Hydrologic History Research Articles

Offshore freshened groundwater reservoirs controlled by submarine faults with a complex dependency on antecedent hydrogeological conditions

Offshore Freshened Groundwater (OFG) reservoirs are gaining attention, as evidence suggests they are more prevalent worldwide than previously thought. OFG systems are generally classified as either passive, a relic of ancient, lower sea levels, or as active, with an onshore-offshore hydrogeologic connection and associated discharge offshore. Previous studies on the mechanisms of OFG were conducted in various hydrogeologic settings, but the role of faults remains understudied. Based on geologic data, we apply hydrogeologic modeling of a faulted submarine confined aquifer in the Levant basin (eastern Mediterranean), to study the impact of faults on OFG. We find that faults that are close to the coastline and within the brackish zone that would have developed without a fault control the offshore salinities regardless of initial conditions. The influence of distal faults, in contrast, depends on antecedent conditions. When initial salinities are such that the distal fault lies in the fresh part of the aquifer, the saline wedge migrates landward toward the fault with sea-level rise, and the fault dictates the steady-state salinity distribution. If the fault is initially within the saline part of the aquifer, freshwater never reaches the fault, likely due to the density-driven flow barrier that the underlying saline wedge generates. These findings suggest a new mode of OFG in which the same geologic system can be either active or passive depending on the hydrologic history. This should be considered in future studies of OFG systems, the functioning of which has implications for marine ecosystems, seafloor geomorphology, and coastal water resources.

A historical overview of experimental hydrology in China

AbstractThe history of experimental hydrology in China is important but poorly documented. Here we review 94 papers (86 of these in Chinese) from the CNKI and Web of Science websites to chronicle the history of experimental studies in China before 2000. Professor Wei‐Zu Gu—the focus of this Special Issue—factors heavily into this history. Perhaps more than any country, the experimental hydrology history of China is influenced by socioeconomic development and political change. Our analysis shows 4 main periods of development associated with (1) an early development stage before 1949, the founding year of People's Republic of China (PRC), (2) an initial period of rapid transition in experimental studies in China (1949–1965), (3) a struggling and recovering stage for during and shortly after the Cultural Revolution, from 1965 to 1978, and (4) significant progress associated with new policies for reform and opening up in China from 1978 to 2000, that included contributions of Wei‐Zu Gu and other scientists. In terms of experimental hydrological findings, two notable contributions are a mathematical description of saturation overland flow derived from streamflow and precipitation data and calculated water storage deficit in the unsaturated zone by Zhao and Zhuang (1963), several years before its process‐based ‘discovery’ in the USA (and elsewhere) and the ‘interface runoff generation law’ of Yu (1985) which was ahead of its time in understanding linking the notion of the commonality of all runoff forms. In terms of model development stemming from experimental studies, the development of the Xinanjiang Model of Zhao (1980) was a significant achievement, later partly adopted into the VIC model in the USA and the ARNO model in Europe. Finally, the Hydrohill catchment developed by Wei‐Zu Gu led the way for the rapid rise in process studies and internationalization of experimental hydrology in China. Overall, the experimental hydrological studies from 1949 to 2000 had a strong engineering focus, with many links to water conservation construction and management.

Cartographic analysis as spatial determinant for climate change adaptation in the Hunter River Estuary, Australia

This paper explores the hydrological history of the Hunter River and Estuary (Newcastle, Australia), to identify pathways for incorporating climate-sensitive adaptation approaches into urban development and planning. The research method utilises mapping as a methodological discovery tools to visually articulate the correlation of pre-colonial hydrological landscapes, the transformation of the estuary over two centuries, the areas identified as at risk, and the opportunities for developing a climate-resilient estuary. This research aims to contribute to the redefinition of the discourse on the role of estuary planning for changing climate, focusing on four critical aspects: identify the impacts of urbanisation and industrialisation on ecosystems and its correlation with climate hazard at the estuary; visualise such transformations over time and space to identify critical spatial and climate factors threatening inhabitation; propose strategic spatial practices towards adaptation and resilience; and synthesising the options to foster reflective thinking and establish a correlation with novel policies, governance and practices. The study highlights that adopting new urbanism aligned with cultural and ecological principles can mitigate future climate impacts through re-naturalisation and urban adaptation to sea-level rise by focusing on proactive approaches to building resilient communities. This paper also acknowledges the need for site-specific adaptive design and planning strategies at multiple scales and governance levels.

