Current Problems of Hydrogeology in Urban Areas, Urban Agglomerates and Industrial Centres

Many of the world’s urbanised regions grew at a slow but consistent rate for thousands of years. In many countries, urban growth rates accelerated in the 19th century due to the industrial revolution. Today, however, most rapid growth is occurring in Asian and Latin American countries where concerns have been raised that the rates may be environmentally unsustainable. Currently, three billion people live in urban areas, representing half the world’s population. This number could double within fifty years. Large urban areas are the economic engines of the world. However, they exert an enormous stress on natural resources and the immediate environment—groundwater, in particular, is seriously compromised. The earliest impacts were recognised in areas where excessive use of groundwater led to a regional lowering of the Potentiometrie surface and promoted such problems as reduced well yields, saline intrusion and land subsidence. Today, the most common urban groundwater issues concern groundwater pollution from urban and industrial sources and recharge management, mainly in the context of rising water levels. As a science, urban hydrogeology is relatively young. Issues are complex and much remains to be done. Nevertheless, a wealth of knowledge has been gained, many issues are well documented and problems are generally well understood. Solutions are beginning to emerge and there is encouraging evidence that better methods of impact prediction, groundwater protection and urban groundwater management will provide major benefits. There is now a recognition that groundwater must form an integral part of the urban planning process if large urban and industrial regions are to be environmentally sustainable. It is essential, however, that groundwater professionals adopt a proactive role if their skills and knowledge are to be fully incorporated in this process.

Analysis of recent hydrogeological conditions indicates that industry in Azerbaijan has intensively affected the groundwater. The resulting déstabilisation of the natural groundwater regime threatens to damage the ecology and economy of the country. Regional assessments of the anthropogenic impacts on groundwater were conducted through an analysis of seasonal and long-term variations of hydrodynamic and hydrochemical parameters. Using developed criteria, the following levels of impact were identified: a) naturally low, b) abnormal c) intensively abnormal. It was found that groundwater in the urban territories, namely in the cities of Baku, Gyandja and Sumgayit, had been most affected by anthropogenic activity. This formed the basis for detailed studies which showed that, irrespective of the natural conditions, all long-term changes to the groundwater regime were caused by technogenic impacts. The degree of change was determined by the hydrogeologic setting and economic conditions. Detailed mapping of the groundwater regime and hydrogeological conditions allowed areas most affected by the processes of urbanisation to be identified. Recommendations have now been made that will alleviate the problem.

In the developed world, ‘mature’ cities have been through a number of distinct phases of development including industrialisation and post-industrialisation. Associated with these stages of development are changes in infrastructure, particularly in sanitation and water supply. These changes in development and infrastructure have impacted both underlying groundwater quantity and quality. The deterioration in water quality during early stages of development, largely as a result of absent or on-site sanitation facilities, is seen in many developing or rapidly urbanising cities today.

Since 1993, the Environment Modelling Centre (EMC) of Riga Technical University has been active in developing specialised software for creating hydrogeological models (HM). These new tools have been applied in conjunction with commercial models for solving practical problems regarding drinking water supply and the dynamics of contaminated groundwater. EMC s new software tools and major projects are considered in this paper. The knowledge and methodologies presented are particularly appropriate for complex hydrogeological problems as typically encountered in urban and industrial environments.

The inexorable expansion of the world’s urban population and the realisation that water resources are finite have forced many developing cities in emergent economies to consider how sustainability can be introduced into their plans for infrastructural improvement. Groundwater dependent cities feel this need most. However, the pace of urban aquifer management remains slow. Simple but context-sensitive aquifer protection policies would help plan for sustainable urban development, especially if stakeholder involvement increases the chances for the gap between policy enactment and enforcement/compliance to be closed. The experience of two such developing cities in Bangladesh and Kyrghyzstan that are attempting to develop their own groundwater protection plan along sound hydrogeological principles is discussed.

Coastal plains are found on all continents, and are regional features bounded on the continental side by highlands and on the seaward side by a coastline. Many urban settlements are located on coastal plains, and many of these rely on underlying groundwater for water supplies. Saltwater intrusion (the invasion of freshwater by saltwater from the sea or from marine deposits due to groundwater withdrawal) threatens groundwater supplies in many such areas. The encroachment of saltwater into freshwater supplies has become a cause for concern over the last century as populations in coastal areas have risen sharply and placed greater demands on fresh groundwater reserves. Saltwater intrusion causes many problems in these areas, perhaps the most severe being the limitation of potable drinking water. This critical problem requires appropriate management solutions. Four basic components are necessary: investigation, monitoring, modelling, and control and prevention. These four tasks must be integrated within a cost-effective framework. Such an approach should facilitate the sustainable utilisation of groundwater resources in coastal urban areas.

