Groundwater flushing of solutes at wetland and hillslope positions during storm events in a small glaciated catchment in western New York,USA     

Shreeram Inamdar  Julia Rupp  Myron Mitchell 《水文研究》2009,23(13):1912-1926

While the role of groundwater in flushing of solutes has long been recognized, few studies have explicitly studied the within‐event changes in groundwater chemistry. We compared the changes in groundwater chemistry during storm events for a wetland and hillslope position in a small (1·5 ha) glaciated, forested catchment in western New York. Flushing responses for dissolved organic carbon (DOC) and nitrogen (DON), nitrate (NO₃) and sulfate (SO₄) in wetland and hillslope groundwaters were also compared against the corresponding responses in stream water. Eight storm events with varying intensity, amount, and antecedent moisture conditions were evaluated. Solute flushing patterns for wetland and hillslope groundwaters differed dramatically. While DOC concentrations in wetland groundwater followed a dilution trend, corresponding values for hillslope groundwater showed a slight increase. Concentrations for NO₃ in wetland groundwater were below detection limits, but hillslope groundwaters displayed high NO₃ concentrations with a pronounced increase during storm events. Flushing responses at all positions were also influenced by the size of the event and the time between events. We attributed the differences in flushing to the differences in hydrologic flow paths and biogeochemical conditions. Flushing of the wetland did appear to influence storm‐event stream chemistry but the same could not be said for hillslope groundwaters. This suggests that while a variety of flushing responses may be observed in a catchment, only a subset of these responses affect the discharge chemistry at the catchment outlet. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Hillslope‐swamp interactions and flow pathways in a hypermaritime rainforest,British Columbia     

D. F. Fitzgerald  J. S. Price  J. J. Gibson 《水文研究》2003,17(15):3005-3022

The process of water delivery to a headwater stream in a hypermaritime rainforest was examined using a variety of physical techniques and tracing with dissolved organic carbon (DOC) and the stable isotopes of water. Headwater swamps, often the major discharge zones for water draining off steep forest slopes, strongly affect the physical and chemical character of streamflow in the region. The headwater swamp selected for detailed investigation was sustained by relatively constant groundwater input from the steep colluvial slopes that maintained the water table above the ground surface. During significant storm events the water table rose quickly and the swamp expanded to engulf marginal pools that developed rapidly on the adjacent ground surfaces. The corresponding release of surface water directly to the stream typically comprised up to 95% of total stream discharge. The proportion of groundwater seepage to the stream by matrix flow (<1%) and via macropore‐fed springs (up to 73%) increased during the recession period, but could not be sustained over the longer term. In more protracted drying periods, deep groundwater contributions to the stream were routed first to the headwater swamp. Dissolved organic carbon (DOC) in the stream, measured daily or more frequently during storm events, was found to be directly proportional to discharge, owing to the domination of DOC‐rich headwater‐swamp water sources. Although δ¹⁸O and δ²H composition of rainwater, groundwater and stream flow were found to be similar, deuterium excess (d ? δ²H ? 8δ¹⁸O) of water components was often found to be distinct, and suggested short water residence times of roughly 12 days for one event. Overall, observations of a typical headwater swamp reveal that the groundwater regime is dominated by rapid infiltration and short, emergent flow paths. With a relatively short turnover time, potential disturbances to the system by harvesting of upslope areas can be expected to occur rapidly. Forest managers can mitigate some of the harmful effects of logging operations by respecting the integrity of headwater wetland systems. The nature and magnitude of such perturbations will require further study. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Factors controlling nitrogen and dissolved organic carbon exports across timescales in two watersheds with different land uses          下载免费PDF全文

Rui Jiang  Ryusuke Hatano  Ying Zhao  Kanta Kuramochi  Atsushi Hayakawa  Krishna P. Woli  Mariko Shimizu 《水文研究》2014,28(19):5105-5121

