Literatura científica selecionada sobre o tema "Water salinization Measurement"

Abstract. Water is essential for life. Specifically in the oases of inland arid basins, water is a critically limited resource, essential for the development of socio-economy and sustainability of eco-environmental systems. Due to the unique hydrological regime present in arid oases, a moderate groundwater table is the goal of sustainable water management. A shallow water table induces serious secondary salinization and collapse of agriculture, while a deep water table causes deterioration of natural vegetation. From the hydrological perspective, the exchange flux between unsaturated vadose zone and groundwater reservoir is a critical link to understand regional water table dynamics. This flux is substantially influenced by anthropogenic activities. In Tarim River Basin of western China, where agriculture consumes over 90% of available water resources, the exchange flux is influenced strongly by irrigation. Recently, mulched drip irrigation, a very advanced water-saving irrigation method, has been widely applied in the Tarim River Basin, which greatly impacted the exchange flux and thus the regional groundwater dynamics. Capitalizing on recent progress in evaporation measurement techniques, we can now close the water balance and directly quantify the exchange flux at the field scale, thus gain a better understanding of regional groundwater dynamics. In this study, comprehensive observations of water balance components in an irrigated cropland were implemented in 2011 and 2012 in a typical oasis within Tarim River Basin. The water balance analysis showed that the exchange flux and groundwater dynamics were significantly altered by the application of water-saving irrigation. The exchange flux is mostly downward (310.5 mm yr−1), especially during drip irrigation period and spring flush period, while the upward flux is trivial (−16.1 mm yr−1) due to the moderate groundwater table depth (annual average depth 2.9 m). Traditional secondary salinization caused by intense phreatic evaporation (fed by upward exchange flux) is alleviated. However, a new form of secondary salinization may be introduced unwittingly if there is lack of water for periodic flushing, especially when brackish water is used in the irrigation. Furthermore, the water saved via drip irrigation has been used in further growth of irrigated lands instead of supporting ecological system. This would lead to increasing risk of eco-environmental degradation and calls for improved governance schemes. The insights gained from this study can be potentially applied to other arid inland areas (e.g., central Asia, sub-Saharan Africa) which face similar water shortages and human development problems.

Abstract. Water is essential for life. Specifically in the oases of inland arid basins, water is a critically limited resource, essential for the development of the socio-economy and the sustainability of eco-environmental systems. Due to the unique hydrological regime present in arid oases, a moderate groundwater table is the goal of sustainable water management. A shallow water table induces serious secondary salinization and collapse of agriculture, while a deep water table causes deterioration of natural vegetation. From the hydrological perspective, the exchange flux between the unsaturated vadose zone and groundwater reservoir is a critical link to understanding regional water table dynamics. This flux is substantially influenced by anthropogenic activities. In the Tarim River basin of western China, where agriculture consumes over 90% of available water resources, the exchange flux between the unsaturated vadose zone and groundwater reservoir is influenced strongly by irrigation. Recently, mulched drip irrigation, a sophisticated water-saving irrigation method, was widely applied in the Tarim River basin, which greatly impacted the exchange flux and thus the regional groundwater dynamics. Capitalizing on recent progress in evaporation measurement techniques, we can now close the water balance and directly quantify the exchange flux at the field scale, thus gaining a better understanding of regional groundwater dynamics. In this study, comprehensive observations of water balance components in an irrigated cropland were implemented in 2012 and 2013 in a typical oasis within the Tarim River basin. The water balance analysis showed that the exchange flux and groundwater dynamics were significantly altered by the application of water-saving irrigation. The exchange flux at the groundwater table is mostly downward (310.5 mm year−1), especially during drip irrigation period and spring flush period, while the upward flux is trivial (16.1 mm year−1) due to the moderate groundwater table depth (annual average depth 2.9 m). Traditional secondary salinization caused by intense phreatic evaporation (fed by upward exchange flux) is alleviated. However, a new form of secondary salinization may be introduced unwittingly if there is lack of water for periodic flushing, especially when brackish water is used in the irrigation. Furthermore, the water saved via drip irrigation has been used in further growth of irrigated lands instead of supporting the ecological system. This could lead to an increased risk of eco-environmental degradation and calls for improved governance schemes. The insights gained from this study can be potentially applied to other arid inland areas (e.g., central Asia) which face similar water shortages and human development problems.