Racial hydrologies

AbstractIn the South Carolina Lowcountry, near‐annual hurricanes and record‐breaking sea levels have led to disastrous flooding, overwhelming the region's historical tidal infrastructures and entrenched racial geographies. In response, Lowcountry governments, institutions, and residents have undertaken efforts at “perimeter protection,” raising dikes and seawalls to safeguard selected urban and rural plantation spaces from tidal flooding. Although perimeter protection is presented as a neutral resilience strategy, its practices and material forms reveal a close relationship between coastal protection and efforts to preserve landscapes of white supremacy. Such logics of perimeter protection contrast with everyday affective encounters with eroding coastlines and with the futures outside of bounded edges imagined by Black Charlestonians. By situating the region's hydrological history within the legacy of slavery and plantation extraction, and by following the effects of current sea level rise, we can see how historical hydrologies—which in this case are also racial hydrologies—are entangled with landscapes of contemporary environmental injustice.

Late quaternary lake level variations of Mabu Co-Gala Co, southern Tibetan plateau, modulated by glacial meltwater, spillover processes and the Indian summer monsoon

Lakes on the Tibetan Plateau (TP) play a major role in the regional hydrological cycle and underpin vital ecosystem services. However, the long-term lake evolution and underlying mechanisms, especially on the exorheic southern TP, remain unclear. Here, we reconstructed the lake level variations of Mabu Co and Gala Co on the southern TP through detailed paleo-shoreline dating using post-infrared infrared stimulated luminescence (pIRIR) signals of K-feldspar single grains, and explored the driving forcings based on a comparison of paleoclimate records and geomorphological analysis. The results show that a unified paleolake at Mabu Co and Gala Co at a level ∼20 m above the modern level (a.m.l.) of Mabu Co developed during the late MIS 3 (35.9 ± 1.9–29.1 ± 1.4 ka) in response to increased glacial meltwater and Indian summer monsoon (ISM) rainfall. Under intensive glacier melting, the paleolake reached its maximum level (∼29 m a.m.l.) and area (190 km2, ∼22 times larger than the modern areas of Mabu Co and Gala Co) during the last deglacial (16.8 ± 1.0–13.6 ± 0.7 ka) and began to outflow, which triggered incision and lowering of the spill-point. The lake level showed an overall decreasing trend since the last deglacial largely influenced by the lowering of the spill-point. During the last deglacial-early Holocene (12.7 ± 0.6–9.8 ± 0.6 ka), a high-stand lower than that in the previous stage (∼24 m a.m.l.) was maintained by the strengthened ISM and glacial meltwater. In the mid-Holocene (8.7 ± 0.9–4.1 ± 0.3 ka), the paleolake experienced two rapid lake level drops in response to the weakening events of the ISM. The exposed shoreline terrace between the two lakes following the lake level drop after ∼6 ka provided an ideal living surface for the inhabitants at the Mabu Co site during 4.5–4.0 ka. We found that glacial meltwater and lake spillover processes, apart from the ISM, have exerted great impacts on the hydrological history of Mabu Co and Gala Co. The paleolakes have provided critical resources for humans at the Mabu Co site living in the alpine anoxic environment. Additionally, we suggest that lakes with low spill-points adjacent to exorheic basins on the southern TP should be given more attention regarding flooding hazard risks against increasing precipitation and glacial meltwater in the future.

