WETLAND AND WATER RESOURCE MODELING AND ASSESSMENT A Watershed Perspective

WETLAND  AND WATER RESOURCE MODELING  AND  ASSESSMENT A Watershed Perspective

Preface: Toward a Watershed Perspective

This is a book about the methods and geospatial techniques for modeling and assessing wetlands and water resources at the watershed scale.The theme of the book, wetland and water resource modeling and assessment, is an active field of research that constantly undergoes theoretical and technical innovations. This book emphasizes a watershed perspective in the modeling and assessment areas. 

The term watershed means a geographic area where water drains into a body of water such as a river, lake, or wetland. Other terms are often used to describe the same concept, such as river basin, drainage basin, and catchment area. Since the early 1990s, watershed management or the watershed approach—coordinated resource planning and management based on hydrologically defined geographic areas—has been promoted as a common strategy of water resource stewardship and other related environmental activities. 

Within Jiangxi Province, China, the surface water of approximately 95% of its land drains into Poyang Lake through several major rivers. The hydrological feature of this watershed is quite unique and important to water resources, biology, ecology, and socioeconomic development in the region. Thus, the watershed perspective in the research and management of the Poyang Lake ecosystem has a long tradition.Sound watershed-based water resource planning and management should rest on scientifically justifiable data and innovative technical tools. 

Thus, assessment and modeling of key processes of terrestrial and aquatic ecosystems are crucial to the success of watershed management, which is becoming, as demonstrated in the studies included in this book, an active field of research and technical development. 

With a watershed perspective, ecosystem assessment and modeling commonly possess the following major characteristics: 

(1) Sufficiently large spatial scales in data collection and analysis in order to encompass major watershed features. This often leads to using remote sensing and GIS (geographic information system) for data acquisition and integration, as well as for spatial analysis. 

(2) Inclusion of landscape features in order to appropriately characterize watershed hydrological processes and related ecosystem components. This usually requires relating land cover and land use dynamics to water features. 

(3) Linking assessment or modeling results to management decisions for specific objectives. This often results in the development of decision support tools to facilitate ecosystem assessment under various management scenarios and criteria. These characteristics of watershed assessment and modeling can be found in many of the studies included in this book.

The book is divided into five parts. 

Part I focuses on geospatial methods and technologies. It includes four research projects on improving remote sensing methods for wetland mapping, which has comprised a fundamental yet challenging area of study for detecting wetlands at a watershed level. The chapters in this part cover topics ranging from expert system techniques for improving the remote sensing identification of wetlands (Torbick et al.; Cai and Chen), to the use of hyperspectral imagery in identifying salt marshes (Yang et al.), to remote sensing spectral techniques for vegetation mapping (Chen et al.).

Part II concentrates on wetland hydrology and water budget. McNulty et al. use a modeling framework to assess the interannual water supply stress over the next 40 years across the southern United States as a function of climate, groundwater supply, and population change. Focusing on the red-soil hilly region of Poyang Lake basin, the work of Dai et al. illustrates the characteristics of temporal distribution of a water budget, which helps us understand the occurrence of seasonal droughts and to adoptbetter measures to increase water use efficiency. 

The chapter by Sun et al. is based on a synthesis of existing worldwide literature on the relations between forestation and watershed hydrology. It identifies the factors affecting hydrologic responses to forestation and discusses the potential hydrologic consequences of large-scale, vegetation-based watershed restoration efforts in China. Carried out in the Xing Feng Catchment within the Zhujiang Watershed, the study by Wen et al. introduces the use of a modified TOPMODEL to simulate streamflow and distinguish subsurface stormflow from the baseflow. 

The chapter contributed by Croley and He provides a description of the development and application of a spatially distributed, physically based surface/subsurface model of hydrology and water quality, which is used to evaluate both agricultural nonpoint-source and point-source pollution loadings at the watershed level.

Part III addresses issues relating to water quality and biogeochemical processes at the watershed scale. In their chapter, He and Croley introduce the application of the model introduced in Part II in the Cass River Watershed, a subwatershed of the Saginaw Bay watersheds in the Great Lakes area, to estimate the potential of non-point-source pollution loadings. The chapter by Gui et al. demonstrates the use of SWAT, an existing watershed assessment model, to simulate changes of nutrients at a temporal scale of one hundred years in Honghu Lake Basin, China. The work of Varnakovida et al. describes the construction of a model to predict total nitrogen, total phosphorous, and total suspended solid concentrations in lakes based on surrounding land cover and land use types and patterns.

Part IV is devoted to issues of wetland biology and ecology. The chapter by Li et al. introduces a method of predicting annual soil losses in Xiushui Watershed in Jiangxi Province using integrated data concerning precipitation, topography, soil, and vegetation cover with GIS. Lougheed et al. describe an investigation that develops and tests field-based methods for the rapid assessment of wetland conditions in Muskegon River Watershed, Michigan. 

In their chapter, Guo and Chen introduce a geospatial techniques–based method of deriving appropriate indicators for analyzing ecological conditions in Poyang Lake Watershed. Focusing on the feeding habitat of the endangered Siberian crane wintering at Poyang Lake, the chapter by Wu et al. propose a conceptual framework for integrating a model of plant biomass with remote sensing and GIS methods to simulate the growth and biomass of one submerged aquatic species under various hydrological conditions. Qi et al. present new research that expands traditional remote sensing to acoustic sensing. Their goal is to improve our knowledge about the usefulness of acoustic signals as a means to measure and interpret ecological characteristics of a landscape—the soundscape.

Part V features innovative development and applications of wetland assessment and management methodologies. The chapter by Ji and Ma covers the research, development, and application issues concerning geospatial decision models for assessing wetland vulnerability to human impact at a watershed scale. They provide prewarning information for regulatory wetland management decision making. Using the study of Muskegon River Watershed in the Great Lakes Region as an example, Stevenson et al. contribute a chapter on a conceptual framework of watershed science. 

It comprehensively reviews and discusses watershed science as related to its essential role in watershed management, its complex nature and the solutions forcomplex watershed problems, and its implementation in a multidisciplinary and collaborative framework. Also dealing with Muskegon River Watershed, Wiley et al. demonstrate the development of a GIS-based approach that uses ecologically defined valley segment units to integrate a landscape transformation model with a variety of hydrologic and other models for assessing risks to key watershed resources under various scenarios. 

The major thrust of the chapter by Yu et al. is a discussion of recent advances in watershed management technology for nonpoint source pollution control. It also discusses a number of issues that should be addressed before implementing watershed pollution-source control measures.