Abstract. Data of surface-atmosphere energy and water transfer from a ten years (2003–2013) period of activity of the ISAC-Lecce micrometeorological station (http://www.basesperimentale.le.isac.cnr.it) have been analyzed: to the authors' knowledge this is the first decadal data set of surface-atmosphere transfer in Salento peninsula. The surface energy budget shows a tendency to a positive bias possibly due to several reasons that require more investigations. Some suitable indices related to the surface water balance, such as the precipitation intensity, the aridity index and the ground water infiltration fraction have been calculated. Possible trends of these annual averages in the decadal period are considered, also taking into account the statistical uncertainty associated to measurement errors and missing data. The results indicate a significant increasing in the precipitation intensity together with an experimental evidence of increasing of the ground water infiltration in the measurement area, that is in agreement with recent estimations for the whole Salento peninsula. On the other hand, recent studies show that seawater intrusion and salinization of the deep underground aquifer keep increasing in the same period.

Wastewater application to soil is an alternative for fertilization and water reuse. However, particular care must be taken with this practice, since successive wastewater applications can cause soil salinization. Time-domain reflectometry (TDR) allows for the simultaneous and continuous monitoring of both soil water content and apparent electrical conductivity and thus for the indirect measurement of the electrical conductivity of the soil solution. This study aimed to evaluate the suitability of TDR for the indirect determination of the electrical conductivity (ECse) of the saturated soil extract by using an empirical equation for the apparatus TDR Trase 6050X1. Disturbed soil samples saturated with swine wastewater were used, at soil proportions of 0, 0.45, 0.90, 1.80, 2.70, and 3.60 m³ m-3. The probes were equipped with three handmade 0.20 cm long rods. The fit of the empirical model that associated the TDR measured values of electrical conductivity (EC TDR) to ECse was excellent, indicating this approach as suitable for the determination of electrical conductivity of the soil solution.

An integrated research approach consisting of hydrogeologic and geochemical methods was applied to a coastal aquifer in the Ostia Antica archaeological park, Roma, Italy, to describe freshwater–saltwater interactions. The archaeological park of Ostia Antica is located on the left bank of the Tevere River delta which developed on a morphologically depressed area. The water monitoring program included the installation of multiparametric probes in some wells inside the archaeological area, with continuous measurement of temperature, electrical conductivity, and water table level. Field surveys, water sampling, and major elements and bromide analyses were carried out on a seasonal basis in 2016. In order to understand the detailed stratigraphic setting of the area, three surface boreholes were accomplished. Two distinct circulations were identified during the dry season, with local interaction in the rainy period: an upper one within the archaeological cover, less saline and with recharge inland; and a deeper one in the alluvial materials of Tevere River, affected by salinization. Oxygen and carbon isotopic signature of calcite in the sediments extracted from the boreholes, along with major elements and Br concentration, allowed us to recognize the sources of salinity (mainly, local interaction with Roman salt pans and agricultural practices) and the processes of gas–water–rock interaction occurring in the area. All these inferences were confirmed and strengthened by PCA analysis of physicochemical data of groundwater.

Soil salinization in irrigated croplands is a key factor in soil degradation and directly affects plant growth and soil hydrological processes such as evaporation and infiltration. In order to support the development of appropriate irrigation strategies, it is important to understand the impact of salt crusts that form during evaporation from saline soils on water flow. The determination of the effective hydraulic properties of salt crusts that control evaporation is still a challenge due to the lack of suitable measurement techniques. In this study, we propose an approach using gas flow to determine the permeability of salt crusts obtained from evaporation of unsaturated saline solutions of three different salt types and investigate the impact of the crust permeability on evaporation. For this, sand columns saturated with initial solutions of sodium chloride (NaCl), magnesium sulfate (MgSO4), and sodium sulfate (Na2SO4) at concentrations corresponding to 33% of the solubility limit were prepared and allowed to evaporate in order to induce crust formation. The results demonstrated that the intrinsic permeability of the dry salt crusts was similar for the different types of salts (≈4 × 10−12 m2), whereas the evaporation of the prepared columns differed significantly. We conclude that the intrinsic crust permeability only partly explains the impact of the crust on evaporation. Other effective crust properties such as porosity or unsaturated hydraulic properties may provide additional information on how evaporation is affected by salt crust formation.

