Key Variables Influencing Surface Water Quality in the Flood Control Area in An Giang province, Vietnam

Abstract

The study was conducted to assess the water quality in the Bac Vam
Nao flood control area in 2020. Surface water quality in the Bac Vam
Nao area was collected at 7 locations with symbols from VN1-VN7.
Water samples were collected three times per year in March, June and
September. The water indicators include temperature, pH, total
suspended solids (TSS), dissolved oxygen (DO), biological oxygen
demand (BOD), chemical oxygen demand (COD), ammonium (NNH4
+
), nitrate (N-NO3
-
) and coliform were used to assess water
quality in the study area. Water quality is assessed using national
technical regulations on surface water quality (QCVN 08-
MT:2015/BTNMT, column A1), water quality index (WQI). The main
sources of variation and the main indicators affecting the water
quality were identified using principal component analysis (PCA). The
results show that the water in the flood control area is contaminated
with organic matter (low DO, high TSS, BOD and COD), nutrient
pollution (P-PO4
3-
, N-NH4
+
) and microbiological contamination
(Coliform). The WQI index (29-88) shows that surface water quality
in the flood control area is classified from bad to good, corresponding
to the use of navigation and domestic purposes, but needing
appropriate treatment. The indicators of temperature and pH have
little seasonal variation. DO, TSS, N-NO3
-
in the dry season were
higher than that in the rainy season while BOD, COD, N-NH4
+
, PPO4
3-
, coliform in the rainy season were higher than that in the dry
season. Water quality in the Bac Vam Nao flood control area is
influenced by four main sources, PC1-PC4, which explain 84.8% of
the variation in water quality. The parameters of temperature, pH, NNH4
+
, N-NO3
-
, P-PO4
3-
, DO, and coliform have the main impact on
water quality and need to be continuously monitored. The findings
show that the water quality in the flood control area has been polluted,
it is necessary to have appropriate solutions to improve the water
quality.