A comprehensive study of floods in Poland in the 17th–18th centuries

Study regionPoland, with the regions of Baltic Coast and Pomerania, Masuria-Podlasie, Greater Poland, Masovia, Silesia, and Lesser Poland located in the basins of the Baltic Coast rivers, the Vistula River and the Oder River. Study focusThis study focused on completing the documentation of historical floods in Poland before the 19th century and providing a valuable source for historical hydrology studies in Europe. To this end, a comprehensive database of all floods for the 17th–18th centuries was used, that was based on documentary evidence from 293 sources and 978 weather notes describing all flood occurrences. New hydrological insights for the regionThe finding of this study revealed the occurrences of 678 floods, including 37 new cases that have been discovered and documented only in this research. Spatial analysis of the results revealed that most of the floods occurred in the Vistula River basin. The number of floods by season was greatest for summer (JJA) (47 %) and smallest for autumn (7 %). Investigation of the origin of floods indicated that rain was the main factor contributing to occurrences of floods in Poland (38 %). The estimation of the intensity of floods showed that most of the floods were “smaller, regional floods” (257 cases) based on the Brázdil et al. (2006b) classification and “extraordinary” (501 cases) in the Barriendos & Coeur (2004) classification.

Non-pollen palynomorph assemblages in mid- to late Holocene wetland deposits and their palaeoenvironments of deposition: Microfossil signatures in sediment sequences of the Yangtze Delta coastal lowlands, East China

Fluvial processes such as sediment deposition within drainage channels and seasonal overbank flooding, and fluvial events such as occasional high intensity floods all leave particular sedimentary signatures in terms of their lithology and also in their contained microfossil assemblages, which represent different environments of deposition. Over several thousand years the Yangtze River in eastern China has developed a coastal lowland plain around its delta that is mainly composed of stacked fluvial sediment facies, but also includes many marine or estuarine layers in some areas, as well as deposits of limnic and semi-terrestrial pool, marsh and mire origin, some of which are highly organic. The fluvial facies are dominantly clastic sequences of sands, silts and clays that reflect a range of deposition from quiet water to high energy conditions and in varying water depths, mainly governed by fluvial input from the Yangtze and the many other, smaller, rivers and streams of the deltaic lowland. The limnic and marshland sediments reflect autochthonous deposition in a range of freshwater wetland types of varying water depth, from lake through marsh/fen to surface peatland. Allied to lithological and pollen data, non-pollen palynomorph spore assemblages and abundances within these complex sedimentary sequences, particularly from algal communities, provide signatures of floodplain wetland depositional history and hydrodynamic patterns. We have used groupings of these microfossil data to characterise the sedimentary facies of the lower Yangtze coastal plain and to reconstruct hydrological history across the area at a range of spatial scales. Fluctuations in the relative taxa abundances are good indicators of changes in water levels at the site scale from surface waterlogging through reedswamp and fen to deeper open water. While some changes seem to be site specific, the data show flooding and increased water depths that correlate with known phases of climatic deterioration.

Detection of dilution due to turbulent mixing vs. precipitation scavenging effects on biomass burning aerosol concentrations using stable water isotope ratios during ORACLES