Over the last several years, there has been increasing interest in amending the soil using cover crops, especially in desert agriculture. One cover crop of interest in the desert Coachella Valley of California is cowpea [Vigna unguiculata (L.) Walp.]. Cowpea is particularly useful in that as an excellent cover crop, fixing abundant amounts of nitrogen which can reduce fertilizer costs. However, soil salinity problems are of increasing concern in the Coachella Valley of California where the Colorado River water is a major source of irrigation water. Unfortunately, little information is available on the response of cowpea growth to salt stress. Thus, we investigated the growth response of 12 major cowpea cultivars (`CB5', `CB27', `CB46', `IT89KD-288', `IT93K-503-1', `Iron Clay', `Speckled Purple Hall', `UCR 134', `UCR 671', `UCR 730', `8517', and `7964') to increasing salinity levels. The experiment was set up as a standard Split Plot design. Seven salinity levels ranging from 2.6 to 20.1 dS·m–1 were constructed, based on Colorado River water salt composition, to have NaCl, CaCl2 and MgSO4 as the salinization salts. The osmotic potential ranged from –0.075 to –0.82 MPa. Salt stress began 7 days after planting by adding the salts into irrigating nutrient solution and ended after 5 consecutive days. The plants were harvested during flowering period for biomass measurement (53 days after planting). Data analysis using SAS analysis of variance indicated that the salinity in the range between 2.6 and 20.1 dS·m–1 significantly reduced leaf area, leaf dry weight, stem dry weight and root dry weight (P ≤ 0.05). We applied the data to a salt-tolerance model, log(Y) = a1 + a2X + a3X2, where Y represents biomass, a1, a2 and a3 are empirical constants, and X represents salinity, and found that the model accounted for 99%, 97%, 96%, 99%, and 96% of salt effect for cowpea shoot, leaf area, leaf dry weight, stem dry weight and root dry weight, respectively. We also found significant differences (P ≤ 0.05) of each biomass parameter among the 12 cultivars and obtained different sets of the empirical constants to quantitatively describe the response of each biomass parameter to salinity for individual cowpea cultivars. Since a significant salt × cultivar interaction effect (P ≤ 0.05) was found on leaf area and leaf dry weight, we concluded that salt tolerance differences exist among the tested cultivars.

Abstract. A study on water infiltration and solute transport in a clayey vadose zone underlying a dairy farm waste source was conducted to assess the impact of desiccation cracks on subsurface evaporation and salinization. The study is based on five years of continuous measurements of the temporal variation in the vadose zone water content and on the chemical and isotopic composition of the sediment and pore water in it. The isotopic composition of water stable isotopes (δ18O and δ2H) in water and sediment samples, from the area where desiccation crack networks prevail, indicated subsurface evaporation down to ~ 3.5 m below land surface, and vertical and lateral preferential transport of water, following erratic preferential infiltration events. Chloride (Cl−) concentrations in the vadose zone pore water substantially increased with depth, evidence of deep subsurface evaporation and down flushing of concentrated solutions from the evaporation zones during preferential infiltration events. These observations led to development of a desiccation-crack-induced salinization (DCIS) conceptual model. DCIS suggests that thermally driven convective air flow in the desiccation cracks induces evaporation and salinization in relatively deep sections of the subsurface. This conceptual model supports previous conceptual models on vadose zone and groundwater salinization in fractured rock in arid environments and extends its validity to clayey soils in semi-arid environments.

Abstract. A study on water infiltration and solute transport in a clayey vadose zone underlying a dairy farm waste source was conducted to assess the impact of desiccation cracks on subsurface evaporation and salinization. The study is based on five years of continuous measurements of the temporal variation in the vadose zone water-content and on the chemical and isotopic composition of the sediment and pore-water in it. The isotopic composition of water stable isotopes (δ18O and δ2H) in water and sediment samples, from the area where desiccation crack networks prevail, indicated subsurface evaporation down to ∼3.5 m below land surface, and vertical and lateral preferential transport of water, following erratic preferential infiltration events. Chloride (Cl-) concentrations in the vadose zone pore water substantially increased with depth, evidence of deep subsurface evaporation and down flushing of concentrated solutions from the evaporation zones during preferential infiltration events. These observations led to development of a Desiccation-Crack-Induced Salinization (DCIS) conceptual model. DCIS suggests that thermally driven convective air flow in the desiccation cracks induces evaporation and salinization in relatively deep sections of the subsurface. This conceptual model supports previous conceptual models on vadose zone and groundwater salinization in fractured rock in arid environments and extends its validity to clayey soils in semi-arid environments.

