| 1. |
- Aminjafari, Saeid, 1988-, et al.
(författare)
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Assessing the Effects of Regulation on Swedish Lake Water Levels with Satellite Altimetry
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lakes are important sources of freshwater for human activities and provide critical ecosystem services. However, despite having approximately 100,000 lakes, Sweden has limited continuous gauged water level data. Although satellite radar altimetry has emerged as a popular alternative to measure water levels in inland water bodies, it is yet to be exploited to understand large-scale changes in inland water bodies in Sweden. Here, we quantify the changes in water levels of 144 lakes using satellite altimetry data and in-situ gauged measurements and examine the effects of flow regulation and hydroclimatic variability. Data from multiple altimetry missions, including ERS-2, ENVISAT, JASON-1,2,3, SARAL, and Sentinel-3A/B, are employed to estimate the variability and yearly and seasonal trends of water levels in two periods, 1995-2022 and 2013-2022. Our study finds that water levels significantly increased in 52% of the lakes during 1995-2022. The increasing trends primarily occurred in northern Sweden and are potentially attributed to earlier snowmelt. On the other hand, 43% of the lakes exhibited a significant decreasing trend, which was mostly concentrated in Southern Sweden. Dividing the set of lakes into regulated and unregulated groups shows how lake regulation in Sweden can partly explain the spatial patterns of water levels and their variability. This study highlights the need to continuously monitor lake water levels for adaptation strategies in the face of climate change and understand the downstream effects of water regulatory schemes.
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| 2. |
- Aminjafari, Saeid, 1988-, et al.
(författare)
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Distinctive Patterns of Water Level Change in Swedish Lakes Driven by Climate and Human Regulation
- 2024
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 60:3
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Tidskriftsartikel (refereegranskat)abstract
- Despite having approximately 100,000 lakes, Sweden has limited continuous gauged lake water level data. Although satellite radar altimetry (RA) has emerged as a popular alternative to measure water levels in inland water bodies, it has not yet been used to understand the large-scale changes in Swedish lakes. Here, we quantify the changes in water levels in 144 lakes using RA data and in situ gauged measurements to examine the effects of flow regulation and hydroclimatic variability. We use data from several RA missions, including ERS-2, ENVISAT, JASON-1,2,3, SARAL, and Sentinel-3A/B. We found that during 1995–2022, around 52% of the lakes exhibited an increasing trend and 43% a decreasing trend. Most lakes exhibiting an increasing trend were in the north of Sweden, while most lakes showing a decreasing trend were in the south. Regarding the potential effects of regulation, we found that unregulated lakes had smaller trends in water level and dynamic storage than regulated ones. While the seasonal patterns of water levels in the lakes in the north are similar in regulated and unregulated lakes, in the south, they differ substantially. This study highlights the need to continuously monitor lake water levels for adaptation strategies in the face of climate change and understand the downstream effects of water regulatory schemes.
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| 3. |
- Aminjafari, Saeid, 1988-, et al.
(författare)
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Evaluating D-InSAR Performance to Detect Small Water Level Fluctuations in Lakes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- It is essential to track lake water level fluctuations, however, the number of conventional gauging stations is declining worldwide due to impractical installation and maintenance procedures. Satellite altimetry is a substitute for traditional gauges. Nevertheless, altimetry sensors cannot identify small lakes owing to poor spatial coverage. Their application is limited to lakes falling exactly below the path of the altimeter. Differential Interferometric Synthetic Aperture Radar (D-InSAR) is commonly used to track land deformation and water surface changes, with the latter being comparatively limited and focused mainly on wetlands. We here explore the potential of D-InSAR to track water level changes in two Swedish lakes, focusing on the shoreline in search of potential double-bounce backscattering and analyzing pixel phase changes and coherence. We use Sentinel-1A and Sentinel-1B data from 2019, generate six-day interferograms, and exclude those when corresponding to in-situ water level changes exceeding one phase cycle. We find that D-InSAR is sensitive to minor water level changes, obtaining Lin's correlations of up to 0.63 and 0.89 (RMSE = 9 & 4 mm, respectively). These results evidence the potential of future L-band SAR missions with larger wavelengths, such as NISAR, to track water level changes in lakes and aid water tracking missions such as the SWOT.
