrating the method with the areal water balance. An assumption of the method is that water fluxes at different positions exhibit identical dynamics although their absolute values can differ. The aim of this study was to investigate uncertainties of that method depending on the particle size distribution and textural heterogeneity in non-layered soils. We performed a numerical experiment using the two-dimensional Richards Equation. A basic model of transient water fluxes beneath the root and capillary zone was setup and used to simulate time series of soil moisture, matric head, and seepage fluxes for 4221 different cases of particle size distribution and intensities of textural heterogeneity. Soil hydraulic parameters were predicted by the pedotransfer function Rosetta. Textural heterogeneity was modeled with Miller and Miller scaling factors arranged in spatial random fields. Seepage fluxes were calculated with the Buckingham-Darcy method from simulated soil moisture and matric head time series and compared with simulated reference fluxes. The median of Root Mean Square Error was about 0.026 cm d−1 and the median of maximum cross correlation was 0.96 when the method was calibrated adequately. The method’s performance was mainly influenced by (i) the soil textural class and (ii) the time period used for flux calibration. It performed best in sandy loam while hotspots of errors occurred in sand and silty texture. Calibrating the method with time periods that exhibit high variance of seepage fluxes yielded the best performance. The geostatistical properties of the Miller and Miller scaling field influenced the performance only slightly. However, the Miller and Miller scaling procedure generated heterogeneous flow fields that were addressed as main reason for mismatches of simulated reference fluxes and fluxes obtained with the Buckingham-Darcy method.
... This drain device has a 150 ml reservoir, ±0.1 mm resolution and 10 ms measurement time. The passive-wick system has some limitations, in that there 5 can be a mismatch between the soil water suction and that applied to the wick by the length of the hanging water column (Meissner et al., 2010). However, the differences may be relatively small, especially for sandy soil. ...
Best practice agriculture is the key to overcome the food security
problem through improvement of water use efficiency. Therefore,
knowledge of the water fluxes within the soil-vegetation-atmosphere
system is crucial. Many studies have tried to quantify these fluxes, but
they encountered difficulties in quantifying the relative contribution
of evaporation and transpiration. In this study, we compared four
different methods to estimate evaporation fluxes during simulated summer
conditions in a grassland lysimeter in the UNESCO-IHE laboratory. Only
two of these methods can be used to partition total evaporation into
transpiration, soil evaporation and interception. A water balance
calculation (whereby rainfall, soil moisture and percolation was
measured) and the Penman-Monteith equation were applied to determine
total evaporation. A HYDRUS-1D model and isotope measurements were used
for the partitioning of total evaporation. The average total evaporation
was 3.2 mm d-1 calculated with the water balance, 3.4 mm
d-1 for the Penman-Monteith equation, 3.4 mm d-1
calculated with HYDRUS-1D, and 3.1 mm d-1 with the isotope
mass balance. By use of the isotopes, we separated the total evaporation
on average into 2.4 mm d-1 transpiration (77.7%), 0.4 mm
d-1 soil evaporation (12.2%), and 0.3 mm d-1
interception (10.1%).
Mass balance modelling often shows that leaching is the main loss pathway for cadmium (Cd) from agricultural soils. There is however a scarcity of Cd leaching data measured under field conditions to support these modelled losses. This study used passive-wick fluxmeters installed at a depth of one metre at six commercial cropping sites to measure Cd in drainage over one year of monitoring. Cadmium concentrations were generally below the method detection limit (0.05 µg Cd L⁻¹) for all sites, with only the occasional detection from two sites and no detection from three other sites. The exception was site A where average Cd concentrations ranged from 0.06 to 0.18 µg L⁻¹ and the mean annual loss (± SE) was 0.33 ± 0.08 g Cd ha⁻¹. This was similar to the amount estimated using the drainage flux multiplied by a modelled estimate of soil solution Cd concentrations for the site, 0.41 g Cd ha⁻¹. Cadmium balance models typically assess the rate of Cd accumulation in the 0–7.5 or 0–30 cm soil depth. Further studies are still required to obtain Cd leaching data collected under field conditions at these soil depths to allow modelled Cd leaching to be validated against measured data.
The specificities of leaching (outflow) of chemicals from soddy-podzolic loamy deeply gleyed soil by infiltration and its return from groundwater during their evaporation are considered in the paper. In the annual cycle calcium is the element which is mostly washed out with amount of 89…106 kg/ha. It was shown that potassium (15…14), manganese (13,6…9,3), zinc (13,6…7,7), calcium (7,5…5,2) and magnesium (7,1…4,7) in percentage of the outflow return in the soil with the capillary rise of groundwater. It is shown that the ratio of infiltration (I) and evaporation of groundwater (K) in soddy-podzolic soil is within the range of 0,3…0,6 for medium arid, 2,6…2,9 for average long-term and 2,6…2,9 for humid conditions of atmospheric moistening. Thus, the lowest values of ratios for medium arid, and the highest ones – for medium humid conditions, which reflects the real specificities of the infiltration and evaporation of groundwater in natural conditions.
The ability to quantify soil water flow is a prerequisite for the accurate prediction of solute transfer within the unsaturated zone. Monitoring these fluxes is a challenge because the results are required for answering not only scientific but also practical questions regarding the protection of groundwater, the sustainable management of agricultural, forestry, mining or set aside industrial areas, the reduction of leachate loss from landfills, and for explaining the fate of environmentally harmful substances. Both direct and indirect methods exist for estimating water flux rates; these have been applied with varying success. In Europe, the use of direct lysimetry methods for measuring water and solute fluxes in soils has increased significantly in recent years. Although this technique generates reliable drainage data, it involves relatively high investment and maintenance costs. New lysimeter techniques have been developed to tackle this problem. It is now possible to collect large monolithic soil columns and to measure the soil water balance of these monoliths (surface area 0.03–2 m2 and depth to 3 m) with a high degree of precision (±20 g). Furthermore, progress in lysimetry enables us to ascertain experimentally the mass input of dew and to calculate actual evapotranspiration, precipitation and seepage rates. Weighable groundwater lysimeters have been developed in addition to gravitation lysimeters. Different lysimeter types and their usage will be presented and explained using practical examples.