Urbanisation has had a major impact on groundwater beneath Évora, an ancient city in the south of Portugal. Land use change, notably the growth of impermeable surfaces, has led to a reduction in groundwater recharge. As the city has grown, impacts have increased. Understanding changes to the water balance are the first step in rationalising the use of groundwater. Currently groundwater is used largely for gardening and farming. In the oldest part of the city, within the city walls, groundwater is little used, while outside the city walls, groundwater usage is high. This study shows how the municipality can take advantage of groundwater to irrigate the majority of the public gardens instead of relying on filtered water from the Monte Novo Dam. This approach would also help solve the problem of pollution that occurs due to losses from the city’s sewage system.

Initial results suggest that the main characteristics of the well water quality of the Birmingham urban Triassic Sandstone aquifer can be described by a simple well catchment model combined with a pollutant flux model. The well catchment model uses recharge, well design, pumping rate, pumping time and sorption data. The pollutant flux model is based on a landuse model, a recharge model and chemical attributes associated with geology and landuse. Features of the system successfully reproduced include the heterogeneity of the pumped water quality distributions, the generally good quality of the pumped waters, the age ranges of the pumped waters, the breakthroughs of metals and some chlorinated solvents, the chemical disequilibrium of some waters and the concentration depth profiles. Initial breakthrough to a pumping well takes decades in this system. Maximum concentrations are unlikely to be achieved in the lifetime of a well. Given the extended times to breakthrough and the large amount of rock through which the recharge travels, attenuation capacity is potentially significant for pollutants recharged some distance from a well. Deepening wells (and to a lesser extent deepening well casing) results in significant improvement in water quality. Increasing pumping rate will also generally improve water quality as the recharge concentration heterogeneity scale is smaller than the sampling scale. However, as the radius of influence increases, so does the number of landuse classes encountered, thus, the chance of intercepting a high concentration/high flux landuse class increases. Concentrations in this system are also sensitive to recharge, unsaturated zone depth and unsaturated zone hydraulic properties. It is clear that the aquifer’s potential for dilution and dispersion of pollutants is not fully utilised. Major information uncertainties precluding calculations at specific sites include knowledge of the solute transport processes in this aquifer and concentrations of recharge waters. The study continues.

Abstract

Urban transport systems and the provision of water have been identified as the factors most critical in determining the future of cities in this new century. The effectiveness of conventional technical urban water concepts has reached a limit, and the sustainability of such practice is in question. There are a number of different types of key urban water indicators which best reflect the quality, quantity, efficiency, and effectiveness of current and future urban water systems. Many of these key indicators are directly related to hydrogeological factors. In order to analyse complex urban water systems within heterogeneous urban hydrogeological settings, a computer-aided tool has been developed to estimate the water flows and contaminant loads. This conceptual urban water and contaminant balance model has been combined with a geographic information system and a groundwater flow model in order to simulate contaminant flows from the surface to urban groundwater. By comparing several alternative scenarios with the model, possible improvements in the system can be identified along with any trade-offs that may need to occur. For instance, moving to water recycling is a potential method that could be used to reduce contaminant loads to the environment.

Tampa Bay Water, Florida’s largest wholesale water supplier, has pioneered development, application and implementation of a unique integrated surface -groundwater simulation model in concert with an optimisation program (S-O) to operate multi-wellfield water supply facilities in west-central Florida. Eleven wellfields are operated as an integrated system using a set of simulation — optimisation — demand (S-O-D) models giving priority to minimisation of environmental impact while reliably meeting municipal water demands subject to a set of regulatory and transmission constraints. This management program, Optimised Regional Operations Plan (OROP), has been in effect since January 1999 and is used to produce a prioritised production schedule for 172 wells in 11 inter-connected facilities on a bi-weekly basis. The OROP database is updated as data become available from various sources including the agency’s environmental and hydrological monitoring programs, the national weather service rainfall stations, and water production information; some of which are automatically relayed through a Supervisory Control And Data Acquisition (SCADA) system.

