Catálogo de publicaciones - libros

This paper describes the application of integrated surface-groundwater (ISGW) models in regard to the planning of urban water supplies, basin water management, sustainability of natural resources, and ecosystem preservation. A brief description of the integrated models is provided to illustrate their flexibility in assessing various schemes used in the management of urban water supply systems and basin water resources. A more detailed discussion of one of the most functional and widely used integrated models (MIKE SHE) and its applications at a rapidly urbanizing site in southwest Florida is also presented.

Quantifying evapotranspiration (ET) rates in urban environments is paramount for understanding and modeling other hydrologic fluxes such as runoff and recharge. Large impermeable fractions of land in urban areas may only experience evaporation following rainfall events. Pervious fractions are believed to support most of the ET burden. Point measurements of land-cover ET in pervious areas can provide better estimates of the overall urban ET budget. These can be made by examining changes in the total soil moisture above the seasonal low water table or the ET extinction depth. Soil moisture can be determined by summing the average soil moisture content measured at various depths with capacitance sensors on a vertical probe. Graphs of total soil moisture above the water table for a riparian area in west-central Florida display two distinct slopes, a flattened slope during the overnight period and a steeper slope between approximately 9:00 am and 6:00 pm. The overnight slope is believed to correspond to a process removing moisture continually from the soil, such as gravity drainage. The daylight portion of the slope corresponds to ET plus the continuing downward gravity drainage. Daylight ET is the cause of the difference between the two slopes. Different plant communities exhibit measurably different ET rates and can be estimated using this methodology.

Reliance on vadose zone models to estimate groundwater recharge in arid and semiarid regions of the United States is increasing due to limited groundwater supplies and continued urbanization. The success of vadose zone models in providing reliable estimates of urban recharge and other fluxes depends on the information content used to constrain the calibration process. In this study, a numerical experiment of artificial recharge through a three-layered vadose zone system revealed several findings related to coupled model calibration. First, the extension of vadose zone model calibration to three dependent variables added information content that enhanced parameter sensitivities. Second, predictive analysis using the calibration-constrained Monte Carlo approach was time-prohibitive because of the tendency toward local minima when using the gradient algorithm. Third, despite a perfect match to historical data, the affect of alternative starting calibration parameters sets on condition number illustrated the limitations of information quality on model uncertainty. Fourth, perfect observed / simulated profiles correlation coefficients for all calibration parameter sets, were, by themselves, poor indicators of model success. Fifth, the range of predictive recharge uncertainty, and uncertainty in energy and solute mass entering the groundwater system, estimated using the likelihood-type approach, is attributed to parameter non-uniqueness due to limited calibration information. For a calibration of a field system, the estimated range of predictive uncertainty would be larger because of additional uncertainty from errors in measurements and/or the conceptual model.

The town of Domodedovo, Russia, is used here as a case study to test a recently developed flow structure modelling method for the delineation of urban well-field capture zones. A three-dimensional capture zone was determined for the well fields used for the town’s water supply. Significant differences in the size of the capture zone intersecting the ground surface and the size of the entire sub-surface capture zone projection were found, suggesting that accurate understanding and prediction of contaminant movement within urban systems cannot ignore the third dimension. The modelling procedure used here performed well.

Leaky sewers have to be considered as potential sources for groundwater contamination in urban areas. The medium-sized city of Rastatt in SWGermany with 50,000 inhabitants was subject of a series of investigations on sewer leakage which are summarized and discussed in this paper. Amongst others factors, the degree of pollution depends on the chemical composition of the wastewater and the amount of exfiltration. The groundwater underneath the city area showed anthropogenic influence resulting in elevated concentrations especially of boron, potassium and sodium as well as a generally increased electrical conductivity. Groundwater in the close vicinity of broken sewers showed typical sewage indicators such as iodated X-ray contrast media and microbiological parameters. Contamination with pharmaceutical residues and gadolinium could not be found in groundwater, despite significant concentrations of pharmaceuticals in wastewater. In autumn, the contents of boron and microbiological pollution were higher than in spring, indicating a higher ratio of wastewater in groundwater during times of less natural recharge. Groundwater monitoring wells near prominent leaks showed short-time fluctuations of EC and groundwater levels which could be correlated to changes of the wastewater composition and the flow regime in the pipe.

