Technical Guidelines for Irrigation Suitability Land Classification U.S. Department of the Interior Bureau of Reclamation Technical Service Center June 2005 Technical Guidelines for Irrigation Suitability Land Classification June 2005 U.S. Department of the Interior Bureau of Reclamation Technical Service Center Land Suitability and Water Quality Group Denver, Colorado Table of Contents Page Chapter I: Basic Requirements .............................................................................................I-1 I.A Purpose and Objectives...............................................................................................I-1 I.B Authority and Justification..........................................................................................I-2 I.C Definitions of Terms...................................................................................................I-3 I.D Principles.....................................................................................................................I-7 I.D.1 Prediction........................................................................................................I-8 I.D.2 Economic Correlation.....................................................................................I-9 I.D.3 Permanent-Changeable Factors......................................................................I-9 I.D.4 Arable-Irrigable Analysis..............................................................................I-10 Chapter II: Factors of Land Classification........................................................................ II-1 II.A General...................................................................................................................... II-1 II.B Economic Factors......................................................................................................II-1 II.B.1 Productive Capacity...................................................................................... II-2 II.B.2 Cost of Production ........................................................................................ II-3 II.B.3 Irrigation Development Costs....................................................................... II-3 II.B.4 Interactions.................................................................................................... II-4 II.B.5 Management.................................................................................................. II-4 II.C Physical and Chemical Factors ................................................................................. II-5 II.C.1 Soil ..............................................................................................................II-5 II.C.2 Soil Quality................................................................................................... II-5 II.C.3 Soil Characteristics ....................................................................................... II-6 II.C.4 Topography................................................................................................. II-10 II.C.5 Drainage...................................................................................................... II-13 II.C.6 Water Supply.............................................................................................. II-17 II.C.7 Climate........................................................................................................ II-21 Chapter III: Land Classification Specifications and Basic Land Classes................... III-1 III.A Land Classification Specifications........................................................................... III-1 III.A.1 Development of Specifications................................................................. III-1 III.A.2 Specification Factors................................................................................. III-4 III.A.3 Specifications and Investigation Detail .................................................... III-6 III.A.4 Review of Specifications .......................................................................... III-8 III.B Basic Classes.......................................................................................................... III-18 III.B.1 Arable Area Classes................................................................................ III-24 III.B.2 Special Use Classes................................................................................. III-28 III.B.3 Basic Subclasses..................................................................................... III-29 III.B.4 Informative Appraisals............................................................................III-29 III.C Irrigable Land Classes............................................................................................ III-31 iii Table of Contents Page Chapter IV: Types of Land Classification Investigations .............................................IV-1 IV.A General ...................................................................................................................IV-1 IV.B Preconstruction Land Classification ........................................................................IV-3 IV.C Levels of Detail........................................................................................................IV-4 IV.C.1 Reconnaissance Level Investigation.........................................................IV-4 IV.C.2 Semi-Detailed Investigation......................................................................IV-7 IV.C.3 Detailed Investigation.............................................................................IV-11 IV.D Postconstruction Land Classification Investigation Types....................................IV-14 IV.D.1 Irrigable Area Determinations ................................................................IV-15 IV.D.2 Productive Area Determinations.............................................................IV-16 IV.D.3 Land Classification on Operating Projects .............................................IV-17 IV.D.4 Land Classification and Class 1 Equivalency.........................................IV-21 IV.D.5 Unapproved Land Classification.............................................................IV-22 Chapter V: Land Classification Techniques ...................................................................... V-1 V.A General .................................................................................................................V-1 V.B Preinvestigation Activities and Coordination ........................................................... V-1 V.B.1 Developing Scope of Work and Data Quality Objectives ......................... V-3 V.B.2 Available Land Data.................................................................................. V-4 V.B.3 Gross Investigation Area............................................................................V-5 V.B.4 Study Guidelines........................................................................................ V-6 V.B.5 Informative Appraisals...............................................................................V-7 V.B.6 Productivity and Land Development ......................................................... V-8 V.B.7 Soils............................................................................................................V-9 V.B.8 Land Use.................................................................................................. V-10 V.B.9 Farm Water Requirement......................................................................... V-10 V.B.10 Drainage................................................................................................... V-11 V.B.11 Present Land Characteristics.................................................................... V-12 V.B.12 Additional Informative Appraisals.......................................................... V-13 V.B.13 Base Maps and Equipment....................................................................... V-13 V.B.14 Personnel.................................................................................................. V-18 V.B.15 Coordination............................................................................................ V-19 V.B.16 Mapping Symbol...................................................................................... V-20 V.C Field Investigations................................................................................................. V-22 V.C.1 Field Orientation...................................................................................... V-23 V.C.2 Field Operation........................................................................................ V-24 V.C.3 Water Quality........................................................................................... V-30 V.C.4 Clay Type................................................................................................. V-30 V.C.5 Additional Factors Affecting Infiltration................................................. V-31 iv Table of Contents Page V.C.6 Additional Factors Affecting Available Water........................................ V-32 V.C.7 Evaluation for Predicted Level................................................................ V-35 V.C.8 Leaching................................................................................................... V-36 V.C.9 Soil Reclamation and Crop Selection ...................................................... V-36 V.C.10 Prediction of Anticipated