Land subsidence caused by groundwater exploitation in the Hangzhou-Jiaxing-Huzhou Plain, China

Hangzhou-Jiaxing-Huzhou Plain in northern Zhejiang Province, located between the Yangtze and Qiantang Rivers, is one of the regions where economic development is most rapid in China. Geological and hydrogeological surveys reveal a multi-layered aquifer system beneath the plain, which includes Holocene phreatic water layers and Pleistocene confined aquifers. Based on the historical records of groundwater extraction, groundwater levels, and ground settlement from 1964 to 2000, it is shown that ground subsidence has resulted from the continuously increasing extraction of groundwater from deep confined aquifers, and that the evolution of land subsidence can be characterized by a multifractal model. Based on this model, a set of empirical power-law relations have been established between: the land subsidence velocity and the annual groundwater extraction; groundwater drawdown and the annual land subsidence velocity; and the amount of land subsidence and the associated area of land. A set of indices are proposed for evaluating dynamic evolution of groundwater exploitation and land subsidence for the Hang-Jia-Hu Plain, from which the critical degree of evolution of land subsidence in the near future can be estimated using data on groundwater exploitation and water level changes.

Impediments to the management of shared aquifers: A political economy perspective

The reliance on aquifers which are shared by more than one country is increasing. Yet, shared aquifers are only rarely addressed in international treaties, despite the wide recognition of the desirability of comprehensive coordinated management. In order to identify the impediments to reaching agreements on the management of shared aquifers, and the factors that may assist in overcoming these impediments, the political economy of transboundary groundwater exploitation is outlined, and the Israeli-Palestinian case examined. It is argued that the main impediment to the conclusion of international agreements on groundwater is the array of domestic power structures, and particularly the power of small cohesive interest groups. The analysis of the Israeli-Palestinian 1995 interim agreement, and the negotiations leading to it, suggest that this impediment can be overcome, if the domestic interests are recognized in advance, and addressed in the agreement. It also shows that high level politics can play a positive role in forcing water negotiators to conclude an agreement.

Modeling stream-aquifer interactions in a shallow aquifer, Choele Choel Island, Patagonia, Argentina

A groundwater/surface-water interaction model was developed for the shallow alluvial aquifer of the Choele Choel Island in Patagonia, Argentina. In this semiarid climate, agriculture is sustained by an irrigation/drainage system. During the irrigation season, seepage losses through unlined distribution canals in irrigated fields contribute to elevated groundwater levels, jeopardizing fruit productivity in some areas. Moreover, high stream stages during the irrigation season interfere with groundwater drainage. The model utilized MODFLOW and its stream package, and was successfully calibrated for a historical irrigation season. Modeling results indicate that drainage through streams is significantly higher than drainage through artificial drains. The stream/aquifer relationship proved very responsive to water table rises caused by irrigation. This response manifested as changes in the gaining/losing character of stream reaches. A synthetic run aimed at isolating the effect of streamflow changes on groundwater levels showed that the effect of higher streamflows dissipates toward the interior of the island, disappearing completely at the island center. Even though some results were qualitative, the model helped to provide a better understanding of the coupled system to elucidate some of the causes of a rising water table on the island.

Is there a significant diffusive “salt-pump mechanism” for the transport of organic contaminants from the marine environment into fresh water aquifers? A discussion contribution

We analyse recent claims of an additional risk of diffusive intrusion by marine organic contamination (OC) into coastal aquifers, and discuss the activity-driven “salt-pump mechanism” which is claimed to accelerate this diffusion. The reported accelerations of transport of OC out of saltwater are far too large to be due to activity effects on simple diffusion. There probably is a small acceleration of diffusion out of saltwater, but there is no direct experimental evidence for this. Possible experimental artefacts are suggested. Larger effects on diffusion in the literature are shown to be not relevant to this problem. Diffusion of suspended OC, present in the experiments, is too slow to be significant; however, this suspended material is shown to have serious implications for the proposed interpretation of the results. Until these results are better understood, no conclusions about any possible environmental implications can be drawn from them.

Development of a conjunctive use model to evaluate alternative management options for surface and groundwater resources

A conjunctive use model has been developed to evaluate alternative management options for surface and groundwater resources. A simple water balance approach was used to estimate net recharge to the aquifer. The groundwater model FEFLOW takes net recharge as an input for the water balance calculation and simulates flow in the groundwater under all boundary stresses. The developed model was applied to an irrigated area in the Indus Basin, Pakistan, to predict groundwater levels up to 2010 in response to the possible need for intervention in irrigation and/or agricultural practices. A geographical information system (GIS) was used to assemble various types of spatial data. The study revealed that an increase in pumpage from the present rate would further strain the scarce water resources. Lining of watercourses and adjustment in cropping pattern could be adopted as alternatives for better management of surface and groundwater resources.

