Water quality assessment at the watershed scale requires not only an investigation of water pollution and the recognition of main pollution factors, but also the identification of polluted risky regions resulted in polluted surrounding river sections. To realize this objective, we collected water samplings from 67 sampling sites in the Honghe River watershed of China with Grid GIS method to analyze six parameters including dissolved oxygen (DO), ammonia nitrogen (NH3-N), nitrate nitrogen (NO3-N), nitrite nitrogen (NO2-N), total nitrogen (TN) and total phosphorus (TP). Single factor pollution index and comprehensive pollution index were adopted to explore main water pollutants and evaluate water quality pollution level. Based on two evaluate methods, Geo-statistical analysis and Geographical Information System (GIS) were used to visualize the spatial pollution characteristics and identifying potential polluted risky regions. The results indicated that the general water quality in the watershed has been exposed to various pollutants, in which TP, NO2-N and TN were the main pollutants and seriously exceeded the standard of Category III. The zones of TP, TN, DO, NO2-N and NH3-N pollution covered 99.07%, 62.22%, 59.72%, 37.34% and 13.82% of the watershed respectively, and they were from medium to serious polluted. 83.27% of the watershed in total was polluted by comprehensive pollutants. These conclusions may provide useful and effective information for watershed water pollution control and management.

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Assessment of water quality and identification of polluted risky regions based on field observations & GIS in the Honghe River watershed, China.

Land use changes and socio-economic development strongly deteriorate river ecosystem health in one of the largest basins in China

The influence of physical and chemical parameters on the abundance and diversity of chironomids was studied in six rivers with moderate to highly polluted water in the Juru River Basin. The rivers: Ceruk Tok Kun (CTKR) as reference site, and polluted rivers of Pasir (PR), Juru (JR), Permatang Rawa (PRR), Ara (AR) and Kilang Ubi (KUR) were sampled over a period of five months (November 2007-March 2008). Nine chirnomid species: Chironimus kiiensis, C. javanus, Polypedilum trigonus, Microchironomus sp., Dicrotendipes sp., Tanytarsus formosanus, Clinotanypus sp., Tanypus punctipennis and Fittkauimyia sp. were identified. Assessment of their relationships with several environmental parameters was performed using the canonical correspondence analysis (CCA). Tanytarsus formosanus was the most dominant in the relatively clean CTKR and moderately polluted JR with mean densities of 19.66 and 25.32 m(-2), respectively while C. kiiensis was abundant in more polluted rivers. Tanytarsus formosanus, Dicrotendipes sp. and Microchironomus sp. were grouped under moderate to high water temperature, total organic matter (TOM), total suspended solids (TSS), velocity, pH, phosphates and sulphates. However, Tanypus punctipennis, Fittkauimyia sp., and Clinotanypus sp. were associated with high contents of river sediment such as TOM, Zn and Mn and water ammonium-N and nitrate-N and they were associated with higher dissolved oxygen (DO) content in the water. Chironomus kiiensis, C. javanus and P. trigonus showed positive relationships with TOM, ammonium-N and nitrate-N as well as trace metals of Zn, Cu and Mn. These three species could be considered as tolerant species since they have the ability to survive in extreme environmental conditions with low DO and high concentrations of pollutants. Based on the water parameter scores in all rivers, the highest diversity of chironomid larvae was reported in CTKR. With higher concentrations of organic and/or inorganic pollutants as reported in PPR, KUR and AR, the chironomid larval diversity decreased, and the abundance of tolerant species, mainly Chironomus spp., increased.

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Distribution of Chironomidae (Insecta: Diptera) in polluted rivers of the Juru River Basin, Penang, Malaysia

Most of the third world countries having rivers passing through them suffer from the water contaminant problem. This problem is considered so difficult to get the water quality within the standard allowable limits for drinking, as well as for industrial and agricultural purposes. This research aims to assess the water quality of the Tigris River using the water quality index method and GIS software. Twelve parameters (Ca, Mg, Na, K, Cl, SO4, HCO3, TH, TDS, BOD5, NO3, and EC) were taken from 14 stations along the river. The weighted arithmetic method was applied to compute the water quality index (WQI). The interpolation method (IDW) was applied in ArcGIS 10.5 to produce the prediction maps for 12 parameters at 11 stations along the Tigris River during the wet and dry seasons in 2016. The regression prediction was applied on three stations in the Tigris River between observed values and predicted values, from the prediction maps, in both seasons. The results showed that the regression prediction for all parameters was given the acceptable values of the determination coefficient (R2). Furthermore, the state of water quality for the Tigris River was degraded downstream of the Tigris River, especially at the station (8) in Aziziyah in the wet and dry seasons and increase degradation clearly at Qurnah (Basrah province) in the south of Iraq. This paper considers the whole length of the Tigris River for the study. This is important to give comprehensive knowledge about the contamination reality of the river. Such that it becomes easier to understand the problem of contamination, analyze it, and then find the suitable treatments and solutions.

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Water quality assessment along Tigris River (Iraq) using water quality index (WQI) and GIS software

Key blackening and stinking pollutants in Dongsha River of Beijing: Spatial distribution and source identification.

The health conditions of Liao River were assessed using 25 sampling sites in April 2005, with water quality index, biotic index and physical habitat quality index. Based on the method of cluster analysis (CA) for water quality indices, it revealed that heavily polluted sites of Liao River are located at estuary and mainstream. The aquatic species surveyed were attached algae and benthic invertebrates. The result showed that the diversity and biomass of attached algae and benthic index of biotic integrity (B-IBI) were degrading as the chemical and physical quality of water bodies deteriorating. Physiochemical parameters, BOD5, COD(Cr), TN, TP, NH3-N, DO, petroleum hydrocarbon and conductivity, were statistically analyzed with principal component analysis and correlation analysis. The statistical results were incorporated into the integrated assessing water quality index, combining fecal coliform count, attached algae diversity, B-IBI and physical habitat quality score. A comprehensive integrated assessing system of river ecological health was established. Based on the systimetic assessment, the assessed sites are categorized into 9 "healthy" and "sub-healthy" sites and 8 "sub-sick" and "sick" sites.

Wei Meng

Papers

Integrated assessment of river health based on water quality, aquatic life and physical habitat.