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Water Quality Management Based on Division of Dry and Wet Seasons in Pearl River Delta, China

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Water Quality Management Based on Division of Dry and Wet Seasons in Pearl River Delta, China Clean – Soil, Air, Water 2012, 40 (4), 381–393 381 Xiaoyun Fan1 Research Article Baoshan Cui1 Kejiang Zhang2 Zhiming Zhang1 Water Quality Management Based on Division of Hongbo Shao3 Dry and Wet Seasons in Pearl River Delta, China 1School of Environment, Beijing Normal University, State Key Joint In the Pearl River Delta (PRD), river water quality deteriorates continually due to the Laboratory of Environmental population increase and ongoing industrialization and urbanization. In this study, a Simulation and Pollution Control, water quality management paradigm based on the seasonal variation is proposed. For Beijing, P. R. China better exploring the seasonal change of water quality, wavelet analysis was used to 2Department of Civil Engineering, University of Calgary, Alberta, analyze the division of dry and wet seasons in the PRD during 1952–2009. Then water Canada quality seasonal variation in 2008 and relevant impact factors were analyzed by multi- 3The CAS / Shandong Provincial Key variate statistic methods as a case to make some management measures. The results Laboratory of Coastal Environmental show that there are some differences of dry and wet seasons division among different Process, Yantai Institute of Costal years. Wet season mainly appear from April to September, which occupy the largest Zone Research, Chinese Academy of Sciences(CAS), Yantai 264003, China proportion among the 58 years (about 70%) and then followed by the wet season from May to October (about 13.8% of the total years). As to the water quality of 2008, significant differences exist between dry and wet seasons for 17 water quality À 2þ 2þ parameters except TP, NO3 ,Fe , and Zn . Levels of parameters pH, EC, CODMn, þ 2À À BOD5,NH4 ,SO4 , and Cl in dry season are much higher than those in wet season. In dry season the variations of river water quality are mainly influenced by domestic sewage, industrial effluents, and salt water intrusion. While in wet season, except the aforementioned pollution sources, drainages from cultivated land and livestock farm are also the main factors influencing water pollution. Thus, water quality management measures are proposed in dry and wet seasons, respectively. The results obtained from this study would further facilitate water quality protection and water resources management in the PRD. Keywords: Multivariate statistic methods; Pollution; Water resources; Wavelet analysis Received: March 4, 2011; revised: June 1, 2011; accepted: June 6, 2011 DOI: 10.1002/clen.201100123 1 Introduction The Pearl River and its various tributaries are the main water resources of the PRD [6]. River system provides water for the major The Pearl River Delta (PRD) is situated in the southeast China. rural, agricultural, urban, and industrial activities in this region. Although the area of this region occupies less than 0.5% of all the The daily water use for human and ecosystem also depends on country’s territory, it has produced about 20% of the national GDP, surrounding river water quality. In the Guangdong province the absorbed about 30% of foreign capital, and the exports have reached 8 8 total discharges of sewage were 67.7 Â 10 t in 2008 and 44.7 Â 10 t to about 40% since the implementation of open-door policy and in 2000. About 50% was increased in the last eight years [7]. The economic reform [1, 2]. Many new cities have appeared on the number of factories in the PRD was close to about 80% of the total previous farm lands with the rapid economic development and number of the whole province [7]. Although regulations of sewage urbanization. Meanwhile, the environmental quality especially river treatment get more restricted in Guangdong province in recent water quality in this region is deteriorating due to the increased years, most sewage is still directly or indirectly discharged into rivers discharges of untreated domestic sewage, industrial wastewater, by various ways due to significant economic activities, extensive and rural non-point pollution arising from the rapid economic development of economy, and lagging of facilities used for sewage growth [3–5]. treatment [8, 9]. A variety of water problems, such as eutrophication, algal blooms, oxygen depletion and contamination of water and loss of resources are also induced by increasing human pressures resulted from agricultural, industrial, and domestic use [10–12]. Correspondence: Professor B. Cui, School of Environment, Beijing The deterioration of river water quality poses great threat to the Normal University, State Key Joint Laboratory of Environmental safety of water supplies [13, 14]. In recent years, although water Simulation and Pollution Control, No. 19 Xinjiekouwai Street, Beijing 100875, P. R. China resource of this region is plentiful, many cities have appeared water E-mail: [email protected]; [email protected] shortages at different periods due to water pollution [15, 16]. The assessment and management of water quality is critical to control Abbreviations: CWT, continuous wavelet transform; PC, principle component; PCA, principle component analysis; PRD, Pearl River Delta; the water contamination and to improve the water quality effec- VF, varifactor tively in the PRD. ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com 382 X. Fan et al. Clean – Soil, Air, Water 2012, 40 (4), 381–393 For now, more concerns focus on the potential water quality rainfall and runoff as well as their relationship change over time. assessment in the rapidly urbanizing PRD [4, 5, 15, 17, 18]. The O¨zger et al. [38] also investigated the low frequency drought varia- changes of water quality are attributed to a number of natural or bility using the wavelet analysis. Beecham and Chowdhury [39] anthropogenic factors. Over recent years, accelerated anthropogenic identified the temporal variability in rainfall intensities and the nutrient discharges have exerted great pressure on the water quality proportion dry ratios by applying the wavelet power spectra. management in the PRD [19]. In Victoria Harbor and its vicinity of In this paper, the water quality management according to the this region, nutrient dynamics of water were driven by an inte- difference in dry and wet seasons was investigated. The main objec- gration of various factors, mainly including Pearl River Estuarine tives are: (1) To class the dry and wet seasons by using wavelet waters, local sewage effluent, coastal/shelf seawater, monsoon analysis of the daily rainfall records; (2) to identify measures of winds, and biological utilization [20]. Ho and Hui [21] presented that water quality management for dry and wet seasons by taking the in Dongjiang River contaminant sources were mainly associated water quality dataset of 2008 as an example. with human activities, such as domestic and industrial discharges, fertilizer and pesticide applications, and soil erosion due to 2 Material and methods deforestation. Chen et al. [22] combined composite pollution index with remote sense to evaluate water quality in the Pearl River 2.1 Study area Estuary. Chau and Jiang [3] simulated the transport of water quality The Pearl River is the largest river system in southeast China con- parameter COD in the Pearl River Estuary using a three-dimensional sisting of three major tributaries: West River, North River, and East numerical pollutant transport model combined with a synchronized River, which all gather into the Pearl River Delta (PRD) [4]. There are numerical hydrodynamic model. some big cities located here, such as Guangzhou, Foshan, Furthermore, river water quality is also influenced by stream flow Zhongshan, Zhuhai, Dongguan, and Shenzhen. The PRD (218400– [23], which is related to local rainfall level and seasonal variation [24]. 238N, 1128–1138200E) occupies 26% of the total land area of The reduction of stream flow might lead to an increase of contami- Guangdong Province [40], and belongs to the subtropical zone with nant concentration. Prathumratana et al. [23] presented that there a mean annual temperature ranging from 14 to 228C and a mean was positive correlations between hydrological parameters (such as annual precipitation from 1200 to 2200 mm [41]. It includes a variety precipitation, mean water level, stream flow) and some water quality þ of water channels, such as main rivers, streams, and ditches [15]. The parameters (such as CODMn, BOD5,NH ). In general, the concen- 4 water system in the PRD is one of the most intricate deltaic river trations of pollutants in surface waters are significantly higher network structures on the earth. The drainage density is about 0.68– during the dry season than that during the wet season, which is 1.07 km kmÀ2 [1, 42] in this region. The study area together with the due to the dilution by large amount of rainfall and stream flow from locations of water quality monitoring stations is illustrated in Fig. 1. upstream in the wet season [12, 24]. During the wet period, the rainfall intensity and runoff all influence the dilution effects of accumulated contaminants and their transportation to the receiv- 2.2 Method for the division of dry and wet seasons ing water [25, 26]. For example, the increased runoff and erosion or period induced by greater rainfall intensities could lead to an increase in phosphorus transport especially particulate phosphorus [27]. Sporre- Wavelet analysis is a mathematical tool for the process and synthesis Money et al. [28] and Shigaki et al. [29] also found that the concen- of signals and images with stationary and non-stationary datasets trations of the reactive and particulate phosphorus in runoff [34, 35]. It can be used to study the temporal variations in detail from increase with the rainfall intensity enhancement based on a rainfall both frequency and time domains by adjusting related signals. The simulation study. And there is also a link between phosphorus continuous wavelet transform (CWT) can be used to identify signifi- runoff from agricultural fields and freshwater eutrophication [29]. cant cycles and their occurrence time in a specified period [36].
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