What is the Vadose Zone? Why Do We Care? Tiffany Messer Assistant Professor Biological Systems Engineering School of Natural Resources University of Nebraska-Lincoln Learning Objectives
• History of Vadose Zone Hydrology • What is the vadose zone? • Why do we care? • Soil Basics • Are there differences between soils? • If so, how do we identify those differences? • Water Movement • What is preferential flow? • What is a vadose lag time? • Nitrate Movement • Are common assumptions correct? • Is groundwater more vulnerable dependent on depth or rainfall timing? History of Vadose Zone Hydrology What is the vadose zone?
The vadose zone, also termed the unsaturated zone, extends from the top of the ground surface to the water table.
The word Vadose means "shallow” in Latin. How far does soil science go back?
A. 1700 BC B. 460 BC C. 1500 AD D. 180 AD History of the Soil Science
Samaria (1700 BC) Instructions on the preparation of land and planting of grain crops in the Euphrates River valley
Democritus (460-370 BC) plant growth involved the cycling of indestructible elements
Aristotle (384-322 BC) Taught that plants absorbed their nutrients from humus through the root system
Homer to Odysseus – using manure as fertilizer
The Bible 1 Sam. 13:20- Israelites to sharpen what would be considered their agricultural implements Deut. 11:10-11- irrigation practices Why do we care about the vadose zone?
1) Drought mitigation
2) Water contaminant movement
3) Food production
4) Flood prevention Soils Basics Particles & Pores
Slide By Trenton Franz Size of Soil Particles
SAND: 0.05 – 2.0 mm
SILT: 0.002 – 0.05 mm
CLAY: < 0.002 mm Soil Texture
Determined by the proportion of sand, silt and clay in a soil.
Soil-texture Triangle
Slide By Trenton Franz Where is the soil profile likely located in Nebraska? A. Table Land Rz = Loamy Sand 15 ft Vadose Zone T = 3-9 months B. Sandhills Sand & Gravel
50 ft C. River Valley Aquifer C = 7 yrs Sand and Gravel D. None of the Above
RZ = Root Zone
T = Travel time to aquifer (years)
C= Time from initial pollution to increase average concentration in aquifer by 10 ppm (years) Where is the soil profile likely located in Nebraska? A. Table Land Rz = Fine Sand B. Sandhills 80 ft Vadose Zone T = 8 – 10 yrs C. River Valley Fine Sand D. None of the Above
RZ = Root Zone
T = Travel time to aquifer (years) 100 ft Aquifer C = 14 yrs Sand and Gravel C= Time from initial pollution to increase average concentration in aquifer by 10 ppm (years) Where is the soil profile likely located in Nebraska? A. Table Land Rz = Silty Clay Loam B. Sandhills 80 ft Vadose Zone T = 25-30 yrs C. River Valley Silt – Silt Loam D. None of the Above
RZ = Root Zone
T = Travel time to aquifer (years) 100 ft Aquifer C = 14 yrs Sand and Gravel C= Time from initial pollution to increase average concentration in aquifer by 10 ppm (years) https://websoilsurvey.sc.egov.usd a.gov/App/HomePage.htm https://websoilsurvey.sc.egov.usd a.gov/App/HomePage.htm https://websoilsurvey.sc.egov.usd a.gov/App/HomePage.htm https://websoilsurvey.sc.egov.usd a.gov/App/HomePage.htm Common Nebraska Soils
Potential for: Holdrege Nora Wymore Valentine
Openland wildlife habitat Good Fair Fair Fair
Nitrate leaching Moderate Low Moderate High
Dryland crop yield potential Good Poor Good Poor
Pesticide runoff Low High Moderate Low Sanitary facilities/septic Fair Fair Poor Good system Recreational development Good Moderate Fair Poor campground
* Taken from UNL Plant and Soil Science Libraryhttp://passel.unl.edu/pages/informationmodule.php?idinformationmodu le=11304470