Pertti Ala-ahoUniversity of Oulu · Water Energy and Environmental Engineering
Pertti Ala-aho
Professor
About
70
Publications
29,226
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Introduction
My research interests:
(1) Tracer-aided hydrological modelling using stable water isotopes
(2) Cold climate processes (snow and soil freeze/thaw) in hydrology
(3) Numerical techniques to study integrated surface and subsurface hydrology
Additional affiliations
January 2015 - July 2015
Publications
Publications (70)
Soil moisture plays a key role in soil nutrient and carbon cycling; plant productivity; and energy, water, and greenhouse gas exchanges between the land and the atmosphere. The knowledge on drivers of spatiotemporal soil moisture dynamics in subarctic landscapes is limited. In this study, we used the Spatial Forest Hydrology (SpaFHy) model, in situ...
Stable isotope ratios of hydrogen (δ2H) and oxygen (δ18O) are crucial for studying ecohydrological dynamics in forests. However, most studies are confined to single sites, resulting in a lack of large-scale isotope data for understanding tree water uptake. Here, we provide a first systematic isotope dataset of soil and stem xylem water collected du...
Peatlands are the most dense terrestrial carbon storage and recent studies have shown that the northern peatlands have continued to expand to new areas to this day. However, depending on the vegetation and hydrological regime in the newly initiated areas, the climate forcing may vary. If these new areas develop as wet, fen-type peatlands with high...
Soil moisture plays a key role in soil nutrient and carbon cycling, plant productivity and in energy, water, and greenhouse gas exchanges between the land and the atmosphere. In this study, we used the Spatial Forest Hydrology (SpaFHy) model, in-situ soil moisture measurements and Sentinel-1 SAR-based soil moisture estimates to explore spatiotempor...
Dissolved organic carbon (DOC) dynamics are evolving in the rapidly changing Arctic and a comprehensive understanding of the controlling processes is urgently required. For example, the transport processes governing DOC dynamics are prone to climate-driven alteration given their strong seasonal nature. Hence, high-resolution and long-term studies a...
The snowpack has a major influence on the land surface energy budget. Accurate simulation of the snowpack energy and radiation budget is challenging due to, e.g., effects of vegetation and topography, as well as limitations in the theoretical understanding of turbulent transfer in the stable boundary layer. Studies that evaluate snow, hydrology and...
Detailed information on seasonal snow cover and depth is essential to the understanding of snow processes, to operational forecasting, and as input for hydrological models. Recent advances in uncrewed or unmanned aircraft systems (UASs) and structure from motion (SfM) techniques have enabled low-cost monitoring of spatial snow depth distribution in...
Snow conditions in the Northern Hemisphere are rapidly changing, and information on snow depth is critical for decision-making and other societal needs. Uncrewed or unmanned aircraft systems (UASs) can offer data resolutions of a few centimeters at a catchment-scale and thus provide a low-cost solution to bridge the gap between sparse manual probin...
Dissolved organic carbon (DOC) dynamics are evolving in the rapidly changing Arctic and a comprehensive understanding of the controlling processes is urgently required. For example, the transport processes governing DOC dynamics are prone to climate driven alteration given their strong seasonal nature. Hence, high-resolution and long-term studies a...
The hydrological cycle of sub-arctic areas is dominated by the snowmelt event. Understanding the mechanisms that control water fluxes during high-volume infiltration events in sub-arctic till soils is needed to assess how future changes in the timing and magnitude of snowmelt can affect soil water storage dynamics. We conducted a tracer experiment...
Snowmelt spring floods regulate carbon transport from land to streams. However, these coupled processes are rarely documented through high‐resolution measurements focused on water‐carbon interactions. We collated a state‐of‐the‐art high‐frequency data set throughout a snowmelt and early post snowmelt period, alongside regular samples of stream wate...
The snowpack has a major influence on the land surface energy budget. Accurate simulation of the snowpack energy budget is challenging due to e.g. vegetation and topography that complicate the radiation budget, and limitations in theoretical understanding of turbulent transfer in the stable boundary layer. Studies that evaluate snow, hydrology and...