The regularities of water infiltration and evaporation of groundwater at different depths of the groundwater table were established for soddy-podzolic and dark gray forest soils. The recharge of the soils with moisture from the groundwater decreased with a lowering of its table, and the infiltration increased. At the high groundwater table (70 cm from the surface), the moisture recharge of the soddy-podzolic soil amounted to 86 mm and the infiltration amounted to 17 mm; at the groundwater table of 145 cm, these values were 13 and 51 mm, respectively. The concentrations of chemical elements in the lysimeters with the high groundwater table were 2–4 times greater than those in the lysimeters with the low groundwater table.
Laboratory experiments and numerical studies are used to study the potential to induce water flux in the vadose zone, which is characterized by significant horizontal components of the water velocity. Specifically, a question is addressed as to whether water can be injected or withdrawn from lenses or layers of fine sediments (bordered by coarse sediments), thus establishing flow in those portions of the vadose zone commonly associated with higher moisture contents and a higher mass of dissolved contaminants. Laboratory experiments provided the base-line proof of concept of the ability to induce horizontal components to flow in unsaturated sediments through use of suction-cup lysimeters, but were limited to ideal media and short distance scales (<0.5 m). A numerical model was used in combination with published moisture retention and relative permeability parameters for a variety of sediment types to study conditions under which such horizontal flow components might be induced over substantially greater distances (e.g., 10 m). While these numerical results support arguments that flow induction is theoretically possible, induced flow will generally result in slow transport velocities such that application will likely be limited either to short flow distances (e.g., less than a meter) or long-term (>50 years)time scales, and only with thorough knowledge of subsurface heterogeneity. Implications of this work beyond the present study may include continuing discussions of constructed capillary barriers and development of improved technologies for removal of water from the vadose zone.
[1] When predicting flow in the unsaturated zone, any method for modeling the flow will have to define how, and to what level, the subsurface structure is resolved. In this paper, we use the Ensemble Kalman Filter to assimilate local soil water content observations from both a synthetic layered lysimeter and a real field experiment in layered soil in an unsaturated water flow model. We investigate the use of colored noise bias corrections to account for unresolved subsurface layering in a homogeneous model and compare this approach with a fully resolved model. In both models, we use a simplified model parameterization in the Ensemble Kalman Filter. The results show that the use of bias corrections can increase the predictive capability of a simplified homogeneous flow model if the bias corrections are applied to the model states. If correct knowledge of the layering structure is available, the fully resolved model performs best. However, if no, or erroneous, layering is used in the model, the use of a homogeneous model with bias corrections can be the better choice for modeling the behavior of the system.
The measured drainage fluxes through a layered volcanic vadose zone exhibited high spatial variability as a consequence of heterogeneous flow conditions. The drainage variability was quantified using close-proximity automated equilibrium tension lysimeters (AETLs), and resulted in high variability in the Br masses recovered from a conservative tracer experiment. The primary cause of the heterogeneous flow was attributed to textural changes occurring at the interface between volcanic layers, resulting in development of funnel-flow patterns, defined as heterogeneous flow, and were further enhanced by the existence of hydrophobic conditions. The Br recoveries in individual AETLs were used to determine the corresponding variable sizes of the surface areas contributing drainage to the lysimeters. The tracer experiment confirmed the existence of unsaturated lateral transport occurring at the interface of the coarse Taupo Ignimbrite material with the silty Palaeosol layer at 4.2 m depth. This study demonstrates that measurements of both flux and solute concentrations at multiple locations are essential when heterogeneous flow is suspected to be present, to be able to determine reliable estimates of contaminant leaching through the vadose zone at the plot scale.
Water supplies throughout the world are rapidly diminishing in quantity and quality. Efforts over the next decade must focus on methods which use water more efficiently for agriculture, industry, and recreational purposes, and at the same time reduce the potential for groundwater pollution. To assist in this effort, we have developed an improved method to simultaneously measure drainage quantity and quality using a water fluxmeter. Our water fluxmeter is a wick-lysimeter fitted with a small tipping-spoon and a solution-collection system. The only moving part is the tipping spoon. We have tested our fluxmeters under a range of conditions, from non-vegetated desert settings in Washington State USA, to irrigated tea plantations in Sri Lanka. Conditions of over-irrigation have been documented with our fluxmeters. When 4200 mm of water was applied to sandy soil via drip irrigation, at the Washington State site, over 3100 mm of drainage occurred. In contrast, at the same site, in the absence of both irrigation and vegetation, drainage was found to range from 0 mm/yr for a 1-m-deep silt loam soil to more than 100 mm/yr for a coarse-gravel surface. Solute transport, related to nitrate leaching can also be analyzed using water fluxmeters. Water fluxmeters have provided a reliable and inexpensive method to assess both quantity and quality of drainage waters over a wide range of environmental conditions.
