CHANGES IN WATER QUALITY AT BUNG RIVER BASIN, QUANG NAM AFTER THE DAM CONSTRUCTION. Vietnam

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1 CHANGES IN WATER QUALITY AT BUNG RIVER BASIN, QUANG NAM AFTER THE DAM CONSTRUCTION Nguyen Viet Hung 1 and Long Bui Ta 1 1 University of Technology, Vietnam National University Hochiminh city, 268 Ly ThuongKiet, Dist. 10, Ho Chi Minh, Vietnam longbt62@hcmut.edu.vn KEY WORDS: Water Quality Index (WQI), GIS, Water Quality Zoning, WQUIZ, Hydropower ABSTRACT: Bung RiverRiver is located in the northwest of the Vu Gia river basin, which flows through the territory of Quang Nam province. This is one of the major tributaries with many important functions: economic and social development of the lowlands basin Vu Gia-Thu Bon river; significant contribution to salinity, water supply and irrigation activities of the people in the region, especially in the province of Quang Nam and Da Nang. Over the years, the pressure of economic development - local society has led to serious contamination of the river water. Therefore, monitoring, supervising and evaluating of water quality this area are urgently needed. Currently, indexing and zoning water quality are effective tools to assess the quality of river water in a general way and help deliver solutions for managing sustainable water quality. This study presents the results of applying the software WQUIZ (Water QUality Index Zoning) and GIS tools to assess the level of pollution of water sources, and also to build quality zoning map in Bung River, downstream segments River dam Bung 4 and 4A in the model of WQI. 1. INTRODUCTION Bung River is located in the northwest of the Vu Gia River Basin, which flows through the territory of Quang Nam province. This is the largest branch of the Vu Gia river system with a length of about 130 km. The basin, an area of 2,530 km 2, comes from the mountains in the Vietnam Laos. It flows mainly from the Northwest - Southeast to Ta Vinh (hydropower reservoirs Bung River 4), then turns to the south - north to the confluence of the A Vuong, and turns west - east into the Cai River (the downstream section is called Vu Gia river). Bung River has narrow and steep parts, steep cliffs on both sides, and tough rapids on almost the entire riverbed rock route. The average slope of the river ranges from The network stream that flows into Bung River flows are dense on both the left and right bank. Most of the short springsare around 1-2 km, each of which has very steep slope. They pour into Bung River in perpendicular form, with the mesh density of 0.83 km river / km 2. This area is located in a tropical climate area. The annual average air temperature varies between 20 C - 28 C. December, January, and February are the coldest months, with annual average temperatures of around 20 C - 22 C. The hottest months are May, June, and July, with average temperatures up to 26 C - 29 C. The rainy season starts from May to December, with the total rainfall in the area range from mm.the main rainy season starts from September - November, which takes over 50% of rainfall throughout the year, and highest peaks appear in October and November. Typically, the flow model in the region have two peaks: a peak in May June, and the other in October November; however, the former one is not as clear as the latter one. The average flow during flood season 3 months (October, November, and December) takes more than 60% of total annual flow. Low streams usually occur in April or July. Bung RiverRiver has a significant role in contributing to salinity, water supply, and irrigation service of the people living in Vu Gia-Thu Bon downstream areas, especially the province of Quang Nam and the Da Nang city. (ADB, 2008), In recent years, our country, Quang Nam province in particular, is developing towards a marketing economy. Especially,upstream rivers,such as Bung River, have also been fully exploit for potential ineconomic and social development. According to the assessment, Bung River holds strategic importance in local economic development. The economic activities of social development has brought obvious benefits; however, they also put pressures on environmental quality and deplete Bung river water quality. Taking advantage of the hilly terrain, many large and small hydro plants have been planned and planted on the Bung River. The deployment of large-scale construction has also contributed to water quality Bung River. According to statistics, over 36 river basins have been identified as locations with useful minerals, notably are gold ores (3 locations), gold placers (22 locations), uranium (1 location)... Currently mining activities are taking place on Bung River upstream, especially the massively illegal exploitation of gold placers by means of motorized made cell condition contamination and degradation exacerbated quality. As one of the major tributaries in the development of economic and social activities of the region, also as the main water supply for downstream areas, Bung River will greatly affect these areas in case of depletion and quality deterioration. Therefore, strengthening and improving management efficiency, synchronizing protection for Bung River water areurgently needed.