Groundwater in shallow aquifers is commonly used for community water supply in cold climates. Shallow groundwaters are inherently susceptible to contamination from land‐use and surface water intrusion threatening drinking water usage. We used a large‐scale snapshot data set of stable water isotopes from shallow glaciofluvial aquifers used for drink...
Understanding the relative importance of different water sources that replenish soil water storage is necessary to assess the vulnerability of sub‐arctic areas to changes in climate and altered rain and snow conditions, reflected in the timing and magnitude of water infiltration. We examine spatiotemporal variability and seasonal origin of soil wat...
This study provides a detailed characterization of spatiotemporal variations of stable water ¹⁸O and ²H isotopes in both snowpack and meltwater in a subarctic catchment. We performed extensive sampling and analysis of snowpack and meltwater isotopic compositions at 11 locations in 2019 and 2020 across three different landscape features: (a) forest...
Detailed information on seasonal snow cover and depth is essential to the understanding of snow processes, operational forecasting, and as input for hydrological models. Recent advances in unmanned aircraft systems (UASs) and structure from motion (SfM) techniques have enabled low-cost monitoring of spatial snow depth distribution in resolutions up...
Snow conditions in the northern hemisphere are rapidly changing, and information on snow depth is critical for decision-making and other societal needs. Unmanned aircraft systems (UASs) can offer data resolutions of a few centimeters at a catchment-scale, and thus provide a low-cost solution to bridge the gap between sparse manual probing and low-r...
As far as I can tell, no abstract is necessary for HPEye submissions
The 21st century has brought new challenges and opportunities and has also increased demands on the Nordic hydrological community. Our hydrological science focus and approaches need rethinking and adaptation to the changing requirements of society in response to climate change and human interventions, in search of more comprehensive and cross-disci...
A soil moisture estimation method was developed for Sentinel-1 synthetic aperture radar (SAR) ground range detected high resolution (GRDH) data to analyze moisture conditions in a gently undulating and heterogeneous subarctic area containing forests, wetlands, and open orographic tundra. In order to preserve the original 10-m pixel spacing, PIMSAR...
Subarctic ecohydrological processes are changing rapidly, but detailed and integrated ecohydrological investigations are not as widespread as necessary. We introduce an integrated research catchment site (Pallas) for atmosphere, ecosystems, and ecohydrology studies in subarctic conditions in Finland that can be used for a new set of comparative cat...
The influence of seasonally frozen ground (SFG) on water, energy, and solute fluxes is important in cold climate regions. The hydrological role of permafrost is now being actively researched, but the influence of SFG has received less attention. Intuitively, SFG restricts (snowmelt) infiltration, thereby enhancing surface runoff and decreasing soil...
The Arctic’s winter water cycle is rapidly changing, with implications for snow moisture sources and transport processes. Stable isotope values (δ18O, δ2H, d-excess) of the Arctic snowpack have potential to provide proxy records of these processes, yet it is unclear how well the isotope values of individual snowfall events are preserved within snow...
Fully integrated physically based hydrological modeling is an essential method for increasing hydrological understanding of groundwater‐surface water (GW‐SW) interactions in peatlands and for predicting anthropogenic impacts on these unique ecosystems. Modeling studies represent peat soil in a simplistic manner, as a homogeneous layer of uniform th...
AGU 2019 poster #H33I-2049 in session H31A - Applications in Snow Hydrology: Linking Seasonal Snow to Natural Processes and Society
Catchment storage sustains ecologically important low flows in headwater systems. Understanding the factors controlling storage is essential in analysis of catchment vulnerability to global change. We calculated catchment storage and storage sensitivity of streamflow for 61 boreal headwater catchments in Finland. We also explored the connection bet...
Freshwater is one of the most precious natural resources and is essential to any prospering society and economy. The supply and quality of freshwater not only impact human health and wellbeing, but are also critical to the functioning of high-latitude coastal, river, lake, and wetland ecosystems. Arctic freshwater distribution and supply is undergo...
The fate of the vast stocks of organic carbon stored in permafrost of the Western Siberian Lowland, the world’s largest peatland, is uncertain. Specifically, the amount of greenhouse gas emissions from rivers in the region is unknown. Here we present estimates of annual CO2 emissions from 58 rivers across all permafrost zones of the Western Siberia...