Abstract. The interaction between biomass burning aerosols and clouds remains challenging to accurately determine, in part because of difficulties using direct observations to account for influences on aerosol concentrations from precipitation scavenging and dilution due to air mass mixing and separating those signals from source contributions. The prevalence of mixing versus precipitation processes in air laden with biomass burning aerosol (BBA) in the southeast Atlantic lower free troposphere (FT) and marine boundary layer (MBL) is assessed during three observation periods (September 2016, August 2017, and October 2018) during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign. Significant sources of BBAs over the African continent combined with regional circulation patterns result in BBA-laden air flowing from the continent over the southeast Atlantic in the lower FT, then subsiding onto the semi-permanent stratocumulus cloud deck, and entraining into the MBL. This study is broken into two parts, first analyzing hydrologic histories of the BBA air in the lower FT and then carrying out a similar assessment in the underlying MBL. Both analyses leverage joint measurements of water concentration and its heavy isotope ratio, interpreted in the previously established (q, δD) phase space framework. For the lower-FT analysis, in situ observations (water concentration, water isotope ratios) in the lower FT are combined with satellite and Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), global reanalysis data into simple analytical models to constrain hydrologic histories. We find that even simple models are capable of detecting and constraining the primary processes at play, e.g., distinguishing air masses that experienced moist convection and precipitation (likely over the continent) from those that underwent dry convection and turbulent mixing. Regression of the aircraft data onto a simple model of convective detrainment is used to develop a metric of total precipitation for the in situ measurements and then compared to an aerosol metric of black carbon scavenging also derived from the in situ measurements (the ratio of black carbon to carbon monoxide, BC/CO). There is a strong correlation between the two, suggesting black carbon scavenging has been detected and partially quantified, if only in a relative manner. In comparison, weak correlation is found between BC/CO and the total water concentration itself. The above method is expanded to test for entrainment and precipitation influences on BBA concentrations in the MBL. This is more difficult than the FT analysis since signals are subtle and limited by imperfect knowledge of the water and isotope ratios of the entrained air mass at cloud top. For some of the MBLs observed during 2016 and 2018, lower cloud condensation nuclei (CCN) concentrations occur in the sub-cloud layer coincident with isotopic evidence of precipitation, indicating aerosol scavenging, but more complex models are needed to produce definitive conclusions. For the 2017 observation period, with the highest sub-cloud CCN concentrations, there is no connection between precipitation signals and CCN concentrations, likely indicating the importance of different geographic sampling and air mass history in that year. Nonetheless, these findings along with the FT analysis suggest that utilizing isotope ratio signals may be an aid in addressing cloud–aerosol challenges. Especially for the FT case, these findings support the pursuit of more complex models combined with targeted in situ data to constrain BC scavenging coefficients in a manner which can guide model parameterizations, leading to improvements in the accuracy of simulated BC concentrations and lifetimes in climate models.

Multi-reservoir system response to alternative stochastically simulated stationary hydrologic scenarios: An evaluation for the Apalachicola-Chattahoochee-Flint (ACF) Basin

Study regionApalachicola-Chattahoochee-Flint (ACF) Basin in the Southeast US Study focusOperational rules of managed river systems are typically developed based on historical hydrology. This approach fails to consider alternative plausible hydrologic conditions that may occur outside the observational period-of-record. Here, we evaluated operational rules of a transboundary managed river system—the ACF Basin—with multiple reservoirs under historical observations and 100 stochastic streamflow realizations representing the current streamflow conditions of the basin. These scenarios, which had comparable averages as the historical records but greater extremes, were simulated by coupling a stochastic streamflow model with a basin-wide river system model. We used these scenarios to evaluate the response of the ACF Basin against metrics for urban water supply, required freshwater inflows, floodplain forest ecosystem water needs and hydropower generation. The evaluation was done based on the magnitude, frequency, duration and seasonality of these metrics. New hydrological insight of the regionThe unique aspect of this paper is using a stochastic streamflow model coupled with a river basin model to evaluate the response of the ACF Basin’s current operational rules under several hypothetical plausible stationary hydrologic scenarios. We found that, overall, the basin response in terms of all the metrics used here was less favorable under the alternative stationary hydrologic scenarios than the historical hydrology. Our evaluations suggested that the reservoir operational rules should be revisited to consider a broader range of plausible hydrologic conditions.

Development of Upper Euphrates Basin hydro-economic model and hydropower generation optimization

Abstract Hydro-economic optimization models are common in hydropower reservoir modeling to aid system operators and planners. In these models, operations are driven by the economic value and constrained by the availability of water. The objective is to either minimize total costs or maximize total benefits. In this study, a hydro-economic optimization model for the integrated reservoir system of the Upper Euphrates Basin, with major tributaries providing water flow to the Euphrates River, is introduced. These model the 10 large-scale reservoirs of the basin with a total installed capacity of 3,255 MW. Water management and hydropower decision-making operations are evaluated with a piecewise linear programming algorithm in monthly time steps using a 45-year historical hydrology between 1971 and 2016. The model aims to maximize hydropower revenue over a long-term time horizon with energy prices varying by month. Reservoir storage and turbine release decisions are optimized for multiple hydropower plants connected in serial or parallel. Hydropower generation, revenue, reservoir storage, capacity ratios and generation reliability results are analyzed. Results show that these hydropower plants generate about 9,481 Gigawatt hour (GWh) of energy with an average turbine capacity use of 36% and obtain a revenue of 620 million $ per year.