Abstract. Local peoples from Niakhar in the Senegalese peanut basin highlight a dramatic increase of water access problems due to marked rainfall deficits and salinization of surface and ground water resources. The chemical quality of groundwaters is often critical because of the salinization process, whereas water surfaces, which should be used in such situations, are up early. More and more, lowlands and rivers beds are pervaded by salt crusts. Then the salinization of wells is increasing, leading to the extension of tans (salty of acidified soils). To study the impacts of climatic pejoration on the agroecosystems and on the living conditions of the populations, we carried out the analysis of the time series of the precipitations with daily and annual time steps from 1950 to 2015 on 6 meteorological stations, in situ measurements on 78 wells for an area of 311 km2, as well as local population interviews and field observation. The results confirm an important climatic break in the region in 1970. The long dry period, from 1970 to 2009, has increased the annual rain variability, decreased the number of rainy days per year. We confirm a real and large extension of well salinization, and salt crusting in the lowlands and the riverbeds. From the local people, it seems the process of degradation of the aquifers continues to progress from a large tidal event in 1984. The rainfall increase noted in the last decade does not seem to be enough to reverse the trend and to ensure both the rise of the piezometric level of the aquifers and the desalinization of surface and ground waters.

This study localizes dimensions of freshwater salinization by directly measuring chloride concentrations in ungauged urban streams, assessing the relationship between chloride, copper and zinc in sample data, measures statewide trends for Iowa, and considers the regulatory and cultural environment of managing winter roads. Chloride concentrations in local, urban streams generally persist at higher levels than what is typical of natural Iowa waters. Runoff from snow melt events violate water quality standards, with chloride concentrations more closely resembling sea water than freshwater. Meanwhile, long-term trends at the statewide scale suggest levels are decreasing over time. Dissolved ions in groundwater from limestone aquifers encourage chemical buffering. Surface runoff in urban areas does not contain groundwater but does contain a large amount of salt from roads and other sources. More salt present year-round in streams influenced by surface water hydrology likely increases the potential for storm sewers, bridge decks and other urban infrastructure to corrode. Public agencies take varied approaches to freshwater salinization and related concerns. Regulation focuses on drinking water protection, and accounts for both household and industrial chloride sources. Snow and ice “fighters” see chloride as a tool, whereas scientists and regulated agencies consider it a pollutant of concern. This split leads to inconsistent patterns in decision-making and prioritization. Salt is a commodity, generating billions of dollars for suppliers throughout North America. Industry can play a significant role in solving what may ultimately become one of the most challenging water quality problems of the 21st Century.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008.
In recent years, concern about the water quality in the Berg River received a fair degree of attention, particularly with the imminent construction of the Berg Water Project (BWP). Particular concerns have been expressed about the water quality with respect to total dissolved salts (TDS) at Misverstand Dam. In previous studies (Fourie and Görgens, 1977) it was identified that the saline water was mostly generated in the lower portion of the Berg River Catchment (Matjies, Moorreesburg and Sandspruit Rivers) and that the abstraction of acceptable quality water higher up in the Berg River could possibly result in salinity problems at Misverstand Dam. Contrary to expectation, these studies also showed that for the most saline catchments, a winter peak in TDS concentrations also existed. To help address these concerns, a Water Research Commission (WRC) project was initiated in 2003 in which the newly-developed salinity module of the daily Agricultural Catchment Research Unit (ACRU) agrohydrological model, known as ACRUSalinity, would be configured for the Berg River Catchment. This model had previously been configured and calibrated for the Mkhomazi Catchment (Teweldebrhan, 2003) which exhibited relatively low streamflow TDS concentrations (100 mg/l) and it was deemed necessary to ascertain whether comparable TDS values could be simulated in the Berg River Catchment, where TDS concentration could rise to well above 1 000 mg/l in certain tributaries. In this project, ACRUSalinity was configured for the Berg River Catchment on a distributed basis, aiming to capture the spatial distribution of rainfall and geophysical characteristics which inherently exist in a catchment as expansive as the Berg. Initial application of the "Beta version" of ACRUSalinity to the Berg River Catchment revealed that it failed to produce simulated TDS values which were representative of the observed data. It became evident that the model required both additional salinity-related functions and modifications of existing functions. After the implementation of these algorithm changes the correspondence of simulated and observed TDS concentrations improved markedly. Verification of the ACRUSalinity simulated flows and calibration of the salinity-related parameters was based on the values of predefined objective functions. Reasonably representative flows could be obtained provided that the catchment discretisation and driver rainfall selection process were adequate. Salinity related parameters were determined purely on an iterative basis, although a priori estimation of these parameters was possible. Preliminary interdependency tests of these parameters revealed that the final calibrated set of salinity-related parameters was probably not unique and that some a priori decision making would be required when selecting the most realistic set of parameters. Quantification of the potential effect of the Berg River Dam on the TDS concentrations at Misverstand Dam was achieved as follows: the ACRUSalinity model was verified for flow and calibrated for TDS at available and reliable flow gauging stations. This was then followed by a long-term simulation run which yielded daily TDS time series for comparison, on an exceedance basis, with the observed record. Since the concern about the possible deterioration of water quality at Misverstand Dam was only a winter concern (May to September), comparisons were only drawn over this period. The flow-routing option in ACRUSalinity was not activated and a 1:1 daily comparison of flows and TDS concentrations, based on values of the objective function, was thus not possible. Results from this study showed that even with a daily model, the exceedance percentages of the TDS concentrations after the construction of the Berg River Dam were comparable with the exceedance percentages obtained from the original monthly modelling study (DWAF, 1993). In this study, however, it was possible to capture the increasing TDS concentration which was evident over winter months in the observed data record for the Matjies River and Sandspruit River catchments. The testing of the model’s effectiveness in the evaluation of engineering options was accomplished as follows: several options for ameliorating the possible deterioration of water quality at Misverstand Dam were defined, based on its practicality and cost of implementation. For example, the Withoogte water treatment works abstracts water from Misverstand Dam for supply to the West Coast region when water quality is acceptable (i.e. a TDS lower than 450 mg/l). It was proposed that to minimise the effect of periods when no abstraction from Misverstand could occur due to unacceptable water quality, a second reservoir at the treatment works should be lined and used to provide bridging storage for water from Misverstand Dam when the water quality was acceptable. The calibrated ACRUSalinity model was then modified to reflect the physical attributes of this engineering scenario of interest to produce sets of flow and TDS time series which could be further analysed to determine assurance of supply, in terms of predetermined TDS concentration thresholds in Misverstand Dam. Using this particular engineering option, the analysis revealed that a 300 mg/l TDS upper-limit at Misverstand was too stringent and that 450 mg/l was probably more realistic.

