scholarly journals Seasonally varied hillslope and groundwater contributions to streamflow in a glacial till and fractured sedimentary bedrock dominated Rocky Mountain watershed

2020 ◽  
Author(s):  
Sheena A. Spencer ◽  
Axel E. Anderson ◽  
Uldis Silins ◽  
Adrian L. Collins
Keyword(s):  
Forest Disturbance ◽  
Stream Water ◽  
Rocky Mountain ◽  
Principal Component ◽  
Dilution Effect ◽  
Glacial Till ◽  
Source Water ◽  
Runoff Generation ◽  
Chemical Signatures ◽  
Flow Pathways

Abstract. Whereas a lack of streamflow response to significant forest disturbance (e.g., forestry, wildfire, and insect infestation) has been observed at multiple locations in the Canadian Rocky Mountains, a region with sedimentary bedrock overlain by glacial till, mechanisms governing this lack of change remain unclear. Some inferences can be drawn from conceptualizations of runoff generation (e.g., runoff thresholds and hydrologic connectivity) in physically similar watersheds, although much of the focus has been on rainfall-runoff dynamics. Thus, there is a need to describe runoff generation in this snow-dominated area to interpret how forest disturbance may impact streamflow quantity for downstream users. Stream water and source water (snow, rain, hillslope groundwater, till groundwater, bedrock groundwater and seeps) were sampled in four sub-watersheds (Star West Lower, Star West Upper, Star East Lower and Star East Upper) in Star Creek, SW Alberta. Principal component analysis was used to determine the relative dominance and timing of source water contributions to streamflow over the 2014 and 2015 hydrologic seasons. An initial displacement of old water stored in the hillslope over winter occurred at the onset of snowmelt, before the stream responded significantly. This was followed by a dilution effect as snowmelt saturated the landscape, recharged groundwater, and connected the hillslope to the stream. Fall baseflows were dominated by either hillslope groundwater or bedrock groundwater in Star West. Conversely, in Star East, stream water was similar to hillslope water in August but was unlike the measured sources in September and October. Temperature and chemical signatures of groundwater seeps suggest highly complex subsurface flow pathways. Hydrologic resilience in the Rocky Mountain eastern slopes may be, in part, due to these complex subsurface pathways in combination with the slow release of groundwater from glacial till.

scholarly journals Hillslope and groundwater contributions to streamflow in a Rocky Mountain watershed underlain by glacial till and fractured sedimentary bedrock

2021 ◽  
Vol 25 (1) ◽  
pp. 237-255
Author(s):  
Sheena A. Spencer ◽  
Axel E. Anderson ◽  
Uldis Silins ◽  
Adrian L. Collins
Keyword(s):  
Stream Water ◽  
Subsurface Flow ◽  
Rocky Mountain ◽  
Principal Component ◽  
Glacial Till ◽  
Spatial And Temporal Variation ◽  
Source Water ◽  
Runoff Generation ◽  
Cold Temperatures ◽  
Flow Pathways

Abstract. Permeable sedimentary bedrock overlain by glacial till leads to large storage capacities and complex subsurface flow pathways in the Canadian Rocky Mountain region. While some inferences on the storage and release of water can be drawn from conceptualizations of runoff generation (e.g., runoff thresholds and hydrologic connectivity) in physically similar watersheds, relatively little research has been conducted in snow-dominated watersheds with multilayered permeable substrates that are characteristic of the Canadian Rocky Mountains. Stream water and source water (rain, snowmelt, soil water, hillslope groundwater, till groundwater, and bedrock groundwater) were sampled in four sub-watersheds (Star West Lower, Star West Upper, Star East Lower, and Star East Upper) in Star Creek, SW Alberta, to characterize the spatial and temporal variation in source water contributions to streamflow in upper and lower reaches of this watershed. Principal component analysis was used to determine the relative dominance and timing of source water contributions to streamflow over the 2014 and 2015 hydrologic seasons. An initial displacement of water stored in the hillslope over winter (reacted water rather than unreacted snowmelt and rainfall) occurred at the onset of snowmelt before stream discharge responded significantly. This was followed by a dilution effect as snowmelt saturated the landscape, recharged groundwater, and connected the hillslopes to the stream. Fall baseflows were dominated by either riparian water or hillslope groundwater in Star West. Conversely, in Star East, the composition of stream water was similar to hillslope water in August but plotted outside the boundary of the measured sources in September and October. The chemical composition of groundwater seeps followed the same temporal trend as stream water, but the consistently cold temperatures of the seeps suggested deep groundwater was likely the source of this late fall streamflow. Temperature and chemical signatures of groundwater seeps also suggest highly complex subsurface flow pathways. The insights gained from this research help improve our understanding of the processes by which water is stored and released from watersheds with multilayered subsurface structures.

