| Groundwater distrubted almost everywhere beneath on the surface of Earth, it is the major source for different uses such as domestic, agricultural and industrial purposes. Nowadays, there are so many factors influencing to groundwater such as variation rainfall, insufficient water surface, human factors impact to the quality of groundwater. The present investigation is aimed at evaluation of spatial and temporal groundwater level, assessing some chemical indicators about groundwater quality and groundwater quality index (GWQI) for applying interpolation map by IDW methods in Xuan Mai town. This study has been carried out by measuring groundwater depth in four drillwells by Rugget Water Level Tape 200 and taking 12 samples of 9 hamlets, then compared with the Vietnam standard 09:2015/Ministry of Natural Resources and Environment (QCVN 09: 2015/BTNMT). For computing GWQI, nine parameters viz., pH, Fe, NO2-,NH4+, NO3-, CaCO3, TDS, Mn2+, Cl-, have been considered. The study was conducted from 10th October, 2018 to 10th October, 2019 with dry season from 03/2017 and 02/2019 to 05/2019, rainy reason from 06/2019 to 08/2019.<br>
The main results of this study is: (1) Groundwater depth experienced a decline trend in dry season with the exception of drillwells 11. (2) Groundwater quality had the fluctuations in both dry and rainy seasons. While the TDS, NH4+, NO3- and Mn2+ indicators witnessed a marked increase in rainy season, the concentrations of Cl-, Fe, NO2- decreased slightly. CaCO3 and pH concentration remain unchanged in safe levels. With NO3-, 8/12 drillwells were polluted in the dry season, especially drillwell 1, exceed 6.5 times. During the rainy season from June to August, NH4+ concentration plummeted, only 4 drillwells exceeded the standard. There are 5 drill-wells polltued of Mn2+, however, in dry seasons, the concentration decreased significantly. (3) Assessment of water quality in Xuan Mai according to the GWQI index for each point, all 12 drill-well was “good” and “excellent” and suitable for eating and living. |