2 Currently, the WQI has been used, and has shown some advantages, such as simplicity, clarity, universality) in assessing water quality index under time and space. Especially in context, since 2011, the country s environmental management agencies have issued the rather complete guidelines on WQI, making this approach increasingly effective. This is the data source for building zoning map by WQI, which will propose measures to protect and control the exploitation and sustainability of water resources. 2. OBJECTIVES AND METHODOLOGY 2.1 Objectives The objectives of this study are the WQI evaluation on the stretch of Bung River 4 and 4A based on the separated parameters of water quality indicators and WQI (The Ministry of Natural Resources and Environment, 2011) ; framework for zoning maps on this stretch of the river based on the parameters, combined with GIS technology and WQUIZ software; requests for protection and control of water quality as well as the exploitation and sustainability of Bung river water resources. (Bui Ta Long et. al., 2012) 2.2 Object and scope of research Target: water quality of Bung mainstream, specifically the downstream segments Bung River 4 hydropower and Bung River 4A, Quang Nam Province. Scope: Space: Bung mainstream, downstream segment Bung River 4 hydropower dam,and segment of Bung River 4A. The total length of the river in the study is 23.4 km. Time range: From 2012 to On the river, researches have been mad, and several hydroelectric plants have been built, including Bung River 4 Hydropower installed capacity of 156 MW. It started storing waterin August 2014, and has regulated reservoirs in the form of lakes. The other hydropower plants include: Bung River 4A, 5, and 6, with an installed capacity of 49 MW, 57 MW, and 29 MW, respectively. Hydropower reservoirs of these plants are regulatory lakes, which startstoring water from September to December Figure 1. Map of the study area

3 Figure 2. Map location for sampling Water quality changes by the water colour indicator between the sampling stages Station point NM4 during 7/2014 Station point NM4 during 9/2014

4 2.3 Methodology Station point during 7/2014 Station point during 9/2014 Figure 3. Field sampling process To assess the quality of surface water, people often rely on the analysis of water parameters separately, and then compare them with each parameter value limits specified in the standards or national standards or international standards. How "traditional" it is and it is difficult to conclude the water quality of a river (or river sector) satisfactory for this purpose, but does not meet the requirements for any other purpose.that leads to the difficulty of partitioning and classifying river water quality, difficult to make decisions about the possibility of exploiting the river (or river sector) for a purpose or some other use. Figure 4. Diagram of steps To overcome these difficulties, there should be a system of indices for quantifying the quality of water, ie water quality by performing an agreed scale, capable of describing the combined effects of multiple composition in water resources and the importance of water quality parameters for one certain purpose use. (Ton That Lang, 2007; Le Trinh et. al., 2008, Nguyen Van Hop et. al., 2010) Map data and monitoring data processing. This process consists of two steps: data preparation and processing necessary maps. The selected data are: SRTM Remote Sensing, GIS maps Saigon River, monitoring data of Saigon River. Map processing steps include: application software IDRISI image manipulation and enhancement of images, using IDRISI software, Surfer determine topography basin, using ENVI software, Rivertools determine flow and river basins, using ArcGIS 10 to select, edit river basin and put it in WQUIZ software The method of construction and calculating WQI index Ten parameters of surface water is used to calculate the water quality index (WQI), including DO, temperature, BOD 5, COD, N-NH 4, P-PO 4, TSS, độ đục, total Coliform, ph. WQI index was calculated for parameters BOD 5, COD, N-NH 4, P-PO 4, TSS, turbidity, total coliforms by the formula as follows: qi -qi+1 WQI = BPi+1 -C p + q SI BPi+1 -BPi i+1

