GIS is a powerful tool for solutions of many environmental challenges and especially in water field such as assessing water quality and managing water resources on a local or regional scale [1,2]. The geo-referenced characteristics and spatial relationships of water system can be represented by GIS. However, the predictive and related analytical capacities are the most powerful functions of GIS which are useful and necessary for water resource problems solving. In this paper we applied the interpolation function in GIS technology and Surfer software to zone the surface water quality in Bac Lieu province according to indicators: pH, DO, BOD5, COD, TSS, NH4 and coli form. A series of data related to these indicators in five years 2007- 2010 and 2013 was collected to be the input data for the interpolation. Then, the interpolation maps of indicators through years were built to compare and assess surface water quality in Bac Lieu province. In addition, the sensible solutions to manage surface water quality are suggested in this paper.
Keywords: surface water quality, GIS, interpolation, environmental management.
The Bac Lieu Province, Vietnam is the part of the Ca Mau Peninsula and Me Kong Delta as well. It shares the border with Can Tho City and Soc Trang Province in the northern, the East Sea in the southeast, Ca Mau and Kien Giang provinces in the western (Figure 1).It has a population of 830,000 with approximately eighty-five per cent of population is engaged in agriculture and fisheries activities [3,4]. According to provincial Department of Natural Resources and Environment [5,6], the water surface of Bac Lieu Province including the rivers, lakes and stream has been significantly polluted by untreated waste water discharged from agriculture, shrimp hatching activities, hospitals and factories. In 2013, samples of surface water from 30 different places were collected to test the indicators pH, DO, BOD5, COD, TSS, NH4 and coli form in water in province. The results of the test revealed that the toxicity levels of water between 1 and 3.7 times of the legal limit . Two main reasons which cause this situation are that most aquaculture processing factories and hospitals were not equipped with proper waste water treatment systems and the use of chemicals and fertilizers still proliferated among agricultural and shrimp hatching activities.
The aim of this paper is zoning the surface water quality in Bac Lieu province according to Water Quality Index (WQI) to support the development of a sustainable water management plan which will be easily adopted from the local authorities. For this reason, some the available hydrological data collected have been integrated and analyzed into GIS technology. Then, through the interpolation function in GIS and Surfer software, several thematic maps have been created using the collected hydrological data. Via these maps, the managers could recognize the change in quality of water in each area of province. From that the suitable solutions would be applied for each case.
The method using interpolation has been applying by many scientists on the world. In his study, Yammani used IDW method to locate groundwater quality zones suitable for different usages like irrigation and drinking water . Similarly, Rangzan et al also used IDW to create the layers of maps to locate promising well sites based on the water quality . Babiker et al based on IDW to zone the groundwater quality index which is synthesized from different water quality data (Cl, Na, Ca) . Raikar & Sneha presented their case study on the water quality analysis which was carried out at the Bhadravathi Taluk, Karnataka, India. The spatial distribution of twelve physico-chemical parameters and thematic maps were created by using IDW function in GIS. As the result, most of the sampling locations are under Good category that present for the suitability of water for human use. The reason was given to explain for this situation is that the industrialization and agricultural disposal some of the sampling locations became unfit . Noha Donia identified the areas on Temsah lake is suitable for each use (swimming, fishing, and other uses) on spatial maps within GIS . Kumar et al attempted to map the spatial variation of surface water quality parameters namely pH, Electrical Conductivity (EC), Total Dissolved Solids, Total hardness, Ammonia, Nitrate and BOD for Thamirabarani River Basin of Tirunelveli District, Tamil Nadu using GIS. The final thematic map shows three priority classes of water quality including Good, Moderate and Poor zones of the study area and provides a guideline for the suitability of water for domestic purposes .
Ton Nu Phuong Anh, Pham Van Tat (*) & Le Trong Dieu Hien (**)
(Source: Tap chi Khoa Hoc & Cong Nghe, 25/09/2014)
(*)Department of Environment, University of Hoa Sen, Ho Chi Minh City
(**) Department of Environment, University of Thu Dau Mot, Binh Duong province