The main components of the Integrated Surface and Groundwater (ISGW) modeling programs (HSPF and MODFLOW) are public domain codes that have gained widespread acceptance within the water resources/environmental engineering community. However, a substantial portion of the computer codes that communicate information across the two models were independently developed and tested. In addition, the unique hydrologie conditions of west-central Florida including a seasonally high water table which responds quickly to hydrologie inputs, numerous environmental features such as wetlands and lakes, and highly variable rainfall, coupled with the use of emerging technologies provide a recipe for contentious debate as to the adequacy of ISGW.

Among the issues to resolve and develop consensus are preferred methods to represent various hydrologie processes, data interpretation and representation, model conceptualisation, model refinements, various operational constraints and a whole host of other issues related to ecosystem protection that are included in a work plan to be addressed in order for the S-O model to gain acceptability by the stakeholders. OROP implementation has brought to light many interesting issues in model application and acceptability that merit consideration in large-scale water management operations. This paper will present the modeling framework and discuss the underlying real-world data and technical issues in order to improve communication and understanding among the parties involved. Recommendations are also made for model development and application that improves chances for operational acceptability and institutional support for implementation.

Processes and problems associated with the interaction between rivers, lakes, wetlands and groundwater in the urban environment are described. Typical forms of surface water/aquifer interaction are identified, as well as commonly associated management problems. Case studies from Germany and the U.S. are used to highlight specific phenomena. A number of recommendations, solutions, and considerations required for effective management of urban groundwater are presented.

Fifteen case histories representative of urban groundwater conditions in Germany are presented in this paper. These include cities, towns, urban agglomerates, industrial centres and spas of different size and in a range of hydrogeological environments. Some are located in river plains overlying aquifers serving as public water supply.

There are very few limitations on groundwater availability from a quantitative standpoint. However, groundwater quality of shallow aquifers can be detrimentally affected by complex sources of urban pollution. Sources of urban pollution (e.g. contaminated surface waters, bank storage and artificial recharge) have to be handled cautiously. In some cases, specific pollutants can be used to identify and possibly quantify sources of contamination. For example, drugs (clofibric acid) and gadolinium (organic complexes) in Berlin’s groundwater indicate the presence of contamination originating from sewage (treatment plants, sewage farms or sewer mains).

Urban groundwater issues in Germany do not principally differ from those in other European countries, e.g. in the United Kingdom. However, town sizes in Germany are predominantly small and population densities exceed 2000 per km² in just 26 (out of a total of 84) urban agglomerates, many of which are also industrial centres. A few of the centres have to import municipal supply water; others are lucky to have access to ample groundwater resources (Hamburg’s water supply is essentially from deep aquifers). Such towns need to protect and manage their groundwater resources. Environmental isotopes have proved especially useful for groundwater management and sustainable utilisation. Examples include Hamburg, Stuttgart and the Singen Basin. The latter two areas are the most progressive in this respect.

Groundwater represents a valuable source of public drinking water in many parts of the Russian Federation but its use varies widely across the country. In part this reflects differences in the hydrological and hydrogeological settings that govern groundwater recharge and safe groundwater yield. However, in some regions, groundwater development is constrained by water management organisations that simply ignore available and well-protected groundwater resources in favour of surface water supply. Locally, significant human impacts on groundwater quality and quantity have been documented. In many populated areas, for example, groundwater recharge has been artificially enhanced and safe yield has increased; in other cases, aquifers have been drained and safe yield has been depleted. It is important that these impacts be understood if future problems are to be resolved. In particular, a full knowledge of the extent to which human activity impacts groundwater resources is essential for adequate assessment of safe yield. Safe yield assessment allows changes in surface runoff and fluctuations of the water table to be predicted; however, an inadequate representation of human influences on annual recharge and discharge will lead to serious error. The depletion of groundwater resources and safe yield is generally localised. The effects of anthropogenic pollution on groundwater also tend to be local. Pollution is most prevalent in the uppermost aquifers, particularly in urbanised and agricultural areas and in river valleys. Deeper confined aquifers used for centralised withdrawal normally produce water of good quality. Where pollution of confined aquifers occurs, it is normally caused by inadequate protection of well capture zones or by the poor design of the water-supply wells.

