Water Table

The porosityofyoung limestonesexperiencing meteoricdiagenesisin the vicinityof theirdeposition(eagenetic karst) is mainly a doubleporosityconsistingoftouching-vug channelsandpreferredpassagewayslacingthrougha matrixof interparticleporosity. Incontrast,the porosityoflimestonesexperiencingsubaerialerosionfollowingburialdiagenesisandupliftitelogenetic karst) ismainlya doubleporosityconsisting ofconduits within a network offractures. The stark contrast between these two kinds of karst is illustratedby their position on a graph showing thehydraulic characteristics ofanequivalentporousmediumconsistingofstraight,cylindricaltubes(II-Dspace,wheren isporosity,D isthediameter ofthe tubes, and log n is plotted against log D).

This paper presents the results of the application of the Ground Penetrating Radar (GPR) method, or Georadar, in outlining a zone of contamination due to solid residues at the waste burial site of Rio Claro in the state of São Paulo, SE Brazil. A total of eight GPR profiles with 50-and 100-MHz antennae were surveyed. Six profiles were located within the landfill site and the remaining two were outside. The main objective of the GPR survey was to evaluate the side extension of contamination. A Vertical Electric Sounding (VES) survey was performed at four points within the site in order to investigate the vertical extent of the contamination plume and to define the bottom of the landfill. Two additional VESs were done outside the landfill with the purpose of determining the top of the ground water table and the geoelectric stratigraphy of the background. From the interpretation of the GPR profiles, it was possible to locate the top of the contamination plume and to infer that it was migrating laterally beyond the limits of the waste disposal site. This was observed along the profile situated close to the highway SP-127, which was about 20 m from the limit of the site. The signature of the contaminant appears as a discontinuous reflector that is believed to be a shallow ground water table. The discontinuity is marked by a shadow zone, which is characteristic of conductive contaminant residues. The contamination did not move far enough to reach a sugar cane plantation located at approximately 100 m from the border of the site. In the regions free from contamination, the ground water table was mapped at approximately 10 m of depth, and it was characterized by a strong and continuous reflector. The radar signal penetrated deep enough and enabled the identification of a second reflector at approximately 14 m deep, interpreted as the contact between the Rio Claro and the Corumbataí formations. The contact is marked by the presence of gravel characterized by ferruginous concretes, which cause the strong amplitude reflection in the GPR profile. Within the landfill site, the quantitative interpretation of the VES results showed the contamination zone. The base of the landfill varies between 11 and 15 m deep. Outside the landfill site, the VES results showed no indication of contamination and allowed the determination of the top of the ground water table and the contact between the Rio Claro and the Corumbataí formations. The results of GPR and VES showed a good agreement and the integrated interpretations were supported by local geology and information from several boreholes, about 17 m depth, on average. The bottom of the landfill reaches a maximum of 14.5 m depth. D

A tropical ombrotrophic peatland ecosystem is one of the largest terrestrial carbon stores. Flux rates of carbon dioxide (CO 2 ) and methane (CH 4 ) were studied at various peat water table depths in a mixed-type peat swamp forest floor in Central Kalimantan, Indonesia. Temporary gas fluxes on microtopographically differing hummock and hollow peat surfaces were combined with peat water table data to produce annual cumulative flux estimates. Hummocks formed mainly from living and dead tree roots and decaying debris maintained a relatively steady CO 2 emission rate regardless of the water table position in peat. In nearly vegetation-free hollows, CO 2 emission rates were progressively smaller as the water table rose towards the peat surface. Methane emissions from the peat surface remained small and were detected only in watersaturated peat. By applying long-term peat water table data, annual gas emissions from the peat swamp forest floor were estimated to be 3493 AE 316 g CO 2 m À2 and less than 1.36 AE 0.57 g CH 4 m À2 . On the basis of the carbon emitted, CO 2 is clearly a more important greenhouse gas than CH 4 . CO 2 emissions from peat are the highest during the dry season, when the oxic peat layer is at its thickest because of water table lowering.

Two sediment cores (Maxus 4 and Maxus 1) were obtained from lowland wetlands situated in the highly diverse rain forests of the western Amazon basin, Ecuador. The cores, separated by ca. 57 km, were analyzed for fossil pollen, charcoal and loss-on-ignition. The Maxus 4 core encompasses the last 9500 years, while the Maxus 1 core provides a record for approximately the last 2000 years. As neither core registered evidence of human impacts or land use, an unobscured image of Holocene vegetation and climate change was obtained. Alternating wet and drier periods on a millennial scale characterized much of the Holocene. The unusually high values of Cecropia in the pollen sum between 8700 and 5800 cal yr BP suggest frequent disturbance or the presence of early successional habitat. After 5800 cal yr BP a series of taxa rising and falling in prominence reveals a hydrarch succession that culminated in a relatively dry period between ca. 4900 and 3700 cal yr BP. Seasonal flooding of the site is evident as local water tables rose between 3700 and ca. 1000 cal yr BP. After 1000 cal yr BP the modern wooded wetland was established. The second site Maxus 1 reveals a detailed history of approximately last 2000 years. The principal feature of the record is a disturbance event at about 1000 cal yr BP, followed by a period of hydrarch succession. ß

1] We examined how landscape hydrogeologic characteristics influence groundwater nitrate removal by eight stream riparian sites on glacial till and outwash landscapes in southern Ontario, Canada. During high water table periods in 2000-2002, mean NO 3 À -N input concentrations from adjacent cropland to the riparian sites ranged from 0.15 to 44.7 mg L À1 . Seven of the eight sites had a mean nitrate removal efficiency of >90%. This removal occurred within the first 15 m of the riparian zone at three sites with loamy sand and sandy loam soils overlying a shallow confining layer at 1-2 m. However, at four of five sites with more conductive sand and cobble sediments the width required for 90% nitrate removal varied from >25 m to a maximum of 176 m at a site with a confining layer at 6 m. Sites linked to an extensive thick (>6 m) upland aquifer with a slope gradient of >15% at the riparian perimeter had high nitrate inputs throughout the year and were large nitrate sinks. Sites with gentle topography (<4-5%) and <2 m of permeable sediments were minor nitrate sinks because of small nitrate inputs that were limited to the late autumn-spring period. A conceptual model linking landscape hydrogeologic characteristics to riparian zone nitrate removal capacity is developed to understand and predict the effectiveness of riparian buffers at the landscape scale.