Dissipation of pesticides by stream biofilms is influenced by hydrological histories.

To evaluate the effects of hydrological variability on pesticide dissipation capacity by stream biofilms, we conducted a microcosm study. We exposed biofilms to short and frequent droughts (daily frequency), long and less frequent droughts (weekly frequency) and permanently immersed controls, prior to test their capacities to dissipate a cocktail of pesticides composed of tebuconazole, terbuthylazine, imidacloprid, glyphosate and its metabolite aminomethylphosphonic acid. A range of structural and functional descriptors of biofilms (algal and bacterial biomass, extracellular polymeric matrix (EPS) concentration, microbial respiration, phosphorus uptake and community-level physiological profiles) were measured to assess drought effects. In addition, various parameters were measured to characterise the dynamics of pesticide dissipation by biofilms in the different hydrological treatments (% dissipation, peak asymmetry, bioconcentration factor, among others). Results showed higher pesticide dissipation rates in biofilms exposed to short and frequent droughts, despite of their lower biomass and EPS concentration, compared to biofilms in immersed controls or exposed to long and less frequent droughts. High accumulation of hydrophobic pesticides (tebuconazole and terbuthylazine) was measured in biofilms despite the short exposure time (few minutes) in our open-flow microcosm approach. This research demonstrated the stream biofilms capacity to adsorb hydrophobic pesticides even in stressed drought environments.

Riparian cottonwood mortality following compound impacts from river water withdrawal and hydroclimatic variation

AbstractOriginating in Glacier Park, Montana, the transboundary St. Mary River has provided a focus for international water sharing for a century. It was dammed and diverted in the USA, and more extensively in Alberta, where it supports Canada's centre for agricultural irrigation. Following water withdrawals, the riparian cottonwoods (Populus angustifolia) collapsed, and we assessed the woodland decline downstream from the St. Mary Dam, through eight sets of aerial photographs over seven decades. These revealed 88% woodland loss from 1951 to 1999 (R2 = 0.984), including a steeper decline with the 1980s drought. Following the implementation of an environmental flow regime that increased minimum flows after 1993, the remnant woodlands were stabilized, with a slight recovery by 2022. Analyses of the historical hydrology revealed compound contributions to the woodland mortality. (1) Annual river flows declined with increasing water diversion, and (2) late summer flows were particularly depleted. (3) Dam operations resulted in abrupt stage recessions and irregular spikes. (4) Accompanying climate warming, the spring snowmelt advanced and late summer flows declined. (5) The greatest climatic influence involved multiple‐year clusters with high versus low flows, corresponding with the Pacific decadal oscillation (PDO) from 1920 to 1990 (R2 = 0.365), but less coupled thereafter. This long‐term study demonstrates the coordination between hydroclimatic variation, water management and the fate of riparian woodlands, which reveal ecosystem health. An environmental flow regime provided benefit, and for other regulated rivers in dry ecoregions, we recommend functional flow regimes that provide sufficient minimum flows and avoid abrupt flow recession or irregular spikes.