The focus of this research is fresh groundwater associated with drift cones that commonly underlie urban agglomerates. The aim of this investigation was to quantify the anthropogenic impacts of urbanisation on the groundwater and define optimal conditions for its exploitation. The study was carried out on the Gyandjachai River drift cone which is completely occupied by Gyandja city (the second largest city in Azerbaijan with regards to its population and commercial potential). The aquifer structure and water quality were characterised. The hydraulic link between aquifer horizons was determined and the migration of contaminants to individual aquifer horizons and wells was evaluated. Analysis of the results provided a basis for optimal aquifer development.

In many areas, sites selected for the disposal of urban waste are inadequately investigated from a hydrogeological standpoint due to data limitations. This can be particularly problematical in areas where karst conditions or coarse granular materials can provide preferential pathways for contaminants. Studies in Portugal demonstrate the value of geostatistical techniques for making optimal use of available borehole and geophysical data. Indicator Geostatistics is a non-parametric approach that proves to be particularly promising in this regard.

With the development of new oil production and transportation techniques in the Republic of Azerbaijan, groundwater protection has become a serious concern. Analysis of hydrogeological conditions suggests that oil resources are a primary cause of groundwater pollution. Oil pipelines and gas transport systems must be modified and updated to prevent excessive impacts on groundwater. Observation wells should be built along the oil pipeline routes in order to detect oil pollution. However, drilling of wells in artesian aquifers should be avoided due to the risk of spreading the contamination. Various suggestions are made for dealing with current environmental conditions. Recommendations are aimed at decreasing anthropogenic impacts at an acceptable cost to the oil industry.

In Slovakia, fresh, mineral and geothermal groundwaters are regarded as part of the natural heritage and important economic, therapeutic and economic assets. Hydrogeological studies including numerical modeling demonstrate that the quality and quantity of the geothermal waters can be protected from anthropogenic impacts by careful management. Greatest threats come from water abstraction and from urban and industrial sources of contamination, including coal mines. Protection measures introduced by the government have fulfilled their function. They include strict protocols for the construction, maintenance and operation of health resorts and establishment of protection zones for recharge, flow and discharge areas.

After 40 years of development, the German legal system incorporates several acts and regulations defining the liability of the owners and operators of plant and equipment for the storage and handling of dangerous material. Environmental legislation also establishes requirements for monitoring all relevant activities and maintaining and renewing facilities. Changes in legislation for groundwater and soil protection have forced technical improvements in storage and handling of dangerous goods, the adoption of new methods of site investigation and site cleanup, and encumbered groundwater authorities with new responsibilities. Hydrocarbons are the most frequently encountered soil and groundwater contaminant with over 90% of the total cases caused by petrol stations, oil distributors and private or company-owned oil tanks. The case of an oil trading company is presented as an example of changes in legislation and technology over a ten year period.

Currently in Tbilisi there are more than 2400 highly deformed buildings. The main causes of the deformation are soil type, the proximity and mineralised nature of near-surface groundwater, changes of the ground water level due to leakage from wastewater and seepage from Tbilisi’s water supply reservoir and the Samgori irrigation system. Typical examples of the destructive effect of groundwater are considered. The current practice of treating each case of building subsidence as a separate problem is not effective and should be replaced by a comprehensive study of the city area with the aim of zoning sectors with similar problems so that counter-deformation measures can be better targeted.

It is widely acknowledged and well documented now that Ukraine suffers from serious groundwater pollution problems. Due to intensive mining and a large number of heavy industries, the Donbass region is the most contaminated part of Ukraine and perhaps one of the most contaminated regions in the world. The threat to groundwater quality comes from different point and non point sources such as waste disposal sites and landfills, wastewater lagoons, sedimentation ponds, coal waste heaps, atmospheric precipitation and from agricultural production. Severe contamination of groundwater is evident in many places. It is expected that many new cases of groundwater contamination will be discovered in near future due to rising of contaminated groundwater levels following recent closures of large coalmines. There is a high risk that large areas will be flooded in response to the rise of water table, and hat drinking water wells will be affected by contaminated groundwater. An assessment of the threat to the groundwater resources from different sources of contamination, and recommendations for essential steps directed to improve groundwater protection and management in Donbass region of Ukraine are discussed in the paper.

Defining the geometry and anatomy of a natural hydrogeologic environment is the most important step in constructing conceptual and numerical models of groundwater flow and solute transport. No matter what type of environment we are dealing with, it is never homogeneous and isotropic under natural conditions. The distribution of heterogeneities reflects the origin and development of rocks during their long geological history. In urbanised and industrialised regions, the heterogeneities environment is complicated further by recently-produced heterogeneities caused by human activities. Heterogeneities typically can be described using intricate hierarchical systems. In a model, however, schematic representation of real conditions is necessary. Therefore it is important to define hydrogeological conditions at scales appropriate to the objective of the study.