5 Where: BP I : the lower limit of the concentration value monitoring parameters are specified in table 1 correspond to i; BP I +1: concentration limits on the values of the parameters monitored are specified in the table 3:10 corresponds to i +1; q i : WQI values in the table i have to correspond to the value of BPI; q i +1: WQI value at i +1 given in the table corresponds to the value of BP I + 1; Cp: value of observed parameters taken into account. After calculated WQI for each parameter mentioned above, the WQI was calculated by the following formula applies: WQI ph WQI WQIa WQI WQIc a 1 2 b 1 b Where: WQI a : WQI value calculated for 05 parameters: DO, BOD 5, COD, N-NH 4, P-PO 4 ; WQI b : WQI value calculated for 02 parameters: TSS, turbidity; WQI c : WQI value calculated for total coliform parameters; WQI ph : WQI value calculated for ph parameters (The Ministry of Natural Resources and Environment, 2011) WQUIZ software This tool was developed by the authors for mapping indicators of environmental quality. Based on the index is calculated from the observation point, the software will compile maps of environmental quality index, the more of monitoring sites, the more accuracy of the map will be higher. The main tasks: enter monitoring data by location and by time, digitized the river sections to be calculated, automatic mapping partitioning pollution, reporting and statistics (Bui Ta Long et. al, 2012). 1/3 3. RESULTS AND DISCUSSION Figure 5. Images from WQUIZ software WQUIZ software was used to create zoning map of water quality, which corresponded to each observation, based on the VEA- D- 879 method.

6 Figure 6. Zoning map of water quality index by VEA D- 879 Table 1. WQI results in research area WQI Result Điểm QT 9/ /2012 7/ / / /2015 NM NM NM NM NM NM NM NM NM WQI reviews, using General Environment Department s method (VEA-D-879), on the river section after Bung River 4 hydropower dams and Bung River 4A show that the water qualityvaries according to space and time. Over time, in 2012, the studied region water shown signs of heavy pollution, which was presented in red on almost all over the map. This result was fairly consistent when assessing WQI for each individual parameter. During the observation period in 2012, turbidity and suspended solids in the water were very high, with point values measured up to 889 NTU turbidity and TSS 30.9 times higher than the value specified in column A2 of Regulation QCVN 08: 2008 / BTNMT. However, WQI has improved greatly in 2014, particularly after Bung River started storing water on August 2014 and formed the reservoir; therefor,values for turbidity and suspended solids were reduced significantly. Besides, the concentration of dissolved oxygen in the water after the Bung River 4 started storing water (August 2014) has decreased slightly; Additionally, BOD 5, COD values have also slightly increased. However, the overall quality of water in 2014 onwards

7 has gradually stabillized and started to becomequite good, which was represented in green onall over the zoning map of water quality. Regarding space, water quality of the studied area tends to get better from upstream to downstream. However, in 2012 this trend was not really clear. Because Bung River 4A s reservoir regulated on a daily basis, the operating mode didn t have much impact on the water quality. The water qualitywas better atpoints from downstream (from the point NM7) but not significantly. By 2014, when Bung River 4 (forms reservoirs Regulators year) started storing water, changes of water quality regarding space were clearer, and water quality were getting better in the direction from upstream to downstream. The reason for these was because the suspended sediment had sunk, making the water quality ofbung River 4 hydropower significantly better. 3. CONCLUSIONS Currently, Bung river water quality is under heavy pressure of the economic development of the local, including mining and hydroelectric development. Results from monitoring Bung river water quality in 2012 shown that the water was seriously contaminated; however, the water quality has gradually become better and has remained stable since This study had built the zoning map of water quality for Bung river, including the downstream section of Song Bung 4 and 4A,by using WQUIZ tools, thus having an intuitive method to assess the water quality; therefor, it gave a better overview on the environment to the environmental management, and provided a convenient way to present information on water quality to the community. Hence, the study established the foundation for using, managing, and controling water pollution in time. 4. REFERENCES The Ministry of Natural Resources and Environment (2011), decision on issuing the manual calculation of Water Quality Index, Hanoi. Nguyen Van Hop et al (2010), Assessment of water quality of the Bo river in Hue province based on water quality index (WQI), Scientific journals of Hue University, No. 58, pages Ton That Lang (2007), Construction of water quality indicators to evaluate and manage the water quality of Dong Nai river system, Proceedings of 10th Scientific Seminar, Hydrometeorological Institute of Science and Environment. Bui Ta Long and collaborator, 2012, Building software to assess environment quality based on method of environmental indicators. Proceedings of GIS national conference in 2012, pages Le Trinh and collaborators (2008), Research water quality zoning based on indicator and assessment of water capability from river water and canals in HCM city area, research topic in Department of Science and Technology of HCM city. ADB, (2008), SEA of the Quang Nam Province Hydropower plan for the Vu Gia Thu Bon river basin.