•There has been little comparison of cold regions flow and heat transport models.•Analytical solutions make excellent benchmarks for inter-code comparison.•We present a solution that includes ...conduction, advection and phase change.•We test its accuracy via comparisons to the Neumann solution and a numerical model.•We report detailed simulation results to facilitate future benchmarking endeavors.
Numerous cold regions water flow and energy transport models have emerged in recent years. Dissimilarities often exist in their mathematical formulations and/or numerical solution techniques, but few analytical solutions exist for benchmarking flow and energy transport models that include pore water phase change. This paper presents a detailed derivation of the Lunardini solution, an approximate analytical solution for predicting soil thawing subject to conduction, advection, and phase change. Fifteen thawing scenarios are examined by considering differences in porosity, surface temperature, Darcy velocity, and initial temperature. The accuracy of the Lunardini solution is shown to be proportional to the Stefan number. The analytical solution results obtained for soil thawing scenarios with water flow and advection are compared to those obtained from the finite element model SUTRA. Three problems, two involving the Lunardini solution and one involving the classic Neumann solution, are recommended as standard benchmarks for future model development and testing.
Although stream temperature energy balance models are useful to predict temperature through time and space, a major unresolved question is whether fluctuations in stream discharge reduce model ...accuracy when not exactly represented. However, high‐frequency (e.g., subdaily) discharge observations are often unavailable for such simulations, and therefore, diurnal streamflow fluctuations are not typically represented in energy balance models. These fluctuations are common due to evapotranspiration, snow pack or glacial melt, tidal influences within estuaries, and regulated river flows. In this work, we show when to account for diurnally fluctuating streamflow. To investigate how diurnal streamflow fluctuations affect predicted stream temperatures, we used a deterministic stream temperature model to simulate stream temperature along a reach in the Quilcayhuanca Valley, Peru, where discharge varies diurnally due to glacial melt. Diurnally fluctuating streamflow was varied alongside groundwater contributions via a series of computational experiments to assess how uncertainty in reach hydrology may impact simulated stream temperature. Results indicated that stream temperatures were more sensitive to the rate of groundwater inflow to the reach compared with the timing and amplitude of diurnal fluctuations in streamflow. Although incorporating observed diurnal fluctuations in discharge resulted in a small improvement in model RMSE, we also assessed other diurnal discharge signals and found that high amplitude signals were more influential on modelled stream temperatures when the discharge peaked at specific times. Results also showed that regardless of the diurnal discharge signal, the estimated groundwater flux to the reach only varied from 1.7% to 11.7% of the upstream discharge. However, diurnal discharge fluctuations likely have a stronger influence over longer reaches and in streams where the daily range in discharge is larger, indicating that diurnal fluctuations in stream discharge should be considered in certain settings.
Widespread lake shrinkage in cold regions has been linked to climate warming and permafrost thaw. Permafrost aggradation, however, has been observed within the margins of recently receded lakes, in ...seeming contradiction of climate warming. Here permafrost aggradation dynamics are examined at Twelvemile Lake, a retreating lake in interior Alaska. Observations reveal patches of recently formed permafrost within the dried lake margin, colocated with discrete bands of willow shrub. We test ecological succession, which alters shading, infiltration, and heat transport, as the driver of aggradation using numerical simulation of variably saturated groundwater flow and heat transport with phase change (i.e., freeze‐thaw). Simulations support permafrost development under current climatic conditions, but only when net effects of vegetation on soil conditions are incorporated, thus pointing to the role of ecological succession. Furthermore, model results indicate that permafrost aggradation is transitory with further climate warming, as new permafrost thaws within seven decades.