Runoff generation processes in permafrost-influenced area of the Heihe River Headwater

2021 ◽  
Author(s):  
Fan Zhang ◽  
Xiong Xiao ◽  
Guanxing Wang
Keyword(s):  
Soil Water ◽  
Stream Water ◽  
Hydrological Regime ◽  
Summer Rainfall ◽  
Frozen Soil ◽  
Heihe River ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Runoff Generation ◽  
Spring Snowmelt

<p>Permafrost degradation under global warming may change the hydrological regime of the headwater catchments in alpine area such as the Tibetan Plateau (TP). In this study, he runoff generation processes in permafrost-influenced area of the Heihe River Headwater were investigated with the following results: 1) The observed stable isotope values of various water types on average was roughly in the order of snowfall and snowmelt < bulk soil water (BSW) < rainfall , stream water, mobile soil water (MSW) , and lateral subsurface flow. The depleted spring snowmelt and enriched summer rainfall formed tightly bound soil water and MSW, respectively. The dynamic mixing between tightly bound soil water and MSW resuted in BSW with more depleted and variable stable isotopic feature than MSW. 2) Along with the thawing of the frozen soil, surface runoff and shallowsubsurface flow (SSF) at 30−60 cm was the major flow pathway in the permafrost influenced alpine meadow hillslope during spring snowmelt and summer rainfall period, reapectively, with the frozen soil maintaining supra-permafrost water level. 3) Comparison between two neighouring catchments under similar precipitation conditions indicated that streamflow of the lower catchment with less permafrost proportion and earlier thawing time has larger SSF and higher based flow component, indicating the potential changes of hydrological regims subject to future warming.</p>

scholarly journals Water flow pathways and the water balance within a head-water catchment containing a dambo: inferences drawn from hydrochemical investigations

1999 ◽  
Vol 3 (4) ◽  
pp. 581-591 ◽  
Author(s):  
M. P. McCartney ◽  
C. Neal
Keyword(s):  
Water Balance ◽  
Stream Water ◽  
Management Strategies ◽  
Dry Season ◽  
Sub Saharan Africa ◽  
Flow Paths ◽  
Headwater Catchments ◽  
Sub Saharan ◽  
Flow Pathways ◽  
Water Catchment

Abstract. Dambos, seasonally saturated wetlands, are widespread in headwater catchments in sub-Saharan Africa. It is widely believed that they play an important role in regional hydrology but, despite research conducted over the last 25 years, their hydrological functions remain poorly understood. To improve conceptualisation of hydrological flow paths and investigate the water balance of a small Zimbabwean catchment containing a single dambo, measurements of alkalinity and chloride in different water types within the catchment have been used as chemical markers. The temporal variation in alkalinity is consistent with the premise that all stream water, including the prolonged dry season recession, is derived predominantly from shallow sources. The proposition that dry season recession flows are maintained by water travelling at depth within the underlying saprolite is not substantiated. There is evidence that a low permeability clay lens, commonly present in many dambos, acts as a barrier for vertical water exchange. However, the highly heterogeneous chemical composition of different waters precludes quantitative hydrograph split-ting using end member mixing analysis. Calculation of the chloride mass-balance confirms that, after rainfall, evaporation is the largest component of the catchment water budget. The study provides improved understanding of the hydrological functioning of dambos. Such understanding is essential for the development and implementation of sustainable management strategies for this landform.

scholarly journals Catchment-scale carbon exports across a subarctic landscape gradient

2013 ◽  
Vol 10 (5) ◽  
pp. 7953-7988
Author(s):  
R. Giesler ◽  
S. W. Lyon ◽  
C.-M. Mörth ◽  
J. Karlsson ◽  
E. J. Jantze ◽  
...  
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Stream Water ◽  
Maximum Flow ◽  
Catchment Scale ◽  
Carbon Export ◽  
Spring Freshet ◽  
Annual Carbon ◽  
Pathway Length ◽  
Flow Pathways ◽  
Thawing Permafrost

Abstract. Climatic change is currently enhancing permafrost thawing and hydrological cycling in subarctic and arctic catchments with major consequences for the carbon export to aquatic ecosystems. We studied stream water carbon export in several tundra dominated catchments in northern Sweden. There were clear seasonal differences in both dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. The highest DOC concentrations occurred during the spring freshet while the highest DIC concentrations were always observed during winter baseflow conditions for the six catchments considered in this study. In these subarctic catchments, DIC accounted for at least about half of the annual mass of C exported. Further, there was a direct relationship between both hydrologic flow pathway length and the maximum flow to minimum flow ratio (which serves as a proxy for fractioning between surface and subsurface flow pathways) and annual carbon fluxes for these six catchments. Further, these relationships were more prevalent for annual DIC exports than annual DOC exports in this region. These results highlight that there can be large regional differences in high latitude ecosystems and emphasize the importance of proper representation of subsurface hydrogeological conditions. This is particularly relevant in subarctic environments were thawing permafrost and changes to subsurface ice due to global warming can influence stream water fluxes of C. The large proportion of stream water DIC flux also has implications on regional C budgets and needs to be considered in order to understand climate induced feedback mechanisms across the landscape.

