Em4885 irrigation management practices to protect ground water

TABLE OF CONTENTS
List of Figures . . . . . . . . . . vii
List of Tables . . . . . . . . . . ix
Chapter 1 - Introduction . . . . . . . . . 1-1
Organization of Manual . . . . . . . . 1-2
How to use the Manual . . . . . . . . 1-3
Chapter 2 - Water Quality Issues in Washington State . . . . . 2-1
Purpose . . . . . . . . . . 2-1
Uses and Sources of Water. . . . . . . . 2-1
Water Quality as an Economic Issue . . . . . . 2-2
Water Quality Law . . . . . . . . 2-3
Assessment of Water Quality . . . . . . . 2-5
Summary of 1992 statewide water quality assessment . . . . 2-7
Standards for ground water quality . . . . . 2-12
Assessment of ground water quality. . . . . . 2-13
Overall Strategy for Reduction of Nonpoint Source Pollution . . . . 2-14
Specific Strategy for Protection of Ground Water Quality
from Agricultural Activities . . . . . . . 2-15
Identification of Practices to Protect Surface and Ground Water Quality . . . 2-17
Chapter 3 - Background Science of Water Pollution . . . . . 3-1
Purpose . . . . . . . . . . 3-1
Pollution Process . . . . . . . . . 3-1
Nitrogen as a Potential Pollutant . . . . . . 3-3
Phosphorus as a Potential Pollutant . . . . . . . 3-5
Other Nutrients as Potential Pollutants . . . . . . 3-6
Pesticides as Potential Pollutants . . . . . . . 3-6
Site Conditions Affecting the Pollution Process . . . . . 3-7
Irrigation and Rainfall as Detachment and Transport Mechanisms . . . 3-8
Basic Soil-Water-Plant Relationships . . . . . . 3-11
Retention of water by soil . . . . . . . 3-12
Volumetric soil water measurement . . . . . . 3-12
Soil water tension . . . . . . . 3-13
Soil water characteristic curve . . . . . . 3-13
Management allowed depletion . . . . . . 3-14
Effective root zone . . . . . . . 3-14
Evapotranspiration . . . . . . . 3-14
Infiltration rate . . . . . . . . 3-15
Soil water movement/percolation . . . . . . 3-15
Salts, Irrigation, and Drainage . . . . . . . 3-15
Leaching . . . . . . . . 3-16
Correcting infiltration and soil structure problems . . . . 3-17
Assumptions in the Guidelines . . . . . . 3-19
Drainage . . . . . . . . 3-20
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