Soil Science
The living foundation beneath your feet — what soil is, how it works, how to improve it
Chapter 9: Water Movement in Soil
Why this matters: Understanding how water moves through your specific soil — how fast it drains, how far it wicks, where it collects — is the foundation of irrigation design, drainage solutions, water harvesting, and drought management. This chapter bridges soil science directly into practical land and water management.
9.1 How Water Enters Soil — Infiltration
INFILTRATION: the rate water moves INTO soil
From: 9.1 How Water Enters Soil — Infiltration
Image file: ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig01.png
Save image as ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig01.png in this folder, then replace this block with:<figure><img src="../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig01.png" alt="INFILTRATION: the rate water moves INTO soil"></figure>
9.2 Percolation and Drainage
PERCOLATION: movement of water THROUGH soil
From: 9.2 Percolation and Drainage
Image file: ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig02.png
Save image as ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig02.png in this folder, then replace this block with:<figure><img src="../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig02.png" alt="PERCOLATION: movement of water THROUGH soil"></figure>
9.3 Capillary Rise — Water Moving Upward
CAPILLARY RISE: water moving UP through soil
From: 9.3 Capillary Rise — Water Moving Upward
Image file: ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig03.png
Save image as ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig03.png in this folder, then replace this block with:<figure><img src="../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig03.png" alt="CAPILLARY RISE: water moving UP through soil"></figure>
9.4 Water and Drought — Texas Specifics
TEXAS WATER CHALLENGES
From: 9.4 Water and Drought — Texas Specifics
Image file: ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig04.png
Save image as ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig04.png in this folder, then replace this block with:<figure><img src="../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig04.png" alt="TEXAS WATER CHALLENGES"></figure>
1. Infiltration is the movement of water into the soil surface.
2. Percolation is the downward movement of water through the soil profile.
3. Capillary rise moves water upward against gravity through small pores.
4. Sandy soils have fast infiltration but low water retention.
5. Clay soils have slow infiltration but high water retention.
6. Field capacity is the maximum amount of water soil can hold against gravity.
7. Wilting point is the soil moisture level at which plants cannot extract water.
8. Plant-available water is the difference between field capacity and wilting point.
9. Macropores (large pores) allow rapid drainage and air exchange.
10. Micropores (small pores) hold water available to plants.
11. Compaction reduces macropores and impairs drainage.
12. The water table is the upper surface of saturated groundwater.
13. Capillary fringe is the zone above the water table where water is pulled up.
14. Hydrophobic soils repel water and are common in some dry Texas areas.
15. Evapotranspiration (ET) is the combined water loss from soil and plants.
16. Mulch significantly reduces soil water evaporation.
17. Hardpan layers can create perched water tables above them.
18. Texas soils lose significant moisture through evaporation in summer.
19. Deep-rooted plants access subsoil water unavailable to shallow-rooted plants.
20. Irrigation should always wet soil as deep as the deepest active roots.
1. What is the difference between infiltration and percolation?
2. What is field capacity and why is it important?
3. What is plant available water?
4. How does soil texture affect water movement?
5. What is capillary rise and how deep can it move water?
6. What is a perched water table and what causes it?
7. How does mulch affect soil water content?
8. What is evapotranspiration and how do you calculate irrigation needs?
9. Describe how deep to irrigate and why.
10. How do macropores and micropores differ in their water-holding functions?
1. The movement of water into the soil surface is called .
2. The downward movement of water through the soil profile is .
3. The soil moisture level above which gravity drains free water is called capacity.
4. The moisture level at which plants can no longer extract water is the point.
5. The difference between field capacity and wilting point is called water.
6. Upward movement of water against gravity through small pores is called rise.
7. Water loss from soil surface and plant transpiration together is called .
8. The zone of soil saturated with water is called the zone.
9. Large pores that allow rapid drainage and oxygen exchange are called .
Complete in the field. Check each off as you go.
1. Infiltration Rate Test: Pour 1 cup of water into a cylinder pressed into the soil. Time absorption. Repeat in 3 locations. Compare: native grassland, vegetable garden, and bare compacted area.
2. Soil Moisture at Different Depths: Dig down 6", 12", 18", and 24" after a significant rain (1"+). Feel the soil at each depth. How deep did moisture penetrate? How long after rain does it persist at each depth?
3. Mulch vs Bare Soil Comparison: Mulch a 4×4 foot bed 3" deep. Leave an identical bed bare. After 2 weeks without rain, dig to 6" in each. Which retains moisture better?
4. ET Estimation: Look up your county's reference evapotranspiration (ET₀) on the Texas ET Network (texaset.tamu.edu). Calculate how much water your vegetable garden needs per week.
5. Percolation Test (for septic/drainage assessment): Dig a 12"×12"×12" hole. Fill with water to presaturate soil. After 24 hours, fill again. Record the time for water to drop from 6" to 5" (1 inch drop). Calculate percolation rate in min/inch.
Chapter Summary
INFILTRATION: rate water enters soil
From: Chapter Summary
Image file: ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig05.png
Save image as ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig05.png in this folder, then replace this block with:<figure><img src="../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig05.png" alt="INFILTRATION: rate water enters soil"></figure>
Next Chapter → Texas Soils — Alkaline, Caliche, Clay, and Sandy Types
Connections to Other Topics
→ C07 Water Harvesting: Applying water movement knowledge to land
From: Connections to Other Topics
Image file: ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig06.png
Save image as ../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig06.png in this folder, then replace this block with:<figure><img src="../../../images/s01-foundation/c03-soil-science/ch09/c03-soil-science_ch09_water_movement_fig06.png" alt="→ C07 Water Harvesting: Applying water movement knowledge to land"></figure>