Optimization of water use in agriculture and quantification of percolation from landfills and watersheds require reliable estimates of vadose zone water fluxes. Current technology is limited primarily to lysimeters, which directly measure water flux but are expensive and may in some way disrupt flow, causing errors in the measured drainage. We report on design considerations and field tests of an alternative approach, passive wick fluxmeters, which use a control tube to minimize convergent or divergent flow. Design calculations with a quasi-three-dimensional model illustrate how convergence and divergence can be minimized for a range of soil and climatic conditions under steady state and transient fluxes using control tubes of varying heights. There exists a critical recharge rate for a given wick length, where the fluxmeter collection efficiency is 100% regardless of the height of the control tube. Otherwise, convergent or divergent flow will occur, especially when the control tube height is small. While divergence is eliminated in coarse soils using control tubes, it is reduced but not eliminated in finer soils, particularly for fluxes 60% annual precipitation) from gravel surfaces and least (no drainage) from silt loam soils. In Oregon and New Mexico, United States, and in New Zealand, drainage showed substantial spatial variability. The New Mexico tests were located in semiarid canyon bottom terraces, with flash flood prone locations having extremely high drainage/precipitation ratios. In the wettest environments, drainage was found to be closely linked to the rate and duration of precipitation events.
Soil solution samplers have certain inadequacies that limit their range of possible applications. Passive capillary samplers (PCAPS), which apply suction to the soil pore water via a hanging water column in a fiberglass wick, have shown promising results in preliminary experiments in regard to collection efficiency of water and Br tracers. The objectives of this study were to evaluate PCAPS with respect to (i) effect of installation procedure and operational characteristics; and (ii) ability to estimate the soil-water and solute flux. We installed 32 PCAPS and 32 ceramic suction cup samplers at a depth of 1.2 m in an undisturbed silt loam soil. For the first year, water flux, NO3-N and Br concentrations in the part of the PCAPS closest (0.3 m) to the refilled trench were 15, 14, and 34% less, respectively, than in the part farthest (0.9 m) away from the refilled trench. This was attributed to installation procedure, since the bias ceased for the second year. Soil-water flux measurements of PCAPS underestimated those determined by a water balance by 20 to 34%. Some of the discrepancy is thought to be due to the lack of accounting for runoff, which was observed but not quantified. The recovery of a Br tracer was low with an average of 29%, ranging from 5 to 77%, which was attributed to lateral water movement due to prominent lateral stratification. To estimate the mean Br concentration with a 30% bound at the 0.05 confidence level on this 1-ha field site, 25 PCAPS and 37 suction cup samplers are necessary. Sampling a more evenly distributed solute such as residual fertilizer NO3 requires only eight PCAPS for this level of confidence.
Fiberglass wicks act as a hanging water column, drawing water from the undisturbed field soil without external application of suction. Flow characteristics of wicks were observed in the laboratory by miscible-displacement tests using Br and an organic dye. The matric potential in the wick as a function of flow rate was measured. Fiberglass wicks behaved like a porous medium that effectively could apply a suction to the soil while only minimally retarding the organic dye. The relationship between matric potential, moisture content, and unsaturated conductivity was determined for several wicks. Based on these relationships, a set of curves was produced depicting travel time of nonadsorbed chemicals and the matric potential in the wick as a function of flow rate. These curves can be used for selecting optimum wick length and diameter for a given sampler configuration. -from Authors
Root zone drainage measurements are needed to improve fertilizer management in areas where agriculture may be impacting groundwater supplies. We present results of field tests where drainage was measured with two types of suction (resolution of 0.16 and 1.6 mm -1) and a nonsuction (resolution of 0.22 mm tip-1) water flux meter (WFM). The soil was a microstructured weathered volcanic ash located on a coral atoll subject to intense rainfall and located in the Kingdom of Tonga. Our objectives were to evaluate water flux measurements by comparing them with (i) simple water balance estimates of cumulative fluxes deduced from soil moisture content changes, and (iii) simulated fluxes using HYDRUS-1D. Soil hydraulic properties were obtained at five soil depths. During the 60-d evaluation period rainfall totaled 340 mm. The WFMs were installed in duplicate using disturbed soil. The consistency of the shape of the drainage curves measured with the WFMs, those derived from soil moisture changes, and those obtained with modeling led us to conclude that soil disturbance during WFM installation did not severely influence measurements. This was attributed to the strong microaggregation and disturbance introduced by plowing. Water balance and HYDRUS model estimates of drainage corresponded well with the measurement by nonsuction WFMs. Suction WFMs overestimated drainage, possibly due to flow convergence created by wick and divergence barrier lengths being not properly sized for the observed flow conditions. After the evaluation period some of the WFMs failed to respond. Nevertheless, flux meters are seen as promising tools to provide remote and continuous measurement of root zone drainage.
Unsaturated water flux densities are needed to quantify water and contaminant transfer within the vadose zone. However, water flux densities are seldom measured directly and often are predicted with uncertainties of an order or magnitude or more. A water fluxmeter was designed, constructed, and tested to directly measure drainage fluxes in field soils. The fluxmeter was designed to minimize divergence. It concentrates flow into a narrow sensing region filled with a fiberglass wick. The wick applies suction, proportional to its length, and passively drains the meter. The meter can be installed in an augured borehole at almost any depth below the root zone. Water flux through the meter is measured with a self-calibrating tipping bucket, with a sensitivity of ∼4 mL tip−1. For our meter this is equivalent to detection limit of ∼0.1 mm. Passive-wick devices previously have not properly corrected for flow divergence. Laboratory measurements supported predictions of a two-dimensional (2-D) numerical model, which showed that control of the collector height H and knowledge of soil hydraulic properties are required for improving divergence control, particularly at fluxes below 1000 mm yr−1. The water fluxmeter is simple in concept, is inexpensive, and has the capability of providing continuous and reliable monitoring of unsaturated water fluxes ranging from less than 1 mm yr−1 to more than 1000 mm yr−1.
