Shallow Groundwater Table Research Articles

Variability of groundwater levels and total organic carbon in the riparian zone of a boreal catchment

[1] The riparian zone is a narrow corridor where hillslopes (and their associated hydrobiogeochemical processes) interface with the river system. As such, the riparian zone serves as the last piece of landscape with which water interacts as it transitions from being water flowing primarily through the landscape (i.e., shallow groundwater) to water flowing primarily on the landscape (i.e., stream water). This study investigates the spatiotemporal variability in riparian-zone soil water total organic carbon (TOC) and its relation to the shallow groundwater table using observations from the recently instrumented riparian observatory in the Krycklan catchment study area located in boreal northern Sweden. In general, there is a decrease in TOC concentration with depth down through the soil profile. The rate of this decrease was variable among the six monthly samplings used in this study. The spatial variability of soil water TOC in the riparian zone was connected to the spatial variability of the shallow groundwater levels. This demonstrated the importance of the temporal variation of flow pathways and the mixing of waters from different sources of TOC moving into and through the riparian zone. The coupled variation of the hydrologic and biogeochemical systems raised questions about the ability of simple lumped approaches to accurately predict how in-stream TOC concentrations will change with climate and/or land use. The integrated sampling approach in the riparian observatory covers both hydrologic and biogeochemical aspects of soil water TOC and provides a basis for development and testing of distributed, physically based transport models.

Mechanism of Soil Sodification at the Local Scale in Songnen Plain, Northeast China, as Affected by Shallow Groundwater Table

Soil sodification in Northeast China is controlled by many other factors besides groundwater level. This research aims to explore the mechanism of sodium buildup in sodic soil based on in-situ observation and laboratory analysis. Results indicate that water and sodium redistribution process on the soil surface at local scale was an additional factor leading to the rapid soil sodification development in Songnen Plain in recent decades. A field observation was conducted in a 35 × 35 m2 area. Mollisols were distributed in depressions and free of natric horizon, while Halaquepts were found on micro slopes and high flats. A natric horizon was found at a depth of 15–30 cm in high flats, with an exchangeable sodium percent (ESP) value of 70. Fluctuation of groundwater table in the freezing period was related, to some extent, to the formation and development of frozen soil. During the freezing period, groundwater table was gradually lowered as a result of the groundwater moving into the frozen layer, leading to higher moisture content therein. During the thawing period, soil moisture content in the surface layer of Mollisols showed a significant enrichment (p < 0.05) from 0.27 to 0.69 m3 m−3(over-saturated). Salt in the surface of Halaquepts enriched quickly, especially in the micro slope, by about 80%. In comparison, insignificant change was observed in Mollisols. Sodic soil should be leveled fully and adequate drainage should be utilized before farming in order to prevent soil sodification. Blocking the capillary pore channels between topsoil and subsoil by plowing before freezing season would help soil desodification in high-latitude arid and semiarid regions.

Potential plant species distribution in the Yellow River Delta under the influence of groundwater level and soil salinity

AbstractThis article describes a multidisciplinary approach to assessing potential vegetation types. The relation between vegetation distribution as derived from field survey and habitat characteristics in the Yellow River Delta (YRD) was analyzed using detrended canonical correspondence analysis (DCCA). The three‐dimensional groundwater numerical simulation model MODFLOW yielded an accurate distribution of the shallow groundwater table within the study area. Groundwater table and soil salinity appeared to have the largest influence on the distribution patterns of specific indicator species. The quantitative relationships between species presence and environmental factors were further explored using logistic regression, allowing for the prediction of potential species distribution in relation to fluctuations in groundwater depth and soil salinity. Based on this, potential distribution maps for specific plant species and their communities were generated using ArcGIS. The potential vegetation map was compared to the actual vegetation map (interpreted from SPOT imagery), which leads to a discussion of the main factors responsible for fragmentation and degradation of the local vegetation system. Copyright © 2010 John Wiley &amp; Sons, Ltd.

