Using Fuzzy Theory and Variable Weights for Water Quality Evaluation in Poyang Lake, China

Achieving water purity in Poyang Lake has become a major concern in recent years, thus appropriate evaluation of spatial and temporal water quality variations has become essential. Variations in 11 water quality parameters from 15 sampling sites in Poyang Lake were investigated from 2009 to 2012. An integrative fuzzy variable evaluation(IFVE) model based on fuzzy theory and variable weights was developed to measure variations in water quality. Results showed that: 1) only chlorophyll-a concentration and Secchi depth differed significantly among the 15 sampling sites(P < 0.01), whereas the 11 water quality parameters under investigation differed significantly throughout the seasons(P < 0.01). The annual variations of all water quality variables except for temperature, electrical conductivity, suspended solids and total phosphorus were considerable(P < 0.05). 2) The IFVE model was reasonable and flexible in evaluating water quality status and any possible ′bucket effect′. The model fully considered the influences of extremely poor indices on overall water quality. 3) A spatial analysis indicated that anthropogenic activities(particularly industrial sewage and dredging) and lake bed topography might directly affect water quality in Poyang Lake. Meanwhile, hydrological status and sewage discharged into the lake might be responsible for seasonal water quality variations.

Application of fuzzy optimization model in the evaluationof urban flood-waterloggedvulnerabilitybased on the synthetic weight ofgame theory

The evaluation of urban flood-waterlogged vulnerability is very important to the safety of urban flood control. In this paper, the evaluation of consolidated index is used. Respectively, AHP and entropy method calculate the subjective and objective weight of the evaluation indicators, and combine them by game theory. So we can obtain synthetic weight based on objective and subjective weights. The evaluation of urban flood-waterlogged vulnerability as target layer, a single variable multi-objective fuzzy optimization model is established. We use the model to evaluate flood-waterlogged vulnerability of 13 prefecture-level city in Hunan, and compare it with other evaluation method. The results show that the evaluation method has certain adaptability and reliability, and it＇ s helpfid to the construction planning of urban flood control.

SCC-UEFAS, an urban-ecological-feature based assessment system for sponge city construction

An effective sponge city construction evaluation system plays a crucial role in evaluating sponge city construction schemes.The construction of a sponge city evaluation system still faces challenges related to incomplete index selection and unscientific weight division.Limited studies have focused on the comprehensive assessment of sponge city construction in the early stages.This study constructed a scientific assessment indicator system and a quantitative indicator weight at all levels by literature review and statistical analysis methods from an objective perspective.To demonstrate how to utilize our evaluation methods,three construction schemes randomly generated by MATLAB were evaluated under evaluation states of constant weight and variable weight,respectively.Scheme 3 had the highest score of 0.638 under the constant weight assessment,but it cannot practically be the final construction scheme due to the imbalance between indicators.Compared to the constant weight assessment,a variable weight assessment can effectively balance the states of the evaluation index with changes in the decision variable.Among the three schemes,Scheme 2 is the best choice with a value of 0.0355 under variable weight evaluation due to punishment and incentives in the variable weight method.The concept of“punishing”a disadvantageous indicator and“motivating”an advantageous indicator increases the relative advantages of the indices,ultimately affecting the assessment results of schemes and leading to a more balanced state.This study provides reasonable analysis and decision-making mechanisms to support decision-making and guide the scientific selection of a construction scheme.