feature abundance. As a result, it has been difficult to extrapolate their saturation data to other sites to make Saturation frequency and duration must be estimated to determine specific interpretations regarding saturation frequency if a site is a jurisdictional wetland, and such data also aid in assessing sites for on-site waste disposal. This study developed a method to or duration. Later work has attempted to define the estimate saturation frequency and duration by calibrating redoximor-relationship between saturation duration and occurphic features to a 40-yr record of water table simulations in a catena rence of redoximorphic features, but because these studof Atlantic Coastal Plain soils in North Carolina. Thirteen plots were ies were short-term (Ͻ3yr), the effects of saturation established along a toposequence with moderately well-drained frequency on morphology could not be addressed (Aquic Paleudults) and very poorly drained soils (Umbric Palea-(Franzmeier et al., 1983; Megonigal et al., 1993; and quults) as end members. A hydrologic model (DRAINMOD) was Jacobs et al., 2002). calibrated for each plot. Redox potential measurements showed that Some land-use regulations require that frequency and an average of 21 consecutive days of continuous saturation was suffiduration of saturated conditions be determined to assess cient for Fe reduction to occur in the soils. Historic rainfall data were a soil's suitability for a given use. For example, jurisdicused in the DRAINMOD model to estimate the number of times each plot was saturated for 21 consecutive days or longer in each tional wetlands must meet a standard for wetland hyyear of a 40-yr period. Redoximorphic features were significantly drology, which requires an area be saturated to the correlated with average number of saturation events computed to surface for at least 5% of the growing season with a have occurred at depths of 45, 60, 75, and 90 cm across all soils. frequency of at least 5 yr out of 10 (Environmental Relationships were linear and varied by depth when all soils were Laboratory, 1987). On-site wetland inspections to deteranalyzed as a single population. The r 2 values for relationships between mine whether a site meets the wetland hydrology reredox depletions and saturation events were Ͼ0.85 for saturation quirement must be completed quickly to keep up with occurring during the growing season, and were Ͼ0.75 for saturation the demand. There is currently no technology known events occurring at any time during the year. These relationships to the authors that would enable a field scientist to allow prediction of the likelihood that a soil will saturate for Ն21 d determine whether a site affected by shallow ground by simply estimating the percentage of redoximorphic features at a given depth.

The LEACHM model developed by Wagenet and Hutson [1989] was used to predict the mineral nitrogen and water content in the soil under a winter wheat crop from February to April in two years and three locations. The model grossly overestimated soil water content, probably due to the bad fitting of the assumed water retentivity function to the experimental data at high water contents, and to the presence of a relatively shallow water table (1.0–1.5m). Measured soil hydraulic conductivity varied with water content in a different manner than predicted by the model. By assuming a sandy or gravelly soil layer between the bottom of the measured soil profile and the water table, prediction of soil water content improved considerably. Simulation showed that, under the experimental conditions studied, soil mineral nitrogen varied mainly due to the fertilizer additions, mineralization and denitrification. Nitrogen uptake by plants and leaching were small. Low values of nitrate leaching were pre...

AB STRA CT: Irregular patterns of precipitations from temporal as well as spatial perspectives not only cause destructions but also waste surface water resources. Hence, controlling surface water and leading the flood to underground stores improve the efficiency of water usage. Selecting appropriate sites for optimal use of water floods is one of the most important factors in recharging underground water tables in dry lands where the agricultural and rangelands are vulnerable. Traditional methods of site selections are, however, time consuming and error prone. This paper attempts to; analyze existing schemes of site selection; introduces an appropriate method of locating flood-spreading sites using Geospatial Information System; implements the strategy in a case study; and scientifically assesses its results. The study area of this research is Samal sub-basin covering 31571.7 ha of Ahrom basin in Boushehr province. In the present research, factors pertain to earth sciences (quaternary units, slope and landuse) and hydrology (runoff infiltration rate and aquifers' depth) are considered. Information layers are weighted, classified and integrated through several models such as boolean logics, index overlay and fuzzy logics. The results are then checked against the existing sites to estimate their accuracy. The results of this research demonstrated that fuzzy logic operators including gamma=0.1, gamma=0.2 and products of fuzzy logics yield the best when compared to control fields and therefore, the models are introduced as the most suitable site selection strategies for flood spreading.

A Wetland Reservoir Subirrigation System (WRSIS) allows for capture, treatment, storage, and reuse of runoff and subsurface drainage waters from cropland, in turn providing both environmental and agricultural production benefits. The three WRSIS sites presently in operation are all located within the northwest Ohio portion of the Maumee River Basin and have been in use for five to six complete growing seasons. WRSIS components include an underground drainage pipe network tied to both a constructed wetland and a water storage reservoir. With this type of system, the drain pipes can be used at different times to either add water (subirrigation) or remove water (subsurface drainage) from the root zone, thereby enhancing crop yields, especially in dry years. Obtaining these crop yield benefits requires a proper water table management approach that includes practicing suggested operational guidelines and initiating as needed system modification improvements. By incorporating a proper water table management approach, and in comparison to control plots, WRSIS subirrigated field crop yield increases for corn and soybeans, respectively, were 34.5 and 38.1% during drier growing seasons, 14.4 and 9.7% during near average to wetter growing seasons, and 19.6 and 17.4% overall.