The Permian Moradi Formation of northern Niger: Paleosol morphology, petrography and mineralogy

Three basic paleosol morphologies, named Type A, Type B and Type C, are described from the middle–upper Permian strata of the Moradi Formation, Tim Mersoi Basin, northern Niger. The Moradi Formation is a typical alluvial redbed succession dominated by red mudrocks with fine to coarse-grained pebbly channel sandstones and matrix-breccias. Type A paleosols are hosted by well-sorted fine to medium grained trough cross bedded and massive sandstones and preserve abundant vertical to horizontal micritic and microspar calcite tubules, interpreted as rhizoliths. Lateral variability of rhizoliths in Type A paleosols, and their close association with fluvial channel-fill sediments suggests they are the roots of grove stands of phreatophytic vegetation that grew within unstable anabranching stream systems. Type B paleosols are hosted by mudrocks and preserve well-developed ped structure, abundant micritic calcite nodules and vertically-stacked micritic calcite nodular bodies, as well as rare calcite with satin-spar texture interpreted as a pseudomorphic replacement of pedogenic gypsum. The morphology of Type B paleosols suggests they were formed in well-drained floodplain deposits on stable landforms. Type C paleosols are similar to Type B but preserve pedogenic structures indicative of soil volume expansion and contraction, as well as more abundant Stage II pedogenic carbonate nodules. The morphology of Type C paleosols suggests that they developed periodically rather than seasonally in poorly-drained deposits that nevertheless occupied a relatively stable part of the landscape such as the plains flanking ephemeral lakes or sabkhas.X-ray diffraction analysis of the <2μm fraction from the Moradi Formation strata indicates that paleosol phyllosilicates are composed of illite, smectite, and occasionally kaolinite and talc. Illite is likely a detrital mineral, whereas smectite and kaolinite are likely pedogenic weathering products. The presence of talc in the Moradi Formation paleosols is unusual. It is limited to paleosol horizons that also preserve evidence for pedogenic gypsum accumulation and is therefore most likely related to a pedogenic weathering process. It is possible that this talc is a relatively low-temperature (~50–100°C) diagenetic alteration product of pedogenic Mg–phyllosilicates such as sepiolite.The range of morphologies, petrographic textures and mineralogy of the paleosol profiles indicates semi-arid to hyper-arid climatic setting. This paleoclimatic reconstruction is in agreement with Middle and Late Permian conceptual paleoclimate models and quantitative general circulation models. Nevertheless, and in spite of an arid climate, Moradi paleosols and their host strata also indicate a relatively shallow groundwater table. Importantly, this shallow groundwater resource undoubtedly helped to support the moderately diverse fossil vertebrate assemblage and large-stature macrophytes preserved in the Moradi Formation.

Tracing subsurface migration of contaminants from an abandoned municipal landfill

This paper aims at determining of inorganic leachate contamination for a capped unsanitary landfill in the absence of hydrogeological data. The 2D geoelectrical resistivity imaging, soil physicochemical characterization, and surface water analysis were used to determine contamination load and extent of selective heavy metal contamination underneath the landfill. The positions of the contaminated subsoil and groundwater were successfully delineated in terms of low resistivity leachate plumes of Zn > Pb > Cr > Cu. Taking into consideration poor physical and chemical characteristics of the local soil, these metals first seem to be attenuated naturally at near surface then remobilize unavoidably due to the soil acidic environment (pH 4.2-6.18) which in turn, may allow an easy washing of these metals in contact with the shallow groundwater table during the periodic fluctuation of the Kelang River. These heavy metals are believed to have originated from hazardous industrial waste that might have been illegally dumped at the site.

Quantification of C and N stocks in grassland topsoils in a Dutch region dominated by dairy farming

