ON THE MISMATCH BETWEEN DATA AND MODELS OF HYDROLOGIC AND WATER RESOURCE SYSTEMS1

ABSTRACT: Many difficulties exist in the matching of models with data. This paper identifies elements of this problem and discusses considerations involved in model evaluation. The well known multivariate linear regression model is used to illustrate the distinctions between accuracy and precision and between estimation and prediction (because the model is commonly misused.) No amount of additional data will improve the accuracy of a poor model. A high R², while indicative of a good matching between the observed data and model estimates, is a poor criterion for judging adequacy of the model to make good predictions of future events. Model evaluation also includes the problem of introducing secondary data and proxy variables into a model. Secondary data frequently enter, for example, the mass, energy and water budget equations because of difficulties in measuring the primary variables. Proxy variables arise because of a desire to collapse a vector of incomparable values, say, of water quality into a single number. Review of the above issues indicates that model evaluation is a multi-criterion problem, often imbedded in a larger framework where models are intended to meet multiple objectives. The mismatch of models and data has increasing legal and social consequences.     

Riparian livestock exclosure research in the western United States: a critique and some recommendations

Over the last three decades, livestock exclosure research has emerged as a preferred method to evaluate the ecology of riparian ecosystems and their susceptibility to livestock impacts. This research has addressed the effects of livestock exclusion on many characteristics of riparian ecosystems, including vegetation, aquatic and terrestrial animals, and geomorphology. This paper reviews, critiques, and provides recommendations for the improvement of riparian livestock exclosure research. Exclosure-based research has left considerable scientific uncertainty due to popularization of relatively few studies, weak study designs, a poor understanding of the scales and mechanisms of ecosystem recovery, and selective, agenda-laden literature reviews advocating for or against public lands livestock grazing. Exclosures are often too small (<50 ha) and improperly placed to accurately measure the responses of aquatic organisms or geomorphic processes to livestock removal. Depending upon the site conditions when and where livestock exclosures are established, postexclusion dynamics may vary considerably. Systems can recover quickly and predictably with livestock removal (the “rubber band” model), fail to recover due to changes in system structure or function (the “Humpty Dumpty” model), or recover slowly and remain more sensitive to livestock impacts than they were before grazing was initiated (the “broken leg” model). Several initial ideas for strengthening the scientific basis for livestock exclosure research are presented: (1) incorporation of meta-analyses and critical reviews. (2) use of restoration ecology as a unifying conceptual framework; (3) development of long-term research programs; (4) improved exclosure placement/design; and (5) a stronger commitment to collection of pretreatment data.     

Quantifying natural resource injuries and ecological service reductions: challenges and opportunities

The natural resource damage assessment (NRDA) provisions of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Oil Pollution Act (OPA) are complex and have been difficult to implement. The complexity and difficulty in implementation arise both from the assessment procedures specified in agency NRDA guidance and from the limited ability of ecologists to quantify impacts of hazardous substances on natural resources. This paper explores the scientific aspects of NRDA implementation, and discusses conceptual and methodological relationships between NRDA and the much broader field of ecological risk assessment (ERA). We discuss three critical components of the NRDA assessment approach: measuring natural resource injuries and reductions in resource services; evaluating causality; and establishing baseline conditions. We identify (1) specific approaches drawn from ERA practice that could improve each of these components, and (2) research needs and institutional changes that may improve the ability of the NRDA process to achieve its stated objectives. We recommend the acceleration of the ongoing dialogue among NRDA practitioners from the Trustee and PRP communities as a first step toward resolving the procedural and technical deficiencies of the NRDA process.     

青岛市可持发展环境优势与战略对策

作为北京奥运的唯一伙伴城市,面对历史性的机遇和挑战,青岛市在加快建设和发展步伐的同时,坚持人与自然和谐、山海城协调、历史与现代交融、经济社会全面进步的可持续发展原则,不断推进青岛的生态城市建设,可以预见,青岛市完全符合举办一流奥运会的要求将成为现实。     

中国长城沿线生态脆弱性分析及生态保护对策

中国长城沿线是半湿润—半干旱和半干旱—干旱气候的过渡地带,也是农牧业的交错地带,生态极其脆弱,生态压力又大,容易发生生态破坏,而且很难恢复。为了保护中国长城沿线的生态环境,必须调整产业结构,合理布局,采用先进技术,加大投入,提高生态意识,加强法制建设。     

营造可持续发展的生态安全建筑

围绕建筑与全球生态环境问题的关系 ,阐述了建筑对生态环境产生的巨大负面影响 ,已经威胁到全球的生态安全 ;指明生态建筑是建筑走可持续发展之路 ,是实现全球生态安全的必然选择 ,并对生态建筑的实施策略进行了探讨。     

锅炉水处理现存问题及对策

锅炉水处理是保证锅炉安全经济运行的重要措施，是锅炉房科学管理的一个十分重要的环节。文章简要分析了目前锅炉水处理方面存在的问题，并提出了解决对策。     

生态安全评价系统及工作程序

全球范围内生态安全形势越来越严峻 ,某些区域生态安全态势已经威胁到人类的生存与可持续发展。生态安全评价研究越来越受到研究人员的关注。笔者从系统工程角度出发 ,提出了生态安全评价系统的新概念 ,介绍了组成生态安全评价系统的 5个要素 ,即评价主体、评价对象、评价目的、评价标准和评价方法 ,并探讨了生态安全评价工作程序 ,将为区域生态安全评价的研究与应用提供理论基础。     

生态城市的数学模型建立

本文首先论述了生态城市的概念和内涵；其次对于目前的生态城市的系统模型和指标体系进行了综述；然后建构了新的生态城市数学模型，重点讨论了建构该模型的理论基础及其指标体系的相关运算；最后指出该生态系统数学模型的理论和实践意义并对今后相关研究进行展望。     

四川盆地农牧区生态失调的综合整治初探

四川盆地农林牧区是处于我省腹心地带，人口稠密，经济发展较快。本文针对该区出现的自然灾害现状，提出该区发展方向，和具体措施，供有关部门领导参考。