| 1. |
- Bishop, K., et al.
(författare)
-
Aqua Incognita: the unknown headwaters
- 2008
-
Ingår i: Hydological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 22, s. 1239–1242-
-
Tidskriftsartikel (refereegranskat)abstract
- Running water comprises just over one millionth of the world’s water. The importance of those streams and rivers as a resource for human welfare and biodiversity, however, is far out of proportion to that minuscule fraction. This explains why protecting running waters (the flow regimes, water quality and biota) is such a vital concern for society. Yet for all the focus and concern, how much do we actually know about these running waters, and the lotic habitat they comprise?
|
|
| 2. |
- Kruitbos, L. M., et al.
(författare)
-
Hydroclimatic and hydrochemical controls on Plecoptera diversity and distribution in northern freshwater ecosystems
- 2012
-
Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 693:1, s. 39-53
-
Tidskriftsartikel (refereegranskat)abstract
- Freshwater ecosystems in the mid- to upper-latitudes of the northern hemisphere are particularly vulnerable to the impact of climate change as slight changes in air temperature can alter the form, timing, and magnitude of precipitation and consequent influence of snowmelt on streamflow dynamics. Here, we examine the effects of hydro-climate, flow regime, and hydrochemistry on Plecoptera (stonefly) alpha (alpha) diversity and distribution in northern freshwater ecosystems. We characterized the hydroclimatic regime of seven catchments spanning a climatic gradient across the northern temperate region and compared them with estimates of Plecoptera genera richness. By a space-for-time substitution, we assessed how warmer temperatures and altered flow regimes may influence Plecoptera alpha diversity and composition at the genus level. Our results show wide hydroclimatic variability among sites, including differences in temporal streamflow dynamics and temperature response. Principal component analysis showed that Plecoptera genera richness was positively correlated with catchment relief (m), mean and median annual air temperature (A degrees C), and streamflow. These results provide a preliminary insight into how hydroclimatic change, particularly in terms of increased air temperature and altered streamflow regimes, may create future conditions more favorable to some Plecopteras in northern catchments.
|
|
| 3. |
- Laudon, Hjalmar, et al.
(författare)
-
Cross-regional prediction of long-term trajectory of stream water DOC response to climate change
- 2012
-
Ingår i: Geophysical Research Letters. - : John Wiley & Sons. - 0094-8276 .- 1944-8007. ; 39
-
Tidskriftsartikel (refereegranskat)abstract
- There is no scientific consensus about how dissolved organic carbon (DOC) in surface waters is regulated. Here we combine recent literature data from 49 catchments with detailed stream and catchment process information from nine well established research catchments at mid- to high latitudes to examine the question of how climate controls stream water DOC. We show for the first time that mean annual temperature (MAT) in the range from -3 degrees to +10 degrees C has a strong control over the regional stream water DOC concentration in catchments, with highest concentrations in areas ranging between 0 degrees and +3 degrees C MAT. Although relatively large deviations from this model occur for individual streams, catchment topography appears to explain much of this divergence. These findings suggest that the long-term trajectory of stream water DOC response to climate change may be more predictable than previously thought. Citation: Laudon, H., J. Buttle, S. K. Carey, J. McDonnell, K. McGuire, J. Seibert, J. Shanley, C. Soulsby, and D. Tetzlaff (2012), Cross-regional prediction of long-term trajectory of stream water DOC response to climate change, Geophys. Res. Lett., 39, L18404, doi: 10.1029/2012GL053033.
|
|
| 4. |
- Lyon, Steve, et al.