SUMMARYEstimates on soil organic carbon (SOC) and nitrogen (N) stocks in soils cannot be directly calculated from routine soil analyses, since these often lack measurements on soil bulk density (Bd). Hence, flexible pedotransfer functions are required that allow the calculation of SOC stocks from gravimetrically determined SOC contents. The present paper aimed to: (1) quantify SOC and N stocks in grassland topsoils for a Northern Dutch region dominated by dairy farming and (2) analyse the relationships between SOC and bulk density at the field level. As estimates of SOC and N stocks are potentially affected by soil compaction, the combined measurements on soil bulk density and soil organic matter (SOM) were also evaluated with respect to critical limits for soil compaction using soil density (Sd) for sandy soils and packing density (Pd) for clay soils. The SOC andBdmeasurements were done in the upper 0·1–0·2 m of grasslands at 18 dairy farms, distributed across sandy, clay and peat soils. Both farm data and grassland management data were collected. Non-linear regressions were used to analyse relationships betweenBdand SOM. Significant non-linear relationships were found between gravimetric SOC contents and bulk density for the 0–0·1 m layer (R2=0·80) and the 0·1–0·2 m layer (R2=0·86). None of the fields on sandy soils or clay soils indicated signs for limited rooting in the topsoil although some fields appear to approach the critical limit for compaction for the 0·1–0·2 m layer. Stocks of SOC in the top 0·2 m at farm level were highest in the peat soils (21·7 kg/m2) and lowest in the sandy soils (9·0 kg/m2). Similarly, N stocks were highest for farms on peat soil (1·30 kg/m2) and lowest for farms on sandy soil (0·60 kg/m2). For the sandy soils, the mean SOC stock was significantly higher in fields with shallow groundwater tables.

The MobiSan approach: informal settlements of Cape Town, South Africa

Pook se Bos informal settlement and the Cape Town Water & Sanitation Services Department are partnering on an urban sanitation project with a Dutch Consortium consisting of Lettinga Associates Foundation (LeAF), Landustrie Sneek and Vitens-Evides International. The aim of the project is to improve the basic sanitation services provided in informal settlements through the implementation of the MobiSan approach. The approach consists of a communal Urine-Diversion and Dehydration Toilet (UDDT) built in a former sea shipping container. The system is independent of water, electricity or sewerage connection and it is maintained by full-time community caretakers who also act as hygiene promoters. The project seeks to link sanitation services with hygiene promotion in informal settlements while enhancing user satisfaction and reducing costs in providing basic sanitation services. This paper describes the preliminary experiences and lessons learnt during the implementation and evaluation of the MobiSan prototype and discusses its potential for replication. The MobiSan has proved to be an appropriate option by means of dealing successfully with shallow groundwater table, land availability and high settlement densities. In addition it has been demonstrated to be cost-competitive in terms of operating cost compared to chemical toilets.

The effects of groundwater table and flood irrigation strategies on soil water and salt dynamics and reed water use in the Yellow River Delta, China

Vegetation management in shallow groundwater table environments requires an understanding of the interactions between the physical and biological factors that determine root-zone soil salinization and moisture. In this study, the effects of groundwater depth and flood irrigation strategies on water and salt dynamics and reed water use were analyzed in the shallow groundwater region of the Yellow River Delta in China using the HYDRUS-1D model. The results indicated that there is a conflict between water, salt stress, and reed water use with variations in groundwater depth. A water table depth of 3.5 m is the minimum limit to maintain a safe level of soil salinity, but at this depth, the environmental stress on reeds is worsened by the decrease in soil water storage. Maintaining the flood pulses on the wetland, especially during May, may be critical for restoring the reed wetland in the Yellow River Delta.

Simulating water use and N response of winter wheat in the irrigated floodplains of Northwest Uzbekistan

The crop-soil simulation model CropSyst was used to simulate growth, water- and N-uptakes of irrigated winter wheat ( Triticum aestivum L. cv. Kupava) in Khorezm, in the dry lands of northwest Uzbekistan, Central Asia. CropSyst was calibrated using the findings of field experiments of 2005/06 and 2006/07 and validated for the 2007/08 season. A relative root mean squared error of 11% proved the accuracy between simulated and observed aboveground biomass and grain yield in 2007/08. Scenario analyses showed that N-leaching was high and ranged from 63 to 106 kg ha −1 when irrigated between 749 and 869 mm during the first two cropping seasons. The simulated N-leaching was lowest and ranged from 7 to 15 kg ha −1 when irrigation was only 148–395 mm during 2007/08. The considerable N losses during leaching and high N-uptakes by wheat together resulted in a negative N-balance even during applications of 180 and 240 kg ha −1 of N-fertilizer. N scarcity in the N-balance was reduced with increasing N-fertilizer amounts and ranged from −29 to −153 kg N ha −1 in 2005/06 and 2006/07. Despite a common shallow groundwater table in the region during some time of the year, scenario analysis revealed that only full irrigation water (580 mm) and N supply according to crop demand (180 kg ha −1) guaranteed high grain yields, unless the water table is permanently shallow to overcome irrigation deficits. Limited irrigation and N application (40% and 55% of ‘optimal’, respectively) in combination with a groundwater table below 3 m resulted in a 55% yield decline. The CropSyst wheat model proved a robust tool for assessing the influence of water and N dynamics under conditions of varying irrigation and shallow groundwater tables. It thus has potential as a decision support not only in northwest Uzbekistan, but also in comparable regions of Central Asia.