In urban areas, groundwater is subject to numerous stresses. These include high rates of groundwater withdrawal which can cause hydrodynamic, hydrogeochemical, and thermal anomalies to develop in the aquifer and may lead to increased karstification. Prolonged, high-rates of groundwater withdrawal have lowered piezometric heads in the Carboniferous aquifers beneath the Moscow city area and have caused, not only hydrodynamic changes but also hydrochemical, hydrobiological and thermal anomalies. High rates of groundwater exploitation have intensified karst formation and promoted erosion.

One-dimensional unsteady-state groundwater flow in various aquifers (uniform, non-uniform, fractured, semi-infinite, finite), resulting from a step change in the stream stage is reviewed as a stream-aquifer interaction problem. An analytical model developed earlier for finite fractured aquifers is extended to the problem of ditch drainage without replenishment in a fractured formation. The equations describing transient water table variations between drains, the evolution of the midpoint water table elevation with time, and the variation of the drain discharge with time are presented. An approximate formula for drain spacing is proposed. The differences between the behaviour of flow in a uniform homogeneous aquifer and that in a fractured aquifer are discussed. The results of the analysis showed that the ratio of storage coefficients of blocks and fractures, and the block-to-fracture hydraulic conductivity contrast are the influencing parameters. The proposed analytical model may be used for the design of unsteady-state drainage systems in fractured soils, and for dewatering problems where the water table is close to the ground surface, for example, in urban environments where rising groundwater levels are a problem.

The city of Gulistan covers 1160 hectares (ha). It is situated on the third terrace of the Syrdarya River flood plain between the Dustlik and K-3 channels. There is a dense system of irrigation and collector return flow networks in the city; the total length of the irrigation canal network, for example, is 101.5 km.. Water for municipal use is supplied by a mains water pipeline. Leakage from the canals and water distribution system has created high water table conditions. Reclamation of lands within the city limits is accomplished by a vertical drainage system consisting of 50 wells each with a mean design discharge of 40 liters per second. The wells are about 30 years old and only 42 are operational. Major rehabilitation of the wells and pumping system is required if the high water table is to be adequately managed.

Field experiments conducted at Oslo airport, Gardermoen during the period 1994 — 1999 investigated the transport and degradation of two potential pollutants — deicing chemicals and water soluble jet-fuel. The experiments were performed in two lysimeter trenches under different boundary conditions. Laboratory experiments and numerical simulations were also performed to increase the understanding of the natural system and to quantify the natural attenuation capacity. The work revealed gravity dominated unsaturated flow in the coarse sandy soil, but also sub-horizontal displacement within dipping layers. The unsaturated zone provides natural capacity for pollutant degradation with a strong positive correlation observed between degradation and initial biomass, temperature and available nutrients (N and P). Whether deicing chemicals reach the groundwater level or not depends on the degradation potential and retention times in the unsaturated zone. If the chemicals do not reach the ground water during the spring, high evapotranspiration during summer months can increase retention times by about two months.

Impacts of urbanisation on groundwater resources are a global problem arising from the fact that many towns and cities are located in areas where aquifers are used for potable water supply. Water table aquifers are particularly vulnerable to pollution but in Lithuania, are still occasionally used for drinking water. In general, deeper aquifers are preferred for supply within city limits and serious problems can arise if these aquifers are not protected from pollution. Other negative consequences of urbanisation can include flooding, water table lowering, and sometimes heating of the subsurface. In Lithuania, all drinking water is supplied by aquifers. Recent work has allowed comprehensive groundwater management plans to be developed that include monitoring and source protection. In developing these plans, full use has been made of GIS and modeling technologies.

Groundwater resources meet 65% of the water demand in Izmir, Turkey. Water and Sewerage Administration controls the water quality in the distribution system. In addition to the municipal water supply system, there are many private wells that belong to individual apartment blocks, industries and houses.

In this study, groundwater quality has been evaluated and contamination sources have been identified. Problems include saltwater intrusion and groundwater contamination by nitrate, organic matter, pesticides, industrial sources and the inflow of surface waters. Recognising that rehabiliation of polluted groundwater is difficult and costly, a range of protective measures is recommended.