Remote sensing and GIS based determination of groundwater dependent ecosystems in the Western Cape, South Africa

Finding the location of groundwater dependent ecosystems (GDEs) is important in determining the extent of restrictions that need to be placed upon the abstraction of groundwater. Remote sensing was combined with geographical information system (GIS) modelling to produce a GDE probability rating map for the Sandveld region, South Africa. Landsat TM imagery identified the areas indicating the probable presence of GDEs and GIS assisted in their delineation. Three GIS models were generated: a GIS model predicting landscape wetness potential (LWP model) based on terrain morphological features; the LWP model was modified to highlight groundwater generated landscape wetness potential (the resulting GglWP model); and a groundwater elevation model was interpolated, combining groundwater level measurements in boreholes in the region with digital elevation model data. Biomass indicators generated from Landsat were classified and combined with the GIS models, followed by field verification of riverine and wetland GDEs. The LWP model provided the most accurate results of the three models tested for GDEs in this region.

Challenges of governing groundwater in U.S. western states

Over the last several decades, water users in the western United States have increasingly turned to groundwater resources to support economic development, but few institutional arrangements were in place to govern groundwater use. Over time, numerous groundwater problems have emerged. Two closely related explanations for this are explored. Surface water sources were the first to be developed, and institutional arrangements to allocate surface water were the first to be devised. These arrangements are not particularly well suited for governing groundwater. Furthermore, the physical differences between rivers and aquifers lead to differences in the development of each type of water, and in production and organization costs. Groundwater development involves low upfront production costs, which individual water users can cover. Once groundwater users have individually invested in productive activities problems emerge, such as declining water tables. Thus, unlike surface water users, groundwater users are faced with devising institutional arrangements to coordinate their water uses after they have invested in and developed productive economic activities. Most western states regulate pumping, although groundwater users, in general, resist pumping limits. The discussion concludes with proposals for modifying the prior appropriation doctrine to better accommodate the active management of groundwater basins for long-term sustainability.

Climate change impacts on groundwater recharge- uncertainty, shortcomings, and the way forward?

An integrated approach to assessing the regional impacts of climate and socio-economic change on groundwater recharge is described from East Anglia, UK. Many factors affect future groundwater recharge including changed precipitation and temperature regimes, coastal flooding, urbanization, woodland establishment, and changes in cropping and rotations.Important sources of uncertainty and shortcomings in recharge estimation are discussed in the light of the results. The uncertainty in, and importance of, socio-economic scenarios in exploring the consequences of unknown future changes are highlighted. Changes to soil properties are occurring over a range of time scales, such that the soils of the future may not have the same infiltration properties as existing soils. The potential implications involved in assuming unchanging soil properties are described.To focus on the direct impacts of climate change is to neglect the potentially important role of policy, societal values and economic processes in shaping the landscape above aquifers. If the likely consequences of future changes of groundwater recharge, resulting from both climate and socio-economic change, are to be assessed, hydrogeologists must increasingly work with researchers from other disciplines, such as socio-economists, agricultural modellers and soil scientists.

Implications of subsurface thermal–hydraulic–mechanical processes associated with glaciation on Shield flow system evolution and performance assessment

A deep geologic repository (DGR) situated on the Canadian Shield will be subject to long-term climate change that will markedly alter surface conditions as a result of glaciation and permafrost penetration. Systematic, two-dimensional and three-dimensional coupled thermal–hydraulic–mechanical finite-element simulations with varying degrees of coupling, including depth-dependent salinity (represented as a change in groundwater density) and temperature-dependent density and viscosity, were undertaken to address the implications of glaciation on groundwater flow system dynamics as it could affect DGR performance. The modelling domain consisted of a 1.6-km deep sub-regional scale (≈100 km²) fractured Shield flow system. Initial and transient thermal, hydraulic and mechanical boundary conditions were developed from two realizations of the University of Toronto Glacial Systems Model of the last Laurentide glaciation. Results indicate that during the glacial loading/unloading cycle, for this particular conceptual model, there is limited penetration of glacial meltwaters to depth and small residual anomalous hydraulic head. During glacial coverage, the mechanical factor of safety increases in the moderately fractured and sparsely fractured rock mass, but principal effective stress reorientation also occurs. Given the assumed nonglacial in situ state of stress and mechanical properties, the fracture zones were predicted to be less stable under glacial conditions.