Passive capillary samplers (PCAPS), which sample water from the vadose
zone via a hanging water column in a fiberglass wick, have shown
potential to provide superior estimates of soil water flux compared to
alternative methods. The objectives of this study were to evaluate the
performance of PCAPS under natural rain-fed conditions concerning (1)
their operational characteristics and (2) their ability to estimate soil
water flux. Forty-two PCAPS were installed in 21 commercial agricultural
fields in Lane County, Oregon. Monthly measurements of soil water flux
and precipitation were recorded at each site for the 4-year project
duration. Of the 42 installed PCAPS, 12 samplers at six sites were
inoperable or did not operate efficiently: 10 samplers were consistently
below the water table, which overflowed the collection vessels rendering
the samplers inoperable. Only two of the PCAPS exhibited technical
failure resulting in unusually low collection efficiencies, thought to
be due to a collapse of the collection vessel from oversuction during
sample retrieval. On average, the 30 remaining PCAPS measured soil water
flux 25% greater than that obtained from a water balance estimate. This
discrepancy represents ˜8% of the total annual precipitation and
irrigation each site received. PCAPS collection efficiency was found to
be significantly correlated (R2 = 0.75) to the water balance
yearly estimated recharge. The difference between PCAPS measured and
water balance estimated percolation could be the result of inaccuracy in
water balance evapotranspiration estimates and/or oversampling in the
presence of high water tables. To estimate the mean yearly recharge at
each site with a 30% bound on the mean at the 0.05 confidence level,
eight PCAPS are required. This number corresponds closely to the results
of Brandi-Dohrn et al. [1996a] and is thought to be due to intrinsic
variability of percolation.
Accurately measuring water fluxes and associated nutrient or contaminant concentrations through the vadose zone is difficult because an appropriate suction needs to be exerted on the soil to sample water under unsaturated conditions. Passive capillary wick sampling systems are cheap and reliable instruments resulting in acceptable measurements of water fluxes in the vadose zone; however, their success in measuring realistic fluxes depends on their compatibility with the soil and climatic conditions in which they are installed. This study was developed in the preplanning phase of a field experiment with its main objective the monitoring of dissolved organic matter and the associated transfer of Cu2+ and pesticides through the vadose zone. We studied a combination of two-dimensional and axisymmetrical three-dimensional numerical analyses using the HYDRUS-2D software to identify what sampler geometry, wick type, wick length, and number of wicks are most suitable for the soil conditions at the experimental site. An AM3/8HI wick with seasonally varying wick length (40 cm in winter and 100 cm in summer) was found to be most appropriate for the soil and climatic conditions of the experimental field. The numerical analysis indicated that well-designed wick samplers had a negligible effect on the soil moisture content close to the sampler. A double-ring wick sampler is proposed to minimize the effect of the area between the installation pit or trench and the sampler. This approach is easily applicable and transferable to other soil and wick types and climatic conditions. The study emphasizes the suitability of numerical modeling to optimize experimental design before installation.
Wick samplers have become a valuable device for collecting soil pore water samples from the unsaturated zone. However, one of the problems with wick samplers has been that water and solutes bypass the samplers. Little work has been done on the nature of soil-wick interrelations. Based on an analytical solution for a layered soil profile, a steady-state solution was developed to predict the pressure head in a wick-soil continuum. The solution was also used to match wick properties to a given soil type in order to minimize the bypass flow. The results of this analysis show that for a good match between wick and soil types, (I) their capillary length (u I) needs to be similar, and (h) the ratio of their saturated hydraulic conductivities should be similar to the inverse ratio of their cross section for flow. Examples for wick type selection based on these two requirements are given for two soil types and two wick types. For sandy soils, the optimal wick length is 30 to 40 cm, while for silt !owns, the optimal length is >100 cm. Sampling with wick samplers in coarse-textured soils was found to be less disturbing of the soil pressure head and moisture profile than sampling in fine-textured soils. Hydraulic properties of fine. textured soils require a large sampling area in order to create an undisturbed zone above the wick sampler.
Four large, weighing, monolithic lysimeters were designed, constructed and installed at Bushland, TX. Each lysimeter has a surface area of 9 m**2 and a soil depth of 2. 3 m. The soil within each lysimeter is an 'undisturbed' monolith of Pullman clay loam. Each soil monolith has a mass of approximately 45 Mg, including the container mass. The lysimeters are installed in a 20 ha field with one lysimeter located in the center of each quarter of the field. The parameters of wind disturbance, water infiltration, drainage, thermal continuity, sidewall water percolation, rooting depth, scale stability, row spacing geometry, and safety were considered in the design. A compact mechanical type weighing system and load cell was used with an overall capability of detecting mass changes equivalent to a minimum of 0. 05 mm of water. Automated data acquisition and telecommunication to offsite computers were utilized.
The knowledge of the composition and fluxes of vadose zone water is essential for a wide range of scientific and practical fields, including water-use management, pesticide registration, fate of xenobiotics, monitoring of disposal from mining and industries, nutrient management of agricultural and forest ecosystems, ecology, and environmental protection. Nowadays, water and solute flow can be monitored using either in situ methods or minimally invasive geophysical measurements. In situ information, however, is necessary to interpret most geophysical data sets and to determine the chemical composition of seepage water. Therefore, we present a comprehensive review of in situ soil water extraction methods to monitor solute concentration, solute transport, and to calculate mass balances in natural soils. We distinguished six different sampling devices: porous cups, porous plates, capillary wicks, pan lysimeters, resin boxes, and lysimeters. For each of the six sampling devices we discuss the basic principles, the advantages and disadvantages, and limits of data acquisition. We also give decision guidance for the selection of the appropriate sampling system. The choice of material is addressed in terms of potential contamination, filtering, and sorption of the target substances. The information provided in this review will support scientists and professionals in optimizing their experimental set-up for meeting their specific goals.