Hydrological process controls on nitrogen export during storm events in an agricultural watershed

The dynamic characteristics of nitrogen (N) and suspended solids (SS) were investigated in stream water during four storm events in 2003 in the Shibetsu watershed, eastern Hokkaido, Japan. Analysis showed that total nitrogen (TN), nitrate-N (NO- 3-N), dissolved organic nitrogen (DON), particulate nitrogen (PN) and SS concentrations all peaked sharply during the rising limb of the discharge hydrograph, but peaks in PN and SS were more significant than the peak in dissolved N. Particulate N and SS consistently displayed clockwise hysteresis with higher concentrations during rising flows, whereas NO- 3-N and DON showed different patterns among the storms depending on the antecedent soil moisture. An M (V) curve, defined as the nutrient mass distribution versus the volume of discharge, showed that a “first flush” of PN, NO- 3-N, DON and SS was observed; however, the distribution of nutrient loads in the discharge was different. Particulate N and SS had a shorter flushing characteristic time constant (t 1/e, defined as the time interval required for a decline in nutrient concentrations in discharge water to e−1 [37%] of their initial concentrations), but contributed 80% of fluxes during the first 50% of the discharge, whereas the longer flush time (t 1/e) of NO- 3-N and DON with slowly decreased concentrations led to half loads during the recession of the discharge. These data indicate that flush mechanisms might be distinguished between particulate nutrients and dissolved N. Analysis showed that the concentrations of PN and SS derived from soil erosion were related to surface run-off. In contrast, NO- 3-N originated from the near-surface soil layer associated with the rising shallow groundwater table and mainly flushed with subsurface run-off. The different flushing mechanisms implied that different watershed best management practices should be undertaken for effectively mitigating water quality degradation.

Climate–soil–vegetation control on groundwater table dynamics and its feedbacks in a climate model

Among the three dynamically linked branches of the water cycle, including atmospheric, surface, and subsurface water, groundwater is the largest reservoir and an active component of the hydrologic system. Because of the inherent slow response time, groundwater may be particularly relevant for long time-scale processes such as multi-years or decadal droughts. This study uses regional climate simulations with and without surface water–groundwater interactions for the conterminous US to assess the influence of climate, soil, and vegetation on groundwater table dynamics, and its potential feedbacks to regional climate. Analyses show that precipitation has a dominant influence on the spatial and temporal variations of groundwater table depth (GWT). The simulated GWT is found to decrease sharply with increasing precipitation. Our simulation also shows some distinct spatial variations that are related to soil porosity and hydraulic conductivity. Vegetation properties such as minimum stomatal resistance, and root depth and fraction are also found to play an important role in controlling the groundwater table. Comparing two simulations with and without groundwater table dynamics, we find that groundwater table dynamics mainly influences the partitioning of soil water between the surface (0–0.5 m) and subsurface (0.5–5 m) rather than total soil moisture. In most areas, groundwater table dynamics increases surface soil moisture at the expense of the subsurface, except in regions with very shallow groundwater table. The change in soil water partitioning between the surface and subsurface is found to strongly correlate with the partitioning of surface sensible and latent heat fluxes. The evaporative fraction (EF) is generally higher during summer when groundwater table dynamics is included. This is accompanied by increased cloudiness, reduced diurnal temperature range, cooler surface temperature, and increased cloud top height. Although both convective and non-convective precipitation are enhanced, the higher EF changes the partitioning to favor more non-convective precipitation, but this result could be sensitive to the convective parameterization used. Compared to simulations without groundwater table dynamics, the dry bias in the summer precipitation is slightly reduced over the central and eastern US Groundwater table dynamics can provide important feedbacks to atmospheric processes, and these feedbacks are stronger in regions with deeper groundwater table, because the interactions between surface and subsurface are weak when the groundwater table is deep. This increases the sensitivity of surface soil moisture to precipitation anomalies, and therefore enhances land surface feedbacks to the atmosphere through changes in soil moisture and evaporative fraction. By altering the groundwater table depth, land use change and groundwater withdrawal can alter land surface response and feedback to the climate system.

