Abstract:The
integrated use of isotopic and hydrochemical tracers is an effective
approach for investigating complex hydrological processes of
groundwater.
Thorough
understanding of recharge and quality of the groundwater is usually a
prerequisite for effective groundwater management. This study
investigated
the water level, stable isotope and hydrochemistry of groundwater around
the Qinghai Lake to reveal the recharge sources, hydrochemical evolution
and water quality of groundwater. The relative altitudes of groundwater
level ranged from -1.27 to 122.91 m (mean 25.70 m) with hydraulic
gradient ranging from -6.20 to 43.14‰ (mean 5.80‰) relative to the water
level of Qinghai Lake, indicating most of the groundwater was flowing
into the lake. Most of the groundwater points lay close to the local
meteoric water line (LMWL: δ2H = 7.80
δ18O+10.98), and the slope of Local Evaporation Line
of groundwater (LEL: δ2H = 6.08
δ18O-3.01) was lower than the slopes of the LMWL,
indicating that the groundwater were recharged primarily from
precipitation at different altitude in the basin, though it had
undergone varying degrees of evaporation. The hydrochemical analysis
showed that the groundwater was mainly freshwater and its hydrochemical
type was Ca-Mg-HCO3. The groundwater chemistry was
mainly controlled by carbonate dissolution around Qinghai Lake.
Furthermore, high TDS and high concentrations of Na+,
Mg2+, Cl-, or
SO42- in several groundwater were
caused by the recharge source of lake water (G29), the recharge source
of fissure water (G1 and G6), or by the dissolution of evaporite (G4 and
G25). The groundwater in location G4, G6, G11, G16, G24 and G25 were all
currently exceed the drinking standards and not suitable for drinking.
The main sources of nitrate (NO3-) in
groundwater around Qinghai Lake were animal feces and sewage, suggesting
that the pollution of groundwater should be paid more attention in
animal husbandry areas on the Qinghai-Tibet Plateau, although the
industrial and urbanization rates were relative low on the plateau. The
scientific planning and engineering management of livestock manure and
wastewater discharge in animal husbandry regions are very necessary to
be carried out urgently, which could not only protect water resources
for drinking, but also contribute to human health and sustainable
development of the ecological environment of the Qinghai-Tibet Plateau.
Key
words:Stable
isotope; Hydrochemistry; Groundwater; Qinghai Lake; Qinghai-Tibet
Plateau.