Use of a structure aware discretisation algorithm for Bayesian networks applied to water quality predictions

Bayesian networks have become a popular modelling technique in many fields, however there are several design decisions that, if poorly made, can result in models with insufficient evidence to make good predictions. One such decision is how to discretise the continuous nodes. The lack of a commonly accepted algorithm for achieving this makes it a difficult task for novice data modellers. We present a structure aware discretisation algorithm that minimises the number of missing values in the conditional probability tables by taking into account the network structure. It also prevents users from having to specify the exact number of bins. Results from two water quality case studies in south-east Queensland showed that the algorithm has potential to improve the discretisation process over equal case discretisation and demonstrates the suitability of Bayesian networks for this field

九龙江流域地表水锰的污染来源和迁移转化机制

锰是人体必需微量元素,但近年来河流湖库等地表水锰超标现象时有发生,威胁供水安全.本文于2016—2017年在福建省九龙江流域开展水系沿程梯度调查及机理实验,结合历史监测资料综合研究,探明九龙江锰含量的时空分布与迁移转化规律,揭示九龙江锰的污染来源、超标成因与调控机制.结果表明,溶解锰高值及超标站位集中在北溪上游矿区支流和干流部分水库,且主要发生在枯水期;上游矿区支流颗粒锰含量最高,随后从上游到下游沿程递减,且与总悬浮颗粒物(TSM)和pH显著正相关(p7.8)环境促进亚热带红壤颗粒富集锰,大量富锰颗粒进入pH逐渐下降的河流下游和电站库区后向溶解锰转化,从而导致锰超标.河流下游及库区pH值下降的主要原因包括酸沉降、酸性废水排放、富营养化条件下有机物分解等.研究结果为我国地表水锰污染防控、饮用水安全保障与流域水环境综合管理提供科学依据.国家重点研发计划(No.2016YFC0502901);;福建省环保科技计划项目(No.2016R017)~

Structurally aware discretisation for Bayesian networks

Bayesian networks represent a versatile probabilistic modelling technique widely used to tackle a range of problems in many different domains. However, they are discrete models, and a significant decision when designing a BN is how to split the continuous variables into discrete bins. Default options offered in most BN packages include assigning an equal number of cases to each bin or assigning equal sized bins. However, these methods discretise nodes independently of each other. When learning probabilities from data, this can result in conditional probability tables (CPTs) with missing or uninformed probabilities because data for particular bin combinations (scenarios) is either missing or scarce. This can result in poor model performance

The water resource in tropical Africa and its exploitation

Deals with water resource & its exploitation in tropical Africa from an engineering point of view, giving an insight into the wide range of problems in water development & providing general guidelines for future planning. Considers such issues as the mechanics of the hydrological cycle, the origins of wide variations in rainfall, the potential for water resources development in pastoral areas & low cost methods of exploiting these resources, & problems of water quality. Includes some recommendations on key areas which play an important role in the successful implementation & continued operation of schemes for water supply

Application of Data-Driven and Process-Based Modeling Approaches for Water Quality Simulation in Lakes and Freshwater Reservoirs

Lakes and freshwater reservoirs often serve as the primary drinking and irrigation water sources for surrounding communities. They provide recreational and tourism opportunities, thereby promoting the prosperity of neighboring communities. Reliable estimates of water quality in lakes and reservoirs can improve management practices to protect water resources. Seasonal water temperature and solar shortwave radiation variations, and their subsequent interactions with water column aquatic life, combined with seasonal variations of mixing intensity throughout the water column, result in variations of water quality constituents with depth during the annual cycle. The complexity of these variations entails the use of advanced water quality modeling approaches to evaluate the trends of water quality variations over time. The current study presents two different modeling approaches for water quality modeling in lakes and reservoirs. In the first approach, a three-dimensional process-based model (AEM3D, HydroNumerics Pty Ltd.) was used for hydrodynamic modeling of Lake Arrowhead, California. The model was calibrated based on in-situ measured meteorological and water quality data. The calibrated process-based model was able to simulate water temperature and salinity profiles in the lake at different depths from May 2018 to April 2019, with mean relative errors of less than 6.1% and 4.2%, respectively. The model was also used to evaluate the mixing intensities at different depths during the study period. The second approach employed two separate data-driven models incorporating wavelet transform and artificial neural networks for water quality modeling of Boulder Basin, Lake Mead. The first data-driven model proposed a cost-effective method for estimating water quality profiles based on environmental data measured at the water surface. The model could estimate water temperature, dissolved oxygen, and electrical conductivity profiles from May 2011 to January 2015 with mean relative errors of 0.52%, 0.62%, and 0.22%, respectively. The second data-driven model was designed to forecast future water quality variations at different depths in Boulder Basin, Lake Mead. This model used a time step of 6 hours based on the availability of water quality data, and forecasted up to 960 step-ahead (240 days) water quality profiles in the basin. The data-driven model was able to successfully forecast 180-day ahead water temperature, dissolved oxygen, and electrical conductivity profiles in the basin with relative errors of less than 7.5%, 15.5%, and 4.7%, respectively. Results of this study can benefit water management practices to evaluate different water quality modeling approaches and select appropriate methods based on their needs and budget to simulate water quality variations of their lakes and reservoirs

Abstracts of manuscripts submitted in 1993 for publication

This volume contains the abstracts of manuscripts submitted for publication during calendar year 1993 by the staff and students of the Woods Hole Oceanographic Institution. We identify the journal of those manuscripts which are in press or have been published. The volume is intended to be informative, but not a bibliography. The abstracts are listed by title in the Table of Contents and ar grouped into one of our five departents, Marine Policy Center, Coastal Research Center, or the student category. An author index is presented in the back to facilitate locating specific papers

Modeling sediment dynamics in the Zhujiang (Pearl River) Basin, China

Master'sMASTER OF SOCIAL SCIENCE

World Water Development Report 3: Water in a Changing World

With the release of this third edition of The United Nations World Water Development Report, it is clear that urgent action is needed if we are to avoid a global water crisis. Despite the vital importance of water to all aspects of human life, the sector has been plagued by a chronic lack of political support, poor governance and underinvestment. As a result, hundreds of millions of people around the world remain trapped in poverty and ill health and exposed to the risks of water-related disasters, environmental degradation and even political instability and conflict. Population growth, increasing consumption and climate change are among the factors that threaten to exacerbate these problems, with grave implications for human security and development.The current Report provides a comprehensive analysis of the state of the world's freshwater resources. It also, for the first time, shows how changes in water demand and supply are affected by and affect other global dynamics. It represents a considerable collaborative achievement for the 26 UN agencies that make up UN-Water and are engaged in the World Water Assessment Programme (WWAP), which leads the monitoring and evaluation behind the Report. UNESCO is very proud to have played a pivotal role in the launch of this flagship programme and to continue to support its work by housing the WWAP Secretariat. I am confident that this third volume will prove crucial as a working tool for policy-makers and other stakeholders, providing solid evidence from which to develop an effective and sustainable approach to water issues

The Future Ocean: Final report = Ozean der Zukunft: Abschlussbericht

2006 - 201