Understanding the nature of streamflow response to precipitation inputs is at the core of hydrological applications and water resource management. Indices such as the base flow index, recession ...constant, and response lag of a watershed retain an important place in hydrology as metrics to compare watersheds and understand the impact of human activity, geology, geomorphology, soils, and climate on precipitation–runoff relations. Extracting characteristics of the hyetograph–hydrograph relationship is often done manually, which is time consuming and may result in subjective and potentially inconsistent outcomes. Here, we present a MATLAB‐based toolbox, called HydRun, for rapid and flexible rainfall–runoff analysis. HydRun uses a series of flexible routines to extract base flow from the hydrograph and then computes commonly used time instants of the rainfall–runoff relationship. HydRun provides users the flexibility to decide thresholds and limits of analysis, but objectively computes hydrometric indices. The toolkit includes a graphical user interface and example files. In this paper, we apply HydRun to 4 watersheds, 3 in Scotland and 1 in Canada, to demonstrate the software functions and highlight important decisions the user must make in its application.
Seasonality plays a critical role in cold mountain regions as variation in air temperature, ground thermal status, and precipitation phase alter the rate, timing and magnitude of hydrological and ...chemical transport. Additionally, cold mountain catchments can have highly variable topography, geology, permafrost, and landcover, which intrinsically add to this irregularity. Understanding how external and internal variability act to control mass fluxes requires sampling at a high spatial resolution over time, which rarely occurs in cold remote regions. In this work, we conduct five snapshot sampling surveys across 34 subcatchments during the ice‐free period in Wolf Creek Research Basin (a mesoscale montane subarctic catchment) and two additional winter surveys across a subset of sites to assess the drivers of variability in stream chemistry and discharge. We sampled for specific conductance (SpC), major ions, and dissolved organic carbon (DOC) and used statistical metrics and Bayesian mixing analysis to quantify patterns of flow and chemistry across space and time. Our results indicate patterns in both flow and chemistry remain largely consistent across seasons for all solutes. However, there was weaker correlation of chemistry between sites, suggesting asynchronous behaviour within the catchment. There was evidence of increasing production of ions and DOC along the stream network during high spring flows but not during low flows. Although concentrations and flows exhibit high seasonality in subarctic mountains, this seasonal variability does not alter spatial patterns that arise from highly variable catchment characteristics.
High spatial heterogeneity drives high spatial stability of discharge and chemistry in a cold subarctic mountain across all four seasons, despite high seasonality often present in cold regions.
Observations and data from long‐term experimental watersheds are the foundation of hydrology as a geoscience. They allow us to benchmark process understanding, observe trends and natural cycles, and ...are prerequisites for testing predictive models. Long‐term experimental watersheds also are places where new measurement technologies are developed. These studies offer a crucial evidence base for understanding and managing the provision of clean water supplies, predicting and mitigating the effects of floods, and protecting ecosystem services provided by rivers and wetlands. They also show how to manage land and water in an integrated, sustainable way that reduces environmental and economic costs.
Key Points
Hydrological data collected over many decades give us the greatest insights into how the water cycle “works” and is changing
Such data have proven essential in understanding and managing water supplies, floods, and other ecosystem services
We need to protect long‐term studies, promote them, and make data available; their value to society increases over time
We compared stable isotopes of water in plant stem (xylem) water and soil collected over a complete growing season from five well‐known long‐term study sites in northern/cold regions. These spanned a ...decreasing temperature gradient from Bruntland Burn (Scotland), Dorset (Canadian Shield), Dry Creek (USA), Krycklan (Sweden), to Wolf Creek (northern Canada). Xylem water was isotopically depleted compared to soil waters, most notably for deuterium. The degree to which potential soil water sources could explain the isotopic composition of xylem water was assessed quantitatively using overlapping polygons to enclose respective data sets when plotted in dual isotope space. At most sites isotopes in xylem water from angiosperms showed a strong overlap with soil water; this was not the case for gymnosperms. In most cases, xylem water composition on a given sampling day could be better explained if soil water composition was considered over longer antecedent periods spanning many months. Xylem water at most sites was usually most dissimilar to soil water in drier summer months, although sites differed in the sequence of change. Open questions remain on why a significant proportion of isotopically depleted water in plant xylem cannot be explained by soil water sources, particularly for gymnosperms. It is recommended that future research focuses on the potential for fractionation to affect water uptake at the soil‐root interface, both through effects of exchange between the vapour and liquid phases of soil water and the effects of mycorrhizal interactions. Additionally, in cold regions, evaporation and diffusion of xylem water in winter may be an important process.
We compared stable isotopes of water in plant stem (xylem) water and soil collected over a complete growing season from five well‐known long‐term study sites in northern/cold regions. Xylem water was isotopically depleted compared to soil waters, most notably for deuterium. At all sites except one, water sources of angiosperms could be associated with soil water, while the sources of water uptake by gymnosperms were much less easily explained.