Investigating factors controlling the temporal patterns of nitrogen (N) and dissolved organic carbon (DOC) exports on the basis of a comparative study of different land uses is beneficial for managing water resources, especially in agricultural watersheds. We focused our research on an agricultural watershed (AW) and a forested watershed (FW) located in the Shibetsu watershed of eastern Hokkaido, Japan, to investigate the temporal patterns of N and DOC exports and factors controlling those patterns at different timescales (inter‐annual, seasonal, and hydrological event scales). Results showed that the annual patterns of N and DOC exports significantly varied over time and were probably controlled by climate. Higher discharge volumes in 2003, a wet year, showed higher N and DOC loadings in both watersheds. However, this process was also regulated by land use associated with N inputs. Higher concentrations and loadings were shown in the agricultural watershed. At the seasonal scale, N and DOC exports in the AW and the FW were more likely controlled by sources associated with land use. The Total N (TN) and Nitrate‐N (NO₃^?‐N) had higher concentrations during snowmelt season in the AW, which may be attributed to manure application in late autumn or early winter in the agricultural watershed. Concentrations of TN, NO₃^?‐N, dissolved organic nitrogen (DON), and DOC showed higher values during the summer rainy season in the FW, related to higher litter decomposition during summer and autumn and the fertilizer application in the agricultural area during summer. Higher DOC concentrations and loadings were observed during the rainy season in the AW, which is probably attributed to higher DOC production related to temperature and microbial activity during summer and autumn in grasslands. Correlations between discharge and concentrations differed during different periods or in different watersheds, suggesting that weather discharge can adequately represent the fact that N export depends on N concentrations, discharge level, and other factors. The differing correlations between N/DOC concentrations and the Si concentration indicated that the N/DOC exports might occur along different flow paths during different periods. During baseflow, the high NO₃^?‐N exports were probably derived from deep groundwater and might have percolated from uplands during hydrological events. During hydrological events, NO₃^?‐N exports may occur along near‐surface flow paths and in deep groundwater, whereas DOC exports could be related to near‐surface flow paths. At the event scale, the relationships between discharge and concentrations of N and DOC were regulated by antecedent soil moisture (shallow groundwater condition) in each watershed. These results indicated that factors controlling N and DOC exports varied at different timescales in the Shibetsu area and that better management of manure application during winter in agricultural lands is urgently needed to control water pollution in streams. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

A coupled hydrology–biogeochemistry model to simulate dissolved organic carbon exports from a permafrost‐influenced catchment          下载免费PDF全文

Jason S. Lessels  Doerthe Tetzlaff  Sean K Carey  Pete Smith  Chris Soulsby 《水文研究》2015,29(26):5383-5396

We outline the development of a simple, coupled hydrology–biogeochemistry model for simulating stream discharge and dissolved organic carbon (DOC) dynamics in data sparse, permafrost‐influenced catchments with large stores of soil organic carbon. The model incorporates the influence of active layer dynamics and slope aspect on hydrological flowpaths and resulting DOC mobilization. Calibration and evaluation of the model was undertaken using observations from Granger Basin within the Wolf Creek research basin, Yukon, northern Canada. Results show that the model was able to capture the dominant hydrological response and DOC dynamics of the catchment reasonably well. Simulated DOC was highly correlated with observed DOC (r² = 0.65) for the study period. During the snowmelt period, the model adequately captured the observed dynamics, with simulations generally reflecting the timing and magnitude of the observed DOC and stream discharge. The model was less successful over the later summer period although this partly reflected a lack of DOC observations for calibration. The developed model offers a valuable framework for investigating the interactions between hydrological and DOC processes in these highly dynamic systems, where data acquisition is often very difficult. © 2015 The Authors Hydrological Processes Published by John Wiley & Sons, Ltd.  相似文献   

An evaluation of the hysteresis in chemical concentration–discharge (C–Q) relationships from drained,intensively managed grasslands in southwest England     

Adebayo O. Eludoyin  Bruce Griffith  Robert J. Orr  Roland Bol  Timothy A. Quine  Richard E. Brazier 《水文科学杂志》2017,62(8):1243-1254

This study examined the hysteresis exhibited in concentration–discharge (C–Q) relationships in the runoff from four hydrologically separated fields (catchments) at an intensively managed grassland. The objectives were to examine C–Q relationships constructed from high-resolution time series of flow, temperature, pH, conductivity, nitrate and turbidity, and their implications for hydrological processes. High-resolution datasets from the quality assured records of the Rothamsted Research North Wyke Farm Platform in the UK were examined using a graphical method and cross-correlation statistics. The study found that storm events based C–Q hysteresis reflects the cross-correlation that is generally hidden in time series analysis of large datasets, and that although Q and water quality variables can be effectively influenced by catchment size, the C–Q relationship is less significantly influenced. The dominant C–Q relationships of the water variables in the study area reflect that saturated overland flow was prevalent during the study period in the catchments, while the CCF results indicate coupled transfer of sediments and solute in the area at lag ≥ 0.