(författare)
-
Variability of groundwater levels and total organic carbon in the riparian zone of a boreal catchment
- 2011
-
Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 116:G01020
-
Tidskriftsartikel (refereegranskat)abstract
- The riparian zone is a narrow corridor where hillslopes (and their associated hydrobiogeochemical processes) interface with the river system. As such, the riparian zone serves as the last piece of landscape with which water interacts as it transitions from being water flowing primarily through the landscape (i.e., shallow groundwater) to water flowing primarily on the landscape (i.e., stream water). This study investigates the spatiotemporal variability in riparian-zone soil water total organic carbon (TOC) and its relation to the shallow groundwater table using observations from the recently instrumented riparian observatory in the Krycklan catchment study area located in boreal northern Sweden. In general, there is a decrease in TOC concentration with depth down through the soil profile. The rate of this decrease was variable among the six monthly samplings used in this study. The spatial variability of soil water TOC in the riparian zone was connected to the spatial variability of the shallow groundwater levels. This demonstrated the importance of the temporal variation of flow pathways and the mixing of waters from different sources of TOC moving into and through the riparian zone. The coupled variation of the hydrologic and biogeochemical systems raised questions about the ability of simple lumped approaches to accurately predict how in-stream TOC concentrations will change with climate and/or land use. The integrated sampling approach in the riparian observatory covers both hydrologic and biogeochemical aspects of soil water TOC and provides a basis for development and testing of distributed, physically based transport models.
|
|
| 5. |
- Lyon, Steve W., et al.
(författare)
-
Controls on snowmelt water mean transit times in northern boreal catchments
- 2010
-
Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 24:12, s. 1672-1684
-
Tidskriftsartikel (refereegranskat)abstract
- Catchment-scale transit times for water are increasingly being recognized as an important control on geochemical processes. In this study, snowmelt water mean transit times (MTTs) were estimated for the 15 Krycklan research catchments in northern boreal Sweden. The snowmelt water MTTs were assumed to be representative of the catchment-scale hydrologic response during the spring thaw period and, as such, may be considered to be a component of the catchment's overall MTT. These snowmelt water MTTs were empirically related to catchment characteristics and landscape structure represented by using different indices of soil cover, topography and catchment similarity. Mire wetlands were shown to be significantly correlated to snowmelt MTTs for the studied catchments. In these wetlands, shallow ice layers form that have been shown to serve as impervious boundaries to vertical infiltration during snowmelt periods and, thus, alter the flow pathways of water in the landscape. Using a simple thought experiment, we could estimate the potential effect of thawing of ice layers on snowmelt hydrologic response using the empirical relationship between landscape structure (represented using a catchment-scale Pe number) and hydrologic response. The result of this thought experiment was that there could be a potential increase of 20-45% in catchment snowmelt water MTTs for the Krycklan experimental catchments. It is therefore possible that climatic changes present competing influences on the hydrologic response of northern boreal catchments that need to be considered. For example, MTTs may tend to decrease during some times of the year due to an acceleration in the hydrologic cycle, while they tend to increase MTTs during other times of the year due to shifts in hydrologic flow pathways. The balance between the competing influences on a catchment's MTT has consequences on climatic feedbacks as it could influence hydrological and biogeochemical cycles at the catchment scale for northern latitude boreal catchments. Copyright (C) 2010 John Wiley & Sons, Ltd.
|
|
| 6. |
- Tetzlaff, D., et al.
(författare)
-
How does landscape structure influence catchment transit time across different geomorphic provinces?
- 2009
-
Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 23:6, s. 945-953
-
Tidskriftsartikel (refereegranskat)abstract
- Despite an increasing number of empirical investigations of catchment transit times (TTs), virtually all are based on individual catchments and there are few attempts to synthesize understanding across different geographical regions. Uniquely, this paper examines data from 55 catchments in five geomorphic provinces in northern temperate regions (Scotland, United States of America and Sweden). The objective is to understand how the role of catchment topography as a control on the TTs differs in contrasting geographical settings. Catchment inverse transit time proxies (ITTPs) were inferred by a simple metric of isotopic tracer damping, using the ratio of standard deviation of delta O-18 in streamwater to the standard deviation of delta O-18 in precipitation. Quantitative landscape analysis was undertaken to characterize the catchments according to hydrologically relevant topographic indices: that could be readily determined from a digital terrain model (DTM). The nature of topographic controls on transit times varied markedly in different geomorphic regions. In steeper montane regions. there are stronger gravitational influences on hydraulic gradients and TTs tend to he lower in the steepest catchments. In provinces where terrain is more subdued, direct topographic control weakened; in particular, where flatter areas with less permeable soils give rise to overland How and lower The steeper slopes within this flatter terrain appear to have a greater coverage of freely draining soils, which increase sub-surface flow, therefore increasing TTs. Quantitative landscape analysis proved a useful tool for intercatchment comparison. However, the critical influence of sub-surface permeability and connectivity may limit the transferability of predictive tools of hydrological function based on topographic parameters alone. Copyright (C) 2009 John Wiley & Sons, Ltd.
|
|
| 7. |
- Winterdahl, Mattias, et al.
