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Our hydro-environmental assessment of small water bodies covers local to global scales. The research topic started from a typical agricultural watershed (the Chenzhuang Watershed) and a small reservoir (the Hengshan Reservoir) in Jiangsu Province, southeastern China. It then expanded to all farm ponds in southern China, and non-floodplain wetlands (i.e., a common type of wetlands, surrounded by uplands outside of floodplains and riparian areas; Mushet et al., 2015) across the globe. To make the story line more understandable, Chapter 2 first introduces farm ponds at the scale of southern China. Chapter 3, 4 and 5 then study hydrological processes and nitrogen pollution in the agricultural watershed with multi-pond systems. Chapter 6 and 7 proposes computational geometry and WebGIS-based technologies to depict inundation in small reservoirs and associated flood control management.At last, Chapter 8 expands these studies to a global scale and proposes new insights into global collaboration opportunities for non-floodplain wetland conservation.
Chapter 1 depicts the background and concludes the research progress of hydro-environmental assessment of small water bodies, suggesting farm ponds is one of the typical small water bodies among global-extensively studied small vulnerable waters.
Chapter 2 introduces the hydrologic, biogeochemical, and socioeconomic benefits provided by farm ponds in southern China for thousands of years,and their contemporary threats and management challenges, including (1) inadequate planning in terms of construction and conservation regulations;(2) rural nonpoint source and mini-point source pollution; (3) climate change induced abnormalities in the hydroperiod and disturbance to wildlife;(4) invasive species; and (5) inadequate social and political capacity to consider ecological conservation. To conserve such neglected wetland ecosystem,this chapter highlights approaches that build public awareness and involve inventory maps as a basis. Policies that integrate top-down regulation and bottom-up engagement and emphasize sustainable management and utilization are recommended to ensure the effectiveness and continuous improvement of conservation programs. Techniques that involve interconnected smart sensors, volunteering and citizen science, and integrated process-based modeling are preferred when conducting comprehensive descriptions of the pond landscape, numerical assessments on their ecosystem services,and associated conservation cost analyses. The analytical framework and conservation suggestions are referential to sustainable rural development and the management of other small, scattered wetlands.
Chapter 3 studies nitrogen pollution and source attribution for a multi-pond system around a village using the HSPF model, taking a typical small watershed in the low mountains of southeastern China as an example. This chapter exhibits distinctive spatial seasonal variations with an overall seriousness rank for the three indicators: total nitrogen (TN) > nitrate/nitrite nitrogen (NO x - -N)> ammonia nitrogen (NH 3 -N), according to the Chinese Surface Water Quality Standard. TN pollution was severe for the entire watershed, while NO x - -N pollution was significant for ponds and ditches far from the village, and the NH 3 -N concentrations were acceptable except for the ponds near the village in summer. Although food and cash crop production accounted for the largest source of N loads, mini-point pollution sources, including animal feeding operations, rural residential sewage and waste, together contributed as high as 47% of the TN and NH 3 -N loads in ponds and ditches. So, apart from eco fertilizer programs and concentrated animal feeding operations, the importance of environmental awareness building for resource management is highlighted for small farmers in headwater agricultural watersheds.
Chapter 4 presents a novel approach to quantify the multi-scale hydrologic regulation of multi-pond systems (MPSs), a common type of small, scattered wetland in humid agricultural regions. A new version of Soil and Water Assessment Tool (SWAT) was developed to incorporate improved representation of: (1) perennial or intermittent spillage connections of pond-to-pond and pond-to-stream, and (2) bidirectional exchange between pond surface water and shallow groundwater. SWAT-MPS, which adopts rule-based artificial intelligence to model the possibilities of different spillage directions and GA-based parameter optimization over the two simulation years (June 2017 to May 2019), successfully replicated streamflow and pond water-level variations in a 4.8 km 2 test catchment, southern China. Water balance analysis and scenario simulations were then executed to assess the hydrologic regulation at single pond, single MPS, and entire catchment scales. Results revealed (1) the presence of 9 series-or series-parallel connected MPSs, in which pond overflow accounted for as much as 59% of the catchment water yield; (2) seasonally-and MPS-independent baseflow support and quick flow attenuation, with ranked level of pond water storage for baseflow support across different land-use types: forest > farm > village, and inversed correlation of pond spillage to baseflow and quick flow variations in the farmland; and (3) MPS-aggregated catchment flood peak reduction (> 20%) and baseflow increment (26%) in the following dry days.