Connecting precipitation inputs and soil flow pathways to stream water in contrasting boreal catchments

2014 ◽  
Vol 29 (16) ◽  
pp. 3546-3555 ◽  
Author(s):  
A. Peralta-Tapia ◽  
R. A. Sponseller ◽  
D. Tetzlaff ◽  
C. Soulsby ◽  
H. Laudon
Keyword(s):  
Stream Water ◽  
Soil Flow ◽  
Flow Pathways

scholarly journals Model-based estimation of pesticides and transformation products and their export pathways in a headwater catchment

2013 ◽  
Vol 17 (12) ◽  
pp. 5213-5228 ◽  
Author(s):  
M. Gassmann ◽  
C. Stamm ◽  
O. Olsson ◽  
J. Lange ◽  
K. Kümmerer ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Transformation Products ◽  
Distributed Hydrological Model ◽  
Runoff Generation ◽  
Soil Matrix ◽  
Successful Model ◽  
Tile Drains ◽  
Flow Pathways ◽  
Preferential Flow Pathways ◽  
Headwater Catchment

Abstract. Pesticides applied onto agricultural fields are frequently found in adjacent rivers. To what extent and along which pathways they are transported is influenced by intrinsic pesticide properties such as sorption and degradation. In the environment, incomplete degradation of pesticides leads to the formation of transformation products (TPs), which may differ from the parent compounds regarding their intrinsic fate characteristics. Thus, the export processes of TPs in catchments and streams may also be different. In order to test this hypothesis, we extended a distributed hydrological model by the fate and behaviour of pesticides and transformation products and applied it to a small, well-monitored headwater catchment in Switzerland. The successful model evaluation of three pesticides and their TPs at three sampling locations in the catchment enabled us to estimate the quantity of contributing processes for pollutant export. Since all TPs were more mobile than their parent compounds (PCs), they exhibited larger fractions of export via subsurface pathways. However, besides freshly applied pesticides, subsurface export was found to be influenced by residues of former applications. Export along preferential flow pathways was less dependent on substance fate characteristics than soil matrix export, but total soil water flow to tile drains increased more due to preferential flow for stronger sorbing substances. Our results indicate that runoff generation by matrix flow to tile drains gained importance towards the end of the modelling period whereas the contributions from fast surface runoff and preferential flow decreased. Accordingly, TPs were to a large extent exported under different hydrological conditions than their PCs, due to their delayed formation and longer half-lives. Thus, not only their different intrinsic characteristics but also their delayed formation could be responsible for the fact that TPs generally took different pathways than their PCs. We suggest that these results should be considered in risk assessment for the export of agricultural chemicals to adjacent rivers and that models should be extended to include both PCs and TPs.

Optimal location of set-aside areas to reduce nitrogen pollution: a modelling study

2018 ◽  
Vol 156 (9) ◽  
pp. 1090-1102 ◽  
Author(s):  
L. Casal ◽  
P. Durand ◽  
N. Akkal-Corfini ◽  
C. Benhamou ◽  
F. Laurent ◽  
...  
Keyword(s):  
Management Practices ◽  
Stream Water ◽  
Landscape Management ◽  
Crop Management ◽  
Dilution Effect ◽  
Mitigation Measures ◽  
Distributed Model ◽  
Main Process ◽  
Distributed Models ◽  
N Input

AbstractDistributed models and a good knowledge of the catchment studied are required to assess mitigation measures for nitrogen (N) pollution. A set of alternative scenarios (change of crop management practices and different strategies of landscape management, especially different sizes and distribution of set-aside areas) were simulated with a fully distributed model in a small agricultural catchment. The results show that current practices are close to complying with current regulations, which results in a limited effect of the implementation of best crop management practices. The location of set-aside zones is more important than their size in decreasing nitrate fluxes in stream water. The most efficient location is the lower parts of hillslopes, combining the dilution effect due to the decrease of N input per unit of land and the interception of nitrate transferred by sub-surface flows. The main process responsible for the interception effect is probably uptake by grassland and retention in soils since the denitrification load tends to decrease proportionally to N input and, for the scenarios considered, is lower in the interception scenarios than in the corresponding dilution zones.

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