Annual emissions of dissolved CO2, CH4, and N2O in the subsurface drainage from three cropping systems

AbstractIndirect emission of nitrous oxide (N2O), associated with nitrogen (N) leaching and runoff from agricultural lands is a major source of atmospheric N2O. Recent studies have shown that carbon dioxide (CO2) and methane (CH4) are also emitted via these pathways. We measured the concentrations of three dissolved greenhouse gases (GHGs) in the subsurface drainage from field lysimeter that had a shallow groundwater table. Aboveground fluxes of CH4 and N2O were monitored using an automated closed‐chamber system. The annual total emissions of dissolved and aboveground GHGs were compared among three cropping systems; paddy rice, soybean and wheat, and upland rice.The annual drainage in the paddy rice, the soybean and wheat, and the upland rice plots was 1435, 782, and 1010 mm yr−1, respectively. Dissolved CO2 emissions were highest in the paddy rice plots, and were equivalent to 1.05–1.16% of the carbon storage in the topsoil. Dissolved CH4 emissions were also higher in the paddy rice plots, but were only 0.03–0.05% of the aboveground emissions. Dissolved N2O emissions were highest in the upland rice plots, where leached N was greatest due to small crop biomass. In the soybean and wheat plots, large crop biomass, due to double cropping, decreased the drainage volume, and thus decreased dissolved GHG emissions. Dissolved N2O emissions from both the soybean and wheat plots and the upland rice plots were equivalent to 50.3–67.3% of the aboveground emissions. The results indicate that crop type and rotation are important factors in determining dissolved GHG emissions in the drainage from a crop field.

Sedimentology of a Permian playa lake: the Boda Claystone Formation, Hungary

The Upper Permian Boda Claystone Formation (BCF) in SW Hungary has been previously been identified as a saline lake deposit. A country-wide screening found this 800–1000 m thick succession the most suitable for the disposal of high-level radioactive waste in Hungary, and research into this formation has consequently been intensified since. The investigations included a detailed study of the sedimentological characteristics. Data obtained by mapping of the 25 km 2 outcrop area of the formation and from more than 40 boreholes were processed. The sedimentary structures were investigated on outcrop to microscopic scales, and cycles in the succession were interpreted. The main lithofacies, sedimentary structures and ichnofossils are presented. They indicate that the major part of the succession was deposited in a playa mudflat and is not of lacustrine origin in a strict sense. The lake sediments are re presented by laminated and ripple-marked/flaser-type cross-laminated claystones and siltstones and by massive dolo mites; trace fossils include crawling traces and burrows. Partial or complete drying out of the lake commonly occurred after the formation of carbonate mud by evaporation. Periodic fluvial influx is recorded by cross-bedded sandstones and unsorted gravelly sandstones of up to pebble-sized angular grains. Fenestral and stromatolitic structures reflect the repeated appearance of playa mudflat conditions. The silty claystones, which compose the major part of the succession, lost their primary structures due to pedogenic processes and indicate prolonged subaerial intervals with soil formation and only ephemeral inundations. The presence of pedogenic carbonate concretions supports the interpretation of an arid climate and a relatively shallow groundwater table. Drying-out events shown by desiccation cracks and authigenic breccias can be traced all over the succession. The various facies form small-scale sedimentary cycles showing a shallowing-upward trend and the growing influence of aridity and subaerial exposure.

