Chapter 1 Introduction 1.1 Background 1.2 Organization of this book References Chapter 2 Challenges and Solutions for Conserving Farm Ponds in Southern China 2.1 Introduction 2.2 Farm ponds in southern China 2.3 Why are these small and scattered waters important? 2.3.1 Hydrological regulation and ecological cleanup 2.3.2 Biodiversity conservation 2.3.3 Socioeconomic benefits 2.4 What are the threats and management challenges? 2.4.1 Inadequate planning and regulations 2.4.2 Rural nonpoint and mini-point source pollution 2.4.3 Climate change 2.4.4 Invasive species 2.4.5 Management challenges 2.5 Policies and approaches for farm pond conservation 2.5.1 Public awareness building 2.5.2 Top-down regulations and bottom-up engagement 2.5.3 Sustainable management and utilization 2.5.4 Inventory mapping 2.5.5 loT-based collaborative monitoring 2.5.6 Numerical assessment tools 2.6 Conclusions References Chapter 3 Assessment of Nitrogen Pollution in a Pond-rich Agricultural Watershed 3.1 Introduction 3.2 Materials and methods 3.2.1 Study area and data collection 3.2.2 HSPF description and data pre-processing 3.2.3 Sensitivity analysis, calibration, and validation 3.2.4 Source attribution of N pollution 3.3 Results and discussion 3.3.1 Calibrated parameters and modeling performance 3.3.2 Spatiotemporal analysis and source attributions of N pollution 3.3.3 Comparisons with previous studies on N source attribution 3.3.4 Implications to headwater agricultural watersheds 3.4 Conclusions References Chapter 4 Quantifying the Hydrologic Regulation Effects of Agricultural Multi-pond Systems 4.1 Introduction 4.2 Materials and methods 4.2.1 Study area and data 4.2.2 The SWAT-MPS model 4.2.3 Model calibration and validation 4.2.4 Model output and hydrologic analysis 4.3 Results 4.3.1 Calibrated parameters and model performance 4.3.2 Pond water balance and MPS identification