Integrating stable isotope tracers into rainfall‐runoff models allows investigation of water partitioning and direct estimation of travel times and water ages. Tracer data have valuable information content that can be used to constrain models and, in integration with hydrometric observations, test the conceptualisation of catchment processes in mod...
Use of isotopes to quantify the temporal dynamics of the transformation of precipitation into runoff has revealed fundamental new insights into catchment flow paths and mixing processes that influence biogeochemical transport. However, catchments underlain by permafrost have received little attention in isotope based studies, despite their global i...
Western Siberia Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilised by permafrost thaw. The fate of mobilized carbon is, however, not well understood, partly because of inadequate knowledge of hydrological controls in the region with a vast low-relief surface area, extensive lake and wetland coverage and gradu...
Continuous data on spatial and temporal patterns of snowmelt rates are essential for hydrological studies, but are commonly not available, especially in the subarctic, mainly due to high monitoring costs. In this study, temperature loggers were used to measure local and microscale variations in snowpack temperature, in order to understand snowmelt...
Transit time estimates in permafrost catchments
Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high-latitude wetland and permafrost influenced landscape, Journal of Hydrology (2017), doi: https://doi. Abstract Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for unde...
In Nordic regions water infiltration into soil is controlled by soil moisture content and frozen soil conditions, which are regulated by soil temperature. For long‐term model predictions of the effects of climate change, models need to be tested with long‐term data to assess model sensitivity to parameter uncertainties under both typical and except...
Understanding water fluxes in the critical zone, the mixing of soil waters and the resulting transit times are crucial to assess hydrological dynamics in the soil-vegetation-atmosphere interface. To better understand how water flows and mixes in soils of northern environments with a strong seasonal climate, we studied the hydrometric conditions and...
Vegetation is fundamentally important to water partitioning and can mediate the hydrological response of catchments to climate forcing. Understanding how plants respond to environmental change and the hydrological impacts of such responses is critical for projecting future ecosystem dynamics and water availability. As part of the ERC funded “VeWa”...
Tracer-aided hydrological models are increasingly used to reveal fundamentals of runoff generation processes and water travel times in catchments. Modelling studies integrating stable water isotopes as tracers are mostly based in temperate and warm climates, leaving catchments with strong snow influences underrepresented in the literature. Such cat...
Supporting Information S1
Use of stable water isotopes has become increasingly popular in quantifying water flow paths and travel times in hydrological systems using tracer-aided modeling. In snow-influenced catchments snow melt produces a traceable isotopic signal, which differs from original snowfall isotopic composition because of isotopic fractionation in the snowpack....
Abstract. Tracer-aided hydrological models are increasingly used to reveal fundamentals of runoff generation processes and water travel times in catchments. Modelling studies integrating stable water isotopes as tracers are mostly based in temperate and warm climates, leaving catchments with strong snow-influences catchments underrepresented in the...
Understanding the role of groundwater for runoff generation in headwater catchments is a challenge in hydrology, particularly so in data-scarce areas. Fully-integrated surface-subsurface modelling has shown potential in increasing process understanding for runoff generation, but high data requirements and difficulties in model calibration are typic...
Springs are unique ecosystems, but in many cases they are severely threatened and there is an urgent need for better spring management and conservation. To this end, we studied water quality and quantity in springs in Oulanka National Park, north-east Finland. Multivariate statistical methods were employed to relate spring water quality and quantit...
Interest in climate change effects on groundwater has increased dramatically during the last decade. The mechanisms of climate-related groundwater depletion have been thoroughly reviewed, but the influence of global warming on groundwater-dependent ecosystems (GDEs) remains poorly known. Here we report long-term water temperature trends in 66 north...
Vast regions of the northern hemisphere are exposed to snowfall and seasonal frost. This has large effects on spatiotemporal distribution of infiltration and groundwater recharge processes as well as on the fate of pollutants. Therefore, snow and frost need to be central inherent elements of risk assessment and management schemes. However, snow and...