HOMECOMING OR NEW PAD: HISTORICAL EVIDENCE FOR CALIFORNIA RED-LEGGED FROGS AND OTHER AMPHIBIANS IN THE YOSEMITE REGION, CALIFORNIA

Establishing historical species distributions can assist conservation translocations for threatened species, and yet, ecological changes necessitate developing restoration targets that are not analogous to historical baselines. Despite its recent conservation translocation to Yosemite Valley in Yosemite National Park, Sierra Nevada Mountains, USA, the historical distribution of the federally threatened California Red-legged Frog (Rana draytonii) in the valley remains unclear. Using archival records, interviews, and museum specimens, we examined the historical evidence for California Red-legged Frogs and sympatric amphibian species in the Yosemite region. We found a paucity of reliable amphibian records for Yosemite Valley since the 19th century, one of the most-visited sites in the US National Park System, and conclude that this is the result of historically low collecting and survey effort prior to the introduction of invasive American Bullfrogs (Lithobates catesbeianus; also Rana catesbeiana after Yuan and others 2016) in concert with a bird and mammal study bias from largely diurnal collecting that occurred when California Red-legged Frogs were extant regionally. We found previously undocumented records for individuals of the genus Rana for Yosemite Valley, consistent with a dominant historical hydrology more compatible for Foothill Yellow-legged Frogs (Rana boylii), though none could be definitively identified as California Red-legged Frogs. We conclude that extensive anthropogenic impacts, including acute ecosystem alteration and American Bullfrog introduction, contributed to the failure to detect California Red-legged Frogs in many places regionally once amphibians became a research priority in the latter 20th century. The conservation translocation of California Red-legged Frogs to Yosemite Valley illustrates the integration of historical baselines with contemporary realities, allowing for the complexities of change over time rather than focusing on restoration to an imagined, ideal environment in the past.

Spatial and temporal distribution of sinuous ridges in southeastern Terra Sabaea and the northern region of Hellas Planitia, Mars☆

Sinuous ridges are an important yet understudied component of Mars' hydrologic history. We have produced a map of sinuous ridges, valleys and channels, and tectonic ridges across southeastern Terra Sabaea and into northern Hellas Planitia (10°-45° S, 35°-80° E) using a CTX mosaic. Although we mapped different types of ridges and negative relief features, the focus of this paper are the sinuous ridges. We present here a new dataset of sinuous ridges that includes basic morphometry (e.g., length, width, sinuosity), morphology, and the types of terrains they are located on. We chose our region of interest because it includes surface ages spanning Mars' geologic history, with emphasis on Noachian and Hesperian terrains. The shift from either a warm and wet or a cold and icy environment to our modern cold and dry climate occurred towards the end of the Noachian and into the Hesperian, a critical temporal window to characterize fluvial landforms.Our CTX-based mapping significantly improved the documentation of fluvial landforms within the study region, with over an order of magnitude increase in the number of valley networks and channels, and nearly 1700 sinuous ridges. Sinuous ridges are found in concentrated settings, with the majority (∼80%) located within impact craters and relatively few (∼20%) on the intercrater plains. Fluvial features are prevalent on Early and Middle Noachian-aged terrain but are relatively rare in the Late Noachian, signifying a shift in fluvial activity that likely led to a decrease in channel incision and subsequent inversion of relief. A subset of sinuous ridges—radial ridges in high-elevation, degraded craters— are possible records of ancient proglacial lakes. The youngest sinuous ridges are associated with intracrater alluvial fans in a narrow zone (∼12°S to 30°S and ∼ 62°E to 77°E). These formed in the Late Hesperian into the Amazonian, reflecting a later epoch of punctuated fluvial events driven by pre-existing topography and solar insolation.

Hydrological History of a Palaeolake and Valley System on the Planetary Dichotomy in Arabia Terra, Mars

AbstractHundreds of ancient palaeolake basins have been identified and cataloged on Mars, indicating the distribution and availability of liquid water as well as sites of astrobiological potential. Palaeolakes are widely distributed across the Noachian aged terrains of the southern highlands, but Arabia Terra hosts few documented palaeolakes and even fewer examples of open‐basin palaeolakes. Here we present a detailed topographic and geomorphological study of a previously unknown set of seven open‐basin palaeolakes adjacent to the planetary dichotomy in western Arabia Terra. High resolution topographic data were used to aid identification and characterization of palaeolakes within subtle and irregular basins, revealing two palaeolake systems terminating at the dichotomy, including a ∼160 km chain of six palaeolakes connected by short valley segments. Analysis and correlation of multiple, temporally distinct palaeolake fill levels within each palaeolake basin indicate a complex and prolonged hydrological history during the Noachian. Drainage catchments and collapse features place this system in the context of regional hydrology and the history of the planetary dichotomy, showing evidence for both groundwater sources and surface accumulation. Furthermore, the arrangement of large palaeolakes fed by far smaller palaeolakes, indicates a consistent flow of water through the system, buffered by reservoirs, rather than a catastrophic overflow of lakes cascading down through the system.