(författare)
-
Riparian soil temperature modification of the relationship between flow and dissolved organic carbon concentration in a boreal stream
- 2011
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 47
-
Tidskriftsartikel (refereegranskat)abstract
- Discharge is often strongly correlated to the temporal variability of dissolved organic carbon concentrations ([DOC]) in watercourses. One recently proposed way to model this is the riparian flow-concentration integration model (RIM) concept that accounts for the role of flow pathway control on [DOC] dynamics in streams. However, in boreal systems, there is also commonly a seasonal pattern, which cannot be explained by variability in discharge alone. The objectives with this study were to (1) demonstrate RIM as a tool for studying variability in stream water chemistry, (2) investigate factors related to stream water DOC variability, and (3) modify RIM to account for these factors. RIM was used with 14 years of daily discharge and almost 500 stream measurements of [DOC] from a forested boreal headwater stream. We used the calibrated RIM to account for discharge influences and then investigated variables that could be related to DOC variability (air and soil temperature, soil moisture, precipitation, antecedent flow and stream sulfate). Five alternative formulations of RIM, with temporally varying soil concentration profiles based on the variability in soil temperature and/or antecedent flow, were evaluated. The model where only the effects of riparian soil temperature on dynamics in DOC depth profiles were included performed best overall. This dynamic RIM improved the Nash-Sutcliffe to 0.58 compared to 0.42 for the flow-only formulation and reduced the median absolute error from 3.0 to 2.1 mg L (-1). This study demonstrates that RIM is a simple way of modeling stream DOC and exploring controls on stream water chemistry.
|
|
| 8. |
- Öhman, Karin, et al.
(författare)
-
An Approach for Including Consideration of Stream Water Dissolved Organic Carbon in Long Term Forest Planning
- 2009
-
Ingår i: AMBIO: A Journal of the Human Environment. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:7, s. 387-393
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to add to a traditional forest planning model by incorporating some consideration of the effects of forestry on dissolved organic carbon (DOC) concentrations in streams over time. In a case study, for a watershed in northern Sweden, we present the best possible solution to a forest planning problem that maximizes the net present value (NPV) while the DOC concentration levels in the watershed are maintained below a defined threshold value. Results from the case study show that the decrease in NPV, when taking DOC into account, was considerable. However, the decrease in possible harvest volume was restricted in the case study area because the model moved harvesting activity from the first 20-year period to later periods to avoid high initial DOC concentrations. The model presented could be a useful tool for predicting the effect of forestry on DOC concentrations over time.
|
|
| 9. |
- Öquist, Mats, et al.
(författare)
-
Dissolved Inorganic Carbon Export Across the Soil/Stream Interface and Its Fate in a Boreal Headwater Stream
- 2009
-
Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). ; 43, s. 7364-7369
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this investigation was to determine the lateral export of dissolved inorganic carbon (DIC) from soils of a Swedish boreal forest to a first order stream and to estimate the partitioning of this DIC into CO2 evasion from the stream surface and the DIC pool exported down through the catchment by streamwater. The groundwater entering the stream was supersaturated with CO2 with values as high as 17 times equilibrium with the atmosphere. Up to 90% of the estimated daily soil DIC export to the stream was emitted to the atmosphere as CO2 within 200 in of the water entering the stream. The annual DIC export from the soil to the stream was estimated to be 3.2 (+/- 0.1) g C m(-2) yr(-1) (normalized to catchment size). Ninety percent of the variation in soil DIC export could be explained by the variation in groundwater discharge and the DIC concentrations per se, were of minor importance. A significant correlation (R-2 = 0.74, P < 0.01) between soil DIC export and CO2 emission from the stream surface suggests that emission dynamics were primarily driven by the export of terrestrial DIC and that in-stream processes were less important Our results reveal that current budget estimates of lateral DIC export from soils to aquatic conduits need to be revised because they do not account for conditions prevailing in headwater streams. Any quantification of lateral stream C export and CO2 emissions from freshwater systems must include headwater streams as well as the lower parts of the aquatic conduit
|
|