In the Boreal region, anticline eskers aquifers are recharged in upland hillslopes and water discharges in the surrounding lowlands. Organic peat soils often confine the aquifer discharge area and drainage of these confining peat layers can decrease the flow resistance in the peat soil, which may cause unintentional groundwater level drawdown. This...
Climate change and land use are rapidly changing the amount and temporal
distribution of recharge in northern aquifers. This paper presents a novel
method for distributing Monte Carlo simulations of 1-D sandy sediment
profile spatially to estimate transient recharge in an unconfined esker
aquifer. The modelling approach uses data-based estimates fo...
Water resources management is moving towards integration, where groundwater (GW), surface water (SW) and related aquatic ecosystems are considered one management unit. Because of this paradigm shift, more information and new tools are needed to understand the ecologically relevant fluxes (water, heat, solutes) at the GW–SW interface. This study est...
Aquifers and groundwater-dependent ecosystems (GDEs) are facing increasing pressure from water consumption, irrigation and climate change. These pressures modify groundwater levels and their temporal patterns and threaten vital ecosystem services such as arable land irrigation and ecosystem water requirements, especially during droughts. This revie...
Groundwater-surface water (GW-SW) interactions cover a broad range of hydrogeological and biological processes and are controlled by natural and anthropogenic factors at various spatio-temporal scales, from watershed to hyporheic/hypolentic zone. Understanding these processes is vital in the protection of groundwater-dependent ecosystems (GDEs) inc...
Climate change and land use are rapidly changing the amount and temporal distribution of recharge
in northern aquifers. This paper presents a novel method for distributing Monte Carlo simulations
of 1-D soil profile spatially to estimate transient recharge in an unconfined esker aquifer. The
modeling approach uses data-based estimates for the most...
Esker aquifers are common groundwater bodies in Europe. Management of these aquifers should take account of the sustainability of groundwater-dependent ecosystems and land use in an integrated way. An unconfined esker aquifer in northern Finland was modelled with MODFLOW to determine how groundwater resources are impacted by the surrounding peatlan...
Multi-criteria decision analysis (MCDA) methods are increasingly used to facilitate both rigorous analysis and stakeholder involvement in natural and water resource planning. Decision-making in that context is often complex and multi-faceted with numerous trade-offs between social, environmental and economic impacts. However, practical applications...
Multi-criteria decision analysis (MCDA) methods are increasingly used to facilitate both rigorous analysis and stakeholder involvement in natural and water resource planning. Decision making in that context is often complex and multi-faceted with numerous trade-offs between social, environmental and economic impacts. However, practical applications...
Quantification of groundwater model uncertainties is one of the key
aspects when using models to direct land use or water management. An
esker aquifer with a size of 90 km2 was studied to understand how the
surrounding peatland forestry drainage, groundwater abstraction and
climate variability can affect the aquifer groundwater level and the
water...
Groundwater discharge from an esker aquifer to a fen was studied to understand relevant hydrological processes for groundwater-surface water interaction in an esker-peatland hillslope. Piezometric levels of the peat layer and esker sand layer were continuously monitored and compared to climate data. Groundwater exfiltration points were spatially ma...
Groundwater discharge from an esker aquifer to a fen was studied to
understand relevant hydrological processes for surface-groundwater
interaction in an esker-peatland hillslope. Piezometric levels of the
peat layer and esker sand layer were continuously monitored and compared
to climate data. Groundwater exfiltration points were spatially mapped
a...
In Finland, the main sources of groundwater are the esker deposits from
the last ice age. Small lakes imbedded in the aquifer with no outlets or
inlets are typically found in eskers. Some lakes at Rokua esker, in
Northern Finland, have been suffering from changes in water stage and
quality. A possible permanent decline of water level has raised
con...
This article presents an application of the choice experiment method in order to provide estimates of economic values generated by water quantity improvements in the environment. More importantly, this is the first choice experiment study valuing scientific information and in particular scientific information on climate change. The case study of in...
Rokua in Northern Finland is a groundwater dependent ecosystem very sensitive to climate change and natural variability. As such, the water level of most of the lakes is a function of the level of the groundwater table of the esker which is naturally recharged. This chapter presents results from an application of a choice experiment and contingent...