Many important geomorphic and ecological attributes center on soil water content, especially over long timescales. In this paper we present an ordinally based index, intended to generally reflect the amount of water that a soil supplies to plants under natural conditions, over long timescales. The Natural Soil Drainage Index (DI) ranges from 0 for the driest soils (e.g., those shallow to bedrock in a desert) to 99 (open water). The DI is primarily derived from a soil's taxonomic subgroup classification, which is a reflection of its long-term wetness. Because the DI assumes that soils in drier climates and with deeper water tables have less plant-useable water, taxonomic indicators such as soil moisture regime and natural drainage class figure prominently in the "base" DI formulation. Additional factors that can impact soil water content, quality, and/or availability (e.g., texture), when also reflected in taxonomy, are quantified and added to or subtracted from the base DI to arrive at a final DI value. In GIS applications, map unit slope gradient can be added as an additional variable. The index has myriad applications in forestry, ecology, geomorphology, and environmental modeling, especially when examined spatially; we provide some examples in this paper. The DI has great potential for many landscape-scale modeling and GIS applications where soil water content is an important variable. DI values for all soils currently classified by the NRCS can be accessed from pull-down menus on the DI web site:

Sewage is the primary source of pathogenic microbial contamination of ground water as it is in surface water. Bacteria are the most diverse microbes within this group with respect to their ability to travel through soil matrix. In addition, many diseases caused by bacteria such as diarrhoeal, dysentery, cholera, and typhoid fever. The threat to public health due to the transmission of pathogenic bacterial organisms from sewage system to ground water is reported worldwide (FAO, 1979). Although, it is generally agreed that the soil complex provides some protection, it is by no means eliminates it.

The simulation model SIDRA is based on a semi-analytical and semi-numerical solution to the Boussinesq equation. It has been developed on the ground of theoretical and field experimental results with the aim of a good prediction of both drainage peak and recession flow rates. Theoretical aspects and basic equations of the model are presented for the most general case where both soll physical properties and watet table shapes are depth-dependent. The parameter sensitivity and field performances of the model are estimated in shallow loamy solls facing a seasonal waterlogging during winter season in France. Watet table shape factors are the most sensitive parameters. Drainable porosity is slightly more sensitive than hydraulic conductivity for drainflow rate prediction whereas hydraulic conductivity is slightly more sensitive for watet table elevation prediction. A comparison of experimental and simulated long term discharge and watet table exceedance duration curves shows that the model could be a useful tool to assess the performances and control the relevance of a given subsurface drainage design.

Estimation of groundwater table by hydrogeologists in
Ghana over the past decades has proven to be difficult due to the
dearth of data on piezometric heads from the very few boreholes
present to access this data. The importance of this information in
infrastructure planning therefore calls for the need to establish a
precise geophysical method that can predict the depth to the
water table at a relatively lower cost and higher efficiency as
compared with prevailing conventional methods. This paper
demonstrates how the ground based ground penetrating radar
(GPR) has been successfully used to delineate water table depths
and possible ground water flow directions. The MALA GPR
equipment with unshielded rough terrain antenna of  25 MHz
central frequency in the common offset mode was employed for
the data collection. Data was taken along 21 profiles with interprofile separation of 50 m over the study site of areal extent 1
km
2
. Water table depths were estimated at an average depth of 21
m in an environment permeated by vertical structures which
possibly served as pathways for groundwater infiltration. The
general groundwater flow pattern was north-east in the northern
and southern parts, and south-west at the central, eastern and
western parts of the study area. The contact between the duricrust
and the weathered saprolite was found at an average depth of 8
m. GPR-derived groundwater table depths were validated by
drilled boreholes which intercepted the groundwater table at an
average depth of 20 m within a lithology  comprised of sandy
clay and granite with varying degrees of weathering.  This paper
demonstrates the use of GPR as an efficient method for the
estimation of groundwater table depth, groundwater flow
direction as well as mapping of near surface lithological units;
hence, it can serve as a baseline study for future applications.

Commercially available cone penetrometer (CPT) fluorescence based sensor platforms have been used to detect non-aqueous phase liquids (NAPLs), such as petroleum oils and lubricants, in situ for more than a decade. These approaches have also been used to detect dense non-aqueous phase liquid (DNAPL) source zones by detecting commingled oils, fuels, and naturally occurring organic materials entrained by DNAPLs and carried to depths below the water table. Several neat NAPLs and mixtures were added to various soil types and analyzed for specific fluorescence characteristics to determine the optimal excitation source for site characterization efforts. Using excitation/emission matrices (EEMs), we demonstrate that an optimized excitation wavelength can be determined for specific fluorophores within the NAPL mixtures, and that available systems can be ranked based on the specific contaminant and site soil types. An optimal excitation wavelength yields the maximum fluorescence within an EEM spectrum. We ranked commercially available cone penetrometer fluorescence detection systems according to the potential for ease of detection based on maximum fluorescence response. When soils were added to complex NAPL mixtures, analyte fluorescence emission was attenuated in preferential portions of the EEM, leading to differences in the optimal excitation source wavelength. Furthermore, impure silica-containing minerals impact the emission signal, potentially leading to incorrect conclusions for several commercially available systems. Our findings suggest that a frequency-agile (e.g., tunable excitation source) probe system would be superior to any other system commercially available, provided the system would be relatively easy to operate and would have rapid in-situ EEM generating capabilities for optimization in the field.

Geohazards caused by rising groundwater can have a considerable effect on the built environment, especially where this is underlain by former coal mines, such as those found in County Durham, UK. Reactivation of faults and the expulsion of gas are two specific geohazards that are known to occur and be potentially dangerous and threatening to human health. However, little substantive research has been undertaken into these problems to date. This paper will present research undertaken recently to understand the various potential geohazards that can be activated directly by rising groundwater associated with cessation of pumping from deep mine systems. The geohazards considered include landslides, ground subsidence, seismicity, gas emission, impacts on structures, salinisation and health hazards, and these will be examined in the context of the Durham Coalfield. Numerical modelling has allowed a detailed examination of the effect of rising groundwater on a variety of geohazards, and the results from this study will be presented in this paper.