Includes bibliographical references (leaves 112-115) Towed DC Resistivity and Transient Electromagnetic arrays have been trialled for suitability in monitoring salt-loads on the Murray River at Waikerie, South Australia.

The work presented in this thesis stemmed out of the apparent lack of a method for incorporating salinity effects into environmental life cycle assessments. Salination of the water resources is a well-known problem in South Africa, and is of strategic concern. Any environmental decision support. tool that does not allow the evaluation of salinity effects therefore has limited applicability in the South African context. The starting-point for the work presented in this thesis was to evaluate existing impact categories, and the characterisation models used to calculate equivalency factors for these impact categories, in an attempt to incorporate salinity effects into existing categories and/or characterisation models. The types of effects that elevated (above normal background levels) dissolved salt concentrations have on the natural and man-made environment were evaluated, and it was concluded that, although there was some overlap with existing impact categories, some of the salinity effects could not be described by existing impact categories. It was also concluded that there are clear and quantifiable causal relationships between releases to the environment and salinity effects. A separate salinity impact category was therefore recommended that includes all salinity effects, including; aquatic ecotoxicity effects, damage to man-made environment, loss of agricultural production (livestock and crops), aesthetic effects and effects to terrestrial fauna and flora. Damage to the man-made environment is evaluated in terms of effects on equipment and structures, interference with processes, product quality and complexity of waste treatment, and is used as an indicator for the environmental consequences derived from the caused additional activity in the man-made environment. Once a conceptual model for a separate salinity impact category had been formulated, existing characterisation models were evaluated to determine their applicability for modelling salinity effects. Salination is a global problem, but generally restricted to local or regional areas, and in order to characterise salinity effects, an environmental fate model would be required in order to estimate salt concentrations in the various compartments, particularly surface and subsurface water. A well-known environmental fate and effect model was evaluated to determine if it could be used either as is, or in modified form to calculate salinity potentiaIs for LCA. It was however concluded that the model is not suitable for the calculation of salinity potentials, and it was therefore decided to develop an environmental fate model that would overcome the limitations of existing model, in terms of modelling the movement of salts in the environment. In terms of spatial differentiation, the same approach that was adopted in the existing model was adopted in developing an environmental fate model for South African conditions. This was done by defining a aunit South African catchmenta (including the air volume above the catchment), which consists of an urban surface; rural agricultural soil (and associated soil moisture); rural natural soil (and associated moisture), groundwater (natural and agricultural) and one river with a flow equal to the sum of the flows of all rivers in South Africa, and a concentration equal to the average concentration of each river in the country. A non steady-state environmental fate model (or, hydrosalinity model) was developed that can predict environmental concentrations at a daily time-step in all the compartments relevant to the calculation of salinity potentials. The environmental fate model includes all the major processes governing the distribution of common ions (sodium, calcium, magnesium, sulphate, chloride and bicarbonate) in the various compartments, and described as total dissolved salts. The effect factors used in the characterisation model were based on the target water quality ranges given by the South African Water Quality Guidelines in order to calculate salinity potentials. The total salinity potential is made up of a number of salinity effects potentials, including; damage to man-made environment, aquatic ecotoxicity effects, damage to man-made environment, loss of agricultural production (livestock and crops), aesthetic effects and effects to terrestrial fauna and flora. The total salinity potentials for emissions into the various initial release compartments are shown in the table below. Initial release compartment