Department of Civil and Environmental Engineering
demands for water by competing users pose new challenges for water resources
managers. Decision makers must understand the interactions between surface
water, groundwater and the environmental system. Additionally, the decisions
made with regard to water transfer and allocation must take into consideration
the diverse objectives that include water supply, cost efficiency and ecosystem
protection. This paper reviews the concept of multiobjective
optimization, and systems analysis approaches and tolls developed for water
resources planning and management with particular emphasis on the linking of
simulation models to optimization. This paper will also review the integrated
management of surface water and groundwater in Southern California as well as
the saltwater intrusion barrier projects in the coastal plain in
T. Prabhakar Clement
In this presentation, I will discuss multiple laboratory, field, and computer simulation datasets to illustrate the contaminant transport issues associated with saltwater intrusion dynamics. This is a short summary of the projects completed by the members of my research group in the past five years. The field dataset is based on a two-year field investigation of a dissolved hydrocarbon plume flowing towards a tidally- and seasonally-forced estuarine river system (Westbrook et al. 2005). Installation and sampling of several multi-port wells along the saline riverbank and into the river enabled us to map both vertical and horizontal definition of the hydrocarbon plume. Using the field data, a conceptual model was developed to illustrate the hydrodynamic controls of groundwater and contaminant discharge patterns occurring near a groundwater and saltwater interface.
Our laboratory research focused on developing physical models to study the transient migration patterns of contaminants in unconfined aquifers (e.g., Simpson et al. 2003). Observations were made in laboratory-scale tanks to record the salt-wedge intrusion and recession processes occurring in an unconfined aquifer. Later, the effect of basement heterogeneity on accumulating salts within an unconfined aquifer was studied. The salt accumulation processes due to gradual invasion of saltwater (due to natural reduction in aquifer flow), and the salt accumulation processes due to sudden invasion of saltwater (due to catastrophic events such as tsunami) were studied. Finally, experiments were completed to record the migration patterns of anthropogenic contaminants (such as nutrients and other organic contaminants) released just beneath and above the salt water wedge. These laboratory observations provide data to develop conceptual models for modeling various types of transport problems occurring near a salt wedge.
Our modeling efforts focus on benchmarking density coupled codes using various types of theoretical and experimental datasets (Simpson and Clement, 2003 & 2004). Two classes of benchmark problems that involve stable and unstable internal interfaces and their respective role in testing density coupled codes will be presented. Further, a brief introduction to the current version of the reactive transport code RT3D (Clement et al. 2000) and its use in modeling reactive contaminants will also be provided.
1) Clement, T.P., C.D., Johnson, Y. Sun, G.M. Klecka, C. Bartlett, Natural attenuation of chlorinated solvent compounds: Model development and field-scale application, Journal of Contaminant Hydrology, vol.42, p.113-140, 2000.
2) Simpson, M.J., T.P. Clement, and T.A. Gallop, Laboratory and numerical investigation of flow and transport near a seepageface boundary, Ground Water, vol 41(5), p.690-700, 2003.
3) Simpson, M.J., and T.P. Clement, Worthiness of the Henry and Elder problems for validating density-dependent flow models, Advances in Water Resources, vol (26) p. 17-31, 2003.
4) Simpson, M.J., and T.P. Clement, Improving the worthiness of the Henry problem as a benchmark for density-dependent groundwater flow models, Water Resources Research, vol 40 (1), W01504, doi:10.1029/2003WR002199, 2004.
5) Westbrook S.J., J.L. Rayner, G.B. Davis, T.P. Clement, P.L. Bjerg, and S.J. Fisher, Interaction between shallow groundwater, saline surface water and contaminant discharge at a seasonally- and tidally-forced estuarine boundary, Journal of Hydrology, vol (302) p. 255-269, 2005.
Scott W. Tyler
Professor of Hydrology
Department of Geologic Science and Engineering
Convective behavior in aquifers and porous media are often overlooked as possible mixing mechanisms of both salinity and contaminants. Vertical or horizontal gradients of fluid density, either from salinity or temperature are quite common in many aquifer systems and can lead to convective fluid motion not easily predicted from water level or peizometric level analysis. The development of convection cells in aquifers is controlled by fluid density contracts, fluid density gradients, and aquifer permeability and the diffusion/dispersion properties of either salinity or heat. System stability can be parameterized through the Rayleigh number, a non-dimensional representation of the ratio of buoyancy forcing to resistive forcing.
Of particular interest to coastal aquifers inundated by tsunami waves may be case of a relatively thin layer of denser seawater infiltrated over a fresher ground water. Such an unstable density contract can lead, depending upon aquifer parameters, to a convective mixing pattern in the aquifer in which the denser seawater descends through the aquifer in plume-like structures. In this lecture, an overview of density driven miscible flows in aquifers will be presented, along with examples of laboratory and field data showing the nature of mixing and stratification that can occur in saline-fresh water aquifer systems. A discussion of the possible application of stability analysis to better understand the salinity distribution in coastal aquifers following the tsunami wave will also be presented.
This discussion will then be
followed by an overview of UNR student/faculty international activities in the
area of public water supply. To date,
UNR students and faculty have led 7 work trips, primarily to developing
countries, to transfer technology on drinking water and water resource
management and also to provide volunteer labor and training to local water
managers. These work trips are
completely volunteer driven and funded by local donations, yet provide a
tremendously valuable educational experience for American students to learn
about other cultures, while also providing a valuable service to the host
country. Work trips have included
drilling water wells in
Rien van Genuchten
George E. Brown, Jr. Salinity Laboratory, USDA, ARS
Many of the tsunami-related problems in coastal regions of
http://www.ussl.ars.usda.gov/models/modelsmenu.htm) should be useful for estimating the general or site-specific effects of salinity (both short- and long-term) on soil and groundwater resources, and for evaluating possible remediation strategies.