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| 4. |
- Aminjafari, Saeid, 1988-
(författare)
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Monitoring Water Availability in Northern Inland Waters from Space
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- River deltas and lakes support biodiversity and offer crucial ecosystem services such as freshwater provision, flood control, and fishing. However, climate change and human activities have affected deltas and lakes globally, altering the services they provide. Since delta and lake surface water occurrence and water levels respond to climate change and anthropogenic activities, we need to monitor their variations to understand the potential drivers for effective water management strategies. However, important deltas like the Selenga River Delta (SRD) in Russia lack a detailed analysis of water occurrence. Regarding lake water level, there has been a decline in the number of gauging stations globally, due to installation and maintenance costs. For example, Sweden has ~100,000 lakes which are sources of freshwater and hydro-power, but only 38 lakes have long and continuous in-situ records of water level.As satellite data are reliable alternatives for conventional methods to monitor deltas and lakes, I employed Earth Observations (EO) to quantify changes in surface water occurrence in the SRD and water levels in Swedish lakes and identify their main drivers. I also developed and explored a novel methodology for lake water level estimation based on Differential Interferometric Synthetic Aperture Radar (D-InSAR) by calculating the six-day phase differences in 30 Swedish lakes.To achieve these objectives, I trained and applied a Maximum Likelihood classification to Landsat images from 1987 to 2020 and quantified surface water occurrence and its changes in the SRD. I found that surface water occurrence in 51% of the delta experienced a decrease. As the Selenga River is the only river flowing into the SRD, the change in surface water occurrence in the SRD correlated with river discharge, but not with the river suspended sediment concentration, the lake water level in the outlet of the SRD, or evapotranspiration over the delta.In Sweden, I used satellite altimetry data from ERS-2, ENVISAT, JASON-1,2,3, SARAL, and Sentinel-3A/B to quantify water levels in 144 lakes from 1995-2022. I found that 52% of the lakes showed increasing trends (mostly in the north) and 43% decreasing trends (mostly in the south). Water level trends and variabilities did not correlate strongly with hydroclimatic changes (precipitation and temperature) but differed in regulated lakes compared to unregulated ones, both in the north and in the south of Sweden.The results of the D-InSAR method for water level estimation in two Swedish lakes (Hjälmaren and Solnen) showed that with water level changes smaller than a complete SAR phase, the phase changes correlate with in-situ water level changes with a minimum Root Mean Square Error of 0.43 cm in some pixels. In all 30 lakes, I accumulated the phase changes of each pixel throughout the whole number of interferograms to construct water levels. This method replicated the direction of water level changes shown by high Pearson’s correlations in at least one pixel in each lake.This thesis highlights the importance of EO for estimating surface water occurrence and lake water levels and brings focus to the future of EO through advanced space missions such as Surface Water and Ocean Topography (SWOT) and NASA-ISRO Synthetic Aperture Radar (NISAR). The findings underscore the need to continuously monitor lake water level and occurrence to adapt to climate change and understand the effects of water-regulatory schemes.
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| 5. |
- Aminjafari, Saeid, 1988-, et al.
(författare)
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The Potential of D-InSAR for Water Level Estimation in Swedish Lakes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lakes are valuable water resources that support aquatic and terrestrial ecosystems and supply fresh water for the agricultural, industrial, and urban sectors worldwide. Although water levels should be tracked to monitor these services, conventional gauging is unfeasible in most lakes. This study explores the potential, advantages, and limitations of using Differential Interferometric Synthetic Aperture Radar (D-InSAR) to estimate small water level changes in lakes (i.e., less than the full cycle of the SAR signal) and overall long-term direction of change. We validated the method across the shores of 30 Swedish lakes with gauged observations during 2019. We used Sentinel-1A/B images with a six-day temporal separation to construct consecutive interferograms and accumulated the phase changes in pixels of high coherence to build time series of water levels. We find that the accumulated phase change replicates the magnitude of water levels in seven lakes in Southern Sweden, where water level changes seldom exceed a complete SAR phase (i.e., 1.8 cm in the vertical direction), evident from the Concordance Correlation Coefficients (0.30 < CCC < 0.55). Furthermore, D-InSAR can estimate the long-term direction of water level change (i.e., increase or decrease) in all 30 lakes. We elaborate on the possible explanation for this last finding. The novel methodology could be used to validate future altimetry missions such as SWOT in lakes worldwide and can be improved with upcoming SAR missions with longer wavelengths.
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| 6. |
- Aminjafari, Saeid, et al.
(författare)
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Tracking Centimeter-Scale Water Level Changes in Swedish Lakes Using D-InSAR
- 2024
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 60:2
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Tidskriftsartikel (refereegranskat)abstract
- Lakes are valuable water resources that support aquatic and terrestrial ecosystems and supply fresh water for the agricultural, industrial, and urban sectors worldwide. Although water levels should be tracked to monitor these services, conventional gauging is unfeasible in most lakes. This study applies Differential Interferometric Synthetic Aperture Radar (D-InSAR) to estimate small water level changes, less than 2 cm, in Swedish lakes over 6-day intervals. We validated the method across the shores of 30 Swedish lakes with gauged observations in 2019. We used Sentinel-1A/B images with a 6-day temporal separation to construct consecutive interferograms and accumulated the phase changes in pixels of high coherence to build a time series of water levels. We find that the accumulated phase change obtained by D-InSAR replicates the magnitude of water levels in seven lakes in Southern Sweden, where water levels change slowly, less than 2 cm per 6-day period, as validated by in-situ gauges. In addition, this study demonstrates the application of D-InSAR to estimate the long-term direction of water level change (i.e., increase or decrease) in all 30 lakes. This work reveals the utility of high temporal resolution water level observations in support of other satellite water level instruments such as conventional altimeters and the recently launched Surface Water and Ocean Topography Mission.
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| 7. |
- Berghuijs, Wouter R., et al.