From Kern Island to the Streets of Bakersfield: Logics of Contamination, Embodied Empiricisms, and the Afterlives of Reclamation

California’s arid San Joaquin Valley was once inundated by lakes and wetlands. Through settler colonial discourses of contamination, a network of canals and aqueducts drained these lakes and wetlands in the late nineteenth century. Now, the Valley’s air and water are contaminated by pesticides, nitrates, and hydrocarbons from oil extraction and large-scale agriculture. Building from archival research and participant observation with environmental justice activists, this paper bridges settler colonial and critical Indigenous studies, work on racial capitalism, and feminist science studies to investigate logics of contamination in the production of private property through hydraulic projects. California’s hydrologic history shows that ideas of contamination were contested alongside emergent ideas of the racialized body. Hydraulic infrastructure, then, was not only an economic project but functioned within a larger logic of contamination that further articulated racial formations and settler sovereignty claims. Yet chemical contamination can also induce futurities, intimacies, and collectivities in powerful ways, as environmental justice activists in the valley consistently highlight. I argue that a critical analytic of contamination can trace how racial categories are ecologically produced and reconfigured, not only through differential relationships to land, but through changes in the land itself.

Holocene hydrological history of a Tibetan glacier-fed lake Taro Co in response to climate change

Lake hydrological fluctuations on the Tibetan Plateau (TP) are highly sensitive to global climate change, which can be reconstructed directly by dating paleoshorelines representing past lake-levels. In this study, we reconstructed the Holocene lake-level history of Taro Co lake system (Taro Co, Zabuye Salt lake and Lagkor Co) on the southwestern TP, based on seventeen optically stimulated luminescence ages of paleoshorelines. The results showed that lake-levels were at the broad highstands of ∼40 m above modern lake-level (amll) from 11.6 to 7.0 ka, during which the three lakes were integrated and formed a mega paleolake. After 7.0 ka, the mega paleolake fluctuantly contracted, and Lagkor Co and Zabuye Salt Lake probably became separated at ∼6.9 and ∼3.4 ka, respectively. Seven rapid millennial low lake stands were identified at 11.3–11.2 ka (14 m amll), 9.9–8.7 ka (< 28 m amll), 8.2–7.9 ka (6 m amll), ∼6.9 ka (5 m amll), ∼3.0 ka (8 m amll), 2.1–1.1 ka (< 6 m amll) and ∼0.4 ka (6 m amll). The large magnitude lake-level declines indicated that they reflected effective moisture in response to global millennial-scale climate events, e.g., the 11.1, 10.3, 9.4, 8.2 and 7.2 ka events in the early and middle Holocene, and the 4.2 ka and Little Ice Age events in the late Holocene. Holocene lake-level fluctuations were simultaneous with that of other lakes on the south-central TP. Comparisons with other paleoclimatic records suggested that the Holocene hydrological history of Taro Co was mainly dominated by both monsoonal precipitation and glacial meltwater supply, as well as evaporation and basin topography. Differences in meltwater supply probably led to different lake-level change histories for endorheic lakes in the lake system. In the future warming and wetting, Tibetan endorheic lakes would keep expanding, hence Taro Co lake system would be formed again through hydrological connections.

