Agricultural drainage water management in arid and semi ... - FAO.org

vContentsPageFOREWORDiiiACKNOWLEDGEMENTSivLIST OF BOXESixLIST OF FIGURESixLIST OF TABLESxiLIST OF ACRONYMS AND SYMBOLSxiiPART I. FRAMEWORK AND TECHNICAL GUIDELINES 11. INTRODUCTION 3Need for drainage of irrigated lands 3Need for water conservation and reuse 5Towards drainage water management 5Scope of this publication 62. DEFINING THE PROBLEM AND SEEKING SOLUTIONS 9System approach in drainage water management 9Defining the problem 11Seeking solutions 13Spatial issues 13The use of models in recommending solutions and anticipated results 15Model characteristics 15Regional models 16Rootzone hydrosalinity models 16Principles of rootzone hydrosalinity models 16Salt balance in the rootzone 183. FRAMEWORK TO SELECTING, EVALUATING AND ASSESSING THE IMPACT OF DRAINAGE WATERMANAGEMENT MEASURES 21Definition of drainage water management and tasks involved 21Driving forces behind drainage water management 21Physical drainage water management options 22Conservation measures 22Reuse measures 23Treatment measures 24Disposal measures 25Non-physical drainage water management options 27Emission levels 27Ambient levels 28Salinity permits 28Charges on inputs 28Subsidies on practices 29Charging/subsidizing outputs 29Combined measures 30