(författare)
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Groundwater recharge is sensitive to changing long-term aridity
- 2024
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Ingår i: Nature Climate Change. - 1758-678X .- 1758-6798. ; 14, s. 357-363
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Tidskriftsartikel (refereegranskat)abstract
- Sustainable groundwater use relies on adequate rates of groundwater recharge, which are expected to change with climate change. However, climate impacts on recharge remain uncertain due to a paucity of measurements of recharge trends globally. Here we leverage the relationship between climatic aridity and long-term recharge measurements at 5,237 locations globally to identify regions where recharge is most sensitive to changes in climatic aridity. Recharge is most sensitive to climate changes in regions where potential evapotranspiration slightly exceeds precipitation, meaning even modest aridification can substantially decrease groundwater recharge. Future climate-induced recharge changes are expected to be dominated by precipitation changes, whereby changes in groundwater recharge will be amplified relative to precipitation changes. Recharge is more sensitive to changes in aridity than global hydrological models suggest. Consequently, the effects of climatic changes on groundwater replenishment and their impacts on the sustainability of groundwater use by humans and ecosystems probably exceed previous predictions.
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| 8. |
- Chrysafi, Anna, et al.
(författare)
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Quantifying Earth system interactions for sustainable food production via expert elicitation
- 2022
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Ingår i: Nature Sustainability. - : Springer Science and Business Media LLC. - 2398-9629. ; 5:10, s. 830-842
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Tidskriftsartikel (refereegranskat)abstract
- Several safe boundaries of critical Earth system processes have already been crossed due to human perturbations; not accounting for their interactions may further narrow the safe operating space for humanity. Using expert knowledge elicitation, we explored interactions among seven variables representing Earth system processes relevant to food production, identifying many interactions little explored in Earth system literature. We found that green water and land system change affect other Earth system processes strongly, while land, freshwater and ocean components of biosphere integrity are the most impacted by other Earth system processes, most notably blue water and biogeochemical flows. We also mapped a complex network of mechanisms mediating these interactions and created a future research prioritization scheme based on interaction strengths and existing knowledge gaps. Our study improves the understanding of Earth system interactions, with sustainability implications including improved Earth system modelling and more explicit biophysical limits for future food production.
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| 9. |
- Fahrländer, Simon Felix, et al.
(författare)
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Hydroclimatic Vulnerability of Wetlands to Upwind Land Use Changes
- 2024
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Ingår i: Earth's Future. - 2328-4277. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Despite their importance, wetland ecosystems protected by the Ramsar Convention are under pressure from climate change and human activities. These drivers are altering water availability in these wetlands, changing water levels or surface water extent, in some cases, beyond historical variability. Attribution of the effects of human and climate activities is usually focused on changes within the wetlands or their upstream surface and groundwater inputs. However, the reliance of wetland water availability on upwind atmospheric moisture supply is less understood. Here, we assess the vulnerability of 40 Ramsar wetlands to precipitation changes caused by land use and hydroclimatic change occurring in their upwind moisture-supplying regions. We use moisture flows from a Lagrangian tracking model, atmospheric reanalysis data, and historical land use change (LUC) data to assess and quantify these changes. Our analyses show that historical LUC has decreased precipitation and terrestrial moisture recycling in most wetland hydrological basins, decreasing surface water availability (precipitation minus evaporation). The most substantial effects on wetland water availability occurred in the tropic subtropical regions of Central Europe and Asia. Overall, we found wetlands in Central Asia and South America to be the most vulnerable by a combination of LUC-driven effects on runoff, high terrestrial precipitation recycling, and recent decreases in surface water availability. This study stresses the need to incorporate upwind effects of land use changes in the restoration, management, and conservation of the world's wetlands.
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| 10. |
- Jaramillo, Fernando, 1977-
(författare)
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Changes in the Freshwater System : Distinguishing Climate and Landscape Drivers
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Freshwater is a vital resource that circulates between the atmosphere, the land and the sea. Understanding and quantifying changes to the partitioning of precipitation into evapotranspiration, runoff and water storage change in the landscape are required for assessing changes to freshwater availability. However, the partitioning processes and their changes are complex due to multiple change drivers and effects. This thesis investigates and aims to identify and separate the effects of atmospheric climate change and various landscape drivers on long-term freshwater change. This is done based on hydroclimatic, land-use and water-use data from the beginning of the twentieth century up to present times and across different regions and scales, from catchment to global. The analyzed landscape drivers include historic developments of irrigated and non-irrigated agriculture and flow regulation. The thesis uses and develops further a data-motivated approach to interpret available hydroclimatic and landscape data for identification of water change drivers and effects, expanding the approach application from local to continental and global scales. Based on this approach development, the thesis identifies hydroclimatic change signals of landscape drivers against the background of multiple coexisting drivers influencing worldwide freshwater change, within and among hydrological basins. Globally, landscape drivers are needed to explain more than 70% of the historic hydroclimatic changes, of which a considerable proportion may be directly human-driven. These landscape- and human-driven water changes need to be considered and accounted for also in modeling and projection of changes to the freshwater system on land.
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