A total of 1400 soil samples from the plow layer (0-20 cm) at an approximate interval of 5 km were collected in the autumn of 2002 over the entire black soil arable crops region to determine the spatial variability of seven variables, such as total organic matter content (OMC), total N, total P, total K, alkali-dissolvable N (AN), available P (AP) and available K (AK), with classical statistics and geostatistical analysis across the entire black soil area in Northeast China. In nonsampled areas ordinary kriging was utilized for interpolation of estimated nutrient determinations. Classical statistics revealed highly significant (P 5 0.01) correlations with all seven of the soil properties, except for OMC with AP and total K with AK. In addition, using coefficients of variation, all soil properties, except for total K, were moderately variable. A geostatistical analysis indicated that structural factors, such as parent material, terrain, and water table, were the main causes of the spatial correlations. Strong spatial correlations were noted with OMC, total N, total P, AN, and AP, while they were moderate for total K and AK. The effective spatial autocorrelation of OMC, total N, total P, and AN ranged from 1037 to 1353 km, whereas the ranges of total K, AP, and AK were only from 6 to 138 km. The fit of the experimental semi-variograms to the theoretical models indicated that except for AN, kriging could successfully interpolate other six variables. Thus, the geostatistical method used on a large scale could accurately evaluate the spatial variability of most black soil nutrient properties in Northeast China.

High perched water table conditions, typically at depths between one and 2.5 metres, have created problems, including the increased occurrence of slope failures along nearby coulees for the city and the University of Lethbridge maintenance engineers. The source of water leading to the development of water tables in this region was determined to be over-irrigation of urban turfgrass. Water table development in the Lethbridge region is related to high tudgrass infiltration rates and high volumes of water received in till of low hydraulic conductivity. A statistical relationship was observed between the logarithm of water percolating beyond the root zone and water table deoth.

To gain an integrated understanding of flow and transport in the vadose zone and its role in transmitting con-A vadose zone flow and transport model for Los Alamos Canyon tamination to the regional aquifer, conceptual flow and is presented that demonstrates that a comprehensive understanding transport models must be combined with site-specific of vadose zone hydrologic processes can be obtained by integrating data from geologic, hydrologic, and site characterization sources. The information on hydrostratigraphy, hydrologic condicomplex hydrostratigraphy of the canyon is captured using geologic tions, and spatially distributed field measurements. In characterization of extensive deep-well drilling samples, along with our study, we developed a large-scale numerical model surface mapping. A water budget study for the surface and shallow of vadose zone flow and transport in Los Alamos Cansubsurface hydrology is used to estimate spatially varying infiltration yon with the objective of advancing our understanding rates along the canyon. Three-dimensional flow model results show of vadose zone processes and behavior. In addition to that mesa-top infiltration rates on the order of 1 mm yr Ϫ1 , and canyonelaborating on the site-specific details of flow and transbottom rates several orders of magnitude higher, capture the water port at this site, the present study provides insights on content profiles from available wells within the model domain. Howthe role of large-scale numerical simulation in the hydroever, a range of a factor of three higher and lower than these mean logic behavior of vadose zones in semiarid systems. values is also consistent with the data. Transient flow simulations show Los Alamos Canyon, shown in Fig. 1, is one of the most that episodic infiltration events can be effectively averaged in steadycomplex sites at the Laboratory. A number of LANL state flow modeling, but transients that last on the order of a decade or facilities have been or are currently located in or adjamore, such as climate related or anthropogenically induced transients, significantly change the predicted water content. Modeling of tritium cent to the canyon, resulting in multiple effluent and transport through the vadose zone indicates that even for a nonsorbcontaminant release locations along the canyon. Because ing contaminant, most, but not all, of the contaminant released since the canyon serves as a collector of a wide range of conin the past 40 yr should still be present in the vadose zone. The mass

To improve the knowledge of the regionally important Continental Terminal 3 (CT3) aquifer in south-western Niger, fifteen magnetic resonance soundings (MRS) were carried out in December 2005 in the vicinity of wells and boreholes. The output MRS geophysical parameters, i.e. water content and decay constants versus depth, were compared to hydrogeological characteristics, i.e. water table depth, total porosity, specific yield and transmissivity estimated from direct measurements, pumping tests and transient groundwater modelling. The MRS-determined parameters were then used to estimate the rates of groundwater recharge.

Phosphogypsum (PG), a by-product of the P industries, has been widely applied as an amendment to reduce Na saturation in soils. However, some concern arises due to its content of some metals and radionuclides. Thus, it is necessary to optimize the PG rates to avoid excessive accumulation of such pollutants in soil. To evaluate the effects of PG on drain flow and on the displacement of Na by Ca in soils, a three-year field experiment was conducted in a commercial farm located in a reclaimed marsh area from SW Spain. It involved two treatments (controlwithout PGand 25 Mg ha −1 of PG, applied in April 2003 and again in September 2004), done in triplicate in 250 × 20 m plots, following a randomized block design. Drainage flows were monitored, and drain-water samples were analyzed for Na and Ca concentrations. The recorded hydrographs revealed unexpected high lateral flows of water within these soils. No statistically significant differences were found in drained volumes, nor in Na and Ca losses through drainage, between both treatments in each of the three growing seasons (Gossypium hirsutum L. in 2003 and 2005; Beta vulgaris L. in 2003 Beta vulgaris L. in -2004. Losses of Na and Ca in each irrigation event were linearly related to the drainage to irrigation volume ratio (p b 0.001); Ca, however, showed significantly different slopes for both treatments. Cation concentration, Na adsorption ratio (SAR), and electrical conductivity (EC) in the saturation extract of soil at different depths were significantly affected by PG and by the oscillation of saline water table during the experiment. The efficiency of PG in displacing Na by Ca was estimated to be about 30%, with the PG-attributable changes in Ca and SAR also appearing in deeper soil layers and in adjacent control plots.