Understanding the physics of flow and transport through the vadose zone has advanced significantly in the last three decades. These advances have been made primarily in humid regions or in irrigated agricultural settings. While some of the techniques are useful, many are not suited to arid regions. The fluxes of water and solutes typically found in arid regions are often orders of magnitude smaller than those found in agricultural settings, while the time scales for transport can be orders of magnitude larger. The depth over which transport must be characterized is also often much greater than in humid regions. Rather than relying on advances in applied tracers, arid-zone researchers have developed natural-tracer techniques that are capable of quantifying transport over tens to thousands of years. Techniques have been developed to measure the hydraulic properties of sediments at all water contents, including the very dry range and at far greater depths. As arid and semiarid regions come under increased development pressures for such activities as hazardous- and radioactive-waste disposal, the development of techniques and the understanding of water and solute transport have become crucial components in defining the environmental impacts of activities at the landsurface. In the past, the movement of water and solutes through the unsaturated zones of arid and semiarid regions was largely ignored, either for the sake of expediency or from a lack of knowledge or misperceptions regarding the extent of water movement. In the High Plains of the United States, water extraction from the Ogallala aquifer proceeded at a rapid rate throughout the 20th century, with little attention paid to the rate of replenishment from natural recharge. As withdrawals began to exceed recharge, water levels dramatically declined and are now necessitating changes in the economic base for this large portion of the agricultural United States. At Hanford, Washington, large amounts of radioactive waste from nuclear weapons production were disposed of at or near the landsurface under the premise that there was no movement of water within the unsaturated zone to transport the contaminants to the underlying aquifer.
Lysimeter leachate collection efficiencies (LCEs), which are the measured leachate volume divided by estimated percolation water, are needed to convert measured leachate volumes to actual leachate fluxes. In this study, LCE of zero‐tension pan and passive capillary fiberglass wick lysimeters were evaluated and directly compared. A total of 18 pan and 18 wick lysimeters were installed 1.2 m below the soil surface in tilled and no‐till plots. From May 1995 to April 2000 the lysimeter LCEs were evaluated using a water‐balance method with evapotranspiration (ET) estimated by the Penman‐Monteith equation. On average, wick lysimeters collected 2.7 times more leachate than did pan lysimeters, and tillage had no effect on the 5‐yr total leachate volume at the 5% significance level. If the anomalous 1997 leaching year with an exceptionally warm and wet winter was excluded, wick and pan lysimeters collected about 50 and 20% of precipitation, respectively, from both tillage systems. The average 4‐yr LCE for wick lysimeters was 101% and that for the pan lysimeters was 40%. The much higher LCEs for both pan and wick lysimeters during the 1997 leaching year were thought to be the result of over‐sampling of leachate during the exceptionally wet and warm winter. Errors of ET estimates associated with estimating crop residue cover and water stress adjustment parameters were small. Errors in LCE estimates can be mathematically shown to be in the same range as those of ET estimates.
To identify the most suitable technique for measuring solute leaching in a sandy soil, we compared three methods in an irrigation experiment (irrigation rates: 5 and 2.4 mm h-1) using Cl- as a tracer. We tested tensiometer-controlled suction plates, wick samplers, and ion-exchange resin boxes installed between fiberglass pads. Ten samplers of each type were installed at a 52-cm depth (suction plates) or a 60-cm depth (wick and resin box samplers) into soil monoliths. The recovery of water and Cl- by the suction plates varied little with irrigation rate (107-118%). The wick samplers performed well during 5 mm h-1 irrigation (Cl- recovery: 111%; water recovery: 103%). However, at the irrigation rate of 2.4 mm h -1, the water recovery was significantly lower (70%), probably because the soil suction exceeded the maximum capillary force of the wicks. The wicks did not induce a retardation or additional dispersion of Cl- compared with suction plates. The recovery of Cl- by the resin boxes was only 6%. Tensiometer-controlled suction plates allowed an overall satisfactory estimation of water and solute fluxes in the sandy soil.
Of the tracer techniques available, Cl balance techniques appear to be the simplest, least expensive, and most universal for recharge estimation. In Australian studies, under native vegetation in semiarid areas, Cl profiles were found to be remarkably uniform, indicating very low and relatively uniform rates of groundwater recharge. Following changes in land use, recharge appeared to become much more variable, increasing more than two orders of magnitude. Methods for scaling point estimates of recharge to large areas using indirect techniques (such as nondestrucive electromagnetic induction) have also been developed. In deep unsaturated zones, the pressure response in the soil water may be recorded in the profile, and simple field measurements may be used to obtain semi-independent verification of recharge rates determined by using Cl balance techniques. -from Authors
Unsaturated hydraulic conductivities, K(h), were measured in wicks. Moisture contents, θ(h) were measured in wicks. Hysteresis was observed, and the draining curves were used to predict K(h) using the van Genuchten equation coupled with the Mualem conductivity model. A solution for unsaturated flow was used to calculate h in wicks given the flux, q, and length. Calculated values of h were within 25% of the measured values for high fluxes and within 5% of the measured values for low fluxes. A least-squares procedure for matching the h vs. q curve of a wick to a soil was used to design passive capillary samplers for application in two soils. -from Authors
Existing unsaturated zone soil water samplers have several deficiencies that jeopardize their utility for field sampling. Suction cups function only when a vacuum is applied, and sample from an unknown volume of soil. Pan samplers sample only saturated flow. A capillary-wick sampler was developed to overcome these problems and was tested in both the laboratory and field to evaluate its performance. Breakthrough curves for selected inorganic ions and organic chemicals were established in the laboratory. No adsorption/ desorption of these chemicals was found for the capillary-wick sampler made entirely of glass. Banks of eight capillary-wick samplers were installed in field plots of Padina sand (loamy, siliceous, thermic, Grossarenic Paleustalf), Weswood silt loam (fine-silty, mixed, thermic Fluventic Ustochrept), and Lufkin clay (fine, montmorillonitic, thermic Vertic Albaqualf) soils. Saturated soil Br breakthrough curves were determined at each location and used to estimate the number of samplers required to characterize the flow of contaminants. To achieve 95% confidence in the chemical data from the three soils and plot sizes tested, 31 samplers were required for the sandy soil, six for the silt loam soil, and only two for the clay soil. The wick-activated sampler collected soil solution samples from soils having soil water potentials ranging from 0 to -6.0 kPa. The capillary-wick sampler collected samples continuously across this range of water potentials without the need for a continuous vacuum and is thus an improvement over existing samplers. While the capillary-wick samplers usually collected sample volumes representative of the flux at potentials of -5 kPa, samples collected at greater and lesser potentials were not representative of the flux.