Evaluation of seismic soil-liquefaction at Guwahati city

Great earthquakes in the past (e.g. 1869 Cachar earthquake, 1897 great Assam earthquake) have caused large scale damage and ground liquefaction in the Guwahati city. Moreover, seismologists are of opinion that a great earthquake might occur in the unruptured segment of the North-East Himalaya that is near to Guwahati city. In this paper, the liquefaction hazard due to these events have been simulated. The obtained results are in general agreement with the reported damages due to the past earthquakes. The central part of the city (i.e. Dispur, GS road), that has large thickness of soft soil deposit and shallow ground water table, is highly vulnerable to liquefaction.

Comparison of different base flow separation methods in a lowland catchment

Abstract. Assessment of water resources available in different storages and moving along different pathways in a catchment is important for its optimal use and protection, and also for the prediction of floods and low flows. Moreover, understanding of the runoff generation processes is essential for assessing the impacts of climate and land use changes on the hydrological response of a catchment. Many methods for base flow separation exist, but hardly one focuses on the specific behaviour of temperate lowland areas. This paper presents the results of a base flow separation study carried out in a lowland area in the Netherlands. In this study, field observations of precipitation, groundwater and surface water levels and discharges, together with tracer analysis are used to understand the runoff generation processes in the catchment. Several tracer and non-tracer based base flow separation methods were applied to the discharge time series, and their results are compared. The results show that groundwater levels react fast to precipitation events in this lowland area with shallow groundwater tables. Moreover, a good correlation was found between groundwater levels and discharges suggesting that most of the measured discharge also during floods comes from groundwater storage. It was estimated using tracer hydrological approaches that approximately 90% of the total discharge is groundwater displaced by event water mainly infiltrating in the northern part of the catchment, and only the remaining 10% is surface runoff. The impact of remote recharge causing displacement of near channel groundwater during floods could also be motivated with hydraulic approximations. The results show further that when base flow separation is meant to identify groundwater contributions to stream flow, process based methods (e.g. the rating curve method; Kliner and Knezek, 1974) are more reliable than other simple non-tracer based methods. Also, the recursive filtering method (proposed by Eckhardt, 2005) can be calibrated well using the results of tracer investigation giving good results. Consequently, non-tracer based base flow separation methods that can be validated for some events may provide a powerful tool for groundwater assessment or model calibration/validation in lowland areas.

Determination of land degradation causes in Tongyu County, Northeast China via land cover change detection

Tongyu County in Northeast China is highly prone to land degradation due to its fragile physical settings characterized by a flat topography, a semi-arid climate, and a shallow groundwater table. This study aims to determine the causes of land degradation through detecting the long-term trend of land cover changes. Degraded lands were mapped from satellite images recorded in 1992 and 2002. These land cover maps revealed that the area subject to land degradation in the form of soil salinization, waterlogging and desertification increased from 2400 to 4214km2, in sharp contrast to most severely degraded land that decreased by 122.5km2. Newly degraded land stems from productive farmland (263km2), harvested farmland (551km2), and grassland (468km2). Therefore, the worsened degradation situation is attributed to excessive reclamation of grassland for farming, over cultivation, overgrazing, and deforestation. Mechanical, biological, ecological and engineering means should be adopted to rehabilitate the degraded land.

Sensitivity of pine flatwoods hydrology to climate change and forest management in Florida, USA

Pine flatwoods (a mixture of cypress wetlands and managed pine uplands) is an important ecosystem in the southeastern U.S. However, long-term hydrologic impacts of forest management and climate change on this heterogeneous landscape are not well understood. Therefore, this study examined the sensitivity of cypress-pine flatwoods hydrology to climate change and forest management by using the physically based, distributed hydrologic modeling system, MIKE SHE. The model was first calibrated and validated with a long-term data set, and then applied using several hypothetical scenarios developed in north central Florida. Our study showed that MIKE SHE could simulate the temporal and spatial dynamics of the shallow ground-water table. The model also identified and confirmed three horizontal ground-water flow patterns at this study site. The modeling results suggested that forest removal and climate change (i.e., warming and drying) would have pronounced impacts on the ground-water table during the dry periods, but these impacts may be minor under wet conditions at this typical flatwoods landscape. At the landscape scale, depressional wetlands may have higher responses to tree removal and climate change than surrounding uplands.