Flow regimes are critical for determining physical and biological processes in rivers and their classification and regionalization traditionally seeks to link patterns of flow to physiographic, ...climate and other information. There are many approaches to, and rationales for, catchment classification, with those focused on streamflow often seeking to relate a particular response characteristic to a physical property or climatic driver. Rationales include such topics as prediction in ungauged basins (PUB), and providing guidance for model selection in poorly understood hydrological systems. The annual daily hydrograph (ADH) is a first‐order easily visualized integrated expression of catchment function, and over many years the average ADH is a distinct hydrological signature that differentiate catchments from each other. In this study, we use t‐SNE, a state‐of‐the‐art technique of dimensionality reduction, to classify 17 110 ADHs for 304 reference catchments in mountainous Western North America. t‐SNE is chosen over other conventional methods of dimensionality reduction (e.g., PCA) as it presents greater separability of ADHs, which are projected on a 2D map where the similarities are evaluated according to their map distance. We then utilize a Deep Learning encoder to upgrade the non‐parametric t‐SNE to a parametric approach, enhancing its capability to address ‘unseen’ samples. Results showed that t‐SNE successfully clustered ADHs of similar flow regimes on the 2D map and allowed more accurate classification with KNN. In addition, many compact clusters on the 2D map in the coastal Pacific Northwest suggest information redundancy in the local streamflow network. The t‐SNE map provides an intuitive way to visualize the similarity of high‐dimensional data of ADHs, groups catchments with like characteristics, and avoids the reliance on subjective hydrometric indicators.
t‐SNE converts Annual Daily Hydrographs (ADHs) into a 2D map, where ADHs from different western North American flow regimes show distinct clusters. This provides an intuitive way to visualize and compare the similarity among a large number of hydrographs. Incorporating a Deep Learning encoder, we provide a convenient tool to project new hydrographs on to the map, identify similar counterparts and establish the flow regime for any given ADH.
Permafrost‐underlain watersheds in the subarctic are sensitive to warming as small changes in ground thermal status will alter all components of the hydrological cycle. Globally, observed increases ...in winter flows and shifting water chemistry have most often been ascribed to permafrost thaw and deepening runoff pathways. However, there remain few studies in headwater catchments that examine coupled flow‐chemistry relations at high frequency over multiple years and seasons to evaluate the implications of environmental change. In this study, we use multi‐year high‐frequency measurement of discharge, specific conductance (SpC) and chromophoric dissolved organic matter (CDOM) along with traditional grab sampling of major ions to understand the sources and pathways of water and evaluate how distinct solutes are mobilized in a well‐studied subarctic basin in Yukon, Canada. Seasonally, the catchment exhibited considerable hysteresis in flow‐solute relations and had both chemostatic and dilution SpC–Q patterns with respect to major ions depending upon season and mobilization CDOM–Q signals. Storm events were extracted from high‐frequency data and normalized C–Q indices were determined and related to flow, catchment and meteorological variables. CDOM–Q events predominantly had an anti‐clockwise hysteresis and increases in DOC concentrations during storms, with some exception in the spring and fall. Conversely, SpC–Q events exhibited clockwise hysteresis and a dilution behaviour during events with less seasonal or inter‐annual variability. Information from this study supports previous conceptual models of thermally regulated runoff generation in a layered soil profile, yet also points to the importance of lateral connectivity and distal sources of solutes.
Annual concentration‐discharge relations for specific conductivity (SpC) and chromophoric dissolved organic matter (CDOM) show dynamic inter‐annual and intra‐season variability.
High-latitude environments store approximately half of the global organic carbon pool in peatlands, organic soils and permafrost, while large Arctic rivers convey an estimated 18–50 Tg C a−1 to the ...Arctic Ocean. Warming trends associated with climate change affect dissolved organic carbon (DOC) export from terrestrial to riverine environments. However, there is limited consensus as to whether exports will increase or decrease due to complex interactions between climate, soils, vegetation, and associated production, mobilization and transport processes. A large body of research has focused on large river system DOC and dissolved organic matter (DOM) lability and observed trends conserved across years, whereas investigation at smaller watershed scales show that thermokarst and fire have a transient impact on hydrologically mediated solute transport. This study, located in the Wolf Creek Research Basin situated ∼20 km south of Whitehorse, YT, Canada, utilizes a nested design to assess seasonal and annual patterns of DOC and DOM composition across diverse landscape types (headwater, wetland and lake) and watershed scales. Peak DOC concentration and export occurred during freshet, as is the case in most northern watersheds; however, peaks were lower than a decade ago at the headwater site Granger Creek. DOM composition was most variable during freshet with high A254 and SUVA254 and low FI and BIX. DOM composition was relatively insensitive to flow variation during summer and fall. The influence of increasing watershed scale and downstream mixing of landscape contributions was an overall dampening of DOC concentrations and optical indices with increasing groundwater contribution. Forecasted vegetation shifts, enhanced permafrost and seasonal thaw, earlier snowmelt, increased rainfall and other projected climate-driven changes will alter DOM sources and transport pathways. The results from this study support a projected shift from predominantly organic soils (high aromaticity and less fresh) to decomposing vegetation (more fresh and lower aromaticity). These changes may also facilitate flow and transport via deeper flow pathways and enhance groundwater contributions to runoff.
