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Fig. 1.
Sampling sites of the Quanmin Reservoir watershed (a). Major geological formation of the watershed (data) (b).Source:
http://www.ngac.cn
Fig. 2.
Cations and anions of groundwater in the watershed during the dry (a) and wet season (b).
Fig. 3.
Piper diagram for the hydrochemical composition of groundwater (a) and (b), and surface water (c) and (d) in the dry and wet season. The color of the points represents the NO3
– concentration.
Fig. 4.
Gibbs diagrams of the hydrochemical components in groundwater during both seasons (a) and (b). Endmember diagram of Ca
2
+/Na+—
HCO3
–/Na+ (c) andCa
2
+/Na+—
Mg
2
+/Na+ (d) in groundwater during both seasons.
Fig. 5.
Relationships between
δ
2
H-H
2
O and
δ
18
O-H
2
O of groundwater and surface water in the watershed during the dry (a) and wet (b) season. Relationship between
δ
18
O-H
2
O and d-excess (c),
δ
18
O-H
2
O and Cl
-
concentrations (d) in groundwater and surface water during the dry and wet season. The local meteoric water line is based on Chinese Network Isotopes in Precipitation (CHNIP).
Fig. 6.
Daily precipitation, potential evaporation (a), overland flow (b), interflow (c) and groundwater (baseflow) in 2023.
Fig. 7.
Plots of
δ
15
N-NO3
– versus
δ
18
O-NO3
– (a), NO3
–/Cl
-
versus
δ
15
N-NO3
– (b), (NO3
–+
Cl
-
)/HCO3
– versus TDS (c), and Cl
-
versus Na+ (d) of groundwater during the dry and wet season.
Fig. 8.
Spatial distributions of the contributions for NO3
− sources in groundwater during the dry (a) and wet (b) season.
Fig. 9.
Plots of
δ
18
O-NO3
– versus
δ
18
O-H
2
O (a), DO versus pH (b),
δ
15
N-NO3
– versus 1/NO3
– (c), and
δ
15
N-NO3
– versus ln(NO3
–) (d) of groundwater samples during the dry and wet season.
Fig. 10.
Conceptual models for the effects of surface water and groundwater interactions on the nitrogen in the watershed.
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