Water flux and solute concentrations must be known to assess contaminant fluxes in the vadose zone but are seldom measured simultaneously at the same location. A water fluxmeter with divergence control was modified to measure solute concentrations by adding a funnel and collection vial to the bottom of the meter. Laboratory experiments using a coarse sand and a fine sand show that measured solute concentrations and known water fluxes combine to give an accurate assessment of solute flux. Using a nitrate tracer applied under steady influx rates of 621 mm yr-1, the breakthrough curves and the water fluxes were measured, and the solute fluxes were calculated. The flow divergence was examined by measuring the soil-water content and pressure head at different positions and by measuring the water flux passing through and around the water fluxmeter. Results show that the modified water fluxmeter provides a convenient way for long-term monitoring of contaminant flux.
Lysimeter leachate collection efficiencies (LCEs), which are the measured leachate volume divided by estimated percolation water, are needed to convert measured leachate volumes to actual leachate fluxes. In this study, LCE of zero-tension pan and passive capillary fiberglass wick lysimeters were evaluated and directly compared. A total of 18 pan and 18 wick lysimeters were installed 1.2 m below the soil surface in tilled and no-till plots. From May 1995 to April 2000 the lysimeter LCEs were evaluated using a water-balance method with evapotranspiration (ET) estimated by the Penman-Monteith equation. On average, wick lysimeters collected 2.7 times more leachate than did pan lysimeters, and tillage had no effect on the 5-yr total leachate volume at the 5% significance level. If the anomalous 1997 leaching year with an exceptionally warm and wet winter was excluded, wick and pan lysimeters collected about 50 and 20% of precipitation, respectively, from both tillage systems. The average 4-yr LCE for wick lysimeters was 101% and that for the pan lysimeters was 40%. The much higher LCEs for both pan and wick lysimeters during the 1997 leaching year were thought to be the result of oversampling of leachate during the exceptionally wet and warm winter. Errors of ET estimates associated with estimating crop residue cover and water stress adjustment parameters were small. Errors in LCE estimates can be mathematically shown to be in the same range as those of ET estimates.
Understanding the physics of flow and transport through the vadose zone has advanced significantly in the last three decades. These advances have been made primarily in humid regions or in irrigated agricultural settings. While some of the techniques are useful, many are not suited to arid regions. The fluxes of water and solutes typically found in arid regions are often orders of magnitude smaller than those found in agricultural settings, while the time scales for transport can be orders of magnitude larger. The depth over which transport must be characterized is also often much greater than in humid regions. Rather than relying on advances in applied tracers, arid-zone researchers have developed natural tracer techniques that are capable of quantifying transport over tens to thousands of years. Techniques have been developed to measure the hydraulic properties of sediments at all water contents, including the very dry range and at far greater depths. As arid and semiarid regions come under increased development pressures for such activities as hazardous- and radioactive-waste disposal, the development of techniques and the understanding of water and solute transport have become crucial components in defining the environmental impacts of activities at the landsurface.
For many years lysimeters have been proven to be effective tools in assessing and predicting the effects of current land use and future land use changes in catchment areas on both water and solute balances. Although due to the diverse aspects of mass transport modelling, many different types of lysimeters exist, water and solute balances are by no means fully understood, especially in post-mining areas. To tackle this problem, a new piece of equipment has been developed which enables the actual weight of a lysimeter to be precisely measured. The newly designed device, which has been used for one of the experiments described in this paper, permits the weighing of for example a 2 m3 lysimeter vessel with an accuracy down to 30 g. The second newly developed appliance presented here is the GAMS (Gas-Migration-Simulator). Basically comparable to a lysimeter, the difference is that the GAMS allows the detailed investigation of soil-gas migration processes and their dependence on parameters like the diffusion coefficient and the gas permeability of the soil, alterations of the groundwater level and on various external influences such as changes of the actual meteorological conditions. These two newly developed techniques are described in this paper, and their respective suitability is demonstrated on the basis of data sets recorded during initial experiments.