Surface oxidation of sulfide minerals, such as that found in the regions of a sulfide ore body near the water table, can have a significant impact upon flotation. This theme has been explored for Merensky ore type sulfides where an ore containing pyrrhotite, pentlandite and chalcopyrite was thermally oxidised and the role of potential remedies investigated. Back-scattered scanning electron microscope images are presented showing the oxidation layer which formed in the mineral surfaces. These oxidation layers were depleted in both sulfur and iron with incorporated oxygen. Flotation recovery rapidly decreased with increasing oxidation, particularly after 27 days and reached a plateau after 50 days. Up to 27 days, this effect could be partially overcome with higher collector additions. Oxidation had more impact upon the finer size fractions, particularly for pyrrhotite. For more heavily surface oxidised samples, ultrasonic treatment prior to collector conditioning was found to improve flotation recoveries. This treatment had the greatest effect upon chalcopyrite particles. Sulfidisation was successful in restoring the flotation recovery of the heavily oxidised sulfide minerals. Longer sulfidisation conditioning times were not conducive to good flotation recoveries of both oxidised pyrrhotite and pentlandite due to oxidation of the freshly formed sulfide surfaces. For maximum flotation recoveries of oxidised pyrrhotite, pentlandite and chalcopyrite, different sulfidisation conditions are indicated. It appears likely that in a mineral processing operation treating oxidised Merensky type ores, two stages of sulfidisation employing different conditions would be required.

Vegetation change in response to restriction of the normal tidal prism of six Connecticut salt marshes is documented. Tidal flow at the study sites was restricted with tide gates and associated causeways and dikes for purposes of flood protection, mosquito control, and/or salt hay farming. One study site has been under a regime of reduced tidal flow since colonial times, while the duration of restriction at the other sites ranges from less than ten years to several decades. The data indicate that with tidal restriction there is a substantial reduction in soil water salinity, lowering of the water table level, as well as a relative drop in the marsh surface elevation. These factors are considered to favor the establishment and spread of Phragmites australis (common reed grass) and other less salt-tolerant species, with an attendant loss of Spartina-dominated marsh. Based on detailed vegetation mapping of the study sites, a generalized scheme is presented to describe the sequence of vegetation change from typical Spartinato Phragmites-dominated marshes. The restoration of these Phragmites systems is feasible following the reintroduction of tidal flow. At several sites dominated by Phragmites, tidal flow was reintroduced after two decades of continuous restriction, resulting in a marked reduction in Phragmites height and the reestablishment of typical salt marsh vegetation along creekbanks. It is suggested that large-scale restoration efforts be initiated in order that these degraded systems once again assume their roles within the salt marsh-estuarine ecosystem.

Île de la Gonâve is a 750-km2 island off the coast of Haiti. The depth to the water table ranges from less than 30 m in the Eocene and Upper Miocene limestones to over 60 m in the 300-m-thick Quaternary limestone. Annual precipitation ranges from 800-1,400 mm. Most precipitation is lost through evapotranspiration and there is virtually no surface water. Roughly estimated from chloride mass balance, about 4% of the precipitation recharges the karst aquifer. Cave pools and springs are a common source for water. Hand-dug wells provide water in coastal areas. Few productive wells have been drilled deeper than 60 m. Reconnaissance field analyses indicate that groundwater in the interior is a calcium-bicarbonate type, whereas water at the coast is a sodium-chloride type that exceeds World Health Organization recommended values for sodium and chloride. Tests for the presence of hydrogen sulfide-producing bacteria were negative in most drilled wells, but positive in cave pools, hand-dug wells, and most springs, indicating bacterial contamination of most water sources. Because of the difficulties in obtaining freshwater, the 110,000 inhabitants use an average of only 7 L per person per day. L'Île de la Gonâve est une île de 750 km2 au large de la côte d'Haïti. La profondeur de la nappe varie entre moins de 30 m dans les calcaires de l'Éocène et du Miocène supérieur à plus de 60 m dans les calcaires quaternaires épais de 300 m. Les précipitations annuelles sont comprises entre 800-1.400 mm. La plus grande partie des précipitations est perdue par évapotranspiration et il n'y a pratiquement pas d'eau de surface. Le bilan de masse des chlorures permet d'estimer à 4% des précipitations le montant de la recharge de l'aquifère karstique. Des bassins dans les grottes et des sources sont la source d'eau courante. Des puits creusés à la main fournissent de l'eau dans les zones côtières. Quelques puits productifs ont été forés dépassant 60 m de profondeur. L'analyse des reconnaissances de terrain indique que les eaux souterraines à l'intérieur de l'île sont de faciès bicarbonaté calcique, tandis que l'eau près de la côte a un faciès chloruré sodique dépassant les valeurs recommandées par l'OMS pour le sodium et les chlorures. Des tests pour la présence de bactéries productrices d'hydrogène sulfuré se sont révélés négatifs dans la plupart des forages, mais positifs dans la plupart des sources captées et tous les autres sources, bassins de grottes et puits creusés à la main, ce qui indique une contamination bactérienne de la plupart des sources d'eau. Du fait des difficultés pour s'approvisionner en eau douce, les 110.000 habitants utilisent en moyenne seulement 7 L par personne et par jour. La Isla de la Gonavê, cercana a la costa de Haití, tiene 750 km2. La profundidad al nivel freático está comprendida entre menos de 30 m para las calcitas del Eoceno y Mioceno Superior y más de 60 m en el acuífero de calcitas cuaternarias, el cual posee 300 m de espesor. La precipitación anual varía entre 800-1.400 mm, si bien la mayor parte se pierde por evapotranspiración y prácticamente no hay aguas superficiales. Según un balance de masas de cloruros, alrededor del 4% de la precipitación recarga el acuífero kárstico. Las cavidades y manantiales son una fuente habitual de agua. Los pozos excavados proporcionan agua en las áreas costeras. Pocos pozos productivos se han perforado a más de 60 m. El reconocimiento de los análisis de campo indica que las aguas subterráneas son de tipo bicarbonatado-cálcico en el interior, mientras que es de tipo clorurado-sódico en la costa, donde se sobrepasan las concentraciones recomendadas por la Organización Mundial de la Salud para sodio y cloruro. Los ensayos efectuados para detectar la presencia de bacterias productoras de sulfuro de hidrógeno resultaron negativos en la mayoría de los pozos perforados, pero fueron positivos en la muchos manantiales explotados y en todos los manantiales, cavidades y pozos excavados, hecho que indica la contaminación bacteriana de la mayor parte de fuentes de agua. Debido a las dificultades para obtener agua dulce, los 110.000 habitantes utilizan una media de sólo 7 L por persona al día.