Currently, post-mining landscape plans in the Athabasca Oil Sand Region include large watersheds terminating in pit lakes. In 2012, Base Mine Lake (BML), was constructed with the aim of demonstrating ...technologies associated with lake reclamation in the region. This paper examines the first 6.5 years of lake-atmosphere energy and carbon exchange. Energetically, BML behaved similar to other northern lakes, storing large quantities of heat in the spring and releasing it in the fall as sensible and latent heat fluxes. At various times a hydrocarbon sheen formed on the lake, which may have suppressed evaporation. However, simple linear relationships failed to statistically quantify the impacts and more comprehensive modelling of the variability may be required. At daily scales, variability in evaporation was well explained by the product of vapour pressure deficit and wind speed as well as the available energy (R2 = 0.74), while sensible heat was explained by the product of wind speed and the difference in air and surface temperature as well as available energy (R2 = 0.85). Spring CH4 fluxes were high, particularly around ice melt, with a maximum flux of 3.3 g m−2 day−1. Otherwise fluxes were low, except during irregular periods. The peak flux of these periods occurred following ~58 h of continuously falling pressure, relating cyclone activity to these large periods of methane emissions. Annually, CO2 and CH4 fluxes were initially high, with median fluxes of 231 mg CO2 m−2 h−1 and 23 mg CH4 m−2 h−1 in 2014. However, the median fluxes reduced quickly and over the least three years of the study (2017 through 2019) the median fluxes declined to 36 mg CO2 m−2 h−1 and 10 mg CH4 m−2 h−1. Overall, BML behaves similar to other boreal lake ecosystems with above average carbon fluxes compared to other constructed reservoirs.
Relative pressure preceeding peak CH4 emissions (top). Grey shading indicates the 32 to 68th percentiles (±1 SD), black line is median. Middle panel shows the 2017 CH4 fluxes (grey), with 24 hour gap filled mean (black), to illustrate the peaks (pink arrows) identified by the detection algorithm. Horizontal dotted line is the 90th percentile of CH4 fluxes used to set the minimum threshold for the peak detection. The bottom panel is the air pressure over the same period. The 2017 timeseries was selected for this example because it had the most complete CH4 flux and pressure records. Display omitted
•Reclamation activities produced a lake energetically similar to other boreal lakes.•Methane emissions are related to cyclone activity.•Methane emissions are largest in the spring, around changing ice conditions.•Initially carbon emissions are high.•After three years' carbon emissions are comparable to other reservoirs.
Mine reclamation in the Athabasca oil sands region is legally required as companies must reconstruct disturbed landscapes into functioning ecosystems which previously existed in the Boreal landscape. ...Upland-wetland systems are relatively new in the constructed landscape and only two exist to date. The objective of this work is to understand the key hydrological changes post-management of a constructed peatland watershed and provide insight on the overall system function. Six years of hydrometric data are presented from the Sandhill Fen Watershed (SFW), a 52-ha upland-wetland catchment built on soft tailings with a pump system to provide fresh water, support drainage, and limit salinization. Wet years (seasonal precipitation > evapotranspiration) occurred in 2013, 2016 and 2018 and dry years (seasonal precipitation < evapotranspiration) occurred in 2014, 2015 and 2017 where wet years had large 5-, 10- and 100-year storms which were absent in dry years. Surface conductance and solar radiation explained most of the variation in ET fluxes. Changes in management practices drove many of the observed hydrological changes. Heavy management in 2013 muted water table (WT) responses to climate as inflow and outflow (via pumps) controlled WT response. After 2014, management efforts declined and hydrological exchanges were predominantly vertical, and saturated storage across the wetland increased. As a result, WT variability was tightly coupled to ET regardless of WT position relative to the ground surface, with greater changes related to deeper water tables, suggesting the absence of water conserving feedback mechanisms. Intra-watershed water movement was primarily towards the wetland from recharge areas in the upland swale, whereas surface runoff was rare and only occurred during extreme rain events and spring snowmelt. Peat properties were degraded compared to those observed in undisturbed peatlands, and natural stratification of the peat profile was absent. Results suggest that current conditions are not favorable for fen-peatland development as marsh-like conditions have developed, limiting water conserving functions and the ability to persist long-term in a changing climate.
Development of the wetland (top) and upland (bottom) in the Sandhill Fen Watershed from 2013 to 2018. Display omitted
•Reduced hydrologic management shifted the dominant water fluxes and WT responses to P and ET.•Upland ET > wetland ET, and upland ET increased year-over-year while wetland ET decreased.•WTs primarily coupled to atmospheric forcing indicating absence of water-conserving functions.•Quality of peat material degraded as natural stratification was absent.•Variable WTs, degraded peat, salinity and marsh-like areas are barriers for fen-peatland success.
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