Watershed development in India. 2. New approaches for managing externalities and meeting sustainability requirements

This paper recognises the need for a revision of watershed development policy in India in relation to the planning of development interventions involving agricultural intensification and rainwater harvesting and the need for new approaches to assist the planning process. Building on, and using as an example, the results of biophysical and societal impact studies carried out on two watershed development projects in Karnataka three new management/dissemination tools, are suggested. These are (1) the web-based geographical information systems exploratory, climate land assessment and impact management tool dissemination tool for disseminating to policymakers and non-specialist stakeholders the downstream impacts of watershed interventions, (2) the ‘quadrant’ approach for ensuring that sustainability criteria are met and (3) Bayesian networks to investigate the biophysical and societal impacts of interventions. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue     

Development and Application of the 2010 Chesapeake Bay Watershed Total Maximum Daily Load Model

The Phase 5.3 Watershed Model simulates the Chesapeake watershed land use, river flows, and the associated transport and fate of nutrient and sediment loads to the Chesapeake Bay. The Phase 5.3 Model is the most recent of a series of increasingly refined versions of a model that have been operational for more than two decades. The Phase 5.3 Model, in conjunction with models of the Chesapeake airshed and estuary, provides estimates of management actions needed to protect water quality, achieve Chesapeake water quality standards, and restore living resources. The Phase 5.3 Watershed Model tracks nutrient and sediment load estimates of the entire 166,000 km² watershed, including loads from all six watershed states. The creation of software systems, input datasets, and calibration methods were important aspects of the model development process. A community model approach was taken with model development and application, and the model was developed by a broad coalition of model practitioners including environmental engineers, scientists, and environmental managers. Among the users of the Phase 5.3 Model are the Chesapeake watershed states and local governments, consultants, river basin commissions, and universities. Development and application of the model are described, as well as key scenarios ranging from high nutrient and sediment load conditions if no management actions were taken in the watershed, to low load estimates of an all‐forested condition.     

Rehabilitation and Flood Management Planning in a Steep,Boulder-Bedded Stream

This study demonstrates the integration of rehabilitation and flood management planning in a steep, boulder-bedded stream in a coastal urban catchment on the South Island of New Zealand. The Water of Leith, the primary stream flowing through the city of Dunedin, is used as a case study. The catchment is steep, with a short time of concentration and rapid hydrologic response, and the lower stream reaches are highly channelized with floodplain encroachment, a high potential for debris flows, significant flood risks, and severely degraded aquatic habitat. Because the objectives for rehabilitation and flood management in urban catchments are often conflicting, a number of types of analyses at both the catchment and the reach scales and careful planning with stakeholder consultation were needed for successful rehabilitation efforts. This included modeling and analysis of catchment hydrology, fluvial geomorphologic assessment, analysis of water quality and aquatic ecology, hydraulic modeling and flood risk evaluation, detailed feasibility studies, and preliminary design to optimize multiple rehabilitation and flood management objectives. The study showed that all of these analyses were needed for integrated rehabilitation and flood management and that some incremental improvements in stream ecological health, aesthetics, and public recreational opportunities could be achieved in this challenging environment. These methods should be considered in a range of types of stream rehabilitation projects.     

Dynamic modeling of chemical fate and transport in multimedia environments at watershed scale-I: theoretical considerations and model implementation

A geo-referenced environmental fate model was developed for analyzing unsteady-state dispersion and distribution of chemicals in multimedia environmental systems. Chemical transport processes were formulated in seven environmental compartments of air, canopy, surface soil, root-zone soil, vadose-zone soil, surface water, and sediment. The model assumed that the compartments were completely mixed and chemical equilibrium was established instantaneously between the sub-compartments within each compartment. A fugacity approach was utilized to formulate the mechanisms of diffusion, advection, physical interfacial transport, and transformation reactions. The governing equations of chemical mass balances in the environmental compartments were solved simultaneously to reflect the interactions between the compartments. A geographic information system (GIS) database and geospatial analysis were integrated into the chemical transport simulation to provide spatially explicit estimations of model parameters at watershed scale. Temporal variations of the environmental properties and source emissions were also considered in the parameter estimations. The outputs of the model included time-dependent chemical concentrations in each compartment and its sub-compartments, and inter-media mass fluxes between adjacent compartments at daily time steps.     

Degradation–environment–society spiral: A spatial auto‐logistic model in Thailand

In this contemporary interpretation of the widespread land degradation problem in Southeast Asia, it is hypothesized that spatial interplay of environmental and socioeconomic predictors determines the occurrence of land degradation. Village surveys, remote sensing and spatial auto‐logistic modelling of the relationship between degradation and land use dynamics in Lam Phra Phloeng watershed of Thailand enabled 80.2% of land to be classified correctly in terms of the presence or absence of erosion and explained 53.2% of the total variation. Cultivation and dependence on agriculture for livelihood positively and significantly affect degradation. Lack of access to institutional credit and land titles significantly increased the probability of occurrence of degradation. On the other hand, education and social cohesion are negatively associated with the occurrence of degradation. The Relative Operating Characteristic (ROC) curve was used to measures the performance of the model. The calculated area under the curve (0.879) suggests that significant predictor variables in the model can be confidently used to forecast the likelihood of occurrence of degradation and thus to identify priority areas for intervention. Policies to reduce land degradation should include measures to reduce pressure on the land, including alternative income sources. Policies could mobilize capital to invest in encouraging nature‐based tourism and other off‐farm income options.     