The evolution of groundwater rights and groundwater management in New Mexico and the western United States

Historically, rights in water originated as public property and only later became individualized rights to utilize the public resource, in a manner consistent with the public welfare needs of society, but protected by principles of property law. Five basic regulatory systems for rights in groundwater in the United States have evolved to date. The problems raised by the hydrologic differences between groundwater hydraulically connected to stream systems and groundwater in non-replenished aquifers have been resolved to some extent by a couple of leading court cases. Numerical modeling and other technical methodologies have also evolved to evaluate the scientific issues raised by the different hydrologic conditions, but these are not immune from criticism. The current role of aquifers is evolving into that of storage facilities for recycled water, and their utilization in this manner may be expanded even further in the future. The policy implications of the choices relating to joint management of ground and surface water cannot be overstated. As this paper demonstrates, proactive administration of future groundwater depletions that affect stream systems is essential to the ultimate ability to plan for exploitation, management and utilization of water resources in a rational way that coordinates present and future demand with the reality of scarcity of supply. The examples utilized in this paper demonstrate the need for capacity building, not just to develop good measurement techniques, or to train talented lawyers and judges to write good laws, but also for practical professional water managers to keep the process on a rational course, avoiding limitless exploitation of the resource as well as conservative protectionism that forever precludes its use.

Is self-regulation a myth? Case study on Spanish groundwater user associations and the role of higher-level authorities

Self-regulation of groundwater users offers tremendous potential for effective groundwater management. The attributes of higher-level authorities that are more likely to facilitate the beneficial management of groundwater in economic, social and environmental terms are discussed. For this purpose, eight groundwater user associations in Spain have been compared. Factors that support institutional change were analyzed, namely: salience, common understanding, trust and reciprocity, autonomy, prior organizational experience and local leadership. These factors are complemented by features that strengthen actions by higher-level authorities that oversee self-regulation by water users (clear boundaries, legitimate recognition of appropriators, facilitating roles, trust in cross-scale linkages, clear division of responsibilities, institutional culture and co-management model choices). Self-regulation includes the creation of reflexive organizations that are capable of learning, provided first, the administration itself is modernized to meet the challenges of self-regulation, and second, that ‘regulatory capture’ is avoided by external organizations, ensuring that the regulator and the regulated are not so close in their relationship as to be detrimental to effectiveness.

Assessment of suffosion-related hazards in karst areas using GIS technology

This paper describes an application of the geographic information system (GIS) technology to a ground stability assessment in the karst area of Dzerzhinsk, Russia. In the stability analysis, the groundwater level changes in the karst aquifer could cause suffosion sinkholes when the gravitational force was greater than the soil strength. The GIS technology was used to combine various data and to delineate the zones of potential gravitational collapse and suffosion collapse in the area.

Modeling the impact of groundwater harvesting on the hydro-salinity of a saline catchment in southeastern Australia

Recharge to a saline, unconfined shallow-water-table aquifer is normally considered as an irrecoverable loss of water, but such thinking could be reviewed empirically. The use of an appropriate groundwater harvesting system does not only provide an opportunity to recover this lost water, but can also help in catchment salinity management and improvement. Agricultural-based land-drainage systems such as those that use serial biological concentration (SBC) of salts, provide examples of such harvesting methods. The impact of groundwater harvesting has been assessed on the hydro-salinity of a saline catchment in southeastern Australia through modeling. For both the below average rainfall and very wet years, the “do nothing” scenario resulted in increasing salinization in the catchment. However, after introducing a SBC system, groundwater salinity showed a decreasing trend while hydraulic heads tended to stabilize around the depth of subsurface collector wells. However, for a successful groundwater harvesting system, proper understanding of the groundwater flows and salt mobilization associated with a catchment is necessary. The outcomes of this modelling study have the potential to address similar issues (salinization) and/or needs (water harvesting) existing elsewhere in the world, particularly in semi-arid regions.

The role of economic analysis in groundwater management in semi-arid regions: the case of Nigeria

The aim of this paper is to use an economic framework to derive decision making rules for river basin management with a focus on groundwater resources. Using an example from northern Nigeria, the paper provides an example of how decision making for sustainable water resources management may be facilitated by comparing net benefits and costs across a river basin. It is argued that economic tools can be used to assess the value of water resources in different uses, identify and analyze management scenarios, and provide decision rules for the sustainable use and management of surface and ground water resources in the region.