Key Points
New permafrost is forming around shrinking arctic lakes
Shading by willow shrubs primarily drives new permafrost formation
Further climate warming thaws new permafrost within 7 decades
Glaciers in the tropical Andes are undergoing rapid retreat with potentially devastating consequences for populations who rely on them for water resources. We measured stable water isotope ratios in ...synoptically sampled streams discharging from glacierized watersheds to associate hydroisotopic variation with relative changes in glacierized area. A total of 73 water samples were collected from hydrological endmembers including streams, glacier meltwater, and groundwater during the dry seasons of 2004−2006 in the Callejon de Huaylas, a 5000 km2 watershed that drains the western side of the Cordillera Blanca in northern Perú. To differentiate the influence of elevation on isotopic values, we use samples from shallow groundwater springs and nonglacierized subcatchments to derive a local meteoric elevation effect. From published historical runoff data and satellite-mapped glacier cover, we estimate an average increase of 1.6 (±1.1)% in the specific discharge of the glacierized catchments as a function of isotopic changes from 2004 to 2006. These results confirm predicted short-term increases in discharge as glaciers melt and demonstrate the utility of stable isotopes in water for tracing relative glacier melt water contributions to watersheds.
The objective of this research is to characterize the variability of trace metals in the Rio Santa watershed based on synoptic sampling applied at a large scale. To that end, we propose a combination ...of methods based on the collection of water, suspended sediments, and riverbed sediments at different points of the watershed within a very limited period. Forty points within the Rio Santa watershed were sampled between June 21 and July 8, 2013. Forty water samples, 36 suspended sediments, and 34 riverbed sediments were analyzed for seven trace metals. The results, which were normalized using the USEPA guideline for water and sediments, show that the Rio Santa water exhibits Mn concentrations higher than the guideline at more than 50% of the sampling points. As is the second highest contaminating element in the water, with approximately 10% of the samples containing concentrations above the guideline. Sediments collected in the Rio Santa riverbed were heavily contaminated by at least four of the tested elements at nearly 85% of the sample points, with As presenting the highest normalized concentration, at more than ten times the guideline. As, Cd, Fe, Pb, and Zn present similar concentration trends in the sediment all along the Rio Santa.
The findings indicate that care should be taken in using the Rio Santa water and sediments for purposes that could affect the health of humans or the ecosystem. The situation is worse in some tributaries in the southern part of the watershed that host both active and abandoned mines and ore-processing plants.
The importance
of water moving between the atmosphere and aquifers has led to efforts to
develop and maintain coupled models of surface water and groundwater.
However, developing inputs to these ...models is usually time-consuming and
requires extensive knowledge of software engineering, often prohibiting their
use by many researchers and water managers, thus reducing these models'
potential to promote science-driven decision-making in an era of global
change and increasing water resource stress. In response to this need, we
have developed GSFLOW–GRASS, a bundled set of open-source tools that
develops inputs for, executes, and graphically displays the results of
GSFLOW, the U.S. Geological Survey's coupled groundwater and surface-water
flow model. In order to create a robust tool that can be widely implemented
over diverse hydro(geo)logic settings, we built a series of GRASS GIS
extensions that automatically discretizes a topological surface-water flow
network that is linked with an underlying gridded groundwater domain. As
inputs, GSFLOW–GRASS requires at a minimum a digital elevation model, a
precipitation and temperature record, and estimates of channel parameters and
hydraulic conductivity. We demonstrate the broad applicability of the toolbox
by successfully testing it in environments with varying degrees of drainage
integration, landscape relief, and grid resolution, as well as the presence
of irregular coastal boundaries. These examples also show how GSFLOW–GRASS
can be implemented to examine the role of groundwater–surface-water
interactions in a diverse range of water resource and land management
applications.
► We examined the dissolved and unfiltered trace element chemistry of a stream fed by glacier melt. ► Cation denudation was elevated in Cordillera Blanca proglacial melt with respect to other world ...glaciers. ► Water quality issues may arise as sulfide minerals are exposed by glacial retreat in the Cordillera Blanca, Peru. ► Several elements occur at concentrations deemed toxic to health.