Water table across much of the western Victoria, Australia have been declining for at least the last 10-15 years, and this is attributed to the consistently low rainfall for these years, but over the same period of time there has been substantial change in land use, with grazing land replaced by cropping and tree plantations appearing in some areas. Hence,

Soil water and temperature conditions were simulated for three years at three sites in the Netherlands, using a model named SOIL. Observed water table depths from one site with a sandy loam soil indicated bypass flow in macropores. Nitrogen turnover was simulated using the output of SOIL as input to a nitrogen model. To improve the nitrogen model, a crop-growth submodel was introduced, and simulations were compared with measured data for two seasons and three fertilizer treatments at the three sites. Mineral-N in the soil after application of fertilizer was substantially higher in the simulation than indicated by measurements in 4 out of 18 simulations. Regression analyses showed that simulated mineral-N content in the uppermost metre explained 64% of the observed variation. The corresponding values for nitrogen content (N ta) and biomass (W ta) of aboveground tissues were 86 and 93%, respectively. With a few exceptions annual values ofW ta andN ta were simulated with an accuracy of approximately 20%. A sensitivity test showed that growth parameters and especially the light use efficiency parameter strongly influenced biomass production for fertilized treatments whereas the control of nitrogen uptake from soil was most important for non-fertilized treatments.

Obtaining values of net infiltration, groundwater travel time, and recharge is necessary at the Yucca Mountain site, Nevada, USA, in order to evaluate the expected performance of a potential repository as a containment system for high-level radioactive waste. However, the geologic complexities of this site, its low precipitation and net infiltration, with numerous mechanisms operating simultaneously to move water through the system, provide many challenges for the estimation of the spatial distribution of recharge. A variety of methods appropriate for arid environments has been applied, including water-balance techniques, calculations using Darcy's law in the unsaturated zone, a soil-physics method applied to neutron-hole water-content data, inverse modeling of thermal profiles in boreholes extending through the thick unsaturated zone, chloride mass balance, atmospheric radionuclides, and empirical approaches. These methods indicate that near-surface infiltration rates at Yucca Mountain are highly variable in time and space, with local (point) values ranging from zero to several hundred millimeters per year. Spatially distributed net-infiltration values average 5 mm/year, with the highest values approaching 20 mm/year near Yucca Crest. Site-scale recharge estimates range from less than 1 to about 12 mm/year. These results have been incorporated into a site-scale model that has been calibrated using these data sets that reflect infiltration processes acting on highly variable temporal and spatial scales. The modeling study predicts highly non-uniform recharge at the water table, distributed significantly differently from the non-uniform infiltration pattern at the surface.

1. This account presents information on all aspects of the biology of Primula veris that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and diseases, history and conservation. 2. Primula veris is a distylous, perennial rosette hemicryptophyte, mostly found in well-drained, herb-rich meadows and grasslands, in scrub or woodland rides and edges, and on calcareous cliffs. It occurs on base-rich loams or clays, on limestone, and sometimes in dunes. 3. Native to the British Isles, it is characteristic of many mesotrophic and calcicolous lowland grassland communities, but it also extends into upland valleys in northern England and Scotland. In Ireland it is also native and most abundant in the central plain. Primula veris occurs throughout the temperate areas of Europe as far east as the Russian border. 4. Primula veris is a shade-intolerant species that shows reduced performance and flowering under shade or increased competition. The species is not able to penetrate anoxic soil layers and is therefore mostly absent from locations that are characterized by a high water table. It has a welldeveloped drought tolerance. 5. Primula veris is an obligate outbreeder which entirely depends on foraging insects for successful pollination. Although the species shows heterostyly, with two reciprocal morphs (pin and thrum), only relatively low levels of intermorph pollination have been reported. Seed dispersal is restricted to a few centimetres from maternal plants, whereas pollen flow is wider, but still limited to a few metres from parental plants. Both are factors that contribute to a significantly fine-scale spatial genetic structure and small neighbourhood size. 6. At several locations throughout the British Isles, P. veris occurs together with P. elatior and especially P. vulgaris . The hybrid P. veris × P. vulgaris = P. × polyantha occurs frequently in mixed populations, whereas the hybrid P. veris × P. elatior = P. × media has been rarely reported in Britain. 7. Although P. veris is still a widespread grassland herb, it is less abundant in the British Isles and continental Europe than before. This decline can be attributed to changes in land-use practices, such as the loss of traditional hay-meadow management, the loss of grazing and an increase of ploughing, in combination with ongoing destruction and nutrient enrichment of permanent grasslands. However, from 1980 onwards the species has increased substantially in many areas of the UK, largely because its seeds are included in wildflower seed-mixtures that are sown on new or upgraded road and motorway verges, embankments and urban conservation areas.

