SEG-21306 Subsurface Solute Transport

Course

Credits 6.00

Language of instruction:

English

Assumed knowledge on:

SEG-20306 Water Quantity and Quality, MAQ-22806 Atmosphere-Vegetation-Soil Interactions

Continuation courses:

SEG30306 Characterization of Regional Subsurface Water

Contents:

Subsurface solute transport by flowing water affects soil and groundwater quality.
During this course students will get acquainted with different aspects around solute transport in the subsoil.
It contain lectures, a laboratory practical and a computer practical
- Lectures
During the lectures the derivation of the convection-dispersion equation CDE for solute transport in soils and groundwater, which is currently the tool of choice for most subsurface solute transport problems, will be presented. The CDE is critically evaluated and juxtaposed to stochastic-convective or stream tube solute transport modeling to clarify the weak and strong points of either approach. Properties of the solid phase of soils are discussed in terms of their relation to water flow and solute behavior. The ion exchange process and adsorption are related with solute transport. The soil hydraulic properties (retention curve, conductivity function) are discussed in relation with flow and (solute) transport. Different preferential flow mechanisms are outlined, together with their effects on solute movement, field observations methods to detect preferential flow, and modeling strategies.
As a computationally efficient and elegant alternative to solving the CDE, random walk simulations are discussed in class and demonstrated during the computer practical. The basic theory underlying the CDE and the stochastic-convective transport models is illustrated for a number of broadly relevant application areas, such as salinity and sodicity hazards in natural ecosystems and agro-ecosystems, pesticide and heavy metal leaching. Relatively simple mathematical tools are provided to give hands-on experience with applying the different transport concepts. Illustrations of complicated transport phenomena in case of spatiotemporal variability and for multicomponent transport processes are explained, giving a clear link with the laboratory and computer practicals. Teaching will be on the basis of new lecture notes that will be available from September 2010
- Laboratory practical
This practical involves monitoring water flow and solute transport in a soil column by various sensors driven by a data logger, soil sampling in the field, various standard soil physical techniques (measurement of saturated hydraulic conductivity and the water retention curve), and several other methods and techniques.

- Computer practical
During this practical emphasis is put on numerical techniques to simulate solute transport in saturated part of groundwater. First attention is paid to the different transport processes with the aid of ready maid models (applets) which are based on several analytical solutions. Next students need to derive different numerical approximations of the CDE which need to be implemented in a spreadsheet to develop numerical models. To clarify certain transport processes, an alternative to the CDE, the Random Walk method will be implemented in a spreadsheet as well. Finally commercial software will be used to setup a three dimensional groundwater and transport model including a heterogenic conductivity field. Mass moment calculations illustrate the effect of the heterogeneity on a contamination plume.

Learning outcomes:

At the end of the course, students will have acquired knowledge, tools, and skills to;
- understand and reproduce various (differential) equations that describe solute transport;
- understand the processes involved in biochemically reactive solute transport;
- appraise the strengths and limitations of the convection-dispersion equation, and judge its value for particular cases;
- handle various soil sensors at an introductory level, and critically evaluate the data they generate;
- determine suitable (combinations of) instruments to observe/monitor solute transport in soils and groundwater;
- perform model simulations of groundwater flow and solute transport;
- understand the complexity of numerically solving the CDE.

Activities:

Attending lectures, laboratory and computer practicals, self study.

Examination:

Written exam, practical report and evaluation of performance during the laboratory practical.

Literature:

Lecture notes.