Oslo Airport is located on a large unconfined aquifer. It follows strict governmental regulations regarding spills of de-icing chemicals. During winter, de-icing of aeroplanes and runways is necessary for safety reasons: propylene glycol (aeroplanes) and potassium formate (runways) are used. During melts releases to the subsurface may potentially occur. The Pollution Control Authority allows Oslo Airport to use the unsaturated zone for remediation. Biodegradation potential although significant is strongly dependent on retention time. If necessary, pump & treat is implemented. Chemical analyses of the groundwater demonstrate capacity for microbial biodegradation. Locally this sometimes changes the composition of inorganic compounds in the groundwater. A simple box-model was created to estimate oxidation potential in the groundwater. The model indicates that the degradation potential is exceeded west of the western runway, but this is not supported by chemical analyses. Estimates of spatial distribution zones of electron-acceptors and estimates of physical spread of contamination and its residues are not fully supported by the box-model.

Clay units have often been assumed to provide good protection for underlying aquifers from contamination. This assumption, however, is rarely proved. The capacity of clays to resist contaminant invasion in urban areas is of significant interest, especially where underlying aquifers are used for supply. We report the initial findings of an on-going field study to investigate organic contaminant penetration of clay strata below a former petrochemical site in the UK. The clay is a thin, relatively continuous unit 6- 7.5m below ground surface within a shallow sandy aquifer contaminated with aromatic hydrocarbons (benzene, toluene, ethylbenzene, and styrene). Concentration/ depth profiles were obtained from cores at four locations and demonstrated transport of aromatic hydrocarbons into the clays with significant penetration in places. Preliminary modelling suggests that the clay penetration cannot always be explained by simple diffusion; advective transport through preferential pathways appears probable. Clay thin sections indicate the presence of palaeo-root holes and worm burrows. These potentially explain the enhanced solute penetration, and suggest that the presence of unconformities should be considered when assessing the protection afforded by thin clay beds.

A study of baseline groundwater chemistry has been carried out in the pristine areas around Eastern Shores, Lake St Lucia, North-eastern South Africa. The study aims to provide a quality baseline against which anthropogenic (urban) impacts elsewhere may be evaluated. In general, groundwater in the Eastern Shores region is of low conductivity, and a vital freshwater source to both Eastern Shores and Lake St Lucia itself. Two distinct groundwater types are recognized in the aquifer, one dominated by sodium and chloride and the other by calcium and bicarbonate. The two are spatially distinct, corresponding to separate groundwater mounds. Variation in electrical conductivity is thought to be related to evapotranspiration. The study provides valuable background data on coastal aquifer natural quality and a suitable baseline to judge impacts upon that aquifer, both from historic and future urbanization.

This investigation of urban groundwater problems in the city of Évora is one of the first in Portugal, its main objective being to develop a hydrochemical knowledge of the city’s groundwater. Thirteen water points, represented by 7 large diameter wells and 6 deep wells, were selected for sampling. The major ions were analysed, as well as temperature, EC, pH and total hardness. The results show that most of the waters are HCO-Mg-Ca-Na type, but some of the samples are Cl in type and one is clearly Cl-Na in type. The EC varies between 230 and 2500 μS/cm. The nitrate content varies between 0.5 and 310 mg/L, but over 50 % of the samples exceed the 25 mg/L maximum recommended by Portuguese Law. The absolute permitted maximum of 50 mg/L is also exceeded in 30 % of the samples. When compared with water quality elsewhere in Alentejo, the results are clearly high in terms of EC, nitrates and chlorides. The high content of nitrates and chlorides may be an indication of urban contamination.

This paper examines the issue of radioactivity within urban groundwater systems in Russia. Since the atomic industry began, the enterprises associated with different elements of the nuclear fuel cycle have become industrially advanced and helped drive the development of satellite cities. However, the groundwater systems of these cities were affected, especially in terms of water balance and quality. Radioactivity as a specific contaminant is a source of concern for both the public and scientists. This paper examines data concerning radioactive pollution produced by nuclear power plants, research reactors, and the Chernobyl accidents. The main conclusion is that radiation pollution is much less of a risk to the health of the Russian population than social and economic factors.