Chapter 5 employs a combined self-organizing map (SOM) and a linear mixed-effects model (LMEM) to relate water quality variation of multi-pond systems (MPSs) to their extrinsic and intrinsic influences. Across the 6 test MPSs with environmental gradients, ammonium nitrogen (NH 4 + -N), total nitrogen (TN),and total phosphate (TP) almost always exceeded the surface water quality standard (2.0, 2.0, and 0.4 mg/L, respectively) in the up-and mid-stream ponds, while chlorophyll-a (Chl-a) exhibited a hypertrophic state (≥28 μg/L) in the midstream ponds during the wet season. Synergistic influences explained 69±12% and 73±10% of the water quality variations in the wet and dry season,respectively. The adverse, extrinsic influences were generally 1.4, 6.9, 3.2, and 4.3 times of the beneficial, intrinsic influences for NH 4 + -N, nitrate nitrogen (NO 3 - -N), TP, and potassium permanganate index (COD Mn ), respectively, although the influencing direction and degree of forest and water area proportion were spatiotemporally unstable. While COD Mn was primarily linked with rural residential areas in the midstream, higher TN and TP concentrations in the up and mid-stream were associated with agricultural land, and NH 4 + -N reflected a small but non-negligible source of free-range poultry feeding. Pond surface sediments exhibited consistent, adverse effects with amplifications during rainfall, while macrophyte biomass can reflect the biological uptake of COD Mn and Chl-a, especially in the mid-and down-stream during the wet season.
Chapter 6 focuses on the combined use of various common tools and GIS techniques to achieve rapid and effective estimation of inundation extent for both small reservoirs and associated hydraulic structures. It revealed that the reservoir terrain surface can be more realistic and coherent, if an airborne LiDAR-derived DEM, bathymetric measurements, and a 3D dam model are integrated. The source flooding algorithm based on a horizontal water surface can be enhanced by introducing the intersection detection from computational geometry, so that submerged areas could spread from terrain mesh cells to the upstream face of embankment dams, although the required neighbouring relationship is absent in the 3D geometric model. Taking the Hengshan Reservoir in southeastern China as the study area, the proposed methods are tested by a historical rainfall event during the typhoon season. They are also proved to support extreme water stages, and better-founded to determine the reservoir stage-storage relationship, which is mostly based on bathymetric measurements and a polynomial extrapolation.
Chapter 7 proposes a WebGIS-based flood control management system to support the flood discharge of small reservoirs during intensive rainfall in the flood season. The agile software development method and a loosely coupled structure are used to combine multidisciplinary knowledge from different experts. A flood level forecasting model for reservoirs in humid regions is established based on rainfall and water level measurements. This chapter aims to provide concise information for reservoir managers to choose an appropriate discharging scheme, so that the capacity is maintained in a safe range on the next day. Using the Hengshan Reservoir in the lower reaches of the Yangtze River as an example, the model verification reveals that it is acceptable for rainfall events whose daily amount is near or above 100 mm (the heavy rainstorm level in China), and the system is verified by a trial operation during the typhoon season. While most existing flood control systems focus on river basins and large reservoirs, this chapter considers the data availability and practical flood discharging scenario of small reservoirs, and provides a useful tool for the flood control management.
Chapter 8 presents a novel 2D and 3D WebGIS-based platform for the management of small, scattered points of interest. These points could be small water bodies and other natural resources, and here, they are landslide hazards, while the management aims at landslide multi-level management and emergency response. The scalable network architecture and three-tier software architecture are designed to support survey data improvement performed by geological surveys in different administrative levels, fast spatial decision support for rescue and evacuation after sudden hazard incidents, as well as prevention information for public access. The web service integration is widely applied in the platform, and proved useful for keeping landslide-related information consistent and up-to-date, since it relies on joint efforts from different government departments with expertise, rather than the local and independent storage pattern. The combined utilization of 2D and 3D WebGIS takes advantage of their respective superiorities, and generates a superior display and analytic web environment for local decision-makers. After elaborating the main modules and key algorithms, this user-friendly platform has been experimented and accepted by three levels of geological surveys in Zhejiang Province, China, and presented as an integrated WebGIS environment for effective management of small, scattered points of interest, such as landslide hazards, in large areas.
Chapter 9 synthesizes recent work to explore how extensively non-flood wetlands (NFWs) have been studied and possible patterns of their research focuses around the world, and discuss new opportunities for sustainable NFW use for the global community. Results indicate that NFWs have been widely studied across all continents, but have strong North America biases in the literature. We hypothesize such biases stem from terminology rather than real geographical bias around existence and functionality. To confirm this, this chapter then explores a set of geographically representative NFW regions around the world, the characteristics of research focuses for these regions, and the monetized ecosystem services of NFWs in the world's major economies. The identified commonalities and patterns suggest that there is more that unites disparate wetland research and management efforts than we might otherwise appreciate. They also support opportunities for learning and collaboration, if we can move beyond terminology and focus on wetland functionality. Based on these findings, this chapter outlines four pathways that will aid in reaching better collaborative actions across scales, including classification and simulation in theoretical and technical aspects, and improved legislative support and educational measures.