The future of the dolomitic springs after mine closure on the Far West Rand,Gauteng, RSA

Approximately 1.2 km of dolomitic limestone overlies the Far West Rand gold reefs southwest of Johannesburg, South Africa. This karst aquifer is partitioned into several groundwater compartments by predominantly north–south trending syenite dykes. Prior to mining, the primary water flow was westwards, decanting over dyke boundaries as a succession of springs along the Lower Wonderfontein Spruit. Dewatering of the overlying dolomitic aquifer for safety and economic reasons by deep gold mining operations, caused the water levels of four compartments to drop and their respective springs to dry up. By perforating dykes, formerly separated aquifers were hydraulically interconnected by mining. Using historical and recent data of water flow—surface and groundwater—and pumping rates, a geohydrological model is presented. The results suggest that the water tables will rise to their pre-mining levels within 30 years after mining ceases and that the dry springs will flow again, despite the compartments being connected by the extensive mining operations.

Glacio-lacustrine stratigraphy,aquifer characterization and contaminant transport: a case study in South Lake Tahoe,California, USA

A hydrogeologic model that has been used by many researchers and consultants to describe an area of South Lake Tahoe, California, USA impacted by MTBE contamination describes a relatively homogeneous unconfined aquifer comprised of poorly sorted glacial outwash deposits, within which water-supply wells are able to exert significant alteration in natural groundwater flow. A re-examination of the area’s hydrogeology is presented, which supports a layered heterogeneous aquifer system constructed of alternating fine and coarser-grained glacio-lacustrine depositional units. This re-evaluation was accomplished through a review of lithologic logs across an area of approximately 1 km², combined with observations of significant hydraulic head differences and knowledge of the depositional environments controlled by Pleistocene Lake Tahoe high stands. Many of the fine-grained units observed at depths from 6 to 15 m, although relatively thin, are generally continuous and serve as significant barriers to groundwater flow. The vertical migration of contamination across these fine-grained units to deeper groundwaters was facilitated by cross-screened monitoring wells installed as part of site investigation activities. This conclusion highlights the importance of geologic characterization and proper monitoring well construction at contaminated site investigations.

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China’s container-related dynamics, 1990–2005

This study seeks to gauge how far China’s container-related dynamics between 1990 and 2005 fit into the wider perspective about transport and development within developing countries. In particular, attention is focussed on the role of specific modes to determine the extent of the penetration of containers within China. Before addressing these key issues extant models relating to an understanding of port and transport evolution in less-developed countries are recalled, synthesized and used as a base upon which an appropriate review of China’s case can be conducted. Applying them to China’s northern, central and southern port ranges not only helps assess the efficacy of these models but also highlights the contribution of individual modes.

Groundwater socio-ecology and governance: a review of institutions and policies in selected countries

Groundwater is crucial for the livelihoods and food security of millions of people, and yet, knowledge formation in the field of groundwater has remained asymmetrical. While, scientific knowledge in the discipline (hydrology and hydrogeology) has advanced remarkably, relatively little is known about the socio-economic impacts and institutions that govern groundwater use. This paper therefore has two objectives. The first is to provide a balanced view of the plus and the down side of groundwater use, especially in agriculture. In doing so, examples are drawn from countries such as India, Pakistan, Bangladesh, China, Spain and Mexico—all of which make very intensive use of groundwater. Second, institutions and policies that influence groundwater use are analyzed in order to understand how groundwater is governed in these countries and whether successful models of governance could be replicated elsewhere. Finally, the authors argue that there is a need for a paradigm shift in the way groundwater is presently perceived and managed—from management to governance mode. In this attempt, a number of instruments such as direct regulation, indirect policy levers, livelihood adaptation and peoples participation will have to be deployed simultaneously in a quest for better governance.

Space Physics Interactive Data Resource—SPIDR

SPIDR (Space Physics Interactive Data Resource) is a standard data source for solar-terrestrial physics, functioning within the framework of the ICSU World Data Centers. It is a distributed database and application server network, built to select, visualize and model historical space weather data distributed across the Internet. SPIDR can work as a fully-functional web-application (portal) or as a grid of web-services, providing functions for other applications to access its data holdings.

Spatial and temporal knowledge representation

Knowledge Representation (KR) originated as a discipline within Artificial Intelligence, and is concerned with the representation of knowledge in symbolic form so that it can be stored and manipulated on a computer. This article surveys that part of KR that is concerned with the representation of space and time, with particular reference to the use of such representations in geographical information science.