Seasonal water temperature variations in response to air temperature and precipitation in a forested headwater stream and an urban river: a case study from the Bukhan River basin, South Korea

Figures & data

Figure 1. Locations of the (a) Yeonyeop stream (YS) and (b) Bukhan River (BR). The river map was taken from the National Institute of Environmental Research database.

Figure 2. (a) One-day and cumulative precipitation, (b) relative humidity, (c) air temperature, and (d) water temperature in the Yeonyeop stream (YS) and Bukhan River (BR) from April to November 2017 and 2018. The dotted and shaded areas indicate values excluded due to data missing from the study sites.

Table 1. Summary of water temperature and other climate observations.

Site	n (days)	Precipitation (mm/day)	Relative humidity (%/day)	Air temperature (°C/day)	Water temperature (°C/day)
YS	391	7.3 ± 21.1 (0.0–155.5)	73.5 ± 16.0 (26.0–99.0)	17.1 ± 5.3 (1.4–29.5)	14.9 ± 3.7 (7.5–24.1)
BR	376	5.7 ± 17.4 (0.0–120.6)	72.9 ± 16.2 (27.0–99.0)	17.1 ± 5.4 (1.5–29.5)	19.7 ± 4.0 (12.2–29.3)

YS: Yeonyeop stream, BR: Bukhan River; ±: standard deviation, Bracket: minimum–maximum values.

Figure 3. Seasonal changes in (a) precipitation (P_T), (b) air temperature (T_A), and (c) water temperature (T_w) at the Yeonyeop stream (YS) and Bukhan River (BR) from April to November 2017 and 2018.

Figure 4. Elasticity distribution (ε_T: temperature elasticity, ε_P: precipitation elasticity) at the (a) Yeonyeop stream (YS) and (b) Bukhan River (BR) from April to November 2017 and 2018. The horizontal dashed lines indicate mean values of ε_T and ε_P. The dotted area indicates values that are not available (N/A) due to data missing from December to March of the study period.

Figure 5. (a) Temperature (ε_T) and (b) precipitation (ε_P) elasticities at the Yeonyeop stream (YS) and Bukhan River (BR) from April to November 2017 and 2018. A two-sample Student’s t-test is indicated in separate bold letters (a and b) above the box.

Figure 6. Seasonal changes in (a) temperature (ε_T) and (b) precipitation (ε_P) elasticities at the Yeonyeop stream (YS) and Bukhan River (BR) from April to November 2017 and 2018. Values above each box indicate mean ± standard deviation. A two-sample Student’s t-test is indicated in separate bold letters (a and b) above the box.

Table 2. Correlation analysis of the seasonal differences between T_w (water temperature) and both temperature (ε_T) and precipitation (ε_P) elasticities at the Yeonyeop stream (YS) and Bukhan River (BR) from April to November 2017 and 2018.

Season	YS				BR
	εT		εP		εT		εP
Spring	–0.83	p = 0.174	–0.92	p = 0.084	–0.85	p = 0.151	–0.99	p = 0.009
Summer	0.92	p = 0.011	–0.93	p = 0.007	0.96	p = 0.002	–0.98	p = 0.001
Fall	–0.07	p = 0.898	–0.997	p < 0.01	–0.99	p < 0.01	–0.85	p = 0.032

YS: Yeonyeop stream, BR: Bukhan River; ε_T: temperature elasticity, ε_P: precipitation elasticity; Significant correlations are shown as bold type.

Figure 7. Relationship between water temperature (T_w) and both (a) temperature (ε_T) and (b) precipitation (ε_P) elasticities at the Yeonyeop stream (YS) and Bukhan River (BR) during the summer season from April to November 2017 and 2018.