Atmosphere River Rural natural surface Rural agricultural surface Total salinity potential (kg TDS equJkg) 0.013 0.16 0.03 1.00 The salinity potentiaIs are only relevant to South African conditions, and their use in LeA in other countries may not be applicable. This, in effect, means that the life cycle activities that generate salts should be within the borders of South Africa. It has been recognised that the LCA methodology requires greater spatial differentiation. Salination is a global problem, but generally restricted to local or regional areas on the globe, and it is foreseen that local or regional salinity potentials would need to be calculated for different areas of the earth where salinity is a problem. The LCA practitioner would then need to know something about the spatial distribution of LCA activities in order to apply the relevant salinity potentials. The LCA practitioner should also take care when applying the salinity potentials to prevent double accounting for certain impacts. Currently, this is simple because no equivalency factors exist for common ions, or for total dissolved salts as a lumped parameter. The distribution of salinity potentials, which make up the total salinity potential, appears to be supported by the environmental policies and legislation of South Africa, in which irrigation using saline water is listed as a controlled activity, and subject to certain conditions. The major recommendations regarding further work are focussed on the collection of data that will allow further refinement of the model, and to decrease the uncertainty and variability associated with the results. The values of the published equivalency factors are dependent on the mathematical definition of the local or regional environment, and these values have been calculated for Westem European conditions. Equivalency factors may vary by several orders of magnitude, depending on how the local or regional conditions have been defined. It is therefore recommended that the model developed in this work ultimately be included into a global nested model that can be used to calculate equivalency factors for other compounds, including heavy metals and organic compounds. This would result in equivalency factors for all compounds that are relevant to South Africa.
Thesis (Ph.D.)-University of Natal, Durban, 2003.

The movement of a fluid and solute through a porous medium is of great practical interest because this describes the spread of contaminants through an aquifer. Many contaminants occur at concentrations sufficient to alter the density of the fluid, in which case the physics is typically modelled mathematically by a pair of coupled, nonlinear partial differential equations. There is disagreement as to the exact form of these governing equations. Codes aiming to solve some version of the governing equations are typically tested against the Henry and Elder benchmark problems. Neither benchmark has an analytic solution, so in practice they are treated as exercises in inter code comparison. Different code developers define the boundary conditions of the Henry problem differently, and the Elder problems results are poorly understood. The Henry, Elder and some other problems are simulated on several different codes, which produce widely-varying results. The existing benchmarks are unable to distinguish which code, if any, simulates the problems correctly, illustrating the benchmarks' limitations. To determine whether these discrepancies might be due to numerical error, one popular code, SUTRA, is considered in detail. A numerical analysis of a special case reveals that SUTRA is numerically dispersive. This is confirmed using the Gauss pulse test, a benchmark that does have an analytic solution. To further explain inter code discrepancies, a testcode is developed which allows a choice of numerical methods. Some of the methods are based on SUTRA's while others are finite difference methods of varying levels of accuracy. Simulations of the Elder problem reveal that the benchmark is extremely sensitive to the choice of solution method: qualitative differences are seen in the flow patterns. Finally, the impact of numerical error on a real-world application, the simulation of saline disposals, is considered. Saline disposal basins are used to store saline water away from rivers and agricultural land in parts of Australia. Existing models of disposal basins are assessed in terms of their resemblance to real fieldsite conditions, and in terms of numerical error. This leads to the development of a new model which aims to combine verisimilitude with numerical accuracy.
Thesis (Ph.D.)--School of Mathematical Sciences (Applied Mathematics), 2004.