Arid-site recharge, while generally low, can be highly variable. Recharge under similar climate and soil conditions but with different plant cover and topography can vary from zero to more than the annual precipitation. Simple estimates of recharge based on fixed fractions of annual precipitation are misleading because they do not reflect the plant and soil factors controlling recharge. Detailed water balance models, successful for irrigated agriculture, fail to predict evapotranspiration accurately under conditions where plants suffer seasonal water stress and cover is sparse. Recharge, when estimated as a residual in water balance models, may be in error by as much as an order of magnitude. Similar errors can occur when soil water flow models are used with measured or estimated soil hydraulic conductivities and tension gradients. Lysimetry and tracer tests offer the best hope for evaluating recharge at arid sites, particularly in siting waste disposal facilities, where reliable recharge estimates are needed. Quantification of drainage using lysimetry over several years under a given set of soil, plant, and climate conditions for a specific site can provide a basis for calibrating models for recharge prediction. Tracer tests using such long-lived tracers as 36Cl or perhaps stable isotopes (180, deuterium) can provide qualitative estimates of recent recharge at a given site.
The objective was to estimate the potential risk of N leaching into the groundwater under various types of agriculture by using lysimeter experiments on the nitrogen(N)-cycle of various soil types. Results were obtained with 12 weighable, monolithic lysimeters with a surface area of 1 m2, a total depth of 3 m, and free drainage. Mean annual N-leaching losses of 5 to 44 kg ha-1 and nitrate concentrations of the seepage water (leachate) between 80 and 200 mg 1-1 were measured during the period of intensive agricultural use. On fallow land with a well-established grass vegetation, some nitrate was removed by the plants. As a result, the nitrate concentrations in the leachate were reduced significantly. Ecological farming measures generally reduced N leaching losses and kept the N-concentration in the leachate below the German threshold value for drinking water with 50 mg 1-1 nitrate. However, ploughing in of clover or leguminous vegetation and the application of farmyard manure in autumn caused the nitrate concentration in the leachate to rise significantly above the mentioned threshold value.
We should know the effects of soil use and management on the contents and forms of soil phosphorus (P) and the resulting potential for leaching losses of P to prevent eutrophication of surface water. We determined P test values, amounts of sequentially extracted forms of P, P sorption capacities and degrees of P saturation in 20 differently treated soils and compared these data with leaching losses in lysimeters. One-way analyses of variance indicated that most fractions of P were significantly influenced by soil texture, land use (grassland, arable or fallow or reafforestation), mineral fertilization and intensity of soil management. Generally, sandy soils under grass and given large amounts of P fertilizer contained the most labile P and showed the largest P test values. Fallow and reafforestation led to smallest labile P fractions and relative increases of P extractable by H2SO4 and residual P. Arable soils with organic and mineral P fertilization given to crop rotations had the largest amounts of total P, labile P fractions and P test values. The mean annual concentrations of P in the lysimeter leachates varied from 0 to 0.81 mg l–1 (mean 0.16 mg l–1) and the corresponding leaching losses of P from < 0.01 to 3.2 kg ha–1 year–1 (mean 0.3 kg P ha–1 year–1). These two sets of data were correlated and a significant exponential function (R2 = 0.676) described this relation. Different soil textures, land uses and management practices resulted in similar values for P leaching losses as those for the amounts of labile P fractions. Surprisingly, larger rates of mineral P fertilizer did not necessarily result in greater leaching losses. The contents of P extracted by NaHCO3 and acid oxalate and the degrees of P saturation were positively correlated with the concentrations of P in leachates and leaching losses. As the P sorption capacity and degree of P saturation predicted leaching losses of P better than did routinely determined soil P tests, they possibly can be developed as novel P tests that meet the requirements of plant nutrition and of water protection.
Exact information about soil water flow is needed to quantify solute transfer within the unsaturated zone. Water flux densities are often measured indirectly, e.g., with water-balance, water content–change, or tracer methods, and, therefore, often predicted with notable uncertainties. Over the last years, direct lysimetry methods have been increasingly used to study water and solute migration in soil profiles. A large weighable lysimeter is the best method to obtain reliable drainage data, but it requires relatively high investment and maintenance expenses. To reduce cost and improve comparability with undisturbed sites, a new technology to collect large monolithic soil columns with a surface area of 0.5–2 m2 and a depth of 1–3 m as well as a containerized polyethylene (PE-HD) lysimeter station were developed. In addition, the station was fitted with a new high-precision weighing technique. In this paper, the latter is demonstrated with data from a newly constructed gravitation lysimeter. Besides recording rainfall and seepage, its weighing precision makes it possible to register mass input by dew, fog, or rime. It also permits a very accurate calculation of actual evapotranspiration. Because this new type of lysimeter allows a very high temporal resolution, it is ideally suited to develop and test models for soil hydrologic processes.
Non-point-sources of nitrogen (N) and phosphorus (P) are recognized as major causes of eutrophication of surface waters. Adoption of policies to reduce pollution in the former German Democratic Republic following re-unification of Germany in 1990 provided an opportunity to examine how taking agricultural land out of production affected nutrient loads and aquatic biota in a small rural watershed. Between 1994 and 1996, soluble reactive phosphorus (SRP) and dissolved inorganic nitrogen (DIN) loads in a first-order agricultural stream decreased by >90% while instream concentrations decreased by 89% for DIN and 40% for SRP. This reduction in nutrients coincided with a decrease in precipitation (from 760 to 440mm between 1994 and 1996) and an increase in the area of land set aside from agricultural production (from 0.3% in 1990 to a maximum of 8% in 1994). The biomass of primary producers (episammic algae) showed no clear response to this decrease in nutrient concentrations. However, benthic invertebrate composition shifted from a chironomid–amphipod to an oligochaete–gastropod dominated community in response to the decrease in DIN and changes in episammic algal abundance and sediment organic carbon concentrations. Results from our 4-year study showed reductions in soil nutrient losses combined with less precipitation resulted in less P and N in a rural stream and a change in benthic invertebrate community composition and abundance.
Different methods exist for measuring soil water and solute fluxes in and below the root zone and have been critically reviewed.