The Integrated Northern Tampa Bay (INTB) model application was developed using the Integrated Hydrologic Model (IHM) simulation engine to improve hydrologic assessment capabilities in a 10,000 square kilometer region of west -central Florida. IHM uses the EPA HSPF model to simulate surface-water processes and the US Geological Survey model MODFLOW to simulate ground-water processes. With near simultaneous integration of HSPF

A ®ve-layered water balance model, with water movement between layers along hydraulic gradients, was developed and parameterized for a eucalypt plantation (Eucalyptus grandis Hill ex. Maiden hybrids) in Brazil. Available soil water controls stomatal conductance and hence transpiration, which is calculated by the Penman±Monteith equation. The model accounts for changes in the depths of the water table. Calculations are supported by measurements: the test period was from October 1995 to September 1996 in a 9-year-old plantation in an experimental catchment in eastern Brazil. Total transpiration for the year was 1116 mm, with 151 mm intercepted and re-evaporated and another 78 mm soil surface evaporation, giving evapotranspiration of 1345 mm compared to rainfall of 1396 mm. The water balance was closed by net¯ow below the root zone of about 25 mm and an increase in water storage (in the ®rst layer) of 24 mm. The model also estimated a transpiration de®cit (difference between the potential and current transpiration) of 125 mm for the period. Upward¯ux from the water table was around 82 mm and piezometric measurements showed 2.5 m recession of the water table for the same period. The upward¯ux into the root zone was about 1 mm day 21 at the end of a long dry season; that kept the water storage in that zone to about 15% of capacity and helped prevent complete stomatal closure.

Phosphogypsum (PG), the major waste material in phosphate fertilizer processing, has been known to contain enhanced levels of naturally-occurring radionuclides especially 226Ra.The lack of radioactivity data regarding Philippine phosphogypsum and its environmental behavior in the Philippine setting has brought concern on possible contamination of groundwater beneath the phosphogypsum ponds in Isabel, Leyte, Philippines. The radioactivity of Philippine phosphogypsum was determined and the leaching of 226Ra from phosphogypsum and through local soil was quantified. Level of 226Ra in groundwater samples in Isabel, Leyte, Philippines was also quantified to address the primary concern. It was found that the 226Ra activity in Philippine phosphogypsum is distributed in a wide range from 91.5 to 935 Bq/kg. As much as 5% of 226Ra can be leached from Philippine PG with deionized water. In vitro soil leach experiments suggest that the soil in the phosphate fertilizer plant area would be able to deter the intrusion of 226Ra into the water table. Compared to reported values of natural groundwater levels of 226Ra, the concentration of this radionuclide in Isabel, Leyte groundwater suggest that there is no 226Ra intrusion brought about by the presence of phosphogypsum ponds in the area.

A potential theory flow solution for the potential function, stream function, and shape of the water table is given for a class of steady state two-and three-dimensional perched groundwater mounds formed under a long rectangular recharge basin or under a circular recharge basin. The solutions are done by a Gram-Schmidt method and a simple iteration scheme. The mounds are formed in a stratum of conductivity kx overlying a perching stratum of much lower conductivity k•.. Capillary fringe effects are neglected. The recharge rate is R. Potential theory mound heights are compared with those given by the Dupuit-Forchheimer (DF) theory. For the cases computed (R/k•. = 10, 100, and 500 and kx/k•. = 50, 100, 500, 600, 750, and 1000) the DF theory gives apex heights of mounds correct to better than 7% for twodimensional mounds. For three-dimensional mounds the DF theory gives in one case a mound height that is 69% too low (for R/k•. = 500 and kx/k•. = 600) and in another case a mound height that is 28% too low (for R/k•. = 500 and k•/k•. = 1000). Profiles of the computed mounds are graphed, and examples of use of the graphs in applications are given. Sample flow nets are presented. Baumann [1952] initiated the study of formation of groundwater mounds. Later on, Hall [1955], Glover (unpublished manuscript, 1961), Bittinger and Trelease [1965], Hantush [1967], Bianchi and Haskell [1966, 1968], and Haskell and Bianchi [1965] contributed to the theory of groundwater mounds. All these theoretical developments, however, are approximate,'being based on Dupt/it-Forchheimer (DF) or lin-earization [Hantush, 1967] assumptions. Bouwer [1962] developed an analog model for analyzing groundwater mounds by a resistance network and reported different conditions under which a groundwater mound may be formed. Wilson [1971] and McWhorter and Brookman [1972] have presented field data on the growth and dissipation of perched .mounds. Perched mounds (Glover, R. E., Mathematical derivations pertaining to groundwater recharge, mimeo, Agr. Res. Serv., U.S. Dep. of Agr., Fort Collins, Colo., 1961) are those that perch on strata of low conductivity and may be contrasted with (unperched) mounds that are sometimes formed at the from the U.S. Department of the Interior, Office of Water Resources

The Integrated Northern Tampa Bay (INTB) model application was developed using the Integrated Hydrologic Model (IHM) simulation engine to improve hydrologic assessment capabilities in a 10,000 square kilometer region of west-central Florida. IHM uses the EPA HSPF model to simulate surface-water processes and the US Geological Survey model MODFLOW to simulate ground-water processes. With near simultaneous integration of HSPF with M ODFLOW, IHM provides the ability to simulate hydrologic transitions that occur between deep (>2 meters) and near-surface (0-2 meters) water-table conditions which influence surface and ground water processes. Compared to prior applications, the INTB model shows improvements in the dynamic response of hydrologic processes while using input data which is better constrained to physical measurements. Parameter estimation and manual calibration was used by employing quantitative metrics for streamflow, spring discharge, ground-water heads, depth to water table, temporal change in head and flow, and target ET. Qualitative metrics were developed for dry/flooded cells and various wet/dry stage metrics for water bodies. Quantitative metrics were applied using statistics for the mean, above and below the median, and within the high and low quartiles. Recent improvements in the dynamic response of the INTB model are the outcome of refinements to the simulation engine, enforcing hydrologic similarity principles within discretization units, constraining the model with average annual ET targets, and applying the calibration metric of depth to water table.