Karsten H. Jensen
Subsurface heterogeneity complicates a proper field characterization of flow and transport properties using traditional using conventional sampling and monitoring techniques. Data obtained at point locations and in wells may not allow for an accurate representation of subsurface characteristics particularly in the horizontal direction. Recent developments within hydrogeophysics have demonstrated that many hydrogeological studies may benefit from the additional information that cross-borehole electrical resistivity tomography (ERT) and transmission radar tomography can provide. Data on changes in water content and salt concentration can be obtained with an attractive spatial resolution and at a spatial scale suitable for testing and calibrating hydrological models for flow and transport. Such data may underpin predictions of future salinity changes of Tsunami affected soil.
will be shown from a site in
Kevin J. Cunningham
The December 26th, 2004, tsunami had a huge impact on fresh ground-water supplies in affected areas due to the rapid degradation of the water quality that resulted from overland saltwater flooding of coastal areas. Important to evaluation of the aquifers and restoration of freshwater supplies will be (1) a reliable characterization of the physical system that composes the coastal aquifers, and (2) numerical hydrologic simulation of the tsunami event and the eventual recovery of the coastal aquifers to normal conditions. Assessment of the geologic, hydrologic, and hydraulic parameters of the aquifer are fundamental information needs for aquifer characterization and revitalization of water-supply needs. Hydrogeologic and geophysical methods are the principal tools in accomplishing this assessment. Characterization of the physical system is also a critical component of numerical hydrologic simulations, which are most reliable using an accurate aquifer framework and description of aquifer ground water.
The U.S. Geological Survey’s (USGS) Office of Ground
Water—Branch of Geophysics in Storrs, Connecticut, and Center for Water and
Restoration Studies in Fort Lauderdale, Florida, have numerous borehole and
surface geophysical tools that have relevance to coastal aquifer
characterization in Sri Lanka. Specific USGS borehole geophysical tools that
could provide important aquifer data include: acoustic televiewer,
three-arm caliper, digital borehole imager, electromagnetic induction, flowmeters (heat-pulse, electromagnetic, and spinner),
fluid resistivity, fluid temperature, natural gamma
ray, spectral gamma ray, single-point resistivity,
spontaneous potential, video camera, and borehole water sampler. In addition,
surface geophysical instrumentation from the USGS that could produce
significant information about the coastal aquifers include: electromagnetic and
transient electromagnetic ground conductivity meters, ground-penetrating radar,
water-borne continuous resistivity profiling,
water-borne seismic reflection profiling, and helicopter electromagnetic
surveys. Principal applications of both borehole and surface geophysical
methods include: (1) depth to freshwater-saltwater interface(s); (2)
measurement of vertical ground-water salinity profiles; (3) determination of
depth to bedrock; (4) detection, measurement, and orientation of bedrock
fractures; (5) delineation of lithology; (6) mapping
of clay (confining) units; (7) detection of porous hydrogeologic
units; (8) detection of ground-water flow units or productive fractures; and
(9) development of a hydrogeologic framework. Many of
these geophysical tools have been practical in characterization of the coastal karst limestone Biscayne aquifer of southern
Suggested for the characterization of the coastal
aquifers and recovery of water supplies in
Ground Water Quality Management Through Risk-Based Decision Analysis
Civil and Environmental Engineering
Management of watersheds with contaminated ground water is becoming
a challenging issue in many parts of the world. Since ground water provides the
majority of water in rural and urban communities of the world, ground water
quality has become an equally priority issue as water quantity. Rural and
semi-urban watersheds are prone to ground water contamination due to non-point
sources commonly present in various land use and land use practices. A good
example is chemicals used in various agricultural activities to increase crop
yield. In a detailed ground water quality management project conducted in the
Whatcom County, Washington State by
Due to the recent tsunami in the south Asian region, ground water quality has been compromised due to the unstable regions salinity formed beneath the land surface. Once adequate field data are collected and conceptual models of the physical systems are developed, a methodology similar to the one discussed here can be applied to evaluate the most cost-efficient and timely actions needed to reverse ground water quality to its native conditions.
Department of Geological Sciences
The consequences of the December 2004 Tsunami were truly
catastrophic. Large populations from
Sumatra, to Thailand and Sri Lanka live and work very close to sea level and
were provided little to no warning of the massive incoming waves. This tragedy illustrated a clear need for
both improved warning systems across the
In addition to the catastrophic loss of life and property during the tsunami, the waves have also had long-term impacts on local water supplies due to contamination of local wells and infiltration of saline waters. Geophysical techniques such as Ground Penetrating Radar (GPR) can be used to map the extent and thickness of tsunami sands deposited during this and potentially previous events, and to evaluate the saline intrusion into the fresh groundwater system. GPR surveys from the surface can be performed to rapidly map the region, and cross borehole radar tomography can provide more detailed information in areas of interest where multiple boreholes exist of can be drilled. Geophysical information can be coupled with flow and transport models to evaluate changes in water quality since the tsunami, and predict recovery of such supplies. Research into the nature of water supply contamination and the its return to a useable state will provide information that can help design future water supplies in a manner that they will be less likely to be impacted by future tsunami.