Rainfall Response of Degraded Soil Following Reforestation in the Copper Basin, Tennessee, USA

2 Copper Basin in southeastern Tennessee became the site of increasingly extensive and successful reforestation efforts. To determine the effectiveness of more than 50 years of reforestation efforts, we compared rainfall infiltration, sediment detachment, and soil organic matter of reforested sites to those properties of unvegetated sites and forested reference sites outside the basin. Results of 54 rainfall simulation experiments conducted in zones of the basin known to have been planted during different decades demonstrate that hydrologic recovery of soils in the Copper Basin lags significantly behind the establishment of tree cover and the protection offered by vegetation against soil erosion. Soils in new “forests” have significantly less organic matter and lower infiltration than forests more than 50 years old. The long-term persistence of low infiltration rates serves as a reminder that, at sites where the A and B soil horizons have been lost, restoration of the hydrologic function of a landscape requires decades, at least.     

红枫湖流域枯水期土壤理化特征与磷素分异研究

对贵州省红枫湖枯水期流域土壤的理化性质、磷素含量与形态分布进行了初步研究。结果表明,土壤偏酸性,以粉砂粒为主,消落带土样含水率略高于林地和荒地。表土全磷和速效磷含量为99.6~679.5mg/kg和1.1~18.6mg/kg,低于我国土壤平均水平,属喀斯特地质性缺磷;最高值分布在受人类活动污染严重的管理处和后午,且随土层深度的增加而降低。土壤中不同磷形态的含量顺序为Residual-PNaOH-PHCl-PNaHCO3-PH2O-P。其中,耕作土壤中有机碳、全氮、全磷和速效磷含量,以及H2O-P、NaHCO3-P和总可提取态磷的比例均显著高于荒地和林地,表明耕作与施肥过程不仅提高了土壤全磷和生物活性磷含量,也加剧了水土流失的环境风险。     

Aquatic biodiversity and the electric utility industry

Results from a 1995 survey of utility company biologists indicate that aquatic biodiversity is an emerging and poorly understood issue. As a result, there is some confusion about what aquatic biodiversity actually is, and how we can best conserve it. Only one fourth (24%) of the respondents said their company has a stated environmental policy that addresses biodiversity. Many respondents indicate that over the years they have not specifically managed for biodiversity, but have been doing that through their efforts to assure balanced indigenous populations. While regulations are still the major driver for biological work, an increasing number of companies are involved in voluntary partnerships in managing water resources. Of these voluntary partnerships, 70% have biodiversity as a goal. Biodiversity is becoming an increasingly common subject of study, and a vast majority (75%) of the respondents suggested it should be a goal for utility resource management. Conservation of aquatic biodiversity is a complex task, and to date most aquatic efforts have been directed toward fish and macroinvertebrates. Ecological research and technological development performed by the utility industry have resulted in a number of successful biopreservation and biorestoration success stories. A common theme to preserving or enhancing aquatic biodiversity is preserving aquatic habitat. Increasingly, ecosystem management is touted as the most likely approach to achieve success in preserving aquatic biodiversity. Several utilities are conducting progressive work in implementing ecosystem management. This paper presents the potential interactions between power plants and biodiversity, an overview of aquatic biodiversity preservation efforts within the electric utility industry, more detail on the results of the survey, and recent initiatives in ecosystem management.     

农户生态移民意愿及影响因素研究——基于新疆三工河流域的农户调查

基于农户访谈与问卷调查,对新疆三工河流域农户的生态移民意愿、移民效果与留居意愿进行调查,并采用Logistic模型对农户移民意愿与留居意愿的主要影响因素进行分析。研究结果显示:①家庭人口数、人均纯收入、主要收入来源、非农收入比重和参与退耕还林情况是影响农户搬迁意愿的主要因素,家庭人口数量越少,非农收入比重越大,对生态环境保护重要性的认知越强,就越能接受生态移民政策;②移民工程对河谷内生态环境改善作用显著,促进了退耕还林进程,草场压力有所缓解,但移民农户没有得到妥善安置,影响了农户家庭收入,其对定居点生产条件与生活环境评价较低,42.35%的农户认为搬迁后生活质量变差;③移民农户的留居意愿普遍不强,71.92%的农户想搬回原居住地,生活质量变化、定居点灌溉条件与耕地质量是影响其留居意愿的主要因素。政府应着力改善定居点水土资源条件与基础设施建设,提供农业技术培训,鼓励外出务工,以增加农户经济收入,改善生产生活环境,加强农户移民与留居意愿,促进移民工程的顺利实施。     

巢湖流域农田生态系统磷代谢分析

采用物质流分析方法,建立巢湖流域农业种植系统的静态磷代谢分析模型,结合统计数据和文献参数,估算了2008年巢湖流域农田生态系统排水含磷来源分配以及流域各县(市)农田生态系统排水的磷含量.结果表明,巢湖流域整个农田生态系统的排向水体的含磷总量为14125.1158t,其中化肥和还田畜禽粪便是巢湖流域农田生态系统磷输入的主要来源,其排入水体的含磷总量分别为37172.0944t和26230.2336t;而肥西县与合肥市辖区是农田种植对水环境影响最大的区域,其农田生态系统排水含磷总量分别为4077.6575t和2849.133t.