The paper provides the approximate closed-form expressions for the .estimation of the amount of ground water infiltration, the seepage exit gradient and the hydraulic pressure distribution on the cutoff elements in the case of sheeted excavations below the water table. The expressions are obtained by a multiple regression-type fitting of the results of an extensive parametric finite-element analysis for the two-dimensional steady-state flow in the soil around a sheeted excavation. In addition to the problem geometry, the effects of an impermeable base and a thin low permeability layer penetrated by the sheeting are also studied. The predictions of the approximate expressions deviate from the corresponding finite-element results by less than 15%, for a wide range of geometries and soil characteristics. It is shown how shape factors might be used to adapt the semi-empirical formulae for the case of excavations with limited length (circular and rectangular).

Desalination plants are being used increasingly in inland areas of many countries for supplying water for domestic purposes. If these areas are too far away from the sea, the opportunity to dispose the reject brine (also known as concentrate, reject water, or wastewater) in the ocean no longer exists, given that ocean disposal is the common practice for plants located in coastal areas. Evaporation ponds are especially suitable to dispose of reject brine from inland desalination plants in add and semi-arid areas due to the abundance of solar energy. In irrigation projects facing a soil salinity problem due to a shallow saline groundwater table, evaporation ponds are also in use. Saline water tables are lowered by pumping or tile draining and the drainage water is stored in evaporation ponds. While evaporation ponds have long been used for salt production in many parts of the world, the disposal of concentrate from desalination plants in inland areas using evaporation ponds is of much significance both economically and environmentally. Guidelines are needed for the design, construction, maintenance, and operation of evaporation ponds for reject brine disposal in an economical and environmentally-sensitive manner. This paper provides a critical review of concentrate disposal technology using evaporation ponds. Relevant topics are also covered including chemistry of brine, brine disposal methods, use of evaporation ponds in agriculture, determination of evaporation rate, and evaporation enhancement methods.

subterráneas). De cara a la estimación independiente de la porosidad efectiva, se debe disponer de ambos tipos de medidas. A menudo, se estima la recarga de forma más eficaz cuando se aplican técnicas de calibración automática. Otras aplicaciones importantes son la delimitación de las áreas de recarga que son captadas por pozos y la estimación de tasas de paleo-recarga por medio del carbono-14.

Due to the increasing demand for food and fiber by its ever-increasing population, the pressure on fresh water resources of Pakistan is increasing. Optimum utilization of surface and groundwater resources has become extremely important to fill the gap between water demand and supply. At Lahore, Pakistan 18 lysimeters, each 3.05 m  3.05 m  6.1 m deep were constructed to investigate the effect of shallow water tables on crop water requirements. The lysimeters were connected to bottles with Marriotte siphons to maintain the water tables at the desired levels and tensiometers were installed to measure soil water potential. The crops studied included wheat, sugarcane, maize, sorghum, berseem and sunflower. The results of these studies showed that the contribution of groundwater in meeting the crop water requirements varied with the water-table depth. With the water table at 0.5 m depth, wheat met its entire water requirement from the groundwater and sunflower absorbed more than 80% of its required water from groundwater. Maize and sorghum were found to be waterlogging sensitive crops whose yields were reduced with higher water table. However, maximum sugarcane yield was obtained with the water table at or below 2.0 m depth. Generally, the water-table depth of 1.5-2.0 m was found to be optimum for all the crops studied. In areas where the water table is shallow, the present system of irrigation supplies and water allowance needs adjustments to avoid over irrigation and in-efficient use of water. #

Soil salinisation is very often due to excessive irrigation. However, irrigation is absolutely essential for obtaining reliable crop yields, particularly under predicted global warming conditions. A simple methodology for assessing the salinisation risk for any water management situation and under predicted global warming conditions is presented. The methodology is illustrated by the assessment of irrigation effects on soil salinity at San Antonio del Sur Valley, in the southeast of Cuba. Irrigation from a new dam will support agriculture in the Valley, but at the same time soil salinity is expected to increase. Soil electrical conductivity at several depths and topographical altitudes were used to create raster layers in a Geographic Information System (GIS), thus, determining the border of the saline-affected zones by a GIS analysis. Water-table depth at the border of the saline zones was assumed to be 2 m. The physically based SWAP model was used to predict future water-table depths after irrigation begins and under global warming conditions. Future temperature and precipitation daily values were calculated from a linear increase/decrease of the daily values corresponding to a typical year, according to a global-change forecast for the zone. Soil hydraulic properties were estimated from pedotransfer function and published soil data. Simulated results predict a fast water-table raise of 1 m, due to the increase of irrigation water. Borders of the new saline zones under these conditions (i.e. the places where the water-table is at a 2 m depth) were calculated using a digital terrain model, assuming that the water-table rose 1 m over the whole valley. According to the simulation results, the original saline zones of the valley will be enlarged from 31.4 to 96.8 ha 15 years after the scheduled start of irrigation. The methodology could be used by farmers and decision-makers to select the most suitable water management solution considering both economical and environmental criteria. # .cu (A. Utset).

A study on flood water infiltration and ground water recharge of a shallow alluvial aquifer was conducted in the hyperarid section of the Kuiseb River, Namibia. The study site was selected to represent a typical desert ephemeral river. An instrumental setup allowed, for the first time, continuous monitoring of infiltration during a flood event through the channel bed and the entire vadose zone. The monitoring system included flexible time domain reflectometry probes that were designed to measure the temporal variation in vadose zone water content and instruments to concurrently measure the levels of flood and ground water. A sequence of five individual floods was monitored during the rainy season in early summer 2006. These newly generated data served to elucidate the dynamics of flood water infiltration. Each flood initiated an infiltration event which was expressed in wetting of the vadose zone followed by a measurable rise in the water table. The data enabled a direct calculation of the infiltration fluxes by various independent methods. The floods varied in their stages, peaks, and initial water contents. However, all floods produced very similar flux rates, suggesting that the recharge rates are less affected by the flood stages but rather controlled by flow duration and available aquifer storage under it. Large floods flood the stream channel terraces and promote the larger transmission losses. These, however, make only a negligible contribution to the recharge of the ground water. It is the flood duration within the active streambed, which may increase with flood magnitude that is important to the recharge process.