Introduction to Vadose Zone Hydrology

1. 1 Introduction to Vadose Zone Hydrology

2. Course objectives • CE/ENVE 320-03 provides theoretical and experimental foundation for understanding and quantifying physical and hydrological properties of soils and other porous media. • The course covers key hydrological processes taking place at or near the Earth’s surface, emphasizing mass and energy exchange, transformation and transport in partially-saturated porous media at multiple scales. • Coupling with atmospheric processes and the role of plants in the hydrological cycle will be studied. • We will examine modern measurement methods and analytical tools for interpretation of hydrological information. • The course provides conceptual and practical basis for addressing vadose-zone related science and environmental engineering challenges.

3. Syllabus (Spring 2004) • Instructor:Dani Or (CAST 313, 486-2768) • Time:MW 4:30-6:00 pm (Lec.) • Location:CAST 206 (and 105, 4 Lab sessions) • Lab Inst. - Jon Drasdis (CAST 203, 486-3211) • Office Hrs:M 2:00-3:00 pm • Text:Classnotes – Vadose Zone Hydrology/Soil Physics, by Or D., J.M. Wraith, and M. Tuller will be available (PDF) to registered students on the course webpage: www.engr.uconn/edu/~environ/dani/courses/VDZ-320/ Supplemental book: Environmental Soil Physics, by: D. Hillel • Grades: • 35% on Homework assignments (due Monday) • 15% on each of three exams (and quizzes) • 15% on lab reports • A>90%; B=80-89%; C=70-79%; D=60-69%; F<60% • Lab reports are due beginning of the following lab session

4. Policies and expectations • Use office hours or contact instructor forassistance – PRIOR to last week of semester. • No late HW returns. • Exams are open book • Engineers and scientists are expected to use ALL information available and make assumptions regarding missing information - never “get stuck” due to lack of information – check, estimate, approximate, and assume. • Pay attention to “rules of thumb” to develop a sense for estimating properties to within an “order of magnitude”. • Check if results make sense – no negative volumes, please! • Use SI units to report results & HW (scientific currency). • Dimensional inspection - a key step to happiness !

5. Course content and schedule • Week 1 to 4 (Section 1): • Physical Properties of Soils and Other Porous Media – Units and dimensions, definitions and basic mass-volume relationships between the solid, liquid and gaseous phases; soil texture; particle size distributions; surface area; soil structure. New addition – Clay behavior (Hillel Chapter 4) • Soil Water Content and its Measurement - Definitions; measurement methods - gravimetric, neutron scattering, gamma attenuation; and time domain reflectometry; soil water storage and water balance. • Demo Lab #1 : Soil bulk density; water content measurement methods -gravimetric, TDR, Neutron Probe. • Please mark your calendars - NO CLASS on February 4th (Wed.)

6. Course content and schedule • Week 1 to 4 (Section 1): • Soil Water Retention and Potential (Hydrostatics) - The energy state of soil water; total water potential and its components; properties of water (molecular, surface tension, and capillary rise); modern aspects of capillarity in porous media; units and calculations and measurement of equilibrium soil water potential components; soil water characteristic curves definitions and measurements; parametric models; hysteresis. • New addition – Capillarity in angular pores and adsorption • Lab #2: Determination of SWC curves using pressure plates, flow cells, and dew point psychrometer. Combining measurements and fitting SWC.

7. Course content and schedule • Water Flow in Porous Media – laminar flow, saturated and unsaturated flow, hydraulic properties, infiltration. • Soil-Plant-Atmospheric Relations – radiation and energy balances, evapotranspiration, evaporation from soil surface and groundwater. • Solute Transport in Soils – transport mechanisms, breakthrough curves, solutions for steady flow, salinity balance. • Temperature and Heat Flow in Porous Media - soil thermal properties; steady state heat flow; nonsteady heat flow; estimation of thermal properties; engineering applications. • Soil Gaseous Phase and Exchange Processes – effective gaseous diffusion; water vapor flow; gaseous fluxes and their measurement. • Questions/comments regarding the syllabus, policies, etc.?

8. Scope of Vadose Zone Hydrology (1) • Soils are among the most complex systems found in nature where physical, chemical, and biological processes taking place simultaneously. • Vadose zone hydrology/soil physics is concerned with the application of physical principles to characterization of soil properties and to understanding of processes occurring in this life-supporting thin crust of the Earth surface. • It has been estimated that globally, soil contains approximately 2.6x1029 prokaryotic cells (compared to 1.2x1029 in ocean water and sediments); concentrated in a relatively small volume on the earth skin (soil volume 1.2x1014 m3 vs 1020 m3 for open ocean) making the unsaturated zone the richest compartment of prokaryotic life on Earth (Whitman et al., 1998, PNS). (Additionally, consider most vegetation and crops on Earth)