Ma'adim Vallis, Mars: Insights into episodic and late-stage water activity from an impact crater

Alluvial fans, a form of sedimentary deposit reported on Mars, offer insight into the evolution and nature of fluvial activity on the planet. Additionally, the region's preserved mineralogy can also be used to study its hydrological history. In this context, we discuss the diverse geomorphology and mineralogy of an unnamed crater that formed on the eastern wall of Ma'adim Vallis, Mars. Ma'adim Vallis is an irregular-shaped, flat-floored valley incised due to the outflow of water from the Eridania basin. The rim of the unnamed crater is breached at multiple locations and it hosts an alluvial fan of an area ~ 50 km2. The CRISM spectral signatures show Mg-rich olivine and Mg-rich smectite. Mg smectite was plausibly transported through water or formed in situ while the underneath terrain was rich in Mg olivine. The crater retention age on the ejecta of the unnamed crater is 3.7 Ga which suggests that the crater likely formed during the Noachian-Hesperian period boundary or earlier. This unnamed crater probably witnessed the last episode of water activity in the Vallis, which was most likely fed by water overflowing from a resurged early Hesperian water activity in Eridania Basin. This study substantiates episodic, late- stage water activity in Ma'adim Vallis, and the unnamed crater formed on the floodplains of the Vallis providing an excellent opportunity for future landing missions to explore astrobiological significance of the region.

Insights into Phytoplankton Dynamics and Water Quality Monitoring with the BIOFISH at the Elbe River, Germany

Understanding the key factors influencing the water quality of large river systems forms an important basis for the assessment and protection of cross-regional ecosystems and the implementation of adapted water management concepts. However, identifying these factors requires in-depth comprehension of the unique environmental systems, which can only be achieved by detailed water quality monitoring. Within the scope of the joint science and sports event “Elbschwimmstaffel” (swimming relay on the river Elbe) in June/July 2017 organized by the German Ministry of Education and Research, water quality data were acquired along a 550 km long stretch of the Elbe River in Germany. During the survey, eight physiochemical water quality parameters were recorded in high spatial and temporal resolution with the BIOFISH multisensor system. Multivariate statistical methods were applied to identify and delineate processes influencing the water quality. The BIOFISH dataset revealed that phytoplankton activity has a major impact on the water quality of the Elbe River in the summer months. The results suggest that phytoplankton biomass constitutes a substantial proportion of the suspended particles and that photosynthetic activity of phytoplankton is closely related to significant temporal changes in pH and oxygen saturation. An evaluation of the BIOFISH data based on the combination of statistical analysis with weather and discharge data shows that the hydrological and meteorological history of the sampled water body was the main driver of phytoplankton dynamics. This study demonstrates the capacity of longitudinal river surveys with the BIOFISH or similar systems for water quality assessment, the identification of pollution sources and their utilization for online in situ monitoring of rivers.

Research advances in shrub dendroecology

The ecological value of shrub-ring data has received more and more attention. The tree-ring data of shrub species have been increasingly used to reveal growth dynamics of regional shrub vegetation and its sensitivity to climate change. Up to now, nearly 70 species of shrubs have been used in the studies of shrub dendrochronology, which considerably broadened the traditional tree-ring research network, enriched the research scope and object of dendrochronology, and certainly with great significance in revealing the characteristics of regional climate fluctuation and annual dynamics of structure, function and service for shrubland ecosystems. In this study, we systematically collected dendrochronological studies based on shrub species during the 1996-2021, and reviewed research progress in four main subfields (physiology, climatology, ecology and hydrology) in dendrochronology for shrub species. The characteristics of shrub growth and xylem anatomy under different environmental stresses were expounded. The main limiting factors for shrub growth in different climatic conditions and the history of regional climate fluctuations based on shrub-ring data were revealed. The individual growth and population dynamics of shrub species driven by climate and the changes in ecosystems caused by non-climatic factors were assessed, and the reconstructions of regional hydrological histories were compiled using tree-ring data of shrub species. Under the context of global warming, dendrochronological studies of shrub species in China should pay more attention to the responses of shrub species radial growth to drought stress under different moisture conditions in the semi-arid and arid regions and the transforming feature of distribution pattern and climate response sensitivity for shrub species under the background of climate change.