Globally, the ongoing retreat of mountain glaciers will ultimately diminish fresh water supplies. This has already begun in watersheds with greatly reduced glacial coverage. Still unknown are the affects of glacial retreat on downstream water quality, including the threats to human and ecosystem health. In the Cordillera Blanca, retreating glaciers have exposed sulfide-rich rock outcrops, negatively affecting the quality of the glacial meltwater. This study has evaluated glacial melt stream hydrogeochemistry in the sulfide-bearing Rio Quilcay watershed (∼9°27′S, ∼77°22′W) during the 2008 dry season. Surface water samples were collected from the upper 12
km of the watershed during the 2008 dry season. Dissolved (0.4
μm) and unfiltered acidified (pH
<
2) Al, Co, Cu, Fe, Ni, Mn, Pb, Zn and dissolved major ions and organic C (DOC) concentrations were quantified and pH and temperature were measured in the field. Twenty of 22 stream samples had pH values below 4, generating significantly (
p
<
0.01,
α
=
0.05) greater cation denudation normalized to discharge than other worldwide glacier-fed streams. Additionally, dissolved trace and minor element concentrations were comparable to acid mine drainage. Non-conservative dissolved element behaviors resulted from adsorption/desorption reactions in tributary mixing zones. At low pH values, hydrous Fe oxides acted as the dominant sorption surfaces. The poor water quality observed in Cordillera Blanca headwaters coupled with the likely exposure of additional sulfide-rich outcrops from ongoing glacial retreat may pose water quality challenges.
Climate change has effects on hydrological change in multiple aspects, particularly in the headwaters of the Yellow River (HWYR), which is widely covered by climate-sensitive frozen ground. In this ...study, the annual runoff was partitioned into four runoff compositions: winter baseflow, snowmelt runoff, rainy season runoff, and recession flow. In addition, the effects of global warming, precipitation change, and frozen ground degradation were considered in long-term variation analyses of the runoff compositions. The moving t-test was employed to detect change points of the hydrometeorological data series from 1961 to 2013, and flow duration curves were used to analyze daily runoff regime change in different periods. It was found that the abrupt change points of cold season runoff, such as recession flow, winter baseflow, and snowmelt runoff, are different from that of the rainy season runoff. The increase in winter baseflow and decrease in snowmelt runoff at the end of 1990s was closely related to global warming. In the 21st century, winter baseflow presented a larger relative increase compared to rainy season runoff. The correlation analyses indicate that winter baseflow and snowmelt runoff are mainly controlled by water-resource-related factors, such as rainy season runoff and the accumulated precipitation in cold season. To analyze the global warming impacts, two runoff coefficients—winter baseflow discharge rate (Rw) and direct snowmelt runoff coefficients (Rs)—were proposed, and their correlation with freezing–thawing indices were analyzed. The increase of Rw is related to the increase in the air temperature thawing index (DDT), but Rs is mainly controlled by the air temperature freezing index (DDF). Meanwhile, the direct snowmelt runoff coefficient (Rs) is significantly and positively correlated to DDF and has decreased at a rate of 0.0011/year since 1980. Under global warming, the direct snowmelt runoff (runoff increment between March to May) of the HWYR could decrease continuously in the future due to the decrease of accumulative snow in cold season and frozen ground degradation. This study provides a better understanding of the long-term runoff characteristic changes in the HWYR.
This article presents a comprehensive hydrometeorological
dataset collected over the past two decades throughout the Cordillera
Blanca, Peru. The data-recording sites, located in the upper portion of ...the
Rio Santa valley, also known as the Callejon de Huaylas, span an elevation
range of 3738–4750 m a.s.l. As many historical hydrological stations
measuring daily discharge across the region became defunct after their
installation in the 1950s, there was a need for new stations to be installed
and an opportunity to increase the temporal resolution of the streamflow
observations. Through inter-institutional collaboration, the
hydrometeorological network described in this paper was deployed with the goal
of evaluating how progressive glacier mass loss was impacting stream
hydrology, and understanding better the local manifestation of climate
change over diurnal to seasonal and interannual time scales. The four
automatic weather stations supply detailed meteorological observations and
are situated in a variety of mountain landscapes, with one on a
high-mountain pass, another next to a glacial lake, and two in glacially
carved valleys. Four additional temperature and relative humidity loggers
complement the weather stations within the Llanganuco valley by providing
these data across an elevation gradient. The six streamflow gauges are
located in tributaries to the Rio Santa and collect high-temporal-resolution
runoff data. The datasets presented here are available freely from
https://doi.org/10.4211/hs.35a670e6c5824ff89b3b74fe45ca90e0 (Mateo et al.,
2021). Combined, the hydrological and meteorological data collected
throughout the Cordillera Blanca enable detailed research of atmospheric and
hydrological processes in tropical high-mountain terrain.
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