5. Conclusions
This study investigated the stable isotope of precipitation and water
level, stable isotope and hydrochemistry of groundwater around Qinghai
Lake. The LMWL was δ2H = 7.80
δ18O+10.98, indicating that some non-equilibrium
evaporation processes occurred as raindrops fell below the cloud base,
and some continental moisture recycled to precipitation under low
relative humidity conditions. Most of the groundwater points lay close
to the LMWL, and the slope of LEL of groundwater was lower than the
slope of LMWL, indicating that the groundwater around Qinghai Lake
mainly came from the precipitation at different altitude in the basin,
which had been undergone variable degrees of evaporation before
infiltration. Most of the groundwater was slightly and moderately hard
freshwater, and the hydrochemical type of groundwater was
Ca-Mg-HCO3. The chemistry of groundwater would be mainly
controlled by carbonate dissolution around Qinghai Lake. Meanwhile, the
groundwater sources at east and west of Qinghai Lake were relative
complex.
Most of the groundwater was slightly and moderately hard freshwater and
fell within the standards for drinking water in all indices. However,
the groundwater in location G4 (TDS, Cl-, and
NO3-), G6 (TDS and
Na+), G11 (NO3-),
G16 (NO3-), G24
(NO3-) and G25 (TDS,
Na+ and NO3-) were
all currently exceed the drinking standards and not suitable for
drinking. Overall, the impacts of livestock manure and waste water on
groundwater quality could not be ignored around the lake. 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
environment of the Qinghai-Tibet Plateau.