9. Where is the Vadose Zone? The vadose zone

10. Vadose Zone Hydrology – Profile Scale

11. Scope of Vadose Zone Hydrology (2) The study of physical properties of soils and other porous media; particle and pore size distribution, water retention and hydraulic conductivity, thermal capacity and conductivity, soil strength, etc.The measurement, prediction, & control (manipulation) of physical processes taking place in & through the vadose zone; water infiltration & redistribution, solute & contaminant transport, heat flow, etc.The study and control of physical conditions and processes affecting water resources, plant growth, and remediation activities concerning atmospheric influences at the top boundary, and groundwater at the lower boundary;e.g., solar radiation, precipitation, evapotranspiration, recharge capillary rise, etc. (In the next few slides we illustrate some of the processes and applications of vadose zone hydrology)

12. Agricultural Water Management Knowledge of physical soil properties and processes is required for agricultural soil water management (design of drainage systems, irrigation scheduling). Excess water in a coastal Area in Texas Irrigated field in Southern Idaho

13. Importance for reducing soil erosion Physical soil properties govern many dynamic processes, such as erosion. Knowledge of physical properties allows estimation of erosion potential and establishment of active measures for prevention of soil erosion.

14. Soil erosion damage

15. Surface Runoff & Colloid-Facilitated Transport Soil erosion and the presence of clay minerals enhance surface runoff and associated transport of agrochemicals with the sediment into surface and subsurface water resources.

16. Soil Water Management - Nutrients Water running off agricultural fields carries sediment and nutrients into streams and creeks.

17. Eutrophication The transport of excess nutrients and sediment into water bodies can cause algae blooms, resulting in the death of many aquatic organisms.

18. Land use - Soil Compaction Management Heavy harvest machinery, grazing, or recreational use often lead to compaction of soils.Knowledge of soil physical soil properties and processes is required for management of our natural resources. Skid trails from logs often initiate erosion.

19. Importance for Soil Compaction Poor drainage in a compacted logging road.

20. Soil Compaction due to Recreational Use Intensive recreational use of forest soils also leads to soil compaction.

21. Military land use and related issues • Landmine detection and clearing is critically dependent on knowledge of soil properties and hydrological conditions in the shallow vadose zone. • Military land use and trafficability rely on knowledge of soil properties and hydrological conditions.

22. Importance for water resource management Shrinkage cracks in dry clay soils, biological macropores, or fracture networks in basalt may lead to fast preferential transport of chemicals and contamination of drinking water resources.

23. Importance for Engineering Applications Certain soils and earth materials (e.g., clays) are often used for engineering applications, such as containment of hazardous waste sites or earth dams.

24. Clay Liners for Waste Isolation

25. Importance of Soil Physics – Engineering Lack of knowledge of soil physical properties and processes might lead to disastrous events like the failure of the Teton Dam near Rexburg in 1976.

26. Teton Dam Failure – Flood in Rexburg

27. Watershed Studies of Runoff Production - Panama • Watershed studies of runoff production mechanisms (Rio Chagres, Panama – Prof. Ogden) – rely on vadose zone hydrological information (e.g., infiltration)

28. Contaminant transport - Hanford Site The Hanford Site located at the Columbia River in southeastern Washington is the world’s largest cleanup operation. Nuclear waste left from the Manhattan project leaks through corroded tanks and migrates towards the Columbia river.

29. Hanford Site

30. Bio- and Phytoremediation • Stimulation of microorganism-based transformation by plant exudates and leachates, and by fluctuating oxygen regimes. • Slowing of contaminant transport from the vegetated zone due to adsorption and increased evapotranspiration. • Plant uptake, followed by metabolism or accumulation. (http://www.wes.army.mil/el/phyto/ )

31. O2 CO2 Advanced Life Support Systems in Space - NASA • Behavior and distribution of liquids in plant growth media under zero gravity is essential for design of advanced life support systems (ALS) part of NASA’s future space missions.

32. The International System of Units SI All physical quantities are measured and expressed in units.We will use the international system of units (SI system) for all calculations throughout this course. The SI system contains seven basic units for length, mass, time, electric current, temperature, amount of substance, and luminous intensity. Other physical quantities are expressed in derived units. Force, for example, is expressed by a derived unit Newton (kgm x m/s2).

33. Derived SI-Units

34. Derived SI-Units

35. The International System of Units SI • A dimension is a qualitative expression of a physical quantity or an attribute. It may be a basic dimension such as length [L], time [t], or mass [M], or a derived dimension such as volume [L3], or density [ML-3]. • Dimensional inspection is an important step in verifying the validity of an equation; the dimensions of all terms must be consistent. • Writing the equation in dimensional form only, leaving out real values (numbers), enables algebraic manipulation of dimensions, i.e., dimensions may be divided, multiplied, and cancelled to simplify the dimensional equation in terms of basic dimensions.

36. Dimensions and Unit Conversion http://www.digitaldutch.com/unitconverter/