Analysis of possible impacts of climate change on the hydrological regimes of different regions in Germany

Abstract. In this study, the impact of climate change scenarios on the hydrological regimes of five different regions in Germany is investigated. These regions (Northwest Germany, Northeast Germany and East German basins, upper and lower Rhine, pre-Alps) differ with respect to present climate and projected climate change. The physically based SVAT-model SIMULAT is applied to theoretical soil columns based on combinations of land use, soil texture and groundwater depth to quantify climate change effects on the hydrological regime. Observed climate, measured at climate stations of the German Weather Service (1991–2007), is used for comparison with climate projections (2071–2100) generated by the regional scale climate model WETTREG. While all climate scenarios implicate an increase in precipitation in winter, a decrease in precipitation in summer and an increase in temperature, the simulated impacts on the hydrological regime are regionally different. In the Rhine region and in Northwest Germany, an increase in the annual runoff and groundwater recharge is simulated despite the increase in temperature and potential evapotranspiration. In the Eastern part of Germany and the pre-Alps, annual runoff and groundwater recharge will decrease. Due to dry conditions in summer, the soil moisture deficit will increase (in Northeast Germany and the East German basins in particular) or remain constant (Rhine region). In all regions the seasonal variability in runoff and soil moisture status will increase. Despite regional warming actual evapotranspiration will decrease in most regions except in areas with shallow groundwater tables and the lower Rhine. Although the study is limited by the fact that only one climate model was used to drive one hydrologic model, the study shows that the hydrological regime will be affected by climate change. The direction of the expected changes seems to be obvious as well as the necessity of the adaptation of future water management strategies.

Transpiration and early growth of tree plantations established on degraded cropland over shallow saline groundwater table in northwest Uzbekistan

This study examined the early growth and water use of tree plantations established on a marginalized irrigated cropland in northwest Uzbekistan, where salinization of agricultural soils is widespread due to shallow saline groundwater tables. During the first two growing seasons in 2003–2004, the tree stands consisting of Elaeagnus angustifolia L., Populus euphratica Oliv., and Ulmus pumila L. were irrigated with 80 mm year −1, and, in 2005, were left to rely on the shallow (0.9–2.0 m deep) groundwater with a salinity of 1–5 dS m −1. Soil salinity increased but remained within the range of moderate-to-strong (4–14 dS m −1) during the three years. In the course of the growing season, plantations transpired 0.1–7 mm day −1 in 2003 and 1–13 mm day −1 in 2004–2005, as determined with the Penman–Monteith model. In the absence of irrigation, the annual stand transpiration averaged 1250, 1030, and 670 mm for E. angustifolia, P. euphratica and U. pumila, respectively. In 2005, the leaf area index of E. angustifolia ranged from 5 to 10, surpassing that of the other two species more than two-fold. Differences in canopy conductance and transpiration were significant among the tree species and the decoupling coefficient at no time exceeded 0.3, indicating strong physiological control of transpiration. The vigorous juvenile growth and high transpiration under deficit irrigation and after irrigation was terminated, suggested that afforestation with well-adapted tree species is a viable land use option for degraded cropland. The plantation responses to increasing soil salinity must be monitored to determine potential leaching demands in the long run.

Modeling Techniques of Best Management Practices: Rain Barrels and Rain Gardens Using EPA SWMM-5

It is well established that the excess storm-water runoff volume from impervious areas can lead to impairments and water pollution originating from the sewer system overflow and combined sewer systems overflow. This redirection of the runoff into wastewater treatment plants and stream channels can also deprive shallow groundwater tables with recharge, as an impervious surface prevents water from infiltrating to aquifers. The runoff from impervious areas and, in particular, directly connected impervious areas, has been proven to cause the majority of the problem. Controlling the runoff at its source and disconnecting the impervious area from the sewer system is a way to resolve and reduce the impact of excess runoff. This is achieved by implementing specialized detention technologies for runoff reduction. This paper builds on new modeling techniques of two best management practices, rain gardens and rain barrels, implemented in the EPA storm-water management model Version 5 (SWMM-5). The behaviors of a con...