Besides indirect methods (e.g. water balance, tensiometer, time domain reflectometry – TDR, frequency domain reflectometry
– FDR, environmental tracer) direct methods (e.g. drainage-type lysimeter, water fluxmeter) have a long tradition and have
been successfully used in seepage research. A large weighable out door lysimeter is the best method for obtaining reliable
data about seepage water quantity and quality, but it involves significant investment and additional expenses for maintenance.
To tackle this problem new methods for the vertical collection of large volume soil monoliths (up to 6m3) as well as for the horizontal collection (up to 6m3) have been developed. For the placement of the lysimeter a container lysimeter unit was constructed, which is cheaper than
a conventional steel or concrete cellar. Furthermore, the technical design of the newly developed lysimeter types as a weighable
gravitation lysimeter, a weighable groundwater lysimeter and a lateral flow lysimeter are presented.
Lysimeters are used to study and monitor water, fertilizers, salts and other contaminants and are particularly valuable in transpiration and evapotranspiration research. Saturation at the soil bottom boundary in a lysimeter is inherent to its design. A drainage extension made of porous media with high hydraulic conductivity and substantial water holding capacity was devised to extend the lysimeter in order to produce soil moisture conditions mimicking those in the field. Design criteria that assure equal discharge in the soil and in the highly conductive drain (HCD) were established and formulated. Desired matric head at the lysimeter base is determined by HCD extension length. Its value can be manipulated and can range between saturation and the soil's field capacity. Conditions where the HCD is not limiting to flow are obtained through selection of the appropriate cross sectional area ratio between the soil in the lysimeter and the HCD. The validity of these criteria was confirmed with 200 l working lysimeters in the field, with and without plants, and with detailed flow tests utilizing smaller (15 l) lysimeters. Comparison of computed and measured matric head and leachate volume indicates that the proposed method can serve to maintain conditions similar to those in the field.
Laboratory studies of solute transport in soils (soil columns) are not totally representative of field conditions (spatial variability, soil structure etc.). Field studies hardly allow quantification of fluxes and mechanisms. In this article, and intermediate approach is suggested, using a lysimeter (1.7 m3) of an almost undisturbed soil, with controlled boundary conditions, the aim being to be able to quantify fluxes and mechanisms at a scale closer to field conditions, thus yielding results that better depict reality. Two experiments, with constant water fluxes of 1.05 and 1.48 mm h−1 were conducted. Solutes were introduced as concentration pulses. Species 2H2O, C1− and Br− were used as tracers, and K+, NH4+, NO3−, atrazine as interactive and/or reactive solutes. Elution curves were analyzed by the method of moments. Results show that about 20% of the water are immobile. As a consequence of anion exclusion, anion tracers appear at the outlet with an advance of about 10% in time as compared to isotopic tracers. The added NH4+is mostly nitrified, and K+ undergoes cation exchange with Ca2+ and Mg2+. Under our experimental conditions, leaching of atrazine is significant with low degradation. A third experiment was conducted, in which the flow was interrupted while the solute peak was within the lysimeter, and 400 soil samples were extracted from the lysimeter. Soil–water content distributions exhibit coefficients of variation within layers between 5% and 27%. Concentration distributions exhibit coefficients of variation within layers between 22% and 59%. There is no correlation between concentration and water content. The observed spatial variability suggests the occurrence of preferential flow. Concentrations in suction cups were 55%–136% of those measured in corresponding soil samples.
Bodenphysikalische Aspekte bei der Erfassung von gelösten Stoffen mit Hilfe von Lysimetern
- E Klaghofer
Klaghofer, E. 1991. Bodenphysikalische Aspekte bei der Erfassung von
gelösten Stoffen mit Hilfe von Lysimetern. Proceedings of the 1st
Lysimeter Conference (ed. K. Chytil), pp. 14-20. BAL, Gumpenstein.
Grö des Wasserhaushaltes verschiedener Bö unter landwirtschaftlicher Nutzung im klimatischen Grenzraum des Mit-teldeutschen Trockengebietes – Ergebnisse der Lysimeterstation Bran-dis. Doctoral dissertation Recharge from precipitation
- U Haferkorn
- Gö
- J M H Hendrickx
- G R Walker
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Soil Map of the World Food and Agricultural Organization of the United Nations Groundwater recharge in arid regions: review and critique of estimation methods
- Rome Gee
- G W Hillel
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Lysimeters for evapotranspiration and environmental measurements
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- A Alfaro
- M Smith
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pp. 79-84. American Society of Civil Engineers, New York, NY.
Recharge from precipitation. In: Recharge of Phreatic Aquifers in (Semi-)Arid Areas (ed. I. Simmers), pp
- J M H Hendrickx
- G R Walker
Hendrickx, J.M.H. & Walker, G.R. 1997. Recharge from precipitation. In:
Recharge of Phreatic Aquifers in (Semi-)Arid Areas (ed. I. Simmers),
pp. 19–111. Balkema, Rotterdam.
Größen des Wasserhaushaltes verschiedener Böden unter landwirtschaftlicher Nutzung im klimatischen Grenzraum des Mitteldeutschen Trockengebietes-Ergebnisse der Lysimeterstation Brandis
- U Haferkorn
Haferkorn, U. 2000. Größen des Wasserhaushaltes verschiedener Böden
unter landwirtschaftlicher Nutzung im klimatischen Grenzraum des Mitteldeutschen Trockengebietes -Ergebnisse der Lysimeterstation Brandis. Doctoral dissertation, Georg-August-Universität, Göttingen.
A modified vadose‐zone fluxmeter with solution collection capability
- Gee G.W.