Surface Water Hydrology Lecture 13: Infiltration Readings: Applied Hydrology Sections 4.3 and 4.4; Handbook of Hydrology Sections 5.1 and 5.2 Soil texture and classification Soil water properties, K(q), Y(q) Infiltration Green-Ampt method

Particle size measurement Seives of progressively smaller size to get size Distribution of soil http://www.soils.agri.umn.edu/academics/classes/soil2125/doc/s2chp1.htm

Soil Classification USDA particle size classification < 0.002mm is clay 0.002 – 0.5mm is silt 0.5mm – 10mm is sand > 10mm is gravel

USDA Soil Texture Triangle A soil with 30% sand, 40% clay and 30% silt is a Clay Loam % Silt = 100 - %Sand - %Clay

Variation of Saturated Hydraulic Conductivity with Soil Texture K Se

Y K q q K Interconnection of Soil water properties Y

Double Ring Infiltrometer Measure rate of fall in inner ring Infilration http://www.alwi.com/wastewater.php

Infiltration by Horton’s method

Infiltration into a soil water column 1 2

Green-Ampt method Relative saturation Incremental change in soil water content as wetting front passes

Green-Ampt Parameter Definitions Relative saturation Incremental change in soil water content as wetting front passes

Math for Green Ampt

Green- Ampt Parameters