Shifts in stream hydrochemistry in responses to typhoon and non-typhoon precipitation

Abstract

Climate change is projected to increase the intensity and frequency of extreme climatic events such as tropical cyclones. However, few studies have examined the responses of hydrochemical processes to climate extremes. To fill this knowledge gap, we compared the relationship between stream discharge and ion input-output budget during typhoon and non-typhoon periods in four subtropical mountain watersheds with different levels of agricultural land cover in northern Taiwan. The results indicated that the high predictability of ion input-output budgets using stream discharge during the non-typhoon period largely disappeared during the typhoon periods. For ions such as Na + , NH + 4 , and PO 3− 4 , the typhoon period and non-typhoon period exhibited opposite discharge-budget relationships. In other cases, the discharge-budget relationship was driven by the typhoon period, which consisted of only 7 % of the total time period. The striking differences in the discharge-ion budget relationship between the two periods likely resulted from differences in the relative contributions of surface runoff, subsurface runoff and groundwater, which had different chemical compositions, to stream discharge between the two periods. Watersheds with a 17-22 % tea plantation cover showed large increases in NO − 3 export with increases in stream discharge. In contrast, watersheds with 93-99 % forest cover showed very mild or no increases in NO − 3 export with increases in discharge and very low levels of NO − 3 export even during typhoon storms. The results suggest that even mild disruption of the natural vegetation could largely alter hydrochemical processes. Our study clearly illustrates significant shifts in hydrochemical responses between regular and typhoon precipitation. We propose that hydrological models should separate hydrochemical processes into regular and extreme conditions to better capture the whole spectrum of hydrochemical responses to a variety of climate conditions.

Effects of Land Cover and Atmospheric Input on Nutrient Budget in Subtropical Mountainous Rivers, Northeastern Taiwan

“…The simulation performed well (KGE = 0.88) and the parameter set (Table S1) was applied to all watersheds, but employing their own climatic inputs and terrain information to simulate their daily streamflow. The annual runoff ratio (estimated streamflow/precipitation) of all the watersheds ranged from 0.70 to 0.80, which was consistent with our previous estimation [5]. The paired weekly ion concentrations and water quantity of precipitation and streamflow were used to calculate the precipitation input, stream water output, and nutrient input-output budgets (stream water output−precipitation input).…”

“…The higher coefficient c of exponent between discharge and Agr Frac presents the magnitude of hydrologic control (Table 3). For NO 3 − export, it is the only ion which necessitates taking the enhancement effect into account (Table 3) [5,45,69]. The higher agricultural land cover could enhance the hydrologic control significantly under the same exponent coefficient, according to Model 4 ( Table 3).…”

“…The current urban expansion and population growth impose stress on ecosystems and raise the cost of watershed management and water treatment [2]. Because water-related ecosystem services (e.g., water quality) are regulated by atmospheric deposition associated with anthropogenic emissions, land use changes, and climate variability [1,[3][4][5], understanding the effects of interactions between climate variabilities and land use on nutrient budgets is essential for better watershed management [6,7].…”

Global Isotope Hydrogeology―Review

“…Geochemical tracer data have been analyzed to evaluate groundwater discharges in many rivers (Cook et al, ; Cook et al, ; Cowie et al, ; Gardner et al, ; Gleeson et al, ; Liu et al, ; McCallum et al, ; McDonnell et al, ; A. Smith, Delavau, et al, ; Soulsby et al, ). Understanding water movements between aquifers, hyporheic zones, and stream channels is important in order to improve conceptual and quantitative models of biogeochemical cycling (Brunke & Gonser, ; Dahm et al, ; Barnes et al, ; Cardenas, ; Dawson et al, ; Gomez et al, ; Gomez‐Velez et al, ; Vonk et al, ; Bieroza & Heathwaite, ; Stegen et al, ; Shuai et al, ; Briody et al, ), watershed carbon balances (Barnes et al, ; Boyer et al, , ; Hornberger et al, ; Hotchkiss et al, ; Johnson et al, ; Raymond et al, ; Raymond & Saiers, ; Zimmer & McGlynn, ), chemical weathering (J. Li, et al, ; Rademacher et al, ), stream water quality (Chang, Huang, et al, ; Hyer et al, ), and riparian vegetation density (Jansson et al, ).…”

Possible Hydrochemical Processes Influencing Dissolved Solids in Surface Water and Groundwater of the Kaidu River Basin, Northwest China

“…Studies at the Hongfeng Lake in Guizhou province, China found that non-point source pollution caused by heavy rainfall results in increasing the total nitrogen content of the lake [40]. Studies in mountain catchments in northern Taiwan found that the hydrochemical processes during typhoon period are significantly different from other times, the high predictability of ion input and output budgets using stream discharge during the non-typhoon period largely disappeared during the typhoon periods [41]. Chiogna et al [